Publications by authors named "Goutam Chowdhury"

89 Publications

Senescence-Induced Chemoresistance in Triple Negative Breast Cancer and Evolution-Based Treatment Strategies.

Front Oncol 2021 24;11:674354. Epub 2021 Jun 24.

Independent Researcher, Greater Noida, India.

Triple negative breast cancer (TNBC) is classically treated with combination chemotherapies. Although, initially responsive to chemotherapies, TNBC patients frequently develop drug-resistant, metastatic disease. Chemotherapy resistance can develop through many mechanisms, including induction of a transient growth-arrested state, known as the therapy-induced senescence (TIS). In this paper, we will focus on chemoresistance in TNBC due to TIS. One of the key characteristics of senescent cells is a complex secretory phenotype, known as the senescence-associated secretory proteome (SASP), which by prompting immune-mediated clearance of senescent cells maintains tissue homeostasis and suppresses tumorigenesis. However, in cancer, particularly with TIS, senescent cells themselves as well as SASP promote cellular reprograming into a stem-like state responsible for the emergence of drug-resistant, aggressive clones. In addition to chemotherapies, outcomes of recently approved immune and DNA damage-response (DDR)-directed therapies are also affected by TIS, implying that this a common strategy used by cancer cells for evading treatment. Although there has been an explosion of scientific research for manipulating TIS for prevention of drug resistance, much of it is still at the pre-clinical stage. From an evolutionary perspective, cancer is driven by natural selection, wherein the fittest tumor cells survive and proliferate while the tumor microenvironment influences tumor cell fitness. As TIS seems to be preferred for increasing the fitness of drug-challenged cancer cells, we will propose a few tactics to control it by using the principles of evolutionary biology. We hope that with appropriate therapeutic intervention, this detrimental cellular fate could be diverted in favor of TNBC patients.
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http://dx.doi.org/10.3389/fonc.2021.674354DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8264500PMC
June 2021

Distribution of virulence factors and its relatedness towards the antimicrobial response of enterotoxigenic Escherichia coli (ETEC) strains isolated from patients in Kolkata, India.

J Appl Microbiol 2021 Jul 9. Epub 2021 Jul 9.

Division of Biochemistry, ICMR-National Institute of Cholera and Enteric Diseases, Kolkata, India.

Aim: Enterotoxigenic Escherichia coli (ETEC) is one of the most widely recognized diarrheal pathogens in developing countries. Advancement of ETEC vaccine development depends on the antigenic determinants of the ETEC isolates from a particular geographical region. So, the aim here was to comprehend the distribution of virulence determinants of the clinical ETEC strains of this region. Additionally, attempt was made to find any correlation with the antimicrobial response pattern.

Methods And Results: Multiplex PCR was employed to identify virulence determinants followed by confirmatory singleplex PCR. For observation of antibiotic response, the Kirby-Bauer method was used. Out of 379 strains, 46% strains harboured both the enterotoxins ST and LT, whereas 15% were LT only. Among the major colonization factors, CS6 (41%) was the most prevalent followed by CFA/I (35%) and CFA/III was the lowest (3%). Among the minor colonization factors, CS21 (25%) was most prevalent, while CS15 showed the lowest (3%) presence. Among the non-classical virulence factors, EatA (69%) was predominant. ETEC strains harbouring CS6 showed resistance towards commonly used drug Ciprofloxacin (70%).

Conclusion: CS6 and elt+est toxin genes co-occurred covering 51% of the isolates. CS21 was found in most strains with est genes (43%). EatA was found to occur frequently when ST was present alone or with LT. CS6-harboring strains showed an independent correlation to antimicrobial resistance.

Significance And Impact Of Study: This study would aid in identifying the commonly circulating ETEC isolates of Kolkata, India, and their prevalent virulence determinants. Knowledge of antibiotic resistance pattern would also help in the appropriate use of antibiotics. Further, the study would aid in identifying the multivalent antigens suitable for region-specific ETEC vaccine with maximum coverage.
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http://dx.doi.org/10.1111/jam.15206DOI Listing
July 2021

Laboratory evaluation of the rapid diagnostic tests for the detection of Vibrio cholerae O1 using diarrheal samples.

PLoS Negl Trop Dis 2021 Jun 15;15(6):e0009521. Epub 2021 Jun 15.

Division of Bacteriology, ICMR-National Institute of Cholera and Enteric Diseases, Kolkata, India.

Background: Cholera, an acute diarrheal disease is a major public health problem in many developing countries. Several rapid diagnostic tests (RDT) are available for the detection of cholera, but their efficacies are not compared in an endemic setting. In this study, we have compared the specificity and sensitivity of three RDT kits for the detection of Vibrio cholerae O1 and compared their efficiency with culture and polymerase chain reaction (PCR) methods.

Methods: Five hundred six diarrheal stool samples collected from patients from two different hospitals in Kolkata, India were tested using SD Bioline Cholera, SMART-II Cholera O1 and Crystal-VC RDT kits. All the stool samples were screened for the presence of V. cholerae by direct and enrichment culture methods. Stool DNA-based PCR assay was made to target the cholera toxin (ctxAB) and O1 somatic antigen (rfb) encoding genes. Statistical evaluation of the RDTs has been made using STATA software with stool culture and PCR results as the gold standards. The Bayesian latent class model (LCM) was used to evaluate the diagnostic tests in the absence of the gold standard.

Results: Involving culture technique as gold standard, the sensitivity and specificity of the cholera RDT kits in the direct testing of stools was highest with SAMRT-II (86.1%) and SD-Cholera (94.4%), respectively. The DNA based PCR assays gave very high sensitivity (98.4%) but the specificity was comparatively low (75.3%). After enrichment, the high sensitivity and specificity was detected with SAMRT-II (78.8%) and SD-Cholera (99.1%), respectively. Considering PCR as the gold standard, the sensitivity and specificity of the RDTs remained between 52.3-58.2% and 92.3-96.8%, respectively. In the LCM, the sensitivity of direct and enrichment testing was high in SAMRT-II (88% and 92%, respectively), but the specificity was high in SD cholera for both the methods (97% and 100%, respectively). The sensitivity/specificity of RDTs and direct culture have also been analyzed considering the age, gender and diarrheal disease severity of the patients.

Conclusion: Overall, the performance of the RDT kits remained almost similar in terms of specificity and sensitivity. Performance of PCR was superior to the antibody-based RDTs. The RTDs are very useful in identifying cholera cases during outbreak/epidemic situations and for making them as a point-of-care (POC) testing tool needs more improvement.
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http://dx.doi.org/10.1371/journal.pntd.0009521DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8232436PMC
June 2021

Evaluation of Low-Cost Phage-Based Microbial Source Tracking Tools for Elucidating Human Fecal Contamination Pathways in Kolkata, India.

Front Microbiol 2021 20;12:673604. Epub 2021 May 20.

Center for Global Safe Water, Sanitation and Hygiene, Rollins School of Public Health, Emory University, Atlanta, GA, United States.

Phages, such as those infecting spp., have been proven to be reliable indicators of human fecal contamination in microbial source tracking (MST) studies, and the efficacy of these MST markers found to vary geographically. This study reports the application and evaluation of candidate MST methods (phages infecting previously isolated strain GB-124, newly isolated strains (K10, K29, and K33) and recently isolated strain ASH-08), along with non-source specific somatic coliphages (SOMCPH infecting strain WG-5) and indicator bacteria () for identifying fecal contamination pathways in Kolkata, India. Source specificity of the phage-based methods was first tested using 60 known non-human fecal samples from common animals, before being evaluated with 56 known human samples (municipal sewage) collected during both the rainy and dry season. SOMCPH were present in 40-90% of samples from different animal species and in 100% of sewage samples. Phages infecting strain GB-124 were not detected from the majority (95%) of animal samples (except in three porcine samples) and were present in 93 and 71% of the sewage samples in the rainy and dry season (Mean = 1.42 and 1.83 logPFU/100mL, respectively), though at lower levels than SOMCPH (Mean = 3.27 and 3.02 logPFU/100mL, respectively). Phages infecting strain ASH-08 were detected in 89 and 96% of the sewage samples in the rainy and dry season, respectively, but were also present in all animal samples tested (except goats). Strains K10, K29, and K30 were not found to be useful MST markers due to low levels of phages and/or co-presence in non-human sources. GB-124 and SOMCPH were subsequently deployed within two low-income neighborhoods to determine the levels and origin of fecal contamination in 110 environmental samples. , SOMCPH, and phages of GB-124 were detected in 68, 42, and 28% of the samples, respectively. Analyses of 166 wastewater samples from shared community toilets and 21 samples from sewage pumping stations from the same districts showed that SOMCPH were present in 100% and GB-124 phages in 31% of shared toilet samples (Median = 5.59 and <1 log PFU/100 mL, respectively), and both SOMCPH and GB-124 phages were detected in 95% of pumping station samples (Median = 5.82 and 4.04 log PFU/100 mL, respectively). Our findings suggest that GB-124 and SOMCPH have utility as low-cost fecal indicator tools which can facilitate environmental surveillance of enteric organisms, elucidate human and non-human fecal exposure pathways, and inform interventions to mitigate exposure to fecal contamination in the residential environment of Kolkata, India.
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http://dx.doi.org/10.3389/fmicb.2021.673604DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8173070PMC
May 2021

Generation of reactive oxygen species is the primary mode of action and cause of survivin suppression by sepantronium bromide (YM155).

RSC Med Chem 2021 Apr 15;12(4):566-578. Epub 2021 Feb 15.

Department of Life Sciences, Shiv Nadar University Greater Noida UP 201314 India

Survivin is a lucrative broad-spectrum drug target for different cancer types, including triple negative breast cancer (TNBC). Sepantronium bromide (YM155) is the first of its class of survivin suppressants and was found to be quite effective in pre-clinical models of TNBC. However, in clinical trials when given in combination with docetaxel, YM55 failed to provide any added advantage. To understand if the clinical outcome is due to YM155 being ineffective or due to an inappropriate choice of combination, we need to elucidate its true mode of action. Hence, to explain the unexpected and unexplained observations pertaining to YM155 biology and its mode of action, we developed isogenic pairs of YM155-sensitive and -resistant TNBC cell lines and characterized them in detail by various biochemical assays. We found that YM155 generates reactive oxygen species (ROS) in the mitochondria in addition to the previously discovered redox cycling pathway. Both survivin suppression and DNA damage are secondary effects resulting from the ROS which contribute to the drug's cytotoxic effects on TNBC cells. Indeed, adaptation to both these pathways was important in conferring YM155 resistance. Finally, we uncovered a unique connection between the ROS and control of survivin expression involving a ROS/AKT/FoxO/survivin axis in TNBC cells. Together, by deciphering the true mode of action of YM155, we present a possible explanation for its poor clinical efficacy when used in combination with docetaxel. The results and conclusions presented here provide the information needed to effectively use YM155 in combination therapy.
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http://dx.doi.org/10.1039/d0md00383bDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8128069PMC
April 2021

Molecular insights of Carbapenem resistance Klebsiella pneumoniae isolates with focus on multidrug resistance from clinical samples.

J Infect Public Health 2021 Jan 21;14(1):131-138. Epub 2020 Nov 21.

Department of Microbiology and Immunology, Division of Biomedical Science, School of Medicine, College of Health Science, Mekelle University, PO. Box: 1871, Mekelle, Ethiopia.

Background: Carbapenem are the last-line antibiotic, defence against Gram-negative extended spectrum ß-lactamases producers (ESBLs). Carbapenem resistance Enterobacteriaceae especially Carbapenem resistant-Klebsiella pneumoniae (CR-KP) is recognized as one of the well-known public health problem, which is increasingly being reported around the world. The present study was focused to analyse the prevalence and characterization of antibiotic resistance K. pneumoniae in centre region of Tamil Nadu, India.

Methodology: Totally 145 suspected K. pneumoniae isolates [Urine, Pus, Sputum, Blood and Biopsy] obtained from hospitals of Central South India. The isolates were subjected to biochemical and molecular identification technique, following with antibiotic resistance pattern by standard antibiotic sensitivity test. Multidrug resistance (MDR) with β-lactamase producing Carbapenem resistant K. pneumoniae (CR-KP) strains were screened by classical sensitivity method and also drug resistance encoded gene. Also, molecular typing of the MDR strains were characterized by Pulsed-Field Gel Electrophoresis (PFGE). Further, the outer membrane protein (OmpK35 and 36) related Carbapenem resistance were characterized.

Results: Totally, 61% of isolates were confirmed as K. pneumoniae, 75 % of isolates were MDR including 58% carbapenem and 97% ESBL antibiotics and grouped into 17 distinct resistant patterns. The MDR KP isolates shows positive for blaCTXM-1 (92 %) gene followed by blaSHV (43 %), blaTEM (36 %), blaNDM-1 (26 %), blaGES (20 %) and blaIMP-1 (8 %). Moreover, 62 % CR-KP isolates loses OmpK36 and 33% isolates loses OmpK35.

Conclusions: Loss of OmpK36 were highly an influence the cefoxitin and carbapenem resistance. Sixteen different PFGE patterns have been observed among the 18 MDR isolates. Eventually, ESBL as well as CR-KP were diverse in genetic makeup and often associated with hyper virulence hvKP should be of serious concern.
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http://dx.doi.org/10.1016/j.jiph.2020.09.018DOI Listing
January 2021

Whole-Genome Analysis of Clinical Vibrio cholerae O1 in Kolkata, India, and Dhaka, Bangladesh, Reveals Two Lineages of Circulating Strains, Indicating Variation in Genomic Attributes.

mBio 2020 11 10;11(6). Epub 2020 Nov 10.

Department of Bacteriology I, National Institute of Infectious Diseases, Tokyo, Japan.

serogroup O1 is responsible for epidemic and pandemic cholera and remains a global public health threat. This organism has been well established as a resident flora of the aquatic environment that alters its phenotypic and genotypic attributes for better adaptation to the environment. To reveal the diversity of clinical isolates of O1 in the Bay of Bengal, we performed whole-genome sequencing of isolates from Kolkata, India, and Dhaka, Bangladesh, collected between 2009 and 2016. Comparison with global isolates by phylogenetic analysis placed the current isolates in two Asian lineages, with lineages 1 and 2 predominant in Dhaka and Kolkata, respectively. Each lineage possessed different genetic traits in the cholera toxin B subunit gene, seventh pandemic island II, integrative and conjugative element, and antibiotic-resistant genes. Thus, although recent global transmission of O1 from South Asia has been attributed only to isolates of lineage 2, another distinct lineage exists in Bengal. Cholera continues to be a global concern, as large epidemics have occurred recently in Haiti, Yemen, and countries of sub-Saharan Africa. A single lineage of O1 has been considered to be introduced into these regions from South Asia and to cause the spread of cholera. Using genomic epidemiology, we showed that two distinct lineages exist in Bengal, one of which is linked to the global lineage. The other lineage was found only in Iran, Iraq, and countries in Asia and differed from the global lineage regarding cholera toxin variant and drug resistance profile. Therefore, the potential transmission of this lineage to other regions would likely cause worldwide cholera spread and may result in this lineage replacing the current global lineage.
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http://dx.doi.org/10.1128/mBio.01227-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7667034PMC
November 2020

Protective Role of Glutathione against Peroxynitrite-Mediated DNA Damage During Acute Inflammation.

Chem Res Toxicol 2020 10 18;33(10):2668-2674. Epub 2020 Sep 18.

Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, United States.

Inflammation is an immune response to protect against various types of infections. When unchecked, acute inflammation can be life-threatening, as seen with the current coronavirus pandemic. Strong oxidants, such as peroxynitrite produced by immune cells, are major mediators of the inflammation-associated pathogenesis. Cellular thiols play important roles in mitigating inflammation-associated macromolecular damage including DNA. Herein, we have demonstrated a role of glutathione (GSH) and other thiols in neutralizing the effect of peroxynitrite-mediated DNA damage through stable GSH-DNA adduct formation. Our observation supports the use of thiol supplements as a potential therapeutic strategy against severe COVID-19 cases and a Phase II (NCT04374461) open-label clinical trial launched in early May 2020 by the Memorial Sloan Kettering Cancer Center.
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http://dx.doi.org/10.1021/acs.chemrestox.0c00299DOI Listing
October 2020

Low Viability of Cholera Toxin-Producing Vibrio cholerae O1 in the Artificial Low Ionic Strength Aquatic Solution.

Biol Pharm Bull 2020 Aug 9;43(8):1288-1291. Epub 2020 Jun 9.

Collaborative Research Center of Okayama University for Infectious Diseases in India.

It has been well known that Vibrio cholerae inhabit in environmental water. As many patients infected with cholera toxin-producing V. cholerae O1 (toxigenic V. cholerae O1) emerge in Kolkata, India, it has been thought that toxigenic V. cholerae O1 is easily detected in environmental water in Kolkata. However, we could not isolate toxigenic V. cholerae O1 from environmental water in Kolkata, though NAG Vibrio (generic name of V. cholerae non-O1/non-O139) is constantly detected. To clear the reason for the non-isolation of toxigenic V. cholerae O1, we examined the viability of V. cholera O1 and NAG Vibrios in the artificial low ionic strength aquatic solution. We found that the viability of toxigenic V. cholerae O1 in the solution is low, but that of NAG Vibrios is high. Subsequently, we examined the viability of NAG Vibrios possessing cholera toxin gene (ctx) in the same condition and found that the viability of these NAG Vibrios is low. These results indicate that the existence of ctx in V. cholerae affects the viability of V. cholerae in the aquatic solution used in this experiment. We thought that there was closely relation between the low viability of toxigenic V. cholerae O1 in the artificial low ionic strength aquatic solution and the low frequency of isolation of the strain from environmental water.
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http://dx.doi.org/10.1248/bpb.b20-00350DOI Listing
August 2020

Genomic characterization of antibiotic resistance-encoding genes in clinical isolates of Vibrio cholerae non-O1/non-O139 strains from Kolkata, India: generation of novel types of genomic islands containing plural antibiotic resistance genes.

Microbiol Immunol 2020 Jun 20;64(6):435-444. Epub 2020 Apr 20.

Collaborative Research Center of Okayama University for Infectious Diseases in India, Okayama University, Kolkata, India.

Non-O1/non-O139 nontoxigenic Vibrio cholerae associated with cholera-like diarrhea has been reported in Kolkata, India. However, the property involved in the pathogenicity of these strains has remained unclear. The character of 25 non-O1/non-O139 nontoxigenic V. cholerae isolated during 8 years from 2007 to 2014 in Kolkata was examined. Determination of the serogroup showed that the serogroups O6, O10, O35, O36, O39, and O70 were represented by two strains in each serogroup, and the remaining isolates belonged to different serogroups. To clarify the character of antibiotic resistance of these isolates, an antibiotic resistance test and the gene analysis were performed. According to antimicrobial drug susceptibility testing, 13 strains were classified as drug resistant. Among them, 10 strains were quinolone resistant and 6 of the 13 strains were resistant to more than three antibiotics. To define the genetic background of the antibiotic character of these strains, whole-genome sequences of these strains were determined. From the analysis of these sequences, it becomes clear that all quinolone resistance isolates have mutations in quinolone resistance-determining regions. Further research on the genome sequence showed that four strains possess Class 1 integrons in their genomes, and that three of the four integrons are found to be located in their genomic islands. These genomic islands are novel types. This indicates that various integrons containing drug resistance genes are spreading among V. cholerae non-O1/non-O139 strains through the action of newly generated genomic islands.
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http://dx.doi.org/10.1111/1348-0421.12790DOI Listing
June 2020

Characterization of non-typhoidal Salmonella isolates from children with acute gastroenteritis, Kolkata, India, during 2000-2016.

Braz J Microbiol 2020 Jun 2;51(2):613-627. Epub 2020 Jan 2.

Division of Bacteriology, ICMR-National Institute of Cholera and Enteric Diseases, P-33 CIT Road, Scheme XM, Beliaghata, Kolkata, 700010, India.

Non-typhoidal Salmonella (NTS) is an important cause of acute gastroenteritis in children. The study was undertaken to determine the isolation rate, serovar prevalence, antimicrobial resistance (AMR) profiles, and molecular subtypes of NTS from a hospital-based diarrheal disease surveillance in Kolkata, India. Rectal swabs were collected from children (< 5 years of age) with acute gastroenteritis from 2000 to 2016. Samples were processed following standard procedures for identification of NTS. The isolates were tested for antimicrobial susceptibility, AMR genes, plasmid profiles, multilocus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE) subtypes. A total of 99 (1.0%) Salmonella isolates were recovered from 9957 samples processed. Of the 17 Salmonella serovars identified, S. Worthington (33%) was predominant followed by S. Enteritidis (13%), S. Typhimurium (12%), and others. The isolates showed high resistance towards nalidixic acid (43%), ampicillin (34%), third-generation cephalosporins (32%), and azithromycin (25%), while low resistance was observed for fluoroquinolones (2%). Extended-spectrum beta-lactamase production (bla and bla genes) and azithromycin resistance (mphA gene) were common in S. Worthington, while fluoroquinolone resistance (gyrA and parC mutations) was found in S. Kentucky. Diverse plasmid profiles were observed among the isolates. PFGE analysis identified genetically related strains of each serovar in circulation. MLST also revealed phylogenetically clonal isolates of which S. Worthington ST592 and ciprofloxacin-resistant S. Kentucky ST198 were not reported earlier from India. NTS resistant to current drugs of choice poses a potential public health problem. Continuous monitoring of AMR profiles and molecular subtypes of NTS serovars is recommended for controlling the spread of resistant organisms.
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http://dx.doi.org/10.1007/s42770-019-00213-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7203375PMC
June 2020

Prevalence of Multidrug Resistant Salmonellae with Increasing Frequency of Salmonella enterica Serovars Kentucky and Virchow among Hospitalized Diarrheal Cases in and around Delhi, India.

Jpn J Infect Dis 2020 Mar 31;73(2):119-123. Epub 2019 Oct 31.

Center for Human Microbial Ecology, Translational Health Science and Technology Institute.

Non-typhoidal salmonellae (NTS) are a major cause of acute diarrhea with characteristic multidrug resistance (MDR). In a hospital-based study, 81 NTS were isolated and tested for serotypes and antimicrobial resistance (AMR). Salmonella enterica isolates were classified into 7 different typable serovars, however, 19 (23%) isolates remained untypable. The most common serovars were S. Kentucky (48%), and S. Virchow (22%). Most of the NTS isolates displayed resistance to nalidixic acid (NA) (73%), ciprofloxacin (CIP) (48%), ampicillin (AM) and norfloxacin (NOR) (36% each), and gentamicin (CN) (31%). The AMR profiles for CN and NA; and AM, CIP, NA and NOR, were found to be high in S. Virchow (83%) and S. Kentucky (43%), respectively. Analysis of the pulsed-field gel electrophoresis patterns of S. Kentucky revealed 3 clusters. S. Kentucky has clones closely related to become prominent in recent years in Delhi. The AMR appears to be consistent with the change in MDR patterns during 2014-2017. The observed prevalence of S. Kentucky and S. Virchow in large numbers of diarrheal cases is novel. The NTS are mostly resistant to fluoroquinolones, which is the current drug of choice for treating diarrheal cases. MDR is very common among clonally related S. Kentucky.
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http://dx.doi.org/10.7883/yoken.JJID.2019.063DOI Listing
March 2020

Altered Integrative and Conjugative Elements (ICEs) in Recent O1 Isolated From Cholera Cases, Kolkata, India.

Front Microbiol 2019 6;10:2072. Epub 2019 Sep 6.

Center for Human Microbial Ecology, Translational Health Science and Technology Institute, Faridabad, India.

The self-transferring integrative and conjugative elements (ICEs) are large genomic segments carrying several bacterial adaptive functions including antimicrobial resistance (AMR). SXT/R391 family is one of the ICEs extensively studied in cholera-causing pathogen . The genetic characteristics of ICE-SXT/R391 in are dynamic and region-specific. These ICEs in are strongly correlated with resistance to several antibiotics such as tetracycline, streptomycin and trimethoprim-sulfamethoxazole. We screened O1 strains isolated from cholera patients in Kolkata, India from 2008 to 2015 for antibiotic susceptibility and the presence of ICEs, and subsequently sequenced their conserved genes. Resistance to tetracycline, streptomycin and trimethoprim-sulfamethoxazole was detected in strains isolated during 2008-2010 and 2014-2015. The genes encoding resistance to tetracycline (), trimethoprim-sulfamethoxazole ( and ), streptomycin (), and chloramphenicol () were detected in the ICEs of these strains. There was a decrease in overall drug resistance in associated with the ICEs in 2011. DNA sequence analysis also showed that AMR in these strains was conferred mainly by two types of ICEs, i.e., ICE (comprising , and ) and ICE (, and ). Based on the genetic structure, Kolkata strains of O1 had distinct genetic traits different from the ICEs reported in other cholera endemic regions. Transfer of AMR was confirmed by conjugation with sodium azide resistant J53. In addition to the acquired resistance to streptomycin and trimethoprim-sulfamethoxazole, the conjugally transferred (CT) J53 with ICE showed higher resistance to chloramphenicol and tetracycline than the donor Pulsed-field gel electrophoresis (PFGE) based clonal analysis revealed that the strains could be grouped based on their ICEs and AMR patterns. Our findings demonstrate the epidemiological importance of ICEs and their role in the emergence of multidrug resistance (MDR) in El Tor vibrios.
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http://dx.doi.org/10.3389/fmicb.2019.02072DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6743048PMC
September 2019

The H1047R PIK3CA oncogene induces a senescence-like state, pleiotropy and acute HSP90 dependency in HER2+ mammary epithelial cells.

Carcinogenesis 2019 Oct;40(10):1179-1190

Department of Chemistry, Shiv Nadar University, Uttar Pradesh, India.

In pre-clinical models, co-existence of Human Epidermal Growth Factor Receptor-2 (HER2)-amplification and PI3K catalytic subunit (PIK3CA) mutations results in aggressive, anti-HER2 therapy-resistant breast tumors. This is not always reflected in clinical setting. We speculated that the complex interaction between the HER2 and PIK3CA oncogenes is responsible for such inconsistency. We performed series of biochemical, molecular and cellular assays on genetically engineered isogenic mammary epithelial cell lines and breast cancer cells expressing both oncogenes. In vitro observations were validated in xenografts models. We showed that H1047R, one of the most common PIK3CA mutations, is responsible for endowing a senescence-like state in mammary epithelial cells overexpressing HER2. Instead of imposing a permanent growth arrest characteristic of oncogene-induced senescence, the proteome secreted by the mutant cells promotes stem cell enrichment, angiogenesis, epithelial-to-mesenchymal transition, altered immune surveillance and acute vulnerability toward HSP90 inhibition. We inferred that the pleiotropism, as observed here, conferred by the mutated oncogene, depending on the host microenvironment, contributes to conflicting pre-clinical and clinical characteristics of HER2+, mutated PIK3CA-bearing tumor cells. We also came up with a plausible model for evolution of breast tumors from mammary epithelial cells harboring these two molecular lesions.
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http://dx.doi.org/10.1093/carcin/bgz118DOI Listing
October 2019

Pathogenic indiarrhoeal patients, fish and aquatic environments and their potential for inter-source transmission.

Heliyon 2019 May 17;5(5):e01743. Epub 2019 May 17.

Eastern Regional Station, ICAR-Indian Veterinary Research Institute, 37, Belgachia Road, Kolkata, 700037, India.

The role of in causing diarrhoeal disease is well known. However, phenotypic and genetic traits of this pathogen isolated from diverse sources have not been investigated in detail. In this study, we have screened samples from diarrhoeal cases (2603), brackish water fish (301) and aquatic environments (115) and identified in 29 (1.1%), 171 (56.8%) and 43 (37.4%) samples, respectively. Incidence of pathogenic with virulence encoding thermostable-direct haemolysin gene () was detected mostly in fishes (19.3%) and waters (15.6%) than clinical samples (1.04%). The pandemic strain marker genes ( and PGS-sequences) have been detected relatively more in water (6%) and fish (5%) samples than in clinical samples (0.7%). Majority of the isolates from clinical cases and fish samples (26.3%) belonged to classical pandemic serovars (O3:K6). In addition, several newly recognised pandemic serovars have also been identified. Pulsed field-gel electrophoresis (PFGE) analysis showed clonal relatedness (60-85%) of from different sources. The study observation revealed that the brackish water fishes and water bodies may act as a reservoir of pathogenic . Emergence of several new serovars of pandemic signifies the changing phenotypic characteristics of the pathogen.
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http://dx.doi.org/10.1016/j.heliyon.2019.e01743DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6526242PMC
May 2019

Emergence of Azithromycin Resistance Mediated by Phosphotransferase-Encoding (A) in Diarrheagenic Vibrio fluvialis.

mSphere 2019 06 12;4(3). Epub 2019 Jun 12.

Department of Bacteriology, ICMR-National Institute of Cholera and Enteric Diseases, Kolkata, India

The azithromycin resistance conferred by phosphotransferase is encoded in the gene (A). This gene has been discovered in and reported for many bacterial species. We examined the prevalence of azithromycin resistance in (AR-VF) isolated during 2014 to 2015 from the hospitalized acute diarrheal patients in Kolkata, India. Most of the isolates are identified as the sole pathogen (54%). The prevalence of AR-VF was higher in 2015 (19 [68%]) than in 2014 (9 [32%]). Among AR-VF isolates, the azithromycin MICs ranged from 4 to >256 mg/liter. Twenty-eight of the 48 (58%) isolates harbored the gene (A) and phenotypically resistant to azithromycin. All the AR-VF isolates remained susceptible to doxycycline. In addition to azithromycin, other antimicrobial resistance-encoding genes of AR-VF were also characterized. All the AR-VF isolates were positive for class 1 integron, and most of them (17/28) carried the gene cassettes. Only one isolate was positive for the gene, which encodes resistance to erythomycin. The majority of the isolates were resistant to β-lactam antibiotics ( [96%], [93%], and [68%]) and aminoglycoside actetyltransferase, conferring resistance to ciprofloxacin-modifying enzyme [] (96%). Analyses by pulsed-field gel electrophoresis (PFGE) showed that the AR-VF isolates belonged to different genetic lineages. This is the first study to report azithromycin resistance and the presence of the (A) gene in isolates. Circulation of AR-VF isolates with high azithromycin MICs is worrisome, since it may limit the treatment options for diarrheal infections. The progressive rise in antibiotic resistance among enteric pathogens in developing countries is becoming a big concern. India is one of the largest consumers of antibiotics, and their use is not well regulated. is increasingly recognized as an emerging diarrheal pathogen of public health importance. Here we report the emergence of azithromycin resistance in isolates from diarrheal patients in Kolkata, India. Azithromycin has been widely used in the treatment of various infections, both in children and in adults. Resistance to azithromycin is encoded in the gene (A). Emerging azithromycin resistance in is a major public health challenge, and future studies should be focused on identifying ways to prevent the dissemination of this antibiotic resistance gene.
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http://dx.doi.org/10.1128/mSphere.00215-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6563354PMC
June 2019

Post-monsoon waterlogging-associated upsurge of cholera cases in and around Kolkata metropolis, 2015.

Epidemiol Infect 2019 01;147:e167

Division of Bacteriology,National Institute of Cholera & Enteric Diseases,Kolkata,India.

The Infectious Diseases and Beliaghata General Hospital, Kolkata, India witnessed a sudden increase in admissions of diarrhoea cases during the first 2 weeks of August 2015 following heavy rainfall. This prompted us to investigate the event. Cases were recruited through hospital-based surveillance along with the collection of socio-demographic characteristics and clinical profile using a structured questionnaire. Stool specimens were tested at bacteriological laboratory of the National Institute of Cholera and Enteric Diseases (NICED), Kolkata. Admission of 3003 diarrhoea cases, clearly indicated occurrence of outbreak in Kolkata municipal area as it was more than two standard deviation of the mean number (911; s.d. = 111) of diarrhoea admissions during the same period in previous 7 years. Out of 164 recruited cases, 25% were under-5 children. Organisms were isolated from 80 (49%) stool specimens. Vibrio cholerae O1 was isolated from 50 patients. Twenty-eight patients had this organism as the sole pathogen. Among 14 infants, five had cholera. All V. cholerae O1 isolates were resistant to nalidixic acid, followed by co-trimoxazole (96%), streptomycin (92%), but sensitive to fluroquinolones. We confirmed the occurrence of a cholera outbreak in Kolkata during August 2015 due to V. cholerae O1 infection, where infants were affected.
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http://dx.doi.org/10.1017/S0950268819000529DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6518531PMC
January 2019

Poultry: a receptacle for non-typhoidal Salmonellae and antimicrobial resistance.

Iran J Microbiol 2019 Feb;11(1):31-38

Enteric Diseases Division, Department of Microbiology, Kasturba Medical College, Manipal Academy of Higher Education, Manipal, India.

Background And Objectives: Non-typhoidal Salmonellosis, a zoonotic infection associated with acute gastroenteritis is caused by non-typhoidal salmonellae (NTS). The study was carried out to determine the prevalence of NTS serovars and their antimicrobial resistance along with the presence of the virulence gene ( gene) in poultry samples.

Materials And Methods: This is a prospective cross-sectional study carried out at the Enteric Diseases Division, Kasturba Medical College, Manipal, South India from January 2016- December 2017. Poultry samples were collected randomly from two local poultry farms in Udupi district and processed following CDC standard protocol.

Results: From the 396 poultry meat samples, intestinal contents and faecal samples collected, 58 NTS serovars were isolated showing a prevalence of 14.64%. Infantis, 43.1%, 25/58 was the commonest serovar. Resistance to ciprofloxacin 72.41%, ampicillin 32.8%, gentamicin 17.24%, cotrimoxazole 29.31% and amoxicillin-clavulanic acid 6.9% was observed. The gene was detected in 43 NTS isolates (74.13%).

Conclusion: Poultry sources are recognized as a significant cause for non-typhoidal salmonellosis. Therefore, hygienic measures should be initiated to reduce the contamination of meat and poultry products with virulent strains of Salmonella that are of public health significance.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6462268PMC
February 2019

O6 gastroenteritis in a patient with lupus nephritis - a report from coastal Karnataka, South India.

JMM Case Rep 2019 Jan 19;6(1):e005171. Epub 2018 Dec 19.

Enteric Diseases Division, Central Research Lab, Kasturba Medical College, Manipal University, Manipal, Karnataka, India.

Introduction: O1 strains are responsible for pandemics of cholera and major epidemics in the world. All the remaining non-O1/non-O139 strains are less virulent and are responsible for sporadic cases of gastroenteritis. These non-O1/non-O139 serogroups have more than 200 somatic antigens, and mostly lack cholera toxin and toxin co-regulated pilus encoding genes. Toxigenic and non-toxigenic non-O1/non-O139 have caused several diarrhoeal outbreaks in India and other countries. Acute gastroenteritis is the typical clinical sign and symptom of non-O1/non-O139 infection for both periodical and outbreak cases; in contrast, these are rarely associated with extraintestinal infections.

Case Presentation: Here, we present a case of a 27-year-old female with underlying kidney disease (lupus nephritis) presenting with loose stools, vomiting and fever. O6 was isolated from a faecal sample, which was positive for and the type III secretion system. The present case is, to the best of our knowledge, the first such case to be reported from South India.

Conclusion: The O6 associated with autoimmune disease in the present study demonstrates the role of this pathogen in acute gastroenteritis, and if it is left undiagnosed it can lead to septicaemia and other complications. The pathogenic mechanisms of non-O1/non-O139 are multivariate, virulence factors being naturally present in these strains. Therefore, further epidemiological studies are necessary to determine the virulence factors and their pathogenic mechanisms. Non-O1/non-O139 can undoubtedly be the cause of diarrhoea and it would be important to extend bacteriological identification in this line as well as in all cases of gastroenteritis of unknown aetiology.
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http://dx.doi.org/10.1099/jmmcr.0.005171DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6412036PMC
January 2019

Characterization of the clonal profile of methicillin resistant Staphylococcus aureus isolated from patients with early post-operative orthopedic implant based infections.

Ann Clin Microbiol Antimicrob 2019 Feb 13;18(1). Epub 2019 Feb 13.

Division of Bacteriology, National Institute of Cholera and Enteric Diseases, Kolkata, India.

Background: To analyze the molecular epidemiology and to compare between the major methicillin resistant Staphylococcus aureus biotypes for association with patient characteristics who had an implant for closed fracture and developed early post-operative wound infections (POWI) in a tertiary care hospital of India.

Methods: Pulsed-field gel electrophoresis (PFGE), antimicrobial resistance, accessory gene regulator (agr) and staphylococcal cassette chromosome mec (SCCmec) types, Paton-Valentine leukocidin (PVL) gene, toxin gene profiling, biofilm formation and patient demographics were correlated with MLST clonal complexes (CC).

Findings: Overall eight different sequence types (STs) were detected with a predominance of ST239 (66%), ST22 (18%) and some minor types ST772, ST30 (4% each) ST1, ST642, ST6, ST107 (2% each). All ST239 isolates belong to CC239 and SCCmec III whereas ST22 isolates belong to CC22 and SCCmec IV. The isolates varied in the distribution of various toxin genes. With 63.63% biofilm formers ST239 were all multidrug resistant with frequent resistance to erythromycin, clindamycin, gentamicin, cefuroxime, amoxyclav and ciprofloxacin indicating doxycycline, amikacin, vancomycin and linezolid can be the drug of choice.

Conclusion: This study shows that ST239 MRSA is still most prevalent strain with new emergence of ST642 and ST107 isolates in association with orthopedic implant based POWI. As compare to other ST types ST239 strain was associated with adverse treatment outcomes. This highlights the importance of improving nosocomial infection control measures in this unit.
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http://dx.doi.org/10.1186/s12941-019-0307-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6373053PMC
February 2019

Development of a multiplex PCR assay for the detection of major virulence genes in Vibrio cholerae including non-O1 and non-O139 serogroups.

J Microbiol Methods 2019 02 18;157:54-58. Epub 2018 Dec 18.

International Prevention of Epidemics, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Osaka, Japan. Electronic address:

Vibrio cholerae strains producing cholera toxin (CT) and toxin co-regulated pilus (TCP) and belonging to O1 and O139 serogroups are responsible for cholera. However, non-CT producing V. cholerae from non-O1/non-O139 serogroups have been increasingly isolated from diarrheal stools and extra-intestinal infections. In this study, we have developed a multiplex PCR for the simultaneous detection of heat-stable enterotoxin (stn), type three-secretion system (vopF), and cholix toxin (chxA), along with CT (ctx) in V. cholerae strains. As other species from genus Vibrio carries homologous virulence genes, V. cholerae specific ompW was also included to differentiate V. cholerae from other vibrios. This assay was 100% specific and sensitive, and could detect homologous virulence genes like ctxA in V. mimicus and vopF in V. parahaemolyticus. This multiplex PCR assay, which can detect four major virulence genes in V. cholerae, is novel and important for epidemiologic and environmental surveillance of pathogenic V. cholerae.
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http://dx.doi.org/10.1016/j.mimet.2018.12.012DOI Listing
February 2019

Antimicrobial resistance, plasmid, virulence, multilocus sequence typing and pulsed-field gel electrophoresis profiles of Salmonella enterica serovar Typhimurium clinical and environmental isolates from India.

PLoS One 2018 12;13(12):e0207954. Epub 2018 Dec 12.

Division of Bacteriology, Indian Council of Medical Research-National Institute of Cholera and Enteric Diseases, Kolkata, West Bengal, India.

Salmonella enterica serovar Typhimurium (S. Typhimurium) is a common serovar associated with non-typhoidal salmonellosis globally. However, there is insufficient data on molecular characterization of S. Typhimurium isolates from India. This study was undertaken to determine the antimicrobial resistance (AMR), plasmid, virulence profiles and molecular subtypes of S. Typhimurium Indian isolates (n = 70) of clinical and environmental origin isolated during 2010-2017. Antimicrobial susceptibility and minimum inhibitory concentrations were determined by disc diffusion and E-test methods respectively. Plasmid extraction was done following standard protocol. AMR genes, virulence genes and plasmid incompatibility types were detected by PCR; Pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST) were used for molecular subtyping. Majority (57%) of the study isolates was pan susceptible; five AMR profiles were observed among the resistant (43%) isolates. AMR was significantly (p = 0.004) associated with extra-intestinal isolates than intestinal isolates.The class 1 integron and plasmid-mediated quinolone resistance genes (qnrB1, qnrS1) in the resistant isolates were transferable by conjugation. Plasmids (≥1) ranging from 1.9 to 254kb size and of IncFIIS and/or FIB type were found in most isolates. A total of 39 pulsotypes by PFGE and four sequence types by MLST like ST36 (55.7%), ST19 (32.9%), ST313 (10%) and ST213 (1.4%) were observed. ST36 and ST19 were found circulating in both clinical and environmental host, while ST313 isolates had an exclusive clinical origin. All ST19 isolates (100%) were drug-resistant, while isolates belonging to ST313 (100%), ST213 (100%) and ST36 (82%) were pan susceptible. The virulence plasmid (VP) genes (spvB- spvC) were present in all genotypes except ST36. The VP was significantly (p<0.001) associated with extra-intestinal than intestinal isolates. Some environmental and clinical isolates were clonal indicating their zoonotic transmission. Knowledge on the molecular subtypes and AMR profiles of locally prevalent Salmonella serotypes is important for effective control of spread of resistant organisms. The MLST of S. Typhimurium isolates and its association with AMR, virulence profiles was not reported earlier from India.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0207954PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6291080PMC
June 2019

Draft Genome Sequence of subsp. Serotype Typhimurium Sequence Type 313, Isolated from India.

Microbiol Resour Announc 2018 Aug 30;7(8). Epub 2018 Aug 30.

Enteric Diseases Division, Department of Microbiology, Kasturba Medical College, Manipal Academy of Higher Education, Manipal, India.

Salmonella enterica subsp. enterica serotype Typhimurium sequence type 313 (ST313) is most commonly associated with invasive nontyphoidal Salmonella disease in Africa among patients with HIV infection and malignancy. Here, we report a draft genome sequence of S. Typhimurium ST313, isolated from an elderly immunosuppressed patient from India with non-Hodgkins lymphoma.
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http://dx.doi.org/10.1128/MRA.00990-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6256508PMC
August 2018

Detection of Uncommon Enteric Bacterial Pathogens from Acute Diarrheal Specimens Using SYBR-Green Real Time PCR.

Jpn J Infect Dis 2019 Mar 31;72(2):88-93. Epub 2018 Oct 31.

Department of Bacteriology, National Institute of Cholera and Enteric Diseases.

Acute diarrheal disease is a major health problem, and the second most common cause of death in children under 5 years of age. Conventional diagnostic methods are laborious, time consuming, and occasionally inaccurate. We used SYBR-Green real-time PCR for the detection of 10 uncommon bacterial pathogens using fecal specimens from acute diarrheal patients. In the SYBR-Green real-time PCR assay, the products formed were identified based on a melting point temperature curve analysis, and the assay was validated with the respective reference strain. In a retrospective study, we tested 1,184 stool specimens previously examined using conventional culture methods. Enterotoxigenic Bacteriodes fragilis was detected in 6.7% of the samples followed by enterotoxigenic Bacillus cereus (5.1%), Clostridium perfringens (3.9%), and Aeromonas hydrophila (3.8%). In the prospective study, A. hydrophila, Staphylococcus aureus, and C. perfringens were predominantly detected in 11 > 5 years of age, using real-time PCR. The real-time PCR assay is comprehensive, rapid, accurate, and well suited for surveillance or diagnostic purposes to detect uncommon bacterial pathogens, and should be useful in initiating appropriate care and thereby reducing patient risk.
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http://dx.doi.org/10.7883/yoken.JJID.2018.142DOI Listing
March 2019

Adaptation to chronic exposure to sepantronium bromide (YM155), a prototypical survivin suppressant is due to persistent DNA damage-response in breast cancer cells.

Oncotarget 2018 Sep 11;9(71):33589-33600. Epub 2018 Sep 11.

Department of Life Sciences, Shiv Nadar University, Greater Noida, UP 201314, India.

Sepantronium bromide (YM155), originally developed against the anti-apoptotic protein survivin, performed exceptionally well in pre-clinical and phase I clinical trials. However, in phase II trials of several cancer types including breast cancer it performed poorly. Additionally, no definitive correlation between survivin level and response to therapy was found. In an attempt to understand the true reason of the late-stage failure of this promising drug, we developed YM155-resistant MCF-7 breast cancer cell line and characterized side-by-side with the drug-naïve parental cell line. Chronic YM155 treatment resulted in downregulation of survivin expression yet triggered cellular responses typical of adaptation to persistent DNA damage. Lowering endogenous antioxidant glutathione level and activity of cell cycle check-point kinase restored YM155 activity. Thus, contrary to its development as a survivin suppressant, YM155 primarily acts as a chemotherapeutic drug causing oxidative stress-mediated DNA damage. Adaptation to long-term exposure to YM155 can be prevented and/or overcome by interfering with detoxification and DNA damage-response pathways. Finally, proteins associated with DNA damage-response pathway will be more appropriate as predictive biomarkers of YM155 in breast tumor cells.
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http://dx.doi.org/10.18632/oncotarget.26096DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6173358PMC
September 2018

Pulsed-field gel electrophoresis of enterotoxic type A isolates recovered from humans and animals in Kolkata, India.

Int J Vet Sci Med 2018 Jun 15;6(1):123-126. Epub 2017 Dec 15.

Division of Veterinary Public Health, Indian Veterinary Research Institute, Izatnagar 243 122, India.

is one of the most important globally recognised gastroenteric pathogen in humans as well as animals. The present study was aimed to know the similarities/divergence among type A isolates of human and animal origin using the pulsed-field gel electrophoresis (PFGE) as a molecular tool. The enterotoxic isolates obtained by screening of human diarrhoeal cases (n = 130), diarrhoeal cases of pig (n = 52) and goat (n = 50), meat samples ., pork (n = 59) and chevon (n = 57) were characterized by standard cultural and biochemical methods followed by PCR Assays. Accordingly, a total of 11 type A characterized isolates (16S rRNA, , and ) recovered from human diarrhoeal cases (n = 3); diarrhoeal cases of pig (n = 2) and goat (n = 2); meat samples . pork (n = 2) and chevon (n = 2) were examined employing PFGE. The observed clustering pattern in PFGE analysis showed the relatedness between isolates from diarrhoeal goat and chevon (90-100%); diarrhoeal pig and pork (65-68%); moreover, isolates from human diarrhoeal cases were exhibiting lineage to cases from goat and pig diarrhoea as well pork and chevon by 62-68% relatedness. The outcome of the present study indicates the probable contamination of this pathogen to the human food chain through faeces from suspected food animals . goat and pig and their improperly cooked meat.
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http://dx.doi.org/10.1016/j.ijvsm.2017.11.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6147381PMC
June 2018

Dissemination of newly emerged polymyxin B sensitive Vibrio cholerae O1 containing Haitian-like genetic traits in different parts of India.

J Med Microbiol 2018 Sep 21;67(9):1326-1333. Epub 2018 Jun 21.

1​Division of Bacteriology, National Institute of Cholera and Enteric Diseases, Kolkata 700010, India.

Purpose: Two natural epidemic biotypes of Vibrio cholerae O1, classical and El Tor, exhibit different patterns of sensitivity against the antimicrobial peptide polymyxin B. This difference in sensitivity has been one of the major markers in biotype classification system for several decades. A recent report regarding the emergence of polymyxin B-sensitive El Tor V. cholerae O1 in Kolkata has motivated us to track the spread of the strains containing this important trait, along with Haitian-like genetic content, in different parts of India.

Methodology: We have collected 260 clinical V. cholerae O1 strains from 12 states in India and screened them for polymyxin B susceptibility. Genetic characterization was also performed to study the tcpA, ctxB and rtxA genotypes by allele-specific polymerase chain reaction (PCR) and nucleotide sequencing.

Results: Interestingly, 88.85 % of the isolates were found to be sensitive to polymyxin B. All of the states, with the exception of Assam, had polymyxin B-sensitive V. cholerae strains and complete replacement with this strain was found in eight of the states. However, from 2016 onwards, all the strains tested showed sensitivity to polymyxin B. Allele-specific PCR and sequencing confirmed that all strains possessed Haitian-like genetic traits.

Conclusion: Polymyxin B-sensitive strains have begun to spread throughout India and may lead to the revision of the biotype classification. The dissemination of these new variant strains needs to be carefully monitored in different endemic populations through active holistic surveillance to understand their clinical and epidemiological consequences.
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http://dx.doi.org/10.1099/jmm.0.000783DOI Listing
September 2018

Quinone-Based Antitumor Agent Sepantronium Bromide (YM155) Causes Oxygen-Independent Redox-Activated Oxidative DNA Damage.

Chem Res Toxicol 2018 07 26;31(7):612-618. Epub 2018 Jun 26.

Sepantronium bromide (YM155) is a small molecule antitumor agent currently in phase II clinical trials. Although developed as survivin suppressor, YM155's primary mode of action has recently been found to be DNA damage. However, the mechanism of DNA damage by YM155 is still unknown. Knowing the mechanism of action of an anticancer drug is necessary to formulate a rational drug combination and select a cancer type for achieving maximum clinical efficacy. Using cell-based assays, we showed that YM155 causes extensive DNA cleavage and reactive oxygen species generation. DNA cleavage by YM155 was found to be inhibited by radical scavengers and desferal. The reducing agent DTT and the cellular reducing system xanthine/xanthine oxidase were found to reductively activate YM155 and cause DNA cleavage. Unlike quinones, DNA cleavage by YM155 occurs in the presence of catalase and under hypoxic conditions, indicating that hydrogen peroxide and oxygen are not necessary. Although YM155 is a quinone, it does not follow a typical quinone mechanism. Consistent with these observations, a mechanism has been proposed that suggests that YM155 can cause oxidative DNA cleavage upon 2-electron reductive activation.
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http://dx.doi.org/10.1021/acs.chemrestox.8b00094DOI Listing
July 2018

An Outbreak of Foodborne Infection Caused by Shigella sonnei in West Bengal, India.

Jpn J Infect Dis 2018 Mar 28;71(2):162-166. Epub 2018 Feb 28.

Division of Bacteriology, National Institute of Cholera & Enteric Diseases.

A foodborne acute gastroenteritis outbreak due to Shigella sonnei infection occurred in a household after eating foods in a housewarming party at Pakapol Village, South 24 Parganas District of West Bengal, an Indian state, in November 2016. Here, we report the epidemiological and microbiological findings of this outbreak. Thirty-four people attended the party on November 23, 2016, and had lunch together. The median incubation period from the time of food consumption to the development of acute gastroenteritis was 18.5 h (interquartile range, 16.5-22 h). The overall attack rate was 73% (25/34), and 76% (19/25) of them required hospitalization. All age groups were affected with 100% recovery rate. One served food item was significantly associated with the illness, i.e., tomato salad (risk ratio, 4.14; 95% confidence interval, 1.21-14.13). Among the 12 stool specimens tested, 8 (67%; 8/12) were positive for S. sonnei. All S. sonnei strains were completely resistant to nalidixic acid, norfloxacin, ciprofloxacin, ofloxacin, and erythromycin, and partially resistant to tetracycline, doxycycline, streptomycin, and trimethoprim/sulfamethoxazole. Pulsed-field gel electrophoresis analysis showed that the recent outbreak strains of S. sonnei were clonally related with the locally circulating strains in Kolkata.
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http://dx.doi.org/10.7883/yoken.JJID.2017.304DOI Listing
March 2018

Molecular analysis of multidrug resistance in clinical isolates of spp. from 2001-2010 in Kolkata, India: role of integrons, plasmids, and topoisomerase mutations.

Infect Drug Resist 2018 12;11:87-102. Epub 2018 Jan 12.

Department of Human Health and Diseases, Indian Institute of Advanced Research, Koba Institutional Area, Gandhinagar.

To understand the genetic basis of high drug resistance in , 95 clinical isolates of spp. (2001-2010) were obtained from the Infectious Diseases Hospital, Kolkata, India. Ninety-three isolates were resistant to three or more antibiotics. Resistance to nalidixic acid, trimethoprim, streptomycin, and co-trimoxazole was most common in this population. Dendrogram analysis showed that strains were more clonally related when compared to the other species. The role of mobile genetic elements and chromosome-borne resistance factors was analyzed in detail. Integron analysis indicated the preponderance of class 2 and atypical class 1 integrons in that population. Typical class 1 integron was present in only one isolate and harbored trimethoprim resistance-encoding gene , while atypical class 1 integrons harbored or gene cassettes responsible for resistance to trimethoprim, aminoglycosides, and β-lactams. Class 2 integrons harbored either or gene cassettes. Most importantly, a novel gene cassette array was found in class 2 integron of NK4846. Many of the resistance traits for antibiotics such as trimethoprim, co-trimoxazole, kanamycin, ampicillin, and tetracycline were transferred from parent isolates to recipient during conjugation, establishing the role of plasmids in horizontal transfer of resistance genes. Multiple mutations such as S→I, S→L, and D→G/N/Y in quinolone resistance determining regions of topoisomerases from the representative quinolone-resistant isolates could explain the spectrum of minimal inhibitory concentration values for various quinolones. To the best of our knowledge, this is the first comprehensive report that describes the contribution of mobile (plasmids, integrons, and quinolone resistance genes named qnr) and innate genetic elements (mutations in topoisomerases) in determining the resistance phenotype of all the four species of over a span of ten years.
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http://dx.doi.org/10.2147/IDR.S148726DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5769595PMC
January 2018