Publications by authors named "Sandra Rivera-Gutierrez"

20 Publications

  • Page 1 of 1

cAMP Receptor Protein Positively Regulates the Expression of Genes Involved in the Biosynthesis of Tilivalline Cytotoxin.

Front Microbiol 2021 30;12:743594. Epub 2021 Sep 30.

Unidad de Investigación Médica en Enfermedades Infecciosas y Parasitarias, Hospital de Pediatría, Centro Médico Nacional Siglo XXI, Instituto Mexicano del Seguro Social, Mexico City, Mexico.

is a resident of the human gut. However, certain toxigenic strains exist that secrete the nonribosomal peptide tilivalline (TV) cytotoxin. TV is a pyrrolobenzodiazepine that causes antibiotic-associated hemorrhagic colitis (AAHC). The biosynthesis of TV is driven by enzymes encoded by the and NRPS operons. In this study, we determined the effect of environmental signals such as carbon sources, osmolarity, and divalent cations on the transcription of both TV biosynthetic operons. Gene expression was enhanced when bacteria were cultivated in tryptone lactose broth. Glucose, high osmolarity, and depletion of calcium and magnesium diminished gene expression, whereas glycerol increased transcription of both TV biosynthetic operons. The cAMP receptor protein (CRP) is a major transcriptional regulator in bacteria that plays a key role in metabolic regulation. To investigate the role of CRP on the cytotoxicity of , we compared levels of expression of TV biosynthetic operons and synthesis of TV in wild-type strain MIT 09-7231 and a Δ isogenic mutant. In summary, we found that CRP directly activates the transcription of the and NRPS operons and that the absence of CRP reduced cytotoxicity of on HeLa cells, due to a significant reduction in TV production. This study highlights the importance of the CRP protein in the regulation of virulence genes in enteric bacteria and broadens our knowledge on the regulatory mechanisms of the TV cytotoxin.
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http://dx.doi.org/10.3389/fmicb.2021.743594DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8515920PMC
September 2021

Validation and Selection of New Reference Genes for RT-qPCR Analysis in Pediatric Glioma of Different Grades.

Genes (Basel) 2021 Aug 27;12(9). Epub 2021 Aug 27.

Laboratorio de Bioquímica Genética, Instituto Nacional de Pediatría, Secretaría de Salud, Ciudad de México 04530, Mexico.

Gliomas are heterogeneous, solid, and intracranial tumors that originate from glial cells. Malignant cells from the tumor undergo metabolic alterations to obtain the energy required for proliferation and the invasion of the cerebral parenchyma. The alterations in the expression of the genes related to the metabolic pathways can be detected in biopsies of gliomas of different CNS WHO grades. In this study, we evaluated the expression of 16 candidate reference genes in the HMC3 microglia cell line. Then, statistical algorithms such as BestKeeper, the comparative ΔC method, geNorm, NormFinder, and RefFinder were applied to obtain the genes most suitable to be considered as references for measuring the levels of expression in glioma samples. The results show that and are two novel genes suitable for genic expression studies on gliomas. Finally, we analyzed the expression of genes involved in metabolic pathways in clinical samples of brain gliomas of different CNS WHO grades. RT-qPCR analysis showed that in CNS WHO grade 3 and 4 gliomas, the expression levels of , , , , , , , , and were higher than those of CNS WHO grade 1 and 2 glioma biopsies. Hence, our results suggest that reference genes from metabolic pathways have different expression profiles depending on the stratification of gliomas and constitute a potential model for studying the development of this type of tumor and the search for molecular targets to treat gliomas.
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http://dx.doi.org/10.3390/genes12091335DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8468898PMC
August 2021

Occurrence of Nontuberculous Mycobacteria, Salmonella, Listeria monocytogenes, and Staphylococcus aureus in Artisanal Unpasteurized Cheeses in the State of Michoacan, Mexico.

J Food Prot 2021 May;84(5):760-766

Departamento de Microbiologia, Escuela Nacional de Ciencias Biologicas-Instituto Politecnico Nacional, Prolongacion Carpio y Plan de Ayala S/N, Col. Casco de Santo Tomas, Ciudad de Mexico 11340, Mexico.

Abstract: This study investigated the presence of nontuberculous mycobacteria (NTM) for the first time in two types of unpasteurized fresh cheese produced in the state of Michoacan, Mexico. We tested for this pathogen, along with the others, to broaden the study of microbiological quality in 60 samples of cheese, 30 fresh and 30 Adobera, which were collected from six artisanal cheese factories (ACFs). The hygienic conditions of these establishments and the practices of cheese manufacture were generally poor. Although Mycobacterium bovis was not detected, four cheese samples harbored NTM isolates. The four NTM isolates were identified using three molecular markers (hsp65, rrs, and rpoB genes) that corresponded to Mycolicibacterium fortuitum (n = 3) and Mycolicibacterium mageritense (n = 1). All 60 cheese samples analyzed had unsatisfactory microbiological quality according to the Mexican Official Guideline. Regarding fresh cheeses, all 30 samples analyzed were positive for aerobic mesophilic bacteria, total coliforms, fecal coliforms, and yeasts and molds. Escherichia coli and Staphylococcus aureus were present in 23 and 21 samples, respectively. Listeria monocytogenes was identified in a sample and was isolated from a bulk milk tank in the same ACF. With regard to Adobera cheeses, all samples were positive for aerobic mesophilic bacteria, total coliforms, fecal coliforms, yeasts and molds, and S. aureus. E. coli was isolated from 28 samples. Salmonella was isolated from a sample and from a wooden shovel used in the manufacture of the cheeses in the same ACF. Thus, the consumption of unpasteurized fresh cheese may represent a public health risk. Because of this, health authorities should enforce the legislation that forbids the processing of cheese with unpasteurized milk and encourage producers to follow good manufacturing practices from original ingredients, through the production process of the cheese, to its sale to assure a safe product.

Highlights:
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http://dx.doi.org/10.4315/JFP-20-286DOI Listing
May 2021

Bacteriological quality of bottled water obtained from Mexico City small water purification plants: Incidence and identification of potentially pathogenic nontuberculous mycobacteria species.

Int J Food Microbiol 2019 Oct 5;306:108260. Epub 2019 Jul 5.

Departamento de Microbiologia, Escuela Nacional de Ciencias Biologicas, Instituto Politecnico Nacional, Prolongacion Carpio y Plan de Ayala S/N, Col. Casco de Santo Tomas, Ciudad de Mexico 11340, Mexico. Electronic address:

The aim of this study was to determine the bacteriological quality of bottled water samples obtained from small purification plants located in Mexico City and to identify potentially pathogenic nontuberculous mycobacteria (NTM) species found in these samples. All 111 samples analyzed were positive for aerobic mesophilic bacteria (AMB) and 46 (41.4%) did not comply with Mexico's Official Guidelines. Sixty-nine (62.1%) and 23 (20.7%) water samples were positive for total coliforms (TC) and fecal coliforms (FC), respectively. A total of 81 (72.9%) of the water samples exceeded the maximum allowed limit stipulated in the guideline. Thirty-three (29.7%) of the purified water samples were positive for NTM, being recovered a total of 40 isolates. These NTM isolates were identified using three molecular markers (hsp65, rrs and rpoB genes) which corresponded to the fast-growing mycobacteria M. chelonae (n = 12), M. porcinum (n = 8), M. senegalense (n = 5), M. abscessus (n = 4), M. septicum (n = 4), M. wolinskyi (n = 3), M. mucogenicum (n = 2), M. fortuitum (n = 1) and M. sp. (n = 1). In seven purified water samples, two different NTM species were isolated simultaneously. Overall, these results showed that most of the purified bottled water samples analyzed in this study had unsatisfactory microbiological quality and some harbored NTM associated with illness. Our data could hasten health authorities to intensify efforts in the routine monitoring of activities in the purified bottled water industry in order to supply safe and healthy water to the public.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2019.108260DOI Listing
October 2019

Differential expression of miRNA-146a and miRNA-155 in gastritis induced by Helicobacter pylori infection in paediatric patients, adults, and an animal model.

BMC Infect Dis 2018 Sep 15;18(1):463. Epub 2018 Sep 15.

Infectology Laboratory, Hospital Infantil de México Federico Gómez, México City, Mexico.

Background: Helicobacter pylori is a major aetiologic agent associated with gastritis. H. pylori infections increase the expression of the Toll-like receptor (TLR), which in turn modulates the expression of microRNA (miRNA)-146a and miRNA-155. The objective of this study was to compare the expression of miRNA-146a and miRNA-155 in gastric lesions of paediatric and adult patients with different pathologies and in Mongolian gerbils (Meriones unguiculatus) infected with H. pylori 26,695.

Methods: Quantification of miRNA expression was performed by quantitative real-time polymerase chain reaction (qRT-PCR) of paraffin-embedded gastric lesions of children with or without an infection (n = 25), adults with follicular gastritis and metaplasia (n = 32) and eight-week-old M. unguiculatus males (Hsd:MON) infected with H. pylori 26,695 for 0, 3, 6, 12 and 18 months (n = 25). The genes RNU48 and RNU6 were used as endogenous controls for data normalization. Statistical analyses were performed using Kruskal-Wallis, Mann-Whitney, ANOVA and Student's t-test.

Results: The expression of miRNA-146a and miRNA-155 in infected children increased by 247.6- and 79.4-fold (on average), respectively, compared to that observed in the control group. However, these results were not significant (p = 0.12 and p = 0.07 respectively). In some children a gradual increase in expression was observed, while in others, expression was very high. Additionally, the expression levels of miRNA-146a and miRNA-155 increased by an average of 21.7- and 62-fold, respectively, in adult patients with follicular gastritis when compared to those of the controls. In M. unguiculatus infected with H. pylori 26,695, the expression of both miRNAs increased as the infection progressed.

Conclusion: This is the first report to show differences in the expression of miRNA-146a and miRNA-155 in paediatric and adult patients with gastritis who were infected with H. pylori. In addition, in M. unguiculatus infected with H. pylori, miRNA expression was associated with the progression of infection and the ability of the bacteria to adapt to the host.
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http://dx.doi.org/10.1186/s12879-018-3368-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6139157PMC
September 2018

Genetic diversity of drug and multidrug-resistant Mycobacterium tuberculosis circulating in Veracruz, Mexico.

PLoS One 2018 15;13(3):e0193626. Epub 2018 Mar 15.

Instituto de Salud Pública, Universidad Veracruzana, Jalapa, Veracruz, México.

Background: Mexico is one of the most important contributors of drug and multidrug-resistant tuberculosis in Latin America; however, knowledge of the genetic diversity of drug-resistant tuberculosis isolates is limited.

Methods: In this study, the genetic structure of 112 Mycobacterium tuberculosis strains from the southeastern Mexico was determined by spoligotyping and 24-loci MIRU-VNTRs.

Findings: The results show eight major lineages, the most of which was T1 (24%), followed by LAM (16%) and H (15%). A total of 29 (25%) isolates were identified as orphan. The most abundant SITs were SIT53/T1 and SIT42/LAM9 with 10 isolates each and SIT50/H3 with eight isolates. Fifty-two spoligotype patterns, twenty-seven clusters and ten clonal complexes were observed, demonstrating an important genetic diversity of drug and multidrug-resistant tuberculosis isolates in circulation and transmission level of these aggravated forms of tuberculosis. Being defined as orphan or as part of an orphan cluster, was a risk factor for multidrug resistant-tuberculosis (OR 2.5, IC 1.05-5.86 and OR 3.3, IC 1-11.03, respectively). Multiple correspondence analyses showed association of some clusters and SITs with specific geographical locations.

Conclusions: Our study provides one of the most detailed description of the genetic structure of drug and multidrug-resistant tuberculosis strains in southeast Mexico, establishing for the first time a baseline of the genotypes observed in resistant isolates circulating, however further studies are required to better elucidate the genetic structure of tuberculosis in region and the factors that could be participating in their dispersion.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0193626PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5854261PMC
June 2018

Comparative proteomic profiles reveal characteristic Mycobacterium tuberculosis proteins induced by cholesterol during dormancy conditions.

Microbiology (Reading) 2017 08 4;163(8):1237-1247. Epub 2017 Aug 4.

Departamento de Microbiologia, Escuela Nacional de Ciencias Biologicas (ENCB), Instituto Politecnico Nacional (IPN), Prolongacion Carpio y Plan de Ayala s/n, Ciudad de Mexico, 11340, Mexico.

Cholesterol has been reported to play an important role during Mycobacterium tuberculosis infection and during its dormant state inside the host. We present the determination of proteomic profiles of M. tuberculosis H37Rv in the presence of cholesterol as the sole carbon source under exponential growth and in two in vitro dormancy phases (NRP1 and NRP2). Using 2D-PAGE, we detected that M. tuberculosis expressed a high diversity of proteins in both exponential and non-replicative phases. We also found that cholesterol was involved in the overexpression of some proteins related to sulfur metabolism (CysA2), electron transport (FixB), cell wall synthesis (Ald), iron storage (BfrB), protein synthesis (Tig and EF-Tu) and dormancy maintenance (HspX and TB 31.7). According to our results we propose that proteins Ald, BfrB, FadA5 and TB31.7 are likely to play a fundamental role during in vitro dormancy of M. tuberculosis in the presence of cholesterol, helping to counteract its intracellular hostile microenvironment.
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http://dx.doi.org/10.1099/mic.0.000512DOI Listing
August 2017

The sigma factor SigD of Mycobacterium tuberculosis putatively enhances gene expression of the septum site determining protein under stressful environments.

New Microbiol 2017 Jul 4;40(3):199-204. Epub 2017 Jul 4.

Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Mexico City, Mexico.

This work examined the expression of the septum site determining gene (ssd) of Mycobacterium tuberculosis CDC1551 and its ∆sigD mutant under different growing conditions. The results showed an up-regulation of ssd during stationary phase and starvation conditions, but not during in vitro dormancy, suggesting a putative role for SigD in the control of ssd expression mainly under lack-of-nutrients environments. Furthermore, we elucidated a putative link between ssd expression and cell elongation of bacilli at stationary phase. In addition, a -35 sigD consensus sequence was found for the ssd promoter region, reinforcing the putative regulation of ssd by SigD, and in turn, supporting this protein role during the adaptation of M. tuberculosis to some stressful environments.
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July 2017

Cholesterol plays a larger role during Mycobacterium tuberculosis in vitro dormancy and reactivation than previously suspected.

Tuberculosis (Edinb) 2017 03 18;103:1-9. Epub 2016 Dec 18.

Departamento de Microbiologia, Escuela Nacional de Ciencias Biologicas, Instituto Politecnico Nacional, Prolongacion Carpio y Plan de Ayala s/n, Ciudad de Mexico, 11340, Mexico. Electronic address:

It is known that cholesterol plays a key role for Mycobacterium tuberculosis (Mtb) adaptation and survival within the host, thus contributing to the establishment of dormancy. It has been extensively demonstrated that fatty acids are the main energy source of Mtb during infection and dormancy, and it has been proposed that these molecules are implicated in reactivation of bacilli from a dormant state. We used in vitro models to analyze Mtb gene expression during dormancy and reactivation when fatty acids and cholesterol are the unique carbon source in the media. Our results suggest that cholesterol might function as a signal to trigger Mtb expression of some genes required for stress protection earlier than the one induced by fatty acids alone, indicating that cholesterol is very favorable for its development. This process is so conducive that cholesterol-adapted bacilli can reactivate their growth after NRP2 dormancy state even 10 min post ventilation. Thus, we hypothesize that cholesterol is not only involved in Mtb dormancy but that it also plays a critical role for favorable and almost immediate reactivation from an in vitro long-lasting dormant state induced by hypoxia.
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http://dx.doi.org/10.1016/j.tube.2016.12.004DOI Listing
March 2017

Microbiological Quality and Occurrence of Nontuberculous Mycobacteria in Fresh-Squeezed Orange Juice Samples Purchased from Street Vendors in Mexico City.

J Food Prot 2016 12;79(12):2190-2195

Departamento de Microbiologia, Escuela Nacional de Ciencias Biologicas-Instituto Politecnico Nacional, Prolongacion Carpio y Plan de Ayala S/N, Col. Casco de Santo Tomas, México, D.F., C.P. 11340, México.

Nontuberculous mycobacteria (NTM) are potentially pathogenic agents commonly found in a natural ecosystem. For this reason, food is considered another source of NTM transmission for humans. The aims of this study were to evaluate the microbiological quality and the occurrence of NTM in fresh-squeezed orange juice samples purchased from street vendors. All 102 samples analyzed were positive for aerobic mesophilic bacteria (AMB), with limits ranging from 1.8 to 6.2 log CFU/ml. A total of 55 (54%), 25 (25%), and 13 (13%) orange juice samples were positive for total coliforms (TC), fecal coliforms (FC), and Escherichia coli , respectively. TC, FC, and E. coli were present with limits ranging from <3 to >1,100 most probable number (MPN)/ml, <3 to 460 MPN/ml, and <3 to 11 MPN/ml, respectively. Six orange juice samples harbored NTM. These NTM were identified by using three molecular markers (hsp65, rrs, and rpoB genes) and corresponded to the fast-growing mycobacteria: Mycobacterium fortuitum (n = 3), Mycobacterium rhodesiae (n = 1), Mycobacterium obuense (n = 1), and a mixture of M. fortuitum and Mycobacterium mucogenicum in an additional sample (n = 1). No correlation was found between the presence NTM in orange juice samples with the presence and concentration of the indicator microorganisms (aerobic mesophilic bacteria, TC, and FC). Overall, these results suggest that fresh-squeezed orange juice might represent a vehicle for NTM transmission in humans. Therefore, prevention of contamination by humans (proper handling and washing of oranges) during juice preparation should be recommended.
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http://dx.doi.org/10.4315/0362-028X.JFP-16-197DOI Listing
December 2016

Human multidrug-resistant Mycobacterium bovis infection in Mexico.

Tuberculosis (Edinb) 2015 Dec 13;95(6):802-809. Epub 2015 Aug 13.

Instituto de Diagnóstico y Referencia Epidemiológicos, Secretaría de Salud, Mexico City, Mexico.

Here, we describe the molecular characterization of six human Mycobacterium bovis clinical isolates, including three multidrug resistant (MDR) strains, collected in Mexico through the National Survey on Tuberculosis Drug Resistance (ENTB-2008), a nationally representative survey conducted during 2008-2009 in nine states with a stratified cluster sampling design. The genetic background of bovine M. bovis strains identified in three different states of Mexico was studied in parallel to assess molecular relatedness of bovine and human strains. Additionally, resistance to first and second line anti-tuberculosis (TB) drugs and molecular identification of mutations conferring drug resistance was also performed. All strains were characterized by spoligotyping and 24-loci MIRU-VNTRs, and analyzed using the SITVIT2 (n = 112,000 strains) and SITVITBovis (n = 25,000 strains) proprietary databases of Institut Pasteur de la Guadeloupe. Furthermore, data from this study (n = 55 isolates), were also compared with genotypes recorded for M. bovis from USA (n = 203), Argentina (n = 726), as well as other isolates from Mexico (independent from the present study; n = 147), to determine any evidence for genetic relatedness between circulating M. bovis strains. The results showed that all human M. bovis cases were not genetically related between them or to any bovine strain. Interestingly, a high degree of genetic variability was observed among bovine strains. Several autochthonous and presumably imported strains were identified. The emergence of drug-resistant M. bovis is an important public health problem that jeopardizes the success of TB control programs in the region.
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http://dx.doi.org/10.1016/j.tube.2015.07.010DOI Listing
December 2015

Microbiological Quality of Ready-to-Eat Vegetables Collected in Mexico City: Occurrence of Aerobic-Mesophilic Bacteria, Fecal Coliforms, and Potentially Pathogenic Nontuberculous Mycobacteria.

Biomed Res Int 2015 30;2015:789508. Epub 2015 Mar 30.

Departamento de Microbiologia, Escuela Nacional de Ciencias Biologicas-Instituto Politecnico Nacional, Prolongacion Carpio y Plan de Ayala S/N, Colonia Casco de Santo Tomas, Delegacion Miguel Hidalgo, 11340 Mexico, DF, Mexico.

The aims of this study were to evaluate the microbiological quality and the occurrence of nontuberculous mycobacteria (NTM) in a variety of salads and sprouts from supermarkets and street vendors in Mexico City. Aerobic-mesophilic bacteria (AMB) were present in 100% of RTE-salads samples; 59% of samples were outside guidelines range (>5.17 log10 CFU per g). Although fecal coliforms (FC) were present in 32% of samples, only 8% of them exceeded the permissible limit (100 MPN/g). Regarding the 100 RTE-sprouts, all samples were also positive for AMB and total coliforms (TC) and 69% for FC. Seven NTM species were recovered from 7 salad samples; they included three M. fortuitum, two M. chelonae, one M. mucogenicum, and one M. sp. Twelve RTE-sprouts samples harbored NTM, which were identified as M. porcinum (five), M. abscessus (two), M. gordonae (two), M. mucogenicum (two), and M. avium complex (one). Most RTE-salads and RTE-sprouts had unsatisfactory microbiological quality and some harbored NTM associated with illness. No correlation between the presence of coliforms and NTM was found. Overall, these results suggest that RTE-salads and RTE-sprouts might function as vehicles for NTM transmission in humans; hence, proper handling and treatment before consumption of such products might be recommendable.
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http://dx.doi.org/10.1155/2015/789508DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4396000PMC
February 2016

Differential macrophage response to slow- and fast-growing pathogenic mycobacteria.

Biomed Res Int 2014 18;2014:916521. Epub 2014 May 18.

Departamento de Microbiologia, Escuela Nacional de Ciencias Biologicas (ENCB), Instituto Politecnico Nacional (IPN), 11340 México City, DF, Mexico.

Nontuberculous mycobacteria (NTM) have recently been recognized as important species that cause disease even in immunocompetent individuals. The mechanisms that these species use to infect and persist inside macrophages are not well characterised. To gain insight concerning this process we used THP-1 macrophages infected with M. abscessus, M. fortuitum, M. celatum, and M. tuberculosis. Our results showed that slow-growing mycobacteria gained entrance into these cells with more efficiency than fast-growing mycobacteria. We have also demonstrated that viable slow-growing M. celatum persisted inside macrophages without causing cell damage and without inducing reactive oxygen species (ROS), as M. tuberculosis caused. In contrast, fast-growing mycobacteria destroyed the cells and induced high levels of ROS. Additionally, the macrophage cytokine pattern induced by M. celatum was different from the one induced by either M. tuberculosis or fast-growing mycobacteria. Our results also suggest that, in some cases, the intracellular survival of mycobacteria and the immune response that they induce in macrophages could be related to their growth rate. In addition, the modulation of macrophage cytokine production, caused by M. celatum, might be a novel immune-evasion strategy used to survive inside macrophages that is different from the one reported for M. tuberculosis.
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http://dx.doi.org/10.1155/2014/916521DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4052160PMC
February 2015

Occurrence of potentially pathogenic nontuberculous mycobacteria in Mexican household potable water: a pilot study.

BMC Res Notes 2013 Dec 11;6:531. Epub 2013 Dec 11.

Departamento de Microbiologia, Escuela Nacional de Ciencias Biologicas-Instituto Politecnico Nacional, Prolongacion Carpio y Plan de Ayala S/N, Col, Casco de Santo Tomas, Delegacion Miguel Hidalgo, Mexico, D,F, CP 11340, Mexico.

Background: Nontuberculous mycobacteria (NTM) are environmental opportunistic pathogens found in natural and human-engineered waters, including drinking water distribution systems and household plumbing. This pilot study examined the frequency of occurrence of NTM in household potable water samples in Mexico City. Potable water samples were collected from the "main house faucet" and kitchen faucet. The presence of aerobic-mesophilic bacteria (AMB), total coliforms (TC), fecal coliforms (FC) and NTM species were determined. Mycobacteria species were identified by PCR restriction enzyme pattern analysis (PRA) of the 65-kDa heat shock protein gene (hsp65) and sequencing of the hypervariable region 2 (V2) of the 16S rRNA gene and of the rpoB gene.

Results: AMB (<100 CFU/ml) were present in 118 out of 120 samples; only two samples were outside guidelines ranges (>100 CFU/ml). TC and FC were detected in four and one samples, respectively. NTM species were recovered from 16% samples (19/120) and included M. mucogenicum (nine), M. porcinum (three), M. avium (three), M. gordonae (one), M. cosmeticum (one), M. fortuitum (one), and Mycobacterium sp (one). All household water samples that contained NTM complied with the standards required to grade the water as "good quality" potable water.

Conclusion: Household potable water may be a potential source of NTM infection in Mexico City.
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http://dx.doi.org/10.1186/1756-0500-6-531DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3874667PMC
December 2013

Genetic diversity among multidrug-resistant Mycobacterium tuberculosis strains in Mexico.

Infect Genet Evol 2013 Mar 16;14:434-43. Epub 2013 Jan 16.

Instituto de Diagnóstico y Referencia Epidemiológicos, Secretaría de Salud, Mexico City, Mexico.

Tuberculosis is an important public health problem in Mexico. However, limited information about the genetic diversity of Mycobacterium tuberculosis strains circulating in the country is available. In this work, 109 multidrug-resistant (MDR) M. tuberculosis isolates collected in 23 different states of Mexico in 2003 were retrospectively characterized by spoligotyping and MIRU-VNTRs. All isolates, except for a single cluster containing two strains (subcluster E1), were split when information from the 12-loci MIRUs and spoligo-pattern was simultaneously analyzed. The discriminative power of 12-loci MIRU-VNTR and spoligotyping, by the Hunter-Gaston index, were 0.9998 and 0.9011, respectively. These findings suggest that almost all cases were epidemiologically unrelated. Instead, the genetic variations observed among these strains are suggestive of emergence of acquired drug-resistance during the course of treatment. The results suggest a high degree of genetic variability and a high frequency of SIT53 (T1 family) spoligotype among the MDR M. tuberculosis isolates included in the study.
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http://dx.doi.org/10.1016/j.meegid.2012.12.024DOI Listing
March 2013

Evaluation of the cell growth of mycobacteria using Mycobacterium smegmatis mc2 155 as a representative species.

J Microbiol 2012 Jun 30;50(3):419-25. Epub 2012 Jun 30.

Departamento de Microbiologia, Escuela Nacional de Ciencias Biologicas, IPN, Prolong. Carpio y Plan de Ayala s/n, Col. Casco de Santo Tomas, Mexico, D.F., 11340, Mexico.

The study of the in vitro cell growth of mycobacteria still remains a fastidious, difficult, and time-consuming procedure. In addition, assessing mycobacterial growth in the laboratory is often complicated by cell aggregation and slow growth-rate. We now report that the use of a stainless steel spring in the culture led to an absence of large cell clumps, to a decrease of dead cells in the exponential phase and to growth of a more homogeneous population of large cells. We also report that flow cytometry is a rapid, simple and reliable approach to monitor mycobacterial cell growth and viability. Here, we monitored Mycobacterium smegmatis cellular growth by optical density, dry cell mass, and colony forming units; in addition, viability, cell size and granularity profiles were analyzed by flow cytometry, and cell morphology by electron microscopy. Cultures monitored by flow cytometry may lead to a better understanding of the physiology of mycobacteria. Moreover, this methodology may aid in characterizing the cell growth of other fastidious species of microorganisms.
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http://dx.doi.org/10.1007/s12275-012-1556-0DOI Listing
June 2012

Differential expression of dnaA and dosR genes among members of the Mycobacterium tuberculosis complex under oxic and hypoxic conditions.

Int Microbiol 2010 Mar;13(1):9-13

Departament of Microbiology, National School of Biological Sciences, National Polytechnical Institute, Mexico DF, Mexico.

Major differences regarding the pathology and host immune response of the Beijing and Canettii genotypes of Mycobacterium tuberculosis have been reported; however, studies on the genetic expression of these genotypes during in vitro dormancy are scarce. This study examined the expression of five cell-cycle-related genes and two dormancy-related genes in M. canettii, M. tuberculosis H37Rv, and M. tuberculosis Beijing during the Wayne model of dormancy. The results showed that under hypoxic conditions the three tuberculosis genotypes were able to transcribe genes involved in DNA replication and cellular division. In addition, dosR was found to be up-regulated in M. tuberculosis Beijing during the exponential growth phase but down-regulated under hypoxic conditions. In this genotype, the replication-related gene dnaA was also strongly down-regulated. These latter two findings suggest that, compared to M. tuberculosis H37Rv and M. canettii, the Beijing genotype has a lower capacity to synthesize dosR, hspX, and dnaA mRNAs during in vitro dormancy.
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http://dx.doi.org/10.2436/20.1501.01.106DOI Listing
March 2010

First insights into the genetic diversity of Mycobacterium tuberculosis isolates from HIV-infected Mexican patients and mutations causing multidrug resistance.

BMC Microbiol 2010 Mar 17;10:82. Epub 2010 Mar 17.

Departamento de Microbiologia, ENCB-IPN, Mexico City, Mexico.

Background: The prevalence of infections with Mycobacterium tuberculosis (MTb) and nontuberculous mycobacteria (NTM) species in HIV-infected patients in Mexico is unknown. The aims of this study were to determine the frequency of MTb and NTM species in HIV-infected patients from Mexico City, to evaluate the genotypic diversity of the Mycobacterium tuberculosis complex strains, to determine their drug resistance profiles by colorimetric microplate Alamar Blue assay (MABA), and finally, to detect mutations present in katG, rpoB and inhA genes, resulting in isoniazid (INH) and rifampin (RIF) resistance.

Results: Of the 67 mycobacterial strains isolated, 48 were identified as MTb, 9 as M. bovis, 9 as M. avium and 1 as M. intracellulare. IS6110-RFLP of 48 MTb strains showed 27 profiles. Spoligotyping of the 48 MTb strains yielded 21 patterns, and 9 M. bovis strains produced 7 patterns. Eleven new spoligotypes patterns were found. A total of 40 patterns were produced from the 48 MTb strains when MIRU-VNTR was performed. Nineteen (39.6%) MTb strains were resistant to one or more drugs. One (2.1%) multidrug-resistant (MDR) strain was identified. A novel mutation was identified in a RIF-resistant strain, GAG --> TCG (Glu --> Ser) at codon 469 of rpoB gene.

Conclusions: This is the first molecular analysis of mycobacteria isolated from HIV-infected patients in Mexico, which describe the prevalence of different mycobacterial species in this population. A high genetic diversity of MTb strains was identified. New spoligotypes and MIRU-VNTR patterns as well as a novel mutation associated to RIF-resistance were found. This information will facilitate the tracking of different mycobacterial species in HIV-infected individuals, and monitoring the spread of these microorganisms, leading to more appropriate measures for tuberculosis control.
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http://dx.doi.org/10.1186/1471-2180-10-82DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2848023PMC
March 2010

par genes in Mycobacterium bovis and Mycobacterium smegmatis are arranged in an operon transcribed from "SigGC" promoters.

BMC Microbiol 2008 Mar 27;8:51. Epub 2008 Mar 27.

Laboratorio de Biología Molecular, Departamento de Biología Estructural, Instituto Venezolano de Investigaciones Científicas (IVIC), Apartado 20632, Caracas 1020-A, Venezuela.

Background: The ParA/Soj and ParB/Spo0J proteins, and the cis-acting parS site, participate actively in chromosome segregation and cell cycle progression. Genes homologous to parA and parB, and two putative parS copies, have been identified in the Mycobacterium bovis BCG and Mycobacterium smegmatis chromosomes. As in Mycobacterium tuberculosis, the parA and parB genes in these two non-pathogenic mycobacteria are located near the chromosomal origin of replication. The present work focused on the determination of the transcriptional organisation of the ~6 Kb orf60K-parB region of M. bovis BCG and M. smegmatis by primer extension, transcriptional fusions to the green fluorescence protein (GFP) and quantitative RT-PCR.

Results: The parAB genes were arranged in an operon. However, we also found promoters upstream of each one of these genes. Seven putative promoter sequences were identified in the orf60K-parB region of M. bovis BCG, whilst four were identified in the homologous region of M. smegmatis, one upstream of each open reading frame (ORF).Real-time PCR assays showed that in M. smegmatis, mRNA-parA and mRNA-parB levels decreased between the exponential and stationary phases. In M. bovis BCG, mRNA-parA levels also decreased between the exponential and stationary phases. However, parB expression was higher than parA expression and remained almost unchanged along the growth curve.

Conclusion: The majority of the proposed promoter regions had features characteristic of Mycobacterium promoters previously denoted as Group D. The -10 hexamer of a strong E. coli sigma70-like promoter, located upstream of gidB of M. bovis BCG, overlapped with a putative parS sequence, suggesting that the transcription from this promoter might be regulated by the binding of ParB to parS.
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http://dx.doi.org/10.1186/1471-2180-8-51DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2346475PMC
March 2008

The number and organization of the rRNA genes of several strains of Mycobacterium simiae.

FEMS Microbiol Lett 2003 Oct;227(1):133-9

Departamento de Microbiologia, Escuela Nacional de Ciencias Biológicas, IPN, Prolongación Carpio y Plan de Ayala S/N, Col. Santo Tomas, México DF, Mexico 11340.

The type strain of Mycobacterium simiae and four Cuban strains, each representing a group of variants sharing a characteristic pattern of glycopeptidolipids, were investigated. Each of the five strains was found to have a single rRNA (rrn) operon per genome. Each rrn operon was found to be located downstream from murA. Unusually for slow-growing mycobacteria, three transcription start points were identified for each operon. Gene sequences were established extending from near to the 3'-ends of murA, the intergenic regions and the 5'-ends of the 16S rDNAs. Characteristic strain differences were identified.
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http://dx.doi.org/10.1016/S0378-1097(03)00656-6DOI Listing
October 2003
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