Publications by authors named "Marisa Almuzara"

54 Publications

[Corynebacterium kroppenstedtii breast infections: Report of four cases].

Rev Argent Microbiol 2021 Feb 21. Epub 2021 Feb 21.

Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Laboratorio de Bacteriología, Catedra de Microbiología Clínica, Hospital de Clínicas José de San Martin, Buenos Aires, Argentina. Electronic address:

Corynebacterium kroppenstedtii is an immobile, non-sporulated, glucose-fermenting and lipophilic gram-positive rod of the skin microbiota. In recent years, numerous isolates of this species have been reported mainly in breast infections, such as abscesses and granulomatous mastitis. We present here four cases of C. kroppenstedtii infections isolated from breast aspiration samples in women. C. kroppenstedtii was identified by conventional methodology and mass spectrometry (MALDI-TOF MS). Using the epsilometric method, these isolates showed susceptibility to penicillin, ceftriaxone, minocycline, ciprofloxacin, and vancomycin, and variable susceptibility to clindamycin and trimethoprim sulfamethoxazole. Due to the association of C. kroppenstedtii with mammary infections, the identification at the species level of those corynebacteria isolated from this location is highly advisable in order to reach the final diagnosis and to test the antimicrobial susceptibility in order to apply the appropriate antibiotic treatment.
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http://dx.doi.org/10.1016/j.ram.2021.01.002DOI Listing
February 2021

[Analysis of the diversity of Actinomyces/Actinotignum clinical isolates in a university hospital].

Rev Argent Microbiol 2021 Jan 2. Epub 2021 Jan 2.

Facultad de Farmacia y Bioquímica, Departamento de Bioquímica Clínica, Hospital de Clínicas «José de San Martín», Universidad de Buenos Aires, Ciudad Autónoma de Buenos Aires, Argentina.

Actinomyces and related genera are grampositive bacilli, opportunistic pathogens, which have been mainly involved in endogenous infections. However, due to the complexity in identifying them for most clinical laboratories, there is scant knowledge about their real clinical significance. In this work, 166 isolates of 13 different species of Actinomyces/Actinotignum species recovered from clinical samples of patients treated in a university hospital were studied. The identification was performed by MALDI-TOF MS and molecular identification. MALDI-TOF MS identified 91.57% of the isolates (152/166) at the species level using a score ≥ 1.7 and 3.61% (6/166) of the isolates were identified only at the gender level with a score ≥ 1.5. MALDI-TOF MS did not yield reliable identification results for 4.82% (8/166) of the isolates. Actinomyces/Actinotignum species were isolated from: soft tissue (n: 47), urine samples (n: 35), head / neck abscesses (n: 19), genital abscesses (n: 11), blood samples (n: 10), breast abscesses (n: 8), osteoarticular samples (n: 6), abdominal/ascitic fluids (n: 3), abdominal abscesses (n: 5), sputum/BAL (n: 4), brain abscesses (n: 3), and others (n: 15). The results obtained from the statistical analysis showed a high differential frequency (> 2) for the location/species association: urine/A. schaalii/sanguinis; brain abscesses/A. europaeus; osteoarticular samples/A. urogenitalis; abdominal abscesses/ A. turicensis; respiratory samples/A. naeslundii/viscosus. This information provides a greater understanding of the clinical and epidemiological relevance of these species. The pathogenic role of Actinomyces spp. will be increasingly revealed as these microorganisms could be recognized thanks to prolonged culture and the advances in identification technology facilitated by MALDI-TOF MS.
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http://dx.doi.org/10.1016/j.ram.2020.11.005DOI Listing
January 2021

Genomic Analysis of two NDM-1 Providencia stuartii Strains Recovered from a Single Patient.

Curr Microbiol 2020 Dec 13;77(12):4029-4036. Epub 2020 Oct 13.

Center for Applied Biotechnology Studies, Department of Biological Science, California State University Fullerton, Fullerton, CA, USA.

In the last years, an increasing number of untreatable infections caused by drug-resistant microbes have impacted the health care system. Worldwide, infections caused by carbapenem-resistant (CR) Gram-negative bacilli have dramatically increased. Among the CR-Gram-negative bacilli, those producing carbapenemases, such as NDM-1, are the main concern. Different Enterobacterales harboring NDM-1 have been reported lately. Providencia stuartii, a member of the Morganellaceae family, is ubiquitous in the environment, but is also known to cause nosocomial infections. Here we describe the genomic analysis of two NDM-1- producing P. stuartii strains recovered from the same patient as well as other carbapenem resistant strains recovered from the same hospital. As a result of the genomic analysis thirteen resistance genes, including three to β-lactams (bla, bla, bla), four to aminoglycosides (aphA6, aac(3)-IId, aac(2')-Ia, aac(6')-Ib-cr5), one to sulfonamides (sul1), two to chloramphenicol (catB3, catA3), one to rifampicin, one to bleomycin (ble), and one to tetracycline (tet(B)) were found. Moreover, a variety of mobile genetic elements, such as insertion sequences, plasmids and phage- related sequences, were found within P. stuartii genomes. The spread of carbapenem-resistant isolates remains a significant clinical and public health concern. Therefore, we considered that the detection of CR isolates is an essential step in addressing this problem.
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http://dx.doi.org/10.1007/s00284-020-02242-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7680452PMC
December 2020

Infections due to Vagococcus spp. Microbiological and clinical aspects and literature review.

Enferm Infecc Microbiol Clin 2020 Jul 25. Epub 2020 Jul 25.

Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Laboratorio de Bacteriología, Cátedra de Microbiología Clínica, Hospital de Clínicas José de San Martín, Ciudad Autónoma de Buenos Aires, Argentina; Hospital Interzonal de Agudos Eva Perón, San Martín, Provincia de Buenos Aires, Argentina. Electronic address:

Introduction: An increase in recent years in the isolation of Vagococcus spp. is suggestive of emerging infection by this pathogen in our hospital.

Methods: Prospective, descriptive study.

Period: July 2014-January 2019. Phenotypic identification of 15 isolates of Vagococcus spp. was performed by conventional biochemical tests, automated methodology and mass spectrometry (MALDI-TOF MS). Molecular identification was achieved by sequencing the 16S rRNA gene. The Vitek™ 2C automated system was used to test antibiotic susceptibility.

Results: The molecular method identified 11 Vagococcus fluvialis, one Vagococcus lutrae and three Vagococcus spp. MALDI-TOF MS facilitated the rapid recognition of the genus. The most active antibiotics were ampicillin, trimethoprim/sulfamethoxazole, vancomycin, teicoplanin and linezolid. Most of the cases of isolation were associated with skin and soft tissue or osteoarticular infections in patients with diabetes.

Conclusion: This article is the most extensive review of cases of Vagococcus spp. infection reported in the literature and highlights the microbiological and clinical aspects of this pathogen.
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http://dx.doi.org/10.1016/j.eimc.2020.06.010DOI Listing
July 2020

Expansion and improvement of MALDI-TOF MS databases for accurate identification of Achromobacter species.

J Microbiol Methods 2020 05 11;172:105889. Epub 2020 Mar 11.

Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, IBaViM, Laboratorio de Resistencia Bacteriana, Junín 956, 8vo. Piso, Ciudad Autónoma de Buenos Aires, CP 1113, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina. Electronic address:

Different MALDI-TOF MS databases were evaluated for the identification of Achromobacter species. The in-house and extended database generated in this study rendered more accurate identification (58/64 and 57/64 isolates, respectively) in comparison with the Bruker commercial database (42/64 isolates), especially in those infrequent species that are not available or poorly represented.
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http://dx.doi.org/10.1016/j.mimet.2020.105889DOI Listing
May 2020

Genetic and Phenotypic Features of a Novel Acinetobacter Species, Strain A47, Isolated From the Clinical Setting.

Front Microbiol 2019 18;10:1375. Epub 2019 Jun 18.

Department of Biological Science, California State University Fullerton, Fullerton, CA, United States.

In 2014, a novel species of , strain A47, determined to be hospital-acquired was recovered from a single patient soft tissue sample following a traumatic accident. The complexity of the genus has been established, and every year novel species are identified. However, specific features and virulence factors that allow members of this genus to be successful pathogens are not well understood. Utilizing both genomic and phenotypic approaches, we identified distinct features and potential virulence factors of the A47 strain to understand its pathobiology. analyses confirmed the uniqueness of this strain and other comparative and sequence analyses were used to study the evolution of relevant features identified in this isolate. The A47 genome was further analyzed for genes associated with virulence and genes involved in type IV pili (T4P) biogenesis, hemolysis, type VI secretion system (T6SS), and novel antibiotic resistance determinants were identified. A47 exhibited natural transformation with both genomic and plasmid DNA. It was able to form biofilms on different surfaces, to cause hemolysis of sheep and rabbit erythrocytes, and to kill competitor bacteria. Additionally, surface structures with non-uniform length were visualized with scanning electron microscopy and proposed as pili-like structures. Furthermore, the A47 genome revealed the presence of two putative BLUF type photoreceptors, and phenotypic assays confirmed the modulation by light of different virulence traits. Taken together, these results provide insight into the pathobiology of A47, which exhibits multiple virulence factors, natural transformation, and the ability to sense and respond to light, which may contribute to the success of an A47 as a hospital dwelling pathogen.
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http://dx.doi.org/10.3389/fmicb.2019.01375DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6591377PMC
June 2019

Diversity of Achromobacter species recovered from patients with cystic fibrosis, in Argentina.

Rev Argent Microbiol 2020 Jan - Mar;52(1):13-18. Epub 2019 Jun 26.

Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Cátedra de Microbiología, Laboratorio de Resistencia Bacteriana, Ciudad Autónoma de Buenos Aires, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina. Electronic address:

Different phenotype-based techniques and molecular tools were used to describe the distribution of different Achromobacter species in patients with cystic fibrosis (CF) in Argentina, and to evaluate their antibiotic resistance profile. Phenotypic identification was performed by conventional biochemical tests, commercial galleries and MALDI-TOF MS. Genetic approaches included the detection of A. xylosoxidans specific marker bla, the amplification and sequencing of the 16S rRNA gene, nrdA and bla complete sequence, and MLST analysis. Phenotypic approaches, even MALDI-TOF, rendered inconclusive or misleading results. On the contrary, concordant results were achieved with the nrdA sequencing or sequence type (ST) analysis, and the complete bla sequencing, allowing a reliable discrimination of different Achromobacter species. A. xylosoxidans accounted for 63% of Achromobacter infections and A. ruhlandii accounted for 17%. The remaining species corresponded to A. insuavis, A. dolens, A. marplatensis and A. pulmonis. Antimicrobial susceptibilities were determined by the agar dilution method according to CLSI guidelines. Piperacillin, piperacillin/tazobactam and carbapenems were the most active antibiotics. However, the emergence of carbapenem-resistant isolates was detected. In conclusion, prompt and accurate identification tools were necessary to determine that different Achromobacter species may colonize/infect the airways of patients with CF. Moreover, antimicrobial therapy should be administered based on the susceptibility profile of individual Achromobacter sp. isolates.
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http://dx.doi.org/10.1016/j.ram.2019.03.004DOI Listing
January 2021

[Presentation of the National Network for Microbiological Identification by Mass Spectrometry website. Guide for the interpretation of MALDI-TOF MS results].

Rev Argent Microbiol 2020 Jan - Mar;52(1):83-84. Epub 2019 Jun 6.

Departamento de Bacteriología, Laboratorio Bacteriología Especial, Instituto Nacional de Enfermedades Infecciosas (INEI), Administración Nacional de Laboratorios e Institutos de Salud (ANLIS) «Dr. Carlos G. Malbrán», Ciudad Autónoma de Buenos Aires, Argentina.

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http://dx.doi.org/10.1016/j.ram.2019.03.001DOI Listing
March 2021

[Development and evaluation of an in-house database for quick identification of Burkholderia contaminans by MALDI-TOF MS].

Rev Argent Microbiol 2019 Jul - Sep;51(3):255-258. Epub 2018 Dec 15.

Servicio de Bacteriología Especial, Departamento de Bacteriología, Instituto Nacional de Enfermedades Infecciosas (INEI), Administración Nacional de Laboratorios e Institutos de Salud (ANLIS) «Dr. Carlos G. Malbrán», Ciudad Autónoma de Buenos Aires, Argentina.

MALDI-TOF (matrix assisted laser desorption ionization-time of flight) mass spectrometry (MS) proved to be a robust tool for the identification of numerous taxonomic groups. However, it has limitations. A key advantage of this technique is the flexibility for the incorporation of protein profiles of microorganisms not included in the commercial database. Due to the prevalence of Burkholderia contaminans in fibrocystic patients in Argentina and the fact that rapid and reliable microbiological diagnosis is crucial in them, MALDI-TOF MS emerges as a strategic tool. The aim of this work was to develop an additional database with peptide spectra of reference isolates of B. contaminans. This database demonstrated to be successful for the identification of 97% of the isolates analyzed. Therefore, MALDI-TOF MS with the extended database was a useful tool for the identification and differentiation of other related species to B. contaminans.
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http://dx.doi.org/10.1016/j.ram.2018.09.001DOI Listing
March 2020

Genome sequence analysis of an extensively drug-resistant Acinetobacter baumannii indigo-pigmented strain depicts evidence of increase genome plasticity.

Sci Rep 2018 11 16;8(1):16961. Epub 2018 Nov 16.

Center for Applied Biotechnology Studies, Department of Biological Science, California State University Fullerton, Fullerton, CA, USA.

Acinetobacter baumannii is a multidrug resistant nosocomial pathogen that shows an outstanding ability to undergo genetic exchange, thereby acquiring different traits that contribute to its success. In this work, we identified genetic features of an indigo-pigmented A. baumannii strain (Ab33405) that belongs to the clonal complex CC113/CC79. Ab33405 possesses a high number of genes coding for antibiotic resistance and virulence factors that may contribute to its survival, not only in the human host, but also in the hospital environment. Thirteen genes conferring resistance to different antibiotic families (trimethoprim, florfenicol, β-lactams, aminoglycosides and sulfonamide) as well as the adeIJK genes and the capsule locus (KL) and outer core locus (OCL) were identified. Ab33405 includes 250 unique genes and a significant number of elements associated with Horizontal Gene Transfer, such as insertion sequences and transposons, genomic islands and prophage sequences. Also, the indigo-pigmented uncommon phenotype that could be associated with the monooxygenase or dioxygenase enzyme coded for by the iacA gene within the iac cluster was probably conferred by insertion of a 18-kb DNA fragment into the iacG gene belonging to this cluster. The Ab33405 genome includes all type VI secretion system genes and killing assays showed the ability of Ab33045 to kill Escherichia coli. In addition, Ab33405 can modulate susceptibility antibiotics when exposed to blue light.
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http://dx.doi.org/10.1038/s41598-018-35377-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6240043PMC
November 2018

Total nephrectomy following urinary tract infection.

JMM Case Rep 2018 Sep 6;5(9):e005149. Epub 2018 Apr 6.

Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica, Departamento de Bioquímica Clínica, Cátedra de Microbiología Clínica, Hospital de Clínicas José de San Martín, Ciudad Autónoma de Buenos Aires, Argentina.

Introduction: is a Gram-stain-positive non-lipophilic coryneform rod first described in blood samples and pleural fluid. There is scarce information about the clinical relevance of and none on complicated urinary tract infections has been described so far.

Case Presentation: A 36-year-old woman with a history of chronic kidney failure, under thrice-weekly haemodialysis since 2014 due to polycystic kidney disease, presented with hypogastric pain, lower left quadrant pain and nausea. Since 1997, the patient had developed several episodes of urinary tract infection. On admission, the patient presented tenderness in the lower abdomen and fist positive lumbar percussion. Urine culture showed significant bacterial growth (>10 c.f.u. ml). Slightly glistening colonies of 1 mm in diameter were observed after a 24 h incubation. Gram staining showed coryneform Gram-stain-positive rods. The patient was diagnosed as having a complicated urinary tract infection. A bilateral nephrectomy was performed on the fourth day of hospitalization. Two samples of kidney tissue were sent for culture. Direct examination of the material revealed the presence of abundant inflammatory reaction and Gram-positive diphtheroid rods. The organism was identified using MALDI-TOF and conventional biochemical tests; in both isolates further identification was performed by PCR amplification and sequence analysis of the gene as .

Conclusions: is an infrequent species among the genus that should be considered as an emerging pathogen that can be involved in nosocomial infections and complicated urinary tract infections.
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http://dx.doi.org/10.1099/jmmcr.0.005149DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6230760PMC
September 2018

Clinical cases of VIM-producing Pseudomonas mendocina from two burned patients.

J Glob Antimicrob Resist 2018 09 14;14:273-274. Epub 2018 Aug 14.

Center for Applied Biotechnology Studies, Department of Biological Science, California State University Fullerton, 800 N. State College Blvd., Fullerton, CA 92831, USA. Electronic address:

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http://dx.doi.org/10.1016/j.jgar.2018.08.002DOI Listing
September 2018

Comparison between disk diffusion and agar dilution methods to determine in vitro susceptibility of Corynebacterium spp. clinical isolates and update of their susceptibility.

J Glob Antimicrob Resist 2018 09 18;14:246-252. Epub 2018 May 18.

Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Departamento de Bioquímica Clínica, Hospital de Clínicas 'José de San Martín', Avenida Córdoba 2351, Ciudad Autónoma de Buenos Aires, Argentina.

Objectives: Although Corynebacterium spp. are part of the microbiota of the skin and mucous membranes, human infections caused by Corynebacterium spp. have been reported and the multidrug resistance pattern of the recovered isolates was emphasised. Due to the usefulness of disk diffusion in daily practice, the purpose of this study was to compare disk diffusion with agar dilution to determine disk diffusion breakpoints and to review the antimicrobial susceptibility of the most frequent Corynebacterium spp. isolated in clinical samples.

Methods: Susceptibility to 20 antimicrobial agents of 143 Corynebacterium spp. isolates recovered from relevant clinical samples was determined. Comparison between the disk diffusion and agar dilution methods for eight antimicrobial agents was performed to establish new breakpoints using simple linear regression analysis.

Results: All of the isolates tested were susceptible to vancomycin, minocycline and linezolid. A typical susceptibility profile to β-lactam antibiotics among the different species included was not observed. Almost all isolates showed resistance to macrolides and lincosamides. Using a simple linear regression method, it was possible to establish breakpoints for penicillin, erythromycin, clindamycin, gentamicin and ciprofloxacin. However, the low correlation coefficient obtained for vancomycin, minocycline and trimethoprim/sulfamethoxazole did not allow establishment of breakpoints for the disk diffusion method.

Conclusion: The disk diffusion method could only be used to evaluate susceptibility to penicillin, erythromycin, clindamycin, gentamicin and ciprofloxacin. These data show that the presence of a Corynebacterium spp. isolate in a clinical sample demands the performance of antimicrobial susceptibility testing since the susceptibility profile is not predictable.
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http://dx.doi.org/10.1016/j.jgar.2018.05.009DOI Listing
September 2018

Whole-Genome Analysis of an Extensively Drug-Resistance Empedobacter falsenii Strain Reveals Distinct Features and the Presence of a Novel Metallo-ß-Lactamase (EBR-2).

Curr Microbiol 2018 Aug 23;75(8):1084-1089. Epub 2018 Apr 23.

Department of Biological Science, California State University Fullerton, 800 N State College Blvd, Fullerton, CA, 92831, USA.

The spread of antibiotic resistance is rapidly threatening the effectiveness of antibiotics in the clinical setting. Many infections are being caused by known and unknown pathogenic bacteria that are resistant to many or all antibiotics currently available. Empedobacter falsenii is a nosocomial pathogen that can cause human infections. E. falsenii Wf282 strain was found to be resistant to many antibiotics, including carbapenems and colistin. Whole-genome shotgun sequencing of the strain was performed, and distinct features were identified. A novel metallo-β-lactamase, named EBR-2, was found, suggesting a potential role of E. falsenii as a reservoir of β-lactamases and other resistance determinants also found in its genome. The EBR-2 protein showed the highest catalytic efficiency for penicillin G as compared to meropenem and ampicillin and was unable to hydrolyze cefepime. The results described in this work broaden the current understanding of the role of β-lactamases in the Flavobacteriaceae family and suggest that E. falsenii Wf282 may be a reservoir of these novel resistance determinants.
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http://dx.doi.org/10.1007/s00284-018-1498-9DOI Listing
August 2018

Characterisation of OXA-258 enzymes and AxyABM efflux pump in Achromobacter ruhlandii.

J Glob Antimicrob Resist 2018 09 9;14:233-237. Epub 2018 Apr 9.

Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Cátedra de Microbiología, Laboratorio de Resistencia Bacteriana, Ciudad de Buenos Aires, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina. Electronic address:

Objectives: The aim of this study was to characterise OXA-258 variants and other features that may contribute to carbapenem resistance in Achromobacter ruhlandii.

Methods: Kinetic parameters for purified OXA-258a and OXA-258b were determined measuring the rate of hydrolysis of a representative group of antimicrobial agents. Whole-genome shotgun sequencing was performed on A. ruhlandii 38 (producing OXA-258a) and A. ruhlandii 319 (producing OXA-258b), and in silico analysis of antimicrobial resistance determinants was conducted. Substrates of the AxyABM efflux pump were investigated by inhibition assays using phenylalanine-arginine β-naphthylamide (PAβN). Outer membrane protein profiles were resolved by 12% sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE).

Results: Kinetic measurements of purified OXA-258 variants displayed an overall weak catalytic efficiency toward β-lactams. A detectable hydrolysis of imipenem was observed. In silico genomic analysis confirmed the presence of 32 and 35 putative efflux pump-encoding genes in A. ruhlandii strains 38 and 319, respectively. Complete sequences for AxyABM and AxyXY efflux pumps, previously described in Achromobacter xylosoxidans, were detected. Decreases in the MICs for chloramphenicol, nalidixic acid and trimethoprim/sulfamethoxazole were observed in the presence of the inhibitor PAβN, suggesting that these antibiotics are substrates of AxyABM. AxyXY-encoding genes of A. ruhlandii 38 and A. ruhlandii 319 displayed 99% identity. No differences were observed in the outer membrane protein profiles.

Conclusions: The contribution of OXA-258 enzymes to the final β-lactam resistance profile may be secondary. Further studies on other putative resistance markers identified in the whole-genome analysis should be conducted to understand the carbapenem resistance observed in A. ruhlandii.
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http://dx.doi.org/10.1016/j.jgar.2018.03.015DOI Listing
September 2018

Genetic analysis of a PER-2-producing Shewanella sp. strain harbouring a variety of mobile genetic elements and antibiotic resistance determinants.

J Glob Antimicrob Resist 2017 12 29;11:81-86. Epub 2017 Jul 29.

Department of Biological Science, California State University, Fullerton, 800 N. State College Blvd., Fullerton, CA 92831, USA. Electronic address:

The objective of this study was to investigate the molecular mechanisms explaining the multidrug-resistant (MDR) phenotype found in a novel clinical Shewanella sp. strain (Shew256) recovered from a diabetic patient. Whole-genome shotgun sequencing was performed using Illumina MiSeq-I and Nextera XT DNA library. De novo assembly was performed with SPAdes. RAST Server was used to predict the open-reading frames and the predictions were confirmed using BLAST. Further genomic analysis was carried out using average nucleotide identity (ANI), ACT (Artemis), OrthoMCL, ARG-ANNOT, ISfinder, PHAST, tRNAscan-SE, plasmidSPAdes, PlasmidFinder and MAUVE. PCR and plasmid extraction were also performed. Genomic analysis revealed a total of 456 predicted genes unique to Shew256 compared with other Shewanella genomes. Moreover, the presence of different resistance genes, including bla, was found. A complex class 1 integron containing the ISCR1 gene, disrupted by two putative transposase genes, was identified. Furthermore, other resistance genes, a transposon containing aph(3'), insertion sequences, phages and non-coding RNAs were also found. In conclusion, evidence of acquisition of resistance genes and mobile elements that could explain the MDR phenotype were observed. This Shewanella sp. represents a prime example of how antibiotic resistance determinants can be acquired by uncommon pathogens.
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http://dx.doi.org/10.1016/j.jgar.2017.06.005DOI Listing
December 2017

Matrix-assisted Laser Desorption Ionization-Time-of-Flight Mass Spectrometry (MALDI-TOF MS) as a Reliable Tool to Identify Species of Catalase-negative Gram-positive Cocci not Belonging to the Genus.

Open Microbiol J 2016 28;10:202-208. Epub 2016 Dec 28.

Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Laboratorio de Bacteriología, Departamento de Bioquímica Clínica Hospital de Clínicas José de San Martín Ciudad Autónoma de Buenos Aires, Argentina.

Objective: To evaluate the performance of matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) by using 190 Catalase-negative Gram-Positive Cocci (GPC) clinical isolates.

Methods: All isolates were identified by conventional phenotypic tests following the proposed scheme by Ruoff and Christensen and MALDI-TOF MS (Bruker Daltonics, BD, Bremen, Germany). Two different extraction methods (direct transfer formic acid method on spot and ethanol formic acid extraction method) and different cut-offs for genus/specie level identification were used. The score cut-offs recommended by the manufacturer (≥ 2.000 for species-level, 1.700 to 1.999 for genus level and <1.700 no reliable identification) and lower cut-off scores (≥1.500 for genus level, ≥ 1.700 for species-level and score <1.500 no reliable identification) were considered for identification. A minimum difference of 10% between the top and next closest score was required for a different genus or species. MALDI-TOF MS identification was considered correct when the result obtained from MS database agreed with the phenotypic identification result. When both methods gave discordant results, the 16S rDNA or genes sequencing was considered as the gold standard identification method. The results obtained by MS concordant with genes sequencing, although discordant with conventional phenotyping, were considered correct. MS results discordant with 16S or A identification were considered incorrect.

Results: Using the score cut-offs recommended by the manufacturer, 97.37% and 81.05% were correctly identified to genus and species level, respectively. On the other hand, using lower cut-off scores for identification, 97.89% and 94.21% isolates were correctly identified to genus and species level respectively by MALDI-TOF MS and no significant differences between the results obtained with two extraction methods were obtained.

Conclusion: The results obtained suggest that MALDI-TOF MS has the potential of being an accurate tool for Catalase-negative GPC identification even for those species with difficult diagnosis as , , , among others. Nevertheless, expansion of the library, especially including more strains with different spectra on the same species might overcome potential "intraspecies" variability problems. Moreover, a decrease of the identification scores for species and genus-level identification must be considered since it may improve the MALDI-TOF MS accuracy.
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http://dx.doi.org/10.2174/1874285801610010202DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5278551PMC
December 2016

Antimicrobial susceptibility of clinical isolates of Actinomyces and related genera reveals an unusual clindamycin resistance among Actinomyces urogenitalis strains.

J Glob Antimicrob Resist 2017 03 18;8:115-120. Epub 2017 Jan 18.

Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Departamento de Bioquímica Clínica, Hospital de Clínicas José de San Martín, Ciudad Autónoma de Buenos Aires, Argentina.

Objectives: Patterns of antimicrobial susceptibility in Actinomyces and related genera are very limited in the literature. Data of predominant susceptibility profiles could contribute to the establishment of an accurate empirical treatment.

Methods: A total of 113 isolates from clinical samples were included in this study. Each isolate was identified using phenotypic methods and MALDI-TOF/MS. When discrepancies were observed, 16S rRNA gene sequencing was performed. The minimum inhibitory concentrations (MICs) of nine antimicrobial agents (penicillin, ceftriaxone, linezolid, tetracycline, clindamycin, erythromycin, ciprofloxacin, levofloxacin and vancomycin) were tested against the species Actinotignum schaalii (n=23), Actinomyces turicensis (n=18), Actinomyces europaeus (n=13), Actinomyces naeslundii/Actinomyces viscosus group (n=12), Actinomyces urogenitalis (n=11), Actinomyces radingae (n=11), Actinomyces neuii (n=9), Actinomyces odontolyticus (n=8), Bifidobacterium scardovii (n=3), Actinomyces graevenitzii (n=2), Alloscardovia omnicolens (n=2) and Varibaculum cambriense (n=1).

Results: All of the isolates were susceptible to penicillin, ceftriaxone, vancomycin and linezolid. Almost all of the A. urogenitalis isolates (8/11) were resistant to clindamycin and showed susceptibility to erythromycin, suggesting an L-phenotype, however no determinants of clindamycin resistance (lnu and lsa genes) were detected by PCR. High MIC values to quinolones were observed in 54/113 isolates (47.8%). All of the A. urogenitalis isolates were highly resistant to ciprofloxacin and levofloxacin.

Conclusions: These data highlight the importance of ongoing surveillance to provide relevant information for empirical management of infections caused by these organisms.
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http://dx.doi.org/10.1016/j.jgar.2016.11.007DOI Listing
March 2017

The Genetic Analysis of an Acinetobacter johnsonii Clinical Strain Evidenced the Presence of Horizontal Genetic Transfer.

PLoS One 2016 22;11(8):e0161528. Epub 2016 Aug 22.

Instituto de Investigaciones en Microbiología y Parasitología Médica (IMPaM, UBA-CONICET), Buenos Aires, Argentina.

Acinetobacter johnsonii rarely causes human infections. While most A. johnsonii isolates are susceptible to virtually all antibiotics, strains harboring a variety of β-lactamases have recently been described. An A. johnsonii Aj2199 clinical strain recovered from a hospital in Buenos Aires produces PER-2 and OXA-58. We decided to delve into its genome by obtaining the whole genome sequence of the Aj2199 strain. Genome comparison studies on Aj2199 revealed 240 unique genes and a close relation to strain WJ10621, isolated from the urine of a patient in China. Genomic analysis showed evidence of horizontal genetic transfer (HGT) events. Forty-five insertion sequences and two intact prophages were found in addition to several resistance determinants such as blaPER-2, blaOXA-58, blaTEM-1, strA, strB, ereA, sul1, aacC2 and a new variant of blaOXA-211, called blaOXA-498. In particular, blaPER-2 and blaTEM-1 are present within the typical contexts previously described in the Enterobacteriaceae family. These results suggest that A. johnsonii actively acquires exogenous DNA from other bacterial species and concomitantly becomes a reservoir of resistance genes.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0161528PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4993456PMC
August 2017

Draft Genome Sequence of Empedobacter (Formerly Wautersiella) falsenii comb. nov. Wf282, a Strain Isolated from a Cervical Neck Abscess.

Genome Announc 2015 Apr 2;3(2). Epub 2015 Apr 2.

Department of Biological Science, Center for Applied Biotechnology Studies, California State University Fullerton, Fullerton, California, USA

Empedobacter (formerly Wautersiella) falsenii comb. nov. strain Wf282 was isolated from a cervical neck abscess sample from an 18-year-old female patient. The isolate was resistant to many antibiotics, including meropenem and colistin. The total DNA from the multidrug-resistant E. falsenii comb. nov. Wf282 clinical isolate was sequenced.
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http://dx.doi.org/10.1128/genomeA.00235-15DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4384494PMC
April 2015

Evaluation of matrix-assisted laser desorption ionization-time-of-flight mass spectrometry for species identification of nonfermenting Gram-negative bacilli.

J Microbiol Methods 2015 May 10;112:24-7. Epub 2015 Mar 10.

Laboratorio de Bacteriología, Departamento de Bioquímica Clínica, Hospital de Clínicas José de San Martín, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Ciudad Autónoma de Buenos Aires, Argentina.

Matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) to identify 396 Nonfermenting Gram-Negative Bacilli clinical isolates was evaluated in comparison with conventional phenotypic tests and/or molecular methods. MALDI-TOF MS identified to species level 256 isolates and to genus or complex level 112 isolates. It identified 29 genera including uncommon species.
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http://dx.doi.org/10.1016/j.mimet.2015.03.004DOI Listing
May 2015

Draft genome sequence of a taxonomically unique acinetobacter clinical strain with proteolytic and hemolytic activities.

Genome Announc 2015 Mar 5;3(2). Epub 2015 Mar 5.

Acinetobacter sp. strain A47, which has been recovered from several soft tissue samples from a patient undergoing reconstructive surgery due to a traumatic amputation, was categorized as a taxonomically unique bacterial strain. The molecular analysis based on three housekeeping protein-coding genes (16S rRNA, rpoB, and gyrB) showed that strain A47 does not belong to any of the hitherto known taxa and may represent a previously undescribed Acinetobacter species.
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http://dx.doi.org/10.1128/genomeA.00030-15DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4358375PMC
March 2015

Draft Genome Sequence of an Extensively Drug-Resistant Acinetobacter baumannii Indigo-Pigmented Strain.

Genome Announc 2014 Nov 13;2(6). Epub 2014 Nov 13.

Last year in 2013, we reported an outbreak due to indigo-pigmented Acinetobacter baumannii strains in a hospital from Buenos Aires, Argentina. Here, we present the draft genome sequence of one of the strains (A. baumannii A33405) involved in the outbreak. This isolate was categorized as extensively drug-resistant (XDR) and harbors different genetic elements associated with horizontal genetic transfer and multiple antibiotic resistances.
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http://dx.doi.org/10.1128/genomeA.01146-14DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4241659PMC
November 2014

A taxonomically unique Acinetobacter strain with proteolytic and hemolytic activities recovered from a patient with a soft tissue injury.

J Clin Microbiol 2015 Jan 12;53(1):349-51. Epub 2014 Nov 12.

Instituto de Microbiología y Parasitología Médica (IMPaM, UBA-CONICET), Buenos Aires, Argentina Center for Applied Biotechnology Studies, Department of Biological Science, California State University, Fullerton, Fullerton, California, USA

A taxonomically unique bacterial strain, Acinetobacter sp. A47, has been recovered from several soft tissue samples from a patient undergoing reconstructive surgery owing to a traumatic amputation. The results of 16S rRNA, rpoB, and gyrB gene comparative sequence analyses showed that A47 does not belong to any of the hitherto-known taxa and may represent an as-yet-unknown Acinetobacter species. The recognition of this novel organism contributes to our knowledge of the taxonomic complexity underlying infections caused by Acinetobacter.
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http://dx.doi.org/10.1128/JCM.02625-14DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4290954PMC
January 2015

Comparison of the Bruker MALDI-TOF mass spectrometry system and conventional phenotypic methods for identification of Gram-positive rods.

PLoS One 2014 3;9(9):e106303. Epub 2014 Sep 3.

Instituto de Fisiopatología y Bioquímica Clínica, Hospital de Clínicas José de San Martín, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Ciudad Autónoma de Buenos Aires, Argentina.

In recent years, MALDI-TOF Mass Spectrometry (MS) method has emerged as a promising and a reliable tool for bacteria identification. In this study we compared Bruker MALDI-TOF MS and conventional phenotypic methods to identify a collection of 333 Gram-positive clinical isolates comprising 22 genera and 60 species. 16S rRNA sequencing was the reference molecular technique, and rpoB gene sequecing was used as a secondary gene target when 16Sr RNA did not allow species identification of Corynebacterium spp. We also investigate if score cut-offs values of ≥ 1,5 and ≥ 1,7 were accurate for genus and species-level identification using the Bruker system. Identification at species level was obtained for 92,49% of Gram-positive rods by MALDI-TOF MS compared to 85,89% by phenotypic method. Our data validates the score ≥ 1,5 for genus level and ≥ 1,7 for species-level identification in a large and diverse collection of Gram-positive rods. The present study has proved the accuracy of MALDI-TOF MS as an identification method in Gram-positive rods compared to currently used methods in routine laboratories.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0106303PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4153636PMC
May 2015

Presence of OXA-type enzymes in Achromobacter insuavis and A. dolens.

Curr Microbiol 2014 Oct 4;69(4):501-6. Epub 2014 Jun 4.

IMPaM (UBA-CONICET), University of Buenos Aires, Buenos Aires, Argentina.

The accurate species identification of Achromobacter isolates is difficult and the clinical isolates of this genus are mostly referred as A. xylosoxidans. Here, we report new OXA variants in 2 isolates identified as A. insuavis (A114, A79) and 1 isolate identified as A. dolens (A336). These results suggest that different bla OXA genes are ubiquitous in the different species of Achromobacter spp. The role of the other species of Achromobacter in clinical samples needs to be reevaluated, and the proper identification is absolutely necessary to understand the epidemiology of this genus.
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http://dx.doi.org/10.1007/s00284-014-0611-yDOI Listing
October 2014

Bacteremia caused by an Acinetobacter junii strain harboring class 1 integron and diverse DNA mobile elements.

J Infect Dev Ctries 2014 May 14;8(5):666-9. Epub 2014 May 14.

Facultad de Medicina, Universidad de Buenos Aires, Argentina.

Introduction: Infections caused by Acinetobacter junii are rarely reported. However, some outbreaks of septicemia in neonates and pediatric oncology patients, as well as meningitis, peritonitis, and ocular infection have been described. Since it is highly infrequent to find the molecular characterization of A. junii strains in literature, in this study we described the molecular characterization of A. junii isolates recovered from blood samples of a renal transplant patient.

Methodology: The case was defined as a catheter-related bacteremia caused by A. junii. The patient responded favorably after catheter removal and treatment with ciprofloxacin.

Results And Conclusion: The complete molecular characterization of the isolate showed that it harbored a class 1 integron and diverse DNA mobile elements. This explains its genomic plasticity for acquiring antimicrobial resistance determinants and for adapting to a nosocomial niche.
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http://dx.doi.org/10.3855/jidc.3747DOI Listing
May 2014

Actinobaculum schaalii causing urinary tract infections: report of four cases from Argentina.

J Infect Dev Ctries 2014 Feb 13;8(2):240-4. Epub 2014 Feb 13.

Universidad de Buenos Aires, Ciudad Autónoma de Buenos Aires, Argentina.

Actinobaculum schaalii may be a more common urinary tract pathogen than previously described. Here we report four cases of A. schaalii UTIs and we also propose a simple identification scheme to be used in the conventional microbiology laboratory based on standard biochemical tests.
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http://dx.doi.org/10.3855/jidc.3748DOI Listing
February 2014

Outbreak of extensively drug-resistant Acinetobacter baumannii indigo-pigmented strains.

J Clin Microbiol 2013 Nov 28;51(11):3726-30. Epub 2013 Aug 28.

Instituto de Microbiología y Parasitología Médica (IMPaM, UBA-CONICET), Facultad de Medicina, Universidad de Buenos Aires.

Acinetobacter baumannii pigmented strains are not common in clinical settings. Here, we report an outbreak caused by indigo-pigmented A. baumannii strains isolated in an acute care hospital in Argentina from March to September 2012. Pan-PCR assays exposed a unique pattern belonging to the recently described regional CC113(B)/CC79(P) clonal complex that confirms the relevant relationships among the indigo-pigmented A. baumannii strains. All of them were extensively drug resistant and harbored different genetic elements associated with horizontal genetic transfer, such as the transposon Tn2006, class 2 integrons, AbaR-type islands, IS125, IS26, strA, strB, florR, and the small recombinase ISCR2 associated with the sul2 gene preceded by ISAba1.
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http://dx.doi.org/10.1128/JCM.01388-13DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3889758PMC
November 2013

[Bordetella holmesii endocarditis in an asplenic patient].

Rev Argent Microbiol 2013 Apr-Jun;45(2):86-8

Laboratorio de Microbiología, Hospital Naval Pedro Mallo, Ciudad Autónoma de Buenos Aires, Argentina.

The case of a 52-year-old female patient with a history of critical aortic stenosis, hypothyroidism and splenectomy as treatment for her Hodgkin's lymphoma is herein presented. In April 2011, the patient was admitted to the cardiology service due to global heart failure, fever and poor response to diuretic and vasodilator therapy. A transesophageal echocardiogram showed images compatible with vegetations in the aortic, pulmonary, and mitral valves. A diagnosis of infective endocarditis was made. Growth of gram-negative coccobacilli was observed in two blood culture sets. The microorganism was finally identified as Bordetella holmesii. The patient was treated with ceftriaxone 1 g every 12 hours for 28 days with favorable outcome.
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http://dx.doi.org/10.1016/s0325-7541(13)70004-xDOI Listing
November 2013