Antibiotic susceptibility of Listeria monocytogenes in Argentina.

INTRODUCTION: Listeria monocytogenes is the causative agent of listeriosis, a food-borne disease that mainly affects pregnant women, the elderly, and immunocompromised patients. The primary treatment of choice of listeriosis is the combination of ampicillin or penicillin G, with an aminoglycoside, classically gentamicin. The second-choice therapy for patients allergic to ß-lactams is the combination of trimethoprim with a sulfonamide (such as co-trimoxazole). The aim of this study was to analyze the antimicrobial susceptibility profile of strains isolated from human infections and food during the last two decades in Argentina. METHODS: The minimal inhibitory concentration (MIC) of 8 antimicrobial agents was determined for a set of 250 strains of L. monocytogenes isolated in Argentina during the period 1992-2012. Food-borne and human isolates were included in this study. The antibiotics tested were ampicillin, chloramphenicol, trimethoprim-sulfamethoxazole, erythromycin, gentamicin, penicillin G, tetracycline and rifampicin. Breakpoints for penicillin G, ampicillin and trimethoprim-sulfamethoxazole were those given in the CLSI for L. monocytogenes. CLSI criteria for staphylococci were applied to the other antimicrobial agents tested. Strains were serotyped by PCR, and confirmed by an agglutination method. RESULTS: Strains recovered from human listeriosis patients showed a prevalence of serotype 4b (71%), with the remaining 29% corresponding to serotype 1/2b. Serotypes among food isolates were distributed as 62% serotype 1/2b and 38% serotype 4b. All antimicrobial agents showed good activity. CONCLUSION: The strains of L. monocytogenes isolated in Argentina over a period of 20 years remain susceptible to antimicrobial agents, and that susceptibility pattern has not changed during this period.

First Argentine database for the accurate identification of Brucella to species level by MALDI-TOF MS.

MALDI-TOF mass spectrometry (MS) has proven to be a fast and reliable method for the identification of a large number of taxonomic groups. It offers the advantage of being able to incorporate protein spectra of microorganisms that are absent or poorly represented in commercial databases, such as the genus Brucella. The aim of the study was to build the first database of protein spectra of local biological variants of Brucella in Argentina and of standard strains. First, the identification performance of a panel of 135 strains was evaluated with the Swedish database ¨Folkhälsomyndigheten¨ (containing protein spectra of several international standards of the genus Brucella) imported from the open access site https://spectra.folkhalsomyndigheten.se/spectra/. With this library 100 % of the strains were correctly identified by mass spectrometry to genus level, but not to species level. Due to the limitation found, an in-house database was designed with local Brucella isolates from Argentina and standard strains used in routine bacteriological diagnosis. For its validation, a panel of strains, different from those used to develop the extended local database (n: 177), was used to, simultaneously, challenge both libraries. The samples were processed by triplicate and the results obtained were: 177 strains correctly identified to genus and species level compared to the gold standard method (phenotypic typing), meeting the criteria accepted by the literature and the manufacturer as reliable identification. Only 2 of these isolates had score values lower than 2 (1.862) and were therefore not included in the calculation of results. According to these results, MALDI-TOF MS is a fast and reliable method for the routine identification of the different Brucella species, and even has the advantage of reducing the time of exposure to pathogenic microorganisms for laboratorians. It could be considered a valuable technique to replace, in the near future, the current conventional techniques due to the ease of transferring protein spectra, avoiding the use of reference strains that are difficult to find commercially available and commonly used in phenotypic typing.

Rapid and accurate detection of Shiga toxin-producing Escherichia coli (STEC) serotype O157 : H7 by mass spectrometry directly from the isolate, using 10 potential biomarker peaks and machine learning predictive models.

Introduction. The different pathotypes of Escherichia coli can produce a large number of human diseases. Surveillance is complex since their differentiation is not easy. In particular, the detection of Shiga toxin-producing Escherichia coli (STEC) serotype O157 : H7 consists of stool culture of a diarrhoeal sample on enriched and/or selective media and identification of presumptive colonies and confirmation, which require a certain level of training and are time-consuming and expensive.Hypothesis. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a quick and easy way to obtain the protein spectrum of a microorganism, identify the genus and species, and detect potential biomarker peaks of certain characteristics.Aim. To verify the usefulness of MALDI-TOF MS to rapidly identify and differentiate STEC O157 : H7 from other E. coli pathotypes.Methodology. The direct method was employed, and the information obtained using Microflex LT platform-based analysis from 60 clinical isolates (training set) was used to detect differences between the peptide fingerprints of STEC O157 : H7 and other E. coli strains. The protein profiles detected laid the foundations for the development and evaluation of machine learning predictive models in this study.Results. The detection of potential biomarkers in combination with machine learning predictive models in a new set of 142 samples, called 'test set', achieved 99.3 % (141/142) correct classification, allowing us to distinguish between the isolates of STEC O157 : H7 and the other E. coli group. Great similarity was also observed with respect to this last group and the Shigella species when applying the potential biomarkers algorithm, allowing differentiation from STEC O157 : H7Conclusion. Given that STEC O157 : H7 is the main causal agent of haemolytic uremic syndrome, and based on the performance values obtained in the present study (sensitivity=98.5 % and specificity=100.0 %), the implementation of this technique provides a proof of principle for MALDI-TOF MS and machine learning to identify biomarkers to rapidly screen or confirm STEC O157 : H7 versus other diarrhoeagenic E. coli in the future.

A combined approach of MALDI-TOF mass spectrometry and multivariate analysis as a potential tool for the detection of SARS-CoV-2 virus in nasopharyngeal swabs.

Coronavirus disease 2019, known as COVID-19, is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The early, sensitive and specific detection of SARS-CoV-2 virus is widely recognized as the critical point in responding to the ongoing outbreak. Currently, the diagnosis is based on molecular real time RT-PCR techniques, although their implementation is being threatened due to the extraordinary demand for supplies worldwide. That is why the development of alternative and / or complementary tests becomes so relevant. Here, we exploit the potential of mass spectrometry technology combined with machine learning algorithms, for the detection of COVID-19 positive and negative protein profiles directly from nasopharyngeal swabs samples. According to the preliminary results obtained, accuracy = 67.66 %, sensitivity = 61.76 %, specificity = 71.72 %, and although these parameters still need to be improved to be used as a screening technique, mass spectrometry-based methods coupled with multivariate analysis showed that it is an interesting tool that deserves to be explored as a complementary diagnostic approach due to the low cost and fast performance. However, further steps, such as the analysis of a large number of samples, should be taken in consideration to determine the applicability of the method developed.

Utility of platforms Viteks MS and Microflex LT for the identification of complex clinical isolates that require molecular methods for their taxonomic classification.

Mass spectrometry has revolutionized the clinical microbiology field in America's and Europe's industrialized countries, for being a fast, reliable and inexpensive technique. Our study is based on the comparison of the performance of two commercial platforms, Microflex LT (Bruker Daltonics, Bremen, Germany) and Vitek MS (bioMérieux, Marcy l´Etoile, France) for the identification of unusual and hard-to-diagnose microorganisms in a Reference Laboratory in Argentina. During a four-month period (February-May 2018) the diagnostic efficiency and the concordance between both systems were assessed, and the results were compared with the polyphasic taxonomic identification of all isolates. The study included 265 isolates: 77 Gram-Negative Bacilli, 33 Gram-Positive Cocci, 40 Anaerobes, 35 Actinomycetales, 19 Fastidious Microorganisms and 61 Gram-Positive Bacilli. All procedures were practiced according to the manufacturer's recommendations in each case by duplicate, and strictly in parallel. Other relevant factors, such as the utility of the recommended extraction protocols, reagent stability and connectivity were also evaluated. Both systems correctly identified the majority of the isolates to species and complex level (82%, 217/265). Vitex MS achieved a higher number of correct species-level identifications between the gram-positive microorganisms; however, it presented greater difficulty in the identification of non-fermenting bacilli and a higher number of incorrect identifications when the profile of the microorganism was not represented in the commercial database. Both platforms showed an excellent performance on the identification of anaerobic bacteria and fastidious species. Both systems enabled the fast and reliable identification of most of the tested isolates and were shown to be very practical for the user.

Orquiepididimitis por Haemophilus parainfluenzae: caso clínico y revisión de la literatura / Orchiepididymitis due to Haemophilus parainfluenzae: case report and review of the literature / Orquiepididimite por Haemophilus parainfluenzae: caso clínico e revisão da literatura

Resumen Haemophilus parainfluenzae forma parte de la microbiota normal de la cavidad oral y del tracto respiratorio superior. Es un reconocido agente causal de endocarditis y, con menor frecuencia, de enfermedades como neumonía, sepsis, osteomielitis, celulitis, meningitis y gastroenteritis aguda. Aquí se presenta un caso de orquiepididimitis en un joven adulto donde H. parainfluenzae, confirmado por espectrometría de masas (MALDI-TOF MS), fue el único patógeno detectado. Este caso contribuye a valorar el rol de H. parainfluenzae como patógeno humano, aislado a partir de sitios diferentes del torrente sanguíneo y las vías respiratorias.

Abstract Haemophilus parainfluenzae is part of the normal microbiota of the oral cavity and the upper respiratory tract. It is a recognised causal agent of endocarditis and, less frequently, of diseases such as pneumonia, sepsis, osteomyelitis, cellulitis, meningitis, and acute gastroenteritis. A case of orchiepididymitis in a young adult is reported, where H. parainfluenzae, confirmed by mass spectrometry (MALDI-TOF MS), was the only pathogen detected. This case contributes to assess the role of H. parainfluenzae as a human pathogen, isolated from sites other than the bloodstream and the respiratory tract.

Resumo Haemophilus parainfluenzae faz parte da microbiota normal da cavidade oral e do trato respiratório superior. É um reconhecido agente causal de endocardite e, menos frequentemente, de doenças como pneumonia, sepse, osteomielite, celulite, meningite e gastroenterite aguda. Aqui é relatado um caso de orquiepididimite em um adulto jovem onde H. parainfluenzae, confirmado por espectrometria de massa (MALDI-TOF MS), foi o único patógeno detectado. Este caso contribui para avaliar o papel do H. parainfluenzae como patógeno humano, isolado de outros locais que não sejam a corrente sanguínea e o trato respiratório.

Antibiotic susceptibility of Listeria monocytogenes in Argentina / Sensibilidad a los antimicrobianos de L. monocytogenes en Argentina

INTRODUCTION: Listeria monocytogenes is the causative agent of listeriosis, a food-borne disease that mainly affects pregnant women, the elderly, and immunocompromised patients. The primary treatment of choice of listeriosis is the combination of ampicillin or penicillin G, with an aminoglycoside, classically gentamicin. The second-choice therapy for patients allergic to â-lactams is the combination of trimethoprim with a sulfonamide (such as co-trimoxazole). The aim of this study was to analyze the antimicrobial susceptibility profile of strains isolated from human infections and food during the last two decades in Argentina. METHODS: The minimal inhibitory concentration (MIC) of 8 antimicrobial agents was determined for a set of 250 strains of L. monocytogenes isolated in Argentina during the period 1992-2012. Food-borne and human isolates were included in this study. The antibiotics tested were ampicillin, chloramphenicol, trimethoprim-sulfamethoxazole, erythromycin, gentamicin, penicillin G, tetracycline and rifampicin. Breakpoints for penicillin G, ampicillin and trimethoprim-sulfamethoxazole were those given in the CLSI for L. monocytogenes. CLSI criteria for staphylococci were applied to the other antimicrobial agents tested. Strains were serotyped by PCR, and confirmed by an agglutination method. RESULTS: Strains recovered from human listeriosis patients showed a prevalence of serotype 4b (71%), with the remaining 29% corresponding to serotype 1/2b. Serotypes among food isolates were distributed as 62% serotype 1/2b and 38% serotype 4b. All antimicrobial agents showed good activity. CONCLUSION: The strains of L. monocytogenes isolated in Argentina over a period of 20 years remain susceptible to antimicrobial agents, and that susceptibility pattern has not changed during this period

INTRODUCCIÓN: Listeria monocytogenes es el agente etiológico de la listeriosis, una enfermedad transmitida por los alimentos que afecta principalmente a las mujeres embarazadas, los ancianos y pacientes inmunocomprometidos. El tratamiento antibiótico de elección es la combinación de ampicilina o penicilina G con un aminoglucósido; generalmente gentamicina. La segunda opción de terapia para los pacientes alérgicos a los beta-lactámicos es la asociación de trimetoprima con una sulfonamida (cotrimoxazol). El objetivo de este estudio fue analizar el perfil de susceptibilidad antimicrobiana de las cepas aisladas de infección invasiva humana y de alimentos durante las dos últimas décadas en la Argentina. Métodos: Se determinó la concentración inhibitoria mínima (CIM) de 8 agentes antimicrobianos en 250 cepas de L .monocytogenes aisladas durante el período 1992-2012. Se incluyeron aislamientos de origen humano y de alimentos. Los antibióticos ensayados fueron: ampicilina, cloranfenicol, cotrimoxazol, eritromicina, gentamicina, penicilina G, tetraciclina y rifampicina. El criterio de interpretación utilizado fue el indicado por el CLSI. Los aislamientos fueron serotipificados por PCR y por el método de aglutinación. RESULTADOS: Los aislamientos humanos se distribuyeron con una prevalencia del serotipo 4b (71%); el 29% restante correspondió al serotipo 1/2b. Los aislamientos de alimentos correspondieron: 62% serotipo al serotipo 1/2b y 38% al serotipo 4b. Todos los agentes antimicrobianos mostraron buena actividad. Conclusión: Las cepas de L. monocytogenes aisladas en Argentina durante un período de 20 años siguen siendo susceptibles a los agentes antimicrobianos y dicho patrón de susceptibilidad no ha cambiado durante este período