Hetero-antagonism of avibactam and sulbactam with cefiderocol in carbapenem-resistant Acinetobacter spp.

Cefiderocol, a siderophore-cephalosporine conjugate antibiotic, shows promise as a therapeutic option for carbapenem-resistant (CR) Acinetobacter infections. While resistance has already been reported in A. baumannii, combination therapies with avibactam or sulbactam reduce MICs of cefiderocol, extending its efficacy. However, careful consideration is necessary when using these combinations. In our experiments, exposure of A. baumannii and A. lwoffii to cefiderocol and sulbactam or avibactam led to the selection of cefiderocol-resistant strains. Three of those were subjected to whole genome sequencing and transcriptomic analysis. The strains all possessed synonymous and non-synonymous substitutions and short deletions. The most significant mutations affected efflux pumps, transcriptional regulators, and iron homeostasis genes. Transcriptomics showed significant alterations in expression levels of outer membrane proteins, iron homeostasis, and ß-lactamases, suggesting adaptive responses to selective pressure. This study underscores the importance of carefully assessing drug synergies, as they may inadvertently foster the selection of resistant variants and complicate the management of CR Acinetobacter infections.IMPORTANCEThe emergence of carbapenem-resistant Acinetobacter strains as a serious global health threat underscores the urgent need for effective treatment options. Although few drugs show promise against CR Acinetobacter infections, resistance to both drugs has been reported. In this study, the molecular characterization of spontaneous cefiderocol-resistant variants, a CR A. baumannii strain with antagonism to sulbactam, and an A. lwoffii strain with antagonism to avibactam, provides valuable insights into the mechanisms of resistance to cefiderocol. Some mechanisms observed are associated with mutations affecting efflux pumps, regulators, and iron homeostasis genes. These findings highlight the importance of understanding resistance mechanisms to optimize treatment options. They also emphasize the importance of early evaluation of drug synergies to address the challenges of antimicrobial resistance in Acinetobacter infections.

Seven-day antibiotic therapy for Enterobacterales bacteremia in high-risk neutropenic patients: toward a new paradigm.

PURPOSE: Data on short courses of antibiotic therapy for Enterobacterales bacteremia in high-risk neutropenic patients are limited. The aim of the study was to describe and compare the frequency of bacteremia relapse, 30-day overall and infection-related mortality, Clostridiodes difficile infection and length of hospital stay since bacteremia among those who received antibiotic therapy for 7 or 14 days. METHODS: This is a multicenter, prospective, observational cohort study in adult high-risk neutropenic patients with hematologic malignancies or hematopoietic stem cell transplant and monomicrobial Enterobacterales bacteremia. They received appropriate empirical antibiotic therapy, had a clinical response within 7 days, and infection source control. Clinical, epidemiological and outcomes variables were compared based on 7 or 14 days of AT. RESULTS: Two hundred patients were included (100, 7-day antibiotic therapy; 100, 14-day antibiotic therapy). Escherichia coli was the pathogen most frequently isolated (47.5%), followed by Klebsiella sp. (40.5%). Among those patients that received 7-day vs. 14-day antibiotic course, a clinical source of bacteremia was found in 54% vs. 57% (p = 0.66), multidrug-resistant Enterobacterales isolates in 28% vs. 30% (p = 0.75), and 40% vs. 47% (p = 0.31) received combined empirical antibiotic therapy. Overall mortality was 3% vs. 1% (p = 0.62), in no case related to infection; bacteremia relapse was 7% vs. 2% (p = 0.17), and length of hospital stay since bacteremia had a median of 9 days (IQR: 7-15) vs. 14 days (IQR: 13-22) (p = < 0.001). CONCLUSIONS: These data suggest that seven-day antibiotic therapy might be adequate for patients with high-risk neutropenia and Enterobacterales bacteremia, who receive appropriate empirical therapy, with clinical response and infection source control.

Improved Blue Carba test and Carba NP test for detection and classification of major Class A and B carbapenemases, including dual producers, among Gram-negative bacilli.

Prompt and precise identification of carbapenemase-producing organisms is crucial for guiding clinical antibiotic treatments and limiting transmission. Here, we propose modifying the Blue Carba test (BCT) and Carba NP-direct (CNPd) to identify molecular carbapenemase classes, including dual carbapenemase strains, by adding specific Class A and Class B inhibitors. We tested 171 carbapenemase-producing Gram-negative bacilli strains-21 in Class A (KPC, NMC, SME), 58 in Class B (IMP, VIM, NDM, SPM), and 92 with dual carbapenemase production (KPC+NDM, KPC+IMP, KPC+VIM), all previously positive with BCT or CNPd. We also included 13 carbapenemase non-producers. ß-lactamases were previously characterized by PCR. The improved BCT/CNPd methods detect imipenem hydrolysis from an imipenem-cilastatin solution, using pH indicators and Class A (avibactam) and/or Class B (EDTA) inhibitors. Results were interpreted visually based on color changes. CNPd achieved 99.4% sensitivity and 100% specificity in categorizing carbapenemases, while BCT had 91.8% sensitivity and 100% specificity. Performance varied by carbapenemase classes: both tests classified all Class A-producing strains. For Class B, the CNP test identified 57/58 strains (98.3%), whereas the BCT test, 45/58 strains (77.6%), with non-fermenters posing the greatest detection challenge. For Classes A plus B dual producers, both tests performed exceptionally well, with only one indeterminate strain for the BCT. The statistical comparison showed both methods had similar times to a positive result, with differences based on the carbapenemase class or bacterial group involved. This improved assay rapidly distinguishes major Class A or Class B carbapenemase producers among Gram-negative bacilli, including dual-class combinations, in less than 2 hours. IMPORTANCE: Rapid and accurate identification of carbapenemase-producing organisms is of vital importance in guiding appropriate clinical antibiotic treatments and curbing their transmission. The emergence of negative bacilli carrying multiple carbapenemase combinations during and after the severe acute respiratory syndrome coronavirus 2 pandemic has posed a challenge to the conventional biochemical tests typically used to determine the specific carbapenemase type in the isolated strains. Several initiatives have aimed to enhance colorimetric methods, enabling them to independently identify the presence of Class A or Class B carbapenemases. Notably, no previous efforts have been made to distinguish both classes simultaneously. Additionally, these modifications have struggled to differentiate between carriers of multiple carbapenemases, a common occurrence in many Latin American countries. In this study, we introduced specific Class A and Class B carbapenemase inhibitors into the Blue Carba test (BCT) and Carba NP-direct (CNP) colorimetric assays to identify the type of carbapenemase, even in cases of multiple carbapenemase producers within these classes. These updated assays demonstrated exceptional sensitivity and specificity (≥ 90%) all within a rapid turnaround time of under 2 hours, typically completed in just 45 minutes. These in-house enhancements to the BCT and CNP assays present a rapid, straightforward, and cost-effective approach to determining the primary carbapenemase classes. They could serve as a viable alternative to molecular biology or immuno-chromatography techniques, acting as an initial diagnostic step in the process.

Comparison of available methods to evaluate cefiderocol susceptibility in Acinetobacter spp.

Recently, considerable uncertainty has arisen concerning the appropriate susceptibility testing for cefiderocol in gram-negative bacilli, particularly in the context of its application to Acinetobacter spp. The optimal method for assessing the susceptibility levels of Acinetobacter spp. to cefiderocol remains a subject of debate due to substantial disparities observed in the values obtained through various testing procedures. This study employed four minimum inhibitory concentration (MIC) methodologies and the disk diffusion to assess the susceptibility of twenty-seven carbapenem resistant (CR)-Acinetobacter strains to cefiderocol. The results from our study reveal significant variations in the minimum inhibitory concentration (MIC) values obtained with the different methods and in the level of agreement in interpretation categories between the different MIC methods and the disk diffusion test. Among the MIC methods, there was relatively more consistency in reporting the interpretation categories. For European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints, the categorical agreement (CA) for MIC methods ranged between 66.7 and 81.5%. On the other hand, the essential agreement (EA) values were as low as 18.5-29.6%. The CA between MIC methods and disk diffusion was 81.5%. These results emphasize the need for a reliable, accurate, and clinically validated methodology to effectively assess the susceptibility of Acinetobacter spp. to cefiderocol. The wide variability observed in our study highlights the importance of standardizing the susceptibility testing process for cefiderocol to ensure consistent and reliable results for clinical decision-making.

Hetero-antagonism of avibactam and sulbactam with cefiderocol in carbapenem-resistant Acinetobacter spp.

The emergence of Gram-negative bacteria resistant to multiple antibiotics, particularly carbapenem-resistant (CR) Acinetobacter strains, poses a significant threat globally. Despite efforts to develop new antimicrobial therapies, limited progress has been made, with only two drugs-cefiderocol and sulbactam-durlobactam-showing promise for CR-Acinetobacter infections. Cefiderocol, a siderophore cephalosporin, demonstrates promising efficacy in the treatment of Gram-negative infections. However, resistance to cefiderocol has been reported in A. baumannii. Combination therapies, such as cefiderocol with avibactam or sulbactam, show reduced MICs against cefiderocol-non-susceptible strains with in vivo efficacy, although the outcomes can be complex and species-specific. In the present work, the molecular characterization of spontaneous cefiderocol-resistant variants, a CRAB strain displaying antagonism with sulbactam and an A. lwoffii strain showing antagonism with avibactam, were studied. The results reveal intriguing insights into the underlying mechanisms, including mutations affecting efflux pumps, transcriptional regulators, and iron homeostasis genes. Moreover, gene expression analysis reveals significant alterations in outer membrane proteins, iron homeostasis, and ß-lactamases, suggesting adaptive responses to selective pressure. Understanding these mechanisms is crucial for optimizing treatment strategies and preventing adverse clinical outcomes. This study highlights the importance of preemptively assessing drug synergies to navigate the challenges posed by antimicrobial resistance in CR-Acinetobacter infections.

KPC-2 allelic variants in Klebsiella pneumoniae isolates resistant to ceftazidime-avibactam from Argentina: blaKPC-80, blaKPC-81, blaKPC-96 and blaKPC-97.

Ceftazidime-avibactam (CZA) therapy has significantly improved survival rates for patients infected by carbapenem-resistant bacteria, including KPC producers. However, resistance to CZA is a growing concern, attributed to multiple mechanisms. In this study, we characterized four clinical CZA-resistant Klebsiella pneumoniae isolates obtained between July 2019 and December 2020. These isolates expressed novel allelic variants of blaKPC-2 resulting from changes in hotspots of the mature protein, particularly in loops surrounding the active site of KPC. Notably, KPC-80 had an K269_D270insPNK mutation near the Lys270-loop, KPC-81 had a del_I173 mutation within the Ω-loop, KPC-96 showed a Y241N substitution within the Val240-loop and KPC-97 had an V277_I278insNSEAV mutation within the Lys270-loop. Three of the four isolates exhibited low-level resistance to imipenem (4 µg/mL), while all remained susceptible to meropenem. Avibactam and relebactam effectively restored carbapenem susceptibility in resistant isolates. Cloning mutant blaKPC genes into pMBLe increased imipenem MICs in recipient Escherichia coli TOP10 for blaKPC-80, blaKPC-96, and blaKPC-97 by two dilutions; again, these MICs were restored by avibactam and relebactam. Frameshift mutations disrupted ompK35 in three isolates. Additional resistance genes, including blaTEM-1, blaOXA-18 and blaOXA-1, were also identified. Interestingly, three isolates belonged to clonal complex 11 (ST258 and ST11) and one to ST629. This study highlights the emergence of CZA resistance including unique allelic variants of blaKPC-2 and impermeability. Comprehensive epidemiological surveillance and in-depth molecular studies are imperative for understanding and monitoring these complex resistance mechanisms, crucial for effective antimicrobial treatment strategies. IMPORTANCE: The emergence of ceftazidime-avibactam (CZA) resistance poses a significant threat to the efficacy of this life-saving therapy against carbapenem-resistant bacteria, particularly Klebsiella pneumoniae-producing KPC enzymes. This study investigates four clinical isolates exhibiting resistance to CZA, revealing novel allelic variants of the key resistance gene, blaKPC-2. The mutations identified in hotspots surrounding the active site of KPC, such as K269_D270insPNK, del_I173, Y241N and V277_I278insNSEAV, prove the adaptability of these pathogens. Intriguingly, low-level resistance to imipenem and disruptions in porin genes were observed, emphasizing the complexity of the resistance mechanisms. Interestingly, three of four isolates belonged to clonal complex 11. This research not only sheds light on the clinical significance of CZA resistance but also shows the urgency for comprehensive surveillance and molecular studies to inform effective antimicrobial treatment strategies in the face of evolving bacterial resistance.

Inteligencia artificial en enfermedades infecciosas / Artificial intelligence in infectious diseases

Estamos asistiendo a una verdadera revolución tecnológi-ca en el campo de la salud. Los procesos basados en la aplicación de la inteligencia artificial (IA) y el aprendizaje automático (AA) están llegando progresivamente a todas las áreas disciplinares, y su aplicación en el campo de las enfermedades infecciosas es ya vertiginoso, acelerado por la pandemia de COVID-19.Hoy disponemos de herramientas que no solamente pue-den asistir o llevar adelante el proceso de toma de deci-siones basadas en guías o algoritmos, sino que también pueden modificar su desempeño a partir de los procesos previamente realizados. Desde la optimización en la identificación de microorganis-mos resistentes, la selección de candidatos a participar en ensayos clínicos, la búsqueda de nuevos agentes terapéu-ticos antimicrobianos, el desarrollo de nuevas vacunas, la predicción de futuras epidemias y pandemias, y el segui-miento clínico de pacientes con enfermedades infecciosas hasta la asignación de recursos en el curso de manejo de un brote son actividades que hoy ya pueden valerse de la inteligencia artificial para obtener un mejor resultado. El desarrollo de la IA tiene un potencial de aplicación expo-nencial y sin dudas será uno de los determinantes principa-les que moldearán la actividad médica del futuro cercano.Sin embargo, la maduración de esta tecnología, necesaria para su inserción definitiva en las actividades cotidianas del cuidado de la salud, requiere la definición de paráme-tros de referencia, sistemas de validación y lineamientos regulatorios que todavía no existen o son aún solo inci-pientes

We are in the midst of a true technological revolution in healthcare. Processes based upon artificial intelligence and machine learning are progressively touching all disciplinary areas, and its implementation in the field of infectious diseases is astonishing, accelerated by the COVID-19 pandemic. Today we have tools that can not only assist or carry on decision-making processes based upon guidelines or algorithms, but also modify its performance from the previously completed tasks. From optimization of the identification of resistant pathogens, selection of candidates for participating in clinical trials, the search of new antimicrobial therapeutic agents, the development of new vaccines, the prediction of future epidemics and pandemics, the clinical follow up of patients suffering infectious diseases up to the resource allocation in the management of an outbreak, are all current activities that can apply artificial intelligence in order to improve their final outcomes.This development has an exponential possibility of application, and is undoubtedly one of the main determinants that will shape medical activity in the future.Notwithstanding the maturation of this technology that is required for its definitive insertion in day-to-day healthcare activities, should be accompanied by definition of reference parameters, validation systems and regulatory guidelines that do not exist yet or are still in its initial stages

Plasmidic resistance to colistin mediated by mcr-1 gene in Escherichia coli clinical isolates in Argentina: A retrospective study, 2012–2018

[ABSTRACT]. Objective. To describe the resistance profile and the genetic characteristics of Escherichia coli isolates that harbor the mobilizable colistin resistance gene mcr-1 in Argentina. Methods. This was a retrospective study of 192 E. coli isolates positive for mcr-1 obtained from 69 hospitals of Buenos Aires City and 14 Argentinean provinces in 2012 – 2018. The antimicrobial susceptibility was performed by agar diffusion, broth macrodilution, and/or agar dilution. Standard polymerase chain reaction (PCR) was performed to detect resistance genes and incompatibility groups; specific PCR was applied to discriminate between blaCTX-M allelic groups and mcr-1.5 variant. The genetic relatedness among isolates was evaluated by XbaI-pulsed field gel electrophoresis and multilocus sequence typing in a subset of isolates. Results. All E. coli isolates showed minimal inhibitory concentrations to colistin ≥ 4μg/mL; nearly 50% were resistant to third-generation cephalosporins, with CTX-M-2 being the main extended-spectrum β-lactamase detected. Five E. coli were carbapenemase-producers (3 NDM, 2 KPC). The mcr-1.5 variant was detected in 13.5% of the isolates. No genetic relationship was observed among the mcr-1-positive E. coli clinical isolates, but a high proportion (164/192; 85.4%) of IncI2 plasmids was detected. Conclusions. The presence of IncI2 plasmids among highly diverse E. coli clones suggests that the mcr-1 gene’s wide distribution in Argentina may be driven by the horizontal transmission of IncI2 plasmids.

[RESUMEN]. Objetivo. Describir el perfil de resistencia y las características genéticas de aislamientos clínicos de Escherichia coli que portan el gen movilizable de resistencia a colistina mcr-1 en Argentina. Métodos. Se realizó un estudio retrospectivo para analizar 192 aislamientos de E. coli mcr-1 positivo, obtenidos en 69 hospitales de la Ciudad de Buenos Aires y 14 provincias de Argentina entre 2012 y 2018. La sensibilidad a los antimicrobianos se analizó mediante los métodos de difusión en agar, macrodilución en caldo y/o dilución en agar. Se aplicó la técnica estándar de reacción en cadena de la polimerasa (PCR) para detectar genes de resistencia y grupos de incompatibilidad; se aplicó PCR específica para distinguir entre variantes alélicas del gen blaCTX-M y la variante mcr-1.5. La relación genética entre los aislamientos fue evaluada mediante la técnica de electroforesis en gel de campo pulsado usando la enzima Xbal y la tipificación por secuencias de múltiples locus en un subconjunto de aislamientos. Resultados. Todos los aislamientos de E. coli mostraron concentraciones inhibitorias mínimas de colistina ≥ 4μg/mL. Casi el 50% mostró resistencia a las cefalosporinas de tercera generación y CTX-M-2 fue la β-lactamasa de espectro extendido que más se detectó. Cinco aislamientos de E. coli mostraron ser productoras de carbapenemasas (3 NDM, 2 KPC). La variante mcr-1.5 se detectó en 13,5% de las cepas aisladas. No se observó relación genética entre los aislamientos clínicos estudiados de E. coli positivas para mcr-1, aunque sí se detectó una proporción elevada (164/192; 85,4%) de plásmidos Incl2. Conclusiones. La elevada ocurrencia de plásmidos IncI2 en un grupo altamente diverso de clones de E. coli podría indicar que la amplia difusión del gen mcr-1 en Argentina estaría asociada a la transmisión horizontal de plásmidos IncI2.

[RESUMO]. Objetivo. Descrever o perfil de resistência e as características genéticas de isolados clínicos de Escherichia coli que carregam o gene mobilizábel de resistência à colistina mcr-1 na Argentina. Métodos. Neste estudo retrospectivo, foram analizados 192 isolados de E. coli positivos para mcr-1 obtidos em 69 hospitais da Cidade de Buenos Aires e 14 províncias da Argentina, entre 2012 e 2018. A sensibilidade aos antimicrobianos foi examinada usando métodos de difusão em ágar, macrodiluição em caldo e/ou diluição em ágar. A técnica padrão de reação em cadeia da polimerase (PCR) foi aplicada para detectar genes de resistência e grupos de incompatibilidade; a PCR específica foi aplicada para discriminar entre variantes alélicas do gene blaCTX-M e a variante mcr-1.5. A relação genética entre os isolados foi avaliada por eletroforese em gel de campo pulsado usando a enzima XbaI e a tipagem por sequências de múltiplos lócus, em um subconjunto de isolados. Resultados. Todos os isolados de E. coli apresentaram concentrações inibitórias mínimas de colistina ≥4μg/ mL. Quase 50% foram resistentes às cefalosporinas de terceira geração, e CTX-M-2 foi a β-lactamase de espectro estendido mais detectada. Cinco isolados de E. coli foram produtores de carbapenemase (3 NDM, 2 KPC). A variante mcr-1.5 foi detectada em 13,5% dos isolados. Não foi observada relação genética entre os isolados clínicos de E. coli positivos para mcr-1, mas foi detectada uma alta proporção (164/192; 85,4%) de plasmídeos IncI2. Conclusões. A alta ocorrência de plasmídeos IncI2 em um grupo altamente diverso de clones de E. coli sugere que a ampla distribuição do gene mcr-1 na Argentina estaria associada a transmissão horizontal de plasmídeos IncI2.

Evolución del desempeño de Laboratorios de Referencia de América Latina en la detección de mecanismos de resistencia a los antimicrobianos

[RESUMEN]. Objetivo. El objetivo es presentar los resultados del Programa Latinoamericano de Aseguramiento de la Calidad en Bacteriología y Resistencia a los Antimicrobianos (LA-EQAS) entre 2000 y 2018 y la evolución en la detección de mecanismos de resistencia de impacto clínico. Métodos. Los Laboratorios Nacionales de Referencia (LNR) participantes recibieron 25 encuestas con 10 cepas cada una, representando un total de 86 especies bacterianas y 40 mecanismos de resistencia. Para evaluar el desempeño de los LNR, se analizaron cinco indicadores: identificación bacteriana, interpretación de las pruebas de sensibilidad, rangos de las zonas de inhibición aceptables, mecanismo de resistencia inferido, y tiempo de demora en la respuesta. Resultados. La concordancia media fue 82,6% (rango: 74-95%) en la identificación bacteriana, 93,3% (85-98%) en la interpretación de las pruebas de sensibilidad, 84,6% (70-94%) en las zonas de inhibición, 82,5% (73-96%) en el mecanismo de resistencia inferido, y la demora en la respuesta, 34 días. Se observó una mejora en la detección de mecanismos de relevancia clínica como resistencia a meticilina, macrólidos y glucopéptidos en cocos gram positivos, y betalactamasas de espectro extendido, AmpC plasmídico y carbapenemasas en bacilos gram negativos. Conclusiones. El LA-EQAS es una excelente herramienta para la mejora continua de la calidad en el diagnóstico de las infecciones por microorganismos multirresistentes en los LNR de América Latina.

[RESUMEN]. Objetivo. El objetivo es presentar los resultados del Programa Latinoamericano de Aseguramiento de la Calidad en Bacteriología y Resistencia a los Antimicrobianos (LA-EQAS) entre 2000 y 2018 y la evolución en la detección de mecanismos de resistencia de impacto clínico. Métodos. Los Laboratorios Nacionales de Referencia (LNR) participantes recibieron 25 encuestas con 10 cepas cada una, representando un total de 86 especies bacterianas y 40 mecanismos de resistencia. Para evaluar el desempeño de los LNR, se analizaron cinco indicadores: identificación bacteriana, interpretación de las pruebas de sensibilidad, rangos de las zonas de inhibición aceptables, mecanismo de resistencia inferido, y tiempo de demora en la respuesta. Resultados. La concordancia media fue 82,6% (rango: 74-95%) en la identificación bacteriana, 93,3% (85-98%) en la interpretación de las pruebas de sensibilidad, 84,6% (70-94%) en las zonas de inhibición, 82,5% (73-96%) en el mecanismo de resistencia inferido, y la demora en la respuesta, 34 días. Se observó una mejora en la detección de mecanismos de relevancia clínica como resistencia a meticilina, macrólidos y glucopéptidos en cocos gram positivos, y betalactamasas de espectro extendido, AmpC plasmídico y carbapenemasas en bacilos gram negativos. Conclusiones. El LA-EQAS es una excelente herramienta para la mejora continua de la calidad en el diagnóstico de las infecciones por microorganismos multirresistentes en los LNR de América Latina.

[RESUMO]. Objetivo. O objetivo deste trabalho é apresentar os resultados do Programa Latino-Americano de Garantia da Qualidade em Bacteriologia e Resistência Antimicrobiana (LA-EQAS, na sigla em inglês) entre 2000 e 2018 e a evolução na detecção de mecanismos de resistência com impacto clínico. Métodos. Os Laboratórios Nacionais de Referência (LNRs) participantes receberam 25 inquéritos com 10 cepas bacterianas cada, representando um total de 86 espécies bacterianas e 40 mecanismos de resistência. Para avaliar o desempenho dos LNRs, foram analisados cinco indicadores: identificação bacteriana, interpretação dos testes de sensibilidade, faixas das zonas de inibição aceitáveis, mecanismo de resistência inferido e tempo de demora na resposta. Resultados. A concordância média foi de 82,6% (intervalo: 74-95%) na identificação bacteriana, 93,3% (85-98%) na interpretação dos testes de sensibilidade, 84,6% (70-94%) nas zonas de inibição, 82,5% (73-96%) no mecanismo de resistência inferido e 34 dias na demora na resposta. Observou-se uma melhoria na detecção de mecanismos clinicamente relevantes, como a resistência a meticilina, macrolídeos e glicopeptídeos em cocos Gram-positivos, beta-lactamases de espectro ampliado, AmpC plasmídica e carbapenemases em bacilos Gram-negativos. Conclusões. O LA-EQAS é uma excelente ferramenta para a melhoria contínua da qualidade no diagnóstico de infecções por microrganismos multirresistentes nos LNRs da América Latina.

Resistencia a colistín mediado por el gen mcr-1 identificado en cepas de Escherichia coli y Klebsiella pneumoniae: primeros reportes en el Perú / Resistance to colistin mediated by the mcr-1 gene identified in strains of Escherichia coli and Klebsiella pneumoniae: first reports in Peru

Introducción. Ante la aparición de reportes de la presencia del gen mcr-1 y su posible diseminación por plásmidos en los países de la región y dado que este gen confiere resistencia a colistín, fármaco que es la última línea de tratamiento contra bacterias multirresistentes, es importante conocer su presencia en nuestro país en microorganismos que lo expresen. Métodos. Se realizó un estudio descriptivo y transversal. Se incluyeron microorganismos aislados de urocultivos de pacientes ambulatorios de un centro de salud privado en Lima, Perú, en agosto del año 2017. De 326 urocultivos positivos se seleccionaron 10 aislamientos entre cepas de Escherichia coli y Klebsiella pneumoniae que presentaron concentración mínima inhibitoria ≥ 4µg/ mL (interpretado como resistente para colistín) por el sistema automatizado Microscan Walkaway 96 plus. Se utilizaron los siguientes métodos: colistín agar spot, predifusión con tabletas de colistín, microdilución en caldo colistin y PCR para el gen mcr-1. Resultados. Se determinó que 7 aislamientos, todas Escherichia coli, expresaron la presencia del gen mcr-1 por PCR, el cual confiere resistencia plasmídica a polipéptidos. De las cepas restantes, dos Escherichia coli y una Klebsiella pneumoniae, resultaron positivos para resistencia a colistín en las pruebas fenotípicas pero no en la PCR para gen mcr-1 lo cual sugiere un mecanismo de resistencia a colistín no asociado a gen mcr-1. Conclusiones. Se obtuvieron 7 aislamientos de Escherichia coli resistentes a colistín y con expresión del gen mcr-1.

Introduction. Given the appearance of reports of the presence of the mcr-1 gene and its possible dissemination by plasmids in the countries of the region and given that this gene confers resistance to colistin, the drug that is the last line of treatment against multiresistant bacteria, it is important to know its presence in our country in microorganisms that express it. Methods. Descriptive and cross-sectional study was carried out. Microorganisms isolated from urine culture of outpatients from a private health center in Lima, Peru, were included in august 2017. Out of 326 positive urine cultures, 10 isolates were selected between strains of Escherichia coli and Klebsiella pneumoniae that had a minimum inhibitory concentration ≥4µg/mL (interpreted as resistant for colistín) by the automated system Microscan Walkaway 96 plus. The following methods were used: colistin agar spot, prediffusion with colistin tablets, microdilution in colistin broth and PCR for the mcr-1 gene. Results. It was determined that 7 isolates, all Escherichia coli, expressed the presence of the mcr-1 gene by PCR, which confers plasmid resistance to polypeptides. Of the remaining strains, two Escherichia coli and one Klebsiella pneumoniae, were positive for resistance to colistin in the phenotypic tests but not in the PCR for mcr-1 gene, which suggests a mechanism of colistin resistance not associated with the mcr-1 gene. Conclusions. Seven isolates of Escherichia coli resistant to colistin and with expression of the mcr-1 gene were obtained.

Estrategia de control de la resistencia bacteriana a los antimicrobianos en Argentina / Strategy for controlling bacterial resistance to antimicrobial drugs in Argentina / Estratégia de controle da resistência bacteriana aos antimicrobianos na Argentina

La aceleración observada en las últimas décadas sobre la emergencia y diseminación de la resistencia a los antimicrobianos está vinculada al abuso y/o mal uso de los antimicrobianos. En 2014, el Ministerio de Salud de Argentina, junto a otros organismos e instituciones, implementó una estrategia nacional para el control de la resistencia a los antimicrobianos con el objetivo de retrasar o impedir la emergencia y diseminación de bacterias resistentes. Este trabajo describe las acciones propuestas y los resultados obtenidos durante el primer período de implementación en materia de fortalecimiento de la vigilancia en salud humana, creación de una red de vigilancia en salud animal, planificación de la vigilancia del consumo de antimicrobianos, fiscalización de restricciones en la venta de estos, adecuación de las formas farmacéuticas a las necesidades de tratamiento, actualización del registro de antimicrobianos y de métodos de diagnóstico, restricción de su uso como promotores de crecimiento, promoción de su uso responsable, elaboración de guías de diagnóstico y tratamiento, creación de programas de gestión de antimicrobianos, y fortalecimiento de los programas de prevención y control de infecciones en establecimientos de salud y de producción agropecuaria. Muchas de estas medidas son de implementación inmediata, particularmente en materia de regulación, fiscalización y gestión de antimicrobianos, y pueden reducir su uso innecesario y con ello el impacto sobre la resistencia a los antimicrobianos.

The accelerated emergence and spread of antimicrobial resistance observed in recent decades is associated with the abuse and/or misuse of antimicrobial drugs. In 2014, Argentina’s Ministry of Health, in conjunction with other agencies and institutions, rolled out a national antimicrobial resistance control strategy designed to slow or prevent the emergence and spread of resistant bacteria. This article describes the action proposed and results obtained during the first implementation period in terms of improving human health surveillance, creating an animal health surveillance network, planning antimicrobial drugs consumption surveillance, monitoring restrictions on sales, adapting dosage forms to treatment needs, updating the antimicrobial drugs registry and diagnostic methods, restricting the use of these drugs as growth promoters, encouraging responsible use, preparing diagnostic and treatment guidelines, creating antimicrobial drugs management programs, and strengthening infection prevention and control programs in health facilities and livestock production. Many of these measures, particularly those related to antimicrobial drugs regulation, control, and management, can be implemented immediately, reducing the unnecessary use of these products, and with it, the impact on antimicrobial resistance.

O aceleramento observado nas últimas décadas no surgimento e na disseminação da resistência aos antimicrobianos está vinculado ao uso excessivo e/ou mau uso dos antimicrobianos. Em 2014, o Ministério da Saúde da Argentina, junto com outros órgãos e instituições, implementou uma estratégia nacional para o controle da resistência aos antimicrobianos com o objetivo de retardar ou impedir o surgimento e disseminação de bactérias resistentes. Este estudo descreve as ações propostas e os resultados obtidos no primeiro período de implementação no que se refere ao reforço da vigilância em saúde humana, criação de uma rede de vigilância em saúde animal, planejamento da vigilância do uso de antimicrobianos, fiscalização das restrições na venda de antimicrobianos, adequação das formas farmacêuticas à necessidade de tratamento, atualização do registro de antimicrobianos e de métodos diagnósticos, restrição do uso de antimicrobianos como promotores de crescimento, incentivo ao uso responsável dos antimicrobianos, elaboração de guias de diagnóstico e tratamento, criação de programas de controle de antimicrobianos e fortalecimento dos programas de prevenção e controle de infecções em estabelecimentos de assistência à saúde e de atividade agropecuária. Muitas das medidas são de implementação imediata, em particular a regulamentação, fiscalização e controle dos antimicrobianos, e podem reduzir o uso desnecessário e consequentemente o impacto na resistência aos antimicrobianos.

Etiología aerobia de apendicitis aguda en adultos: Estudio multicéntrico de la sepsis abdominal en Argentina / Aerobic etiology of acute appendicitis in adults. Multicenter study of abdominal sepsis in Argentina

El tratamiento antibiótico de las apendicitis agudas se decide empíricamente basándose en la información epidemiológica. Las resistencias son variables entre regiones y los datos de Argentina son escasos. En el contexto de un estudio multicéntrico, observacional, de infecciones abdominales, se efectuó el análisis de los pacientes adultos con diagnóstico de apendicitis, incorporados al estudio entre enero 2014 y junio 2015, en 16 centros de 5 provincias argentinas. El objetivo fue analizar los gérmenes aeróbicos prevalentes, su resistencia a antibióticos y el patrón de prescripción antimicrobiana. Se estudiaron 131 apendicitis. Se aislaron 184 bacterias aerobias (1.4 bacterias/episodio): Escherichia coli 106 (57.6%), Klebsiella spp 16 (8.7%), Pseudomonas aeruginosa 19 (10.3%), Enterobacter spp. 2 (1%), otros bacilos Gram negativos 5 (2.7%). Enterococcus spp. 16 (8.7%) y otros cocos Gram positivos 20 (10.9%). La resistencia de E. coli y enterobacterias a ampicilina/sulbactam fue mayor a 34% y a ciprofloxacina mayor a 31%. En cambio, la resistencia de enterobacterias a piperacilina/tazobactam fue 4.8%, a ceftriaxona 9.5% y no se halló resistencia a carbapenemes. Respecto a amikacina fue 3.6% y a gentamicina 8.2%. En función de los resultados, el uso de quinolonas o de ampicilina/sulbactam para el tratamiento de las apendicitis debiera ser desaconsejado. Los esquemas basados en aminoglucósidos debieran ser jerarquizados en función de la sensibilidad hallada y su bajo impacto en la inducción de resistencias.

Antibiotic treatment for acute appendicitis is empirically chosen, based on epidemiological information. Resistance rates are different between regions and there are limited data on the situation in Argentina. As a part of a multicenter, observational study of abdominal infections, we performed the analysis of adult patients diagnosed with appendicitis, enrolled in 16 centers of 5 provinces, between Jan/01/2014 and Jun/30/2015. The aim was to analyze the prevalent aerobic pathogens, their resistance rates and the antimicrobial prescription pattern. On a total of 131 appendicitis cases analyzed, we found 184 aerobic pathogens (1.4 bacteria/episode): Escherichia coli 106 (57.6%), Klebsiella spp 16 (8.7%), Pseudomonas aeruginosa 19 (10.3%), Enterobacter spp. 2 (1%), other Gram negative bacilli 5 (2.7%); Enterococcus spp. 16 (8.7%) and other Gram positive cocci 20 (10.9%). The resistance rate of E. coli and enterobacteria to ampicillin/sulbactam was greater than 34% and greater than 31% to ciprofloxacin. However, the resistance of enterobacteria to piperacillin/tazobactam was 4.8%, to ceftriaxone 9.5%, to amikacin 3.6% and 8.2% to gentamicin. No resistance to carbapenems was found. The choice of quinolones or ampicillin/sulbactam for the treatment of appendicitis should be discouraged in our context, due to the high rates of resistance found in this prevalent etiology. Aminoglycoside-based treatments should be considered, given the findings of high antibiotic susceptibility and their low impact on the induction of resistance.

Estrategia de control de la resistencia bacteriana a los antimicrobianos en Argentina / Strategy for controlling bacterial resistance to antimicrobial drugs in Argentina / Estratégia de controle da resistência bacteriana aos antimicrobianos na Argentina

RESUMEN La aceleración observada en las últimas décadas sobre la emergencia y diseminación de la resistencia a los antimicrobianos está vinculada al abuso y/o mal uso de los antimicrobianos. En 2014, el Ministerio de Salud de Argentina, junto a otros organismos e instituciones, imple- mentó una estrategia nacional para el control de la resistencia a los antimicrobianos con el objetivo de retrasar o impedir la emergencia y diseminación de bacterias resistentes. Este trabajo describe las acciones propuestas y los resultados obtenidos durante el primer período de implementación en materia de fortalecimiento de la vigilancia en salud humana, creación de una red de vigilancia en salud animal, planificación de la vigilancia del consumo de antimicrobianos, fiscalización de restricciones en la venta de estos, adecuación de las formas farmacéuticas a las necesidades de tratamiento, actualización del registro de antimicrobianos y de métodos de diagnóstico, restricción de su uso como promotores de crecimiento, promoción de su uso responsable, elaboración de guías de diagnóstico y tratamiento, creación de programas de gestión de antimicrobianos, y fortalecimiento de los programas de prevención y control de infecciones en establecimientos de salud y de producción agropecuaria. Muchas de estas medidas son de implementación inmediata, particularmente en materia de regulación, fiscalización y gestión de antimicrobianos, y pueden reducir su uso innecesario y con ello el impacto sobre la resistencia a los antimicrobianos.(AU)

ABSTRACT The accelerated emergence and spread of antimicrobial resistance observed in recent decades is associated with the abuse and/or misuse of antimicrobial drugs. In 2014, Argentina's Ministry of Health, in conjunction with other agencies and institutions, rolled out a national antimicrobial resistance control strategy designed to slow or prevent the emergence and spread of resistant bacteria. This article describes the action proposed and results obtained during the first implementation period in terms of improving human health surveillance, creating an animal health surveillance network, planning antimicrobial drugs consumption surveillance, monitoring restrictions on sales, adapting dosage forms to treatment needs, updating the antimicrobial drugs registry and diagnostic methods, restricting the use of these drugs as growth promoters, encouraging responsible use, preparing diagnostic and treatment guidelines, creating antimicrobial drugs management programs, and strengthening infection prevention and control programs in health facilities and livestock production. Many of these measures, particularly those related to antimicrobial drugs regulation, control, and management, can be implemented immediately, reducing the unnecessary use of these products, and with it, the impact on antimicrobial resistance.(AU)

RESUMO O aceleramento observado nas últimas décadas no surgimento e na disseminação da resistência aos antimicrobianos está vinculado ao uso excessivo e/ou mau uso dos antimicrobianos. Em 2014, o Ministério da Saúde da Argentina, junto com outros órgãos e instituições, implementou uma estratégia nacional para o controle da resistência aos antimicrobianos com o objetivo de retardar ou impedir o surgimento e disseminação de bactérias resistentes. Este estudo descreve as ações propostas e os resultados obtidos no primeiro período de implementação no que se refere ao reforço da vigilância em saúde humana, criação de uma rede de vigilância em saúde animal, planejamento da vigilância do uso de antimicrobianos, fiscalização das restrições na venda de antimicrobianos, adequação das formas farmacêuticas à necessidade de tratamento, atualização do registro de antimicrobianos e de métodos diagnósticos, restrição do uso de antimicrobianos como promotores de crescimento, incentivo ao uso responsável dos antimicrobianos, elaboração de guias de diagnóstico e tratamento, criação de programas de controle de antimicrobianos e fortalecimento dos programas de prevenção e controle de infecções em estabelecimentos de assistência à saúde e de atividade agropecuária. Muitas das medidas são de implementação imediata, em particular a regulamentação, fiscalização e controle dos antimicrobianos, e podem reduzir o uso desnecessário e consequentemente o impacto na resistência aos antimicrobianos.(AU)

Resistencia antimicrobiana y epidemiología molecular de aislamientos de Staphylococcus pseudintermedius de muestras clínicas de caninos / Antimicrobial resistance and molecular epidemiology of Staphylococcus pseudintermedius strains isolated from dog clinical samples

Se estudiaron 28 aislamientos obtenidos de muestras clínicas de perros e identificados por espectrometría de masas (MALDI-TOF) como Staphylococcus pseudintermedius; el objetivo fue evaluar la sensibilidad a los antimicrobianos por el método de difusión y establecer la relación clonal entre aislamientos por electroforesis en campo pulsado (PFGE). La resistencia a meticilina se evaluó mediante PCR por amplificación del gen mecA y se observó en 3/28 aislamientos (10,7 %). Quince aislamientos (53,6 %) presentaron resistencia a alguno de los antibióticos ensayados y 11 de ellos (39,3 %) presentaron resistencia múltiple (resistencia a 3 o más familias de antibióticos). Once aislamientos (39,3 %) presentaron resistencia a eritromicina, debido a la presencia de metilasa ribosomal ermB, y no se detectó resistencia inducible a clindamicina. Por PFGE se pudieron diferenciar 27 tipos clonales, lo cual demuestra gran diversidad clonal. Se destaca el hallazgo de aislamientos de S. pseudintermedius multirresistentes como una eventual problemática a considerar en el diagnóstico veterinario de laboratorio, el tratamiento de las infecciones caninas y el ámbito de la salud pública.

Twenty-eight strains isolated from dog clinical samples identified as Staphylococcus pseudintermedius by mass spectrometry (MALDI-TOF) were studied to assess antimicrobial susceptibility by the diffusion method and clonal relationship by pulsed field gel electrophoresis (PFGE). Methicillin resistance (3/28 isolates; 10,7 %) was evaluated by mecA PCR. Fifteen strains (53.6 %) were resistant to at least one of the antibiotics tested, and eleven of them (39.3 %) showed multiple resistance (3 or more antimicrobial families). Eleven isolates (39.3 %) were resistant to erythromycin due to the presence of ribosomal methylase ermB, whereas clindamycin inducible resistance was not detected. Twenty-seven (27) clonal types were differentiated by PFGE, suggesting high clonal diversity. We emphasize that the finding of multiresistant S. psedintermedius strains is an emerging problem to be considered in veterinary diagnostic laboratory treatment of canine infections and in public health settings.

Diseminación de blaIMP-8 en enterobacterias aisladas en un hospital de Buenos Aires / [Dissemination of blaIMP-8 among Enterobacteriaceae isolates from a Buenos Aires Hospital].

From August 2008 to December 2011, six metallo-ß-lactamase-producing isolates, four Enterobacter cloacae, one Klebsiella oxytoca and one Citrobacter freundii, were detected at Hospital Interzonal General de Agudos "Evita" in Lanús. All six isolates showed multiresistant profiles and the presence of the blaIMP-8 gene. Five isolates also expressed PER-2 extended spectrum ß-lactamase. The blaIMP-8 gene was found as the first cassette in a class 1 integron. However, the 3´ conserved sequence could not be detected in three isolates. In all cases, blaIMP-8 was transferred by conjugation to azide-resistant Escherichia coli J53. PFGE analysis revealed that the four E. cloacae isolates were not genetically related. These are the first metallo-ß-lactamases detected in this institution and our results suggest a possible intra- and inter-species horizontal dissemination of blaIMP-8.

Diseminación de blaIMP-8 en enterobacterias aisladas en un hospital de Buenos Aires. / [Dissemination of blaIMP-8 among Enterobacteriaceae isolates from a Buenos Aires Hospital].

From August 2008 to December 2011, six metallo-ß-lactamase-producing isolates, four Enterobacter cloacae, one Klebsiella oxytoca and one Citrobacter freundii, were detected at Hospital Interzonal General de Agudos "Evita" in Lanús. All six isolates showed multiresistant profiles and the presence of the blaIMP-8 gene. Five isolates also expressed PER-2 extended spectrum ß-lactamase. The blaIMP-8 gene was found as the first cassette in a class 1 integron. However, the 3´ conserved sequence could not be detected in three isolates. In all cases, blaIMP-8 was transferred by conjugation to azide-resistant Escherichia coli J53. PFGE analysis revealed that the four E. cloacae isolates were not genetically related. These are the first metallo-ß-lactamases detected in this institution and our results suggest a possible intra- and inter-species horizontal dissemination of blaIMP-8.

Descripción clínica y epidemiológica de un brote nosocomial por Klebsiella pneumoniae productora de KPC en Buenos Aires, Argentina / Clinical and epidemiological study of an outbreak of KPC-producing Klebsiella pneumoniae infection in Buenos Aires, Argentina

Introducción Klebsiella pneumoniae (K. pneumoniae) productora de carbapenemasa tipo KPC (Kpn-KPC) representa un patógeno emergente, con elevada capacidad de diseminación nosocomial. El objetivo del presente estudio es describir las características clinicoepidemiológicas de un brote nosocomial por Kpn-KPC en Buenos Aires, Argentina. Métodos Estudio descriptivo y prospectivo. Se registraron los aspectos clinicoepidemiológicos de pacientes con infección por Kpn-KPC (agosto de 2009 a julio de 2010). Se determinó la sensibilidad a los antimicrobianos mediante antibiograma por disco-difusión y por método automatizado (Vitek® 2C-bioMerieux). La búsqueda de carbapenemasa tipo KPC se realizó con la prueba de inhibición con 3-aminofenil-borónico (APB) y se confirmó su presencia por reacción en cadena de la polimerasa (PCR, por sus siglas en inglés). Se realizó tipificación molecular de las cepas aisladas por electroforesis en campo pulsado (PFGE, por sus siglas en inglés).Resultados Se registraron 27 casos de infección por Kpn-KPC (sala de cirugía general: n=8; clínica médica: n=6; unidad de cuidados intensivos: n=5; sala de emergencia: n=4; otras: n=4). Todos los aislamientos de Kpn-KPC pertenecieron a un mismo clon (ST258). Los sitios de infección fueron: tracto urinario (63%), tracto respiratorio (15%), abdomen (15%), sangre (7%) y hueso (4%). Todos los aislamientos de KPn-KPC fueron solamente sensibles a tigeciclina y colistina. Tratamiento empírico inadecuado: 63%. Tratamiento efectivo dirigido: colistina (74%), tigeciclina (4%), tigeciclina+colistina (22%). Mortalidad global: 59% (atribuible: 26%). Cultivos de vigilancia (hisopados) positivos: 7/70 (10%).Conclusiones Se describe la emergencia de un brote nosocomial de Kpn-KPC en Buenos Aires, con alta capacidad de diseminación y elevada mortalidad. La implementación de medidas de control de infecciones es fundamental para reducir la transmisión nosocomial de Kpn-KPC (AU)

Introduction: KPC-producing Klebsiella pneumoniae (Kpn-KPC) is an emerging pathogen, with a highcapacity of nosocomial spread. The aim of this study was to describe the clinical and epidemiological characteristics of a nosocomial outbreak of Kpn-KPC in Buenos Aires, Argentina. Methods: Prospective and descriptive study. We recorded clinical and epidemiological characteristics of patients with Kpn-KPC infection (august 2009 to july 2010). Antimicrobial susceptibility was performed by disk-diffusion antibiogram and an automated method (bioMerieux Vitek®2 C). Screening for K. pneumoniae carbapenemase (KPC) was performed with the 3-aminophenyl-boronic acid (APB) test inhibition and its presence was (..) (AU)

Capacidad de los laboratorios nacionales de referencia en Latinoamérica para detectar mecanismos de resistencia emergentes / Capability of national reference laboratories in Latin America to detect emerging resistance mechanisms

Objetivo. Evaluar la capacidad de 17 laboratorios nacionales de referencia que participan en el Programa Latinoamericano de Control de Calidad en Bacteriología y Resistencia a los Antimicrobianos (LA-EQAS) para detectar mecanismos de resistencia emergentes, a saber: resistencia de enterobacterias a carbapenemes por presencia de Klebsiella pneumoniae carbapenemasa (KPC); resistencia de enterobacterias a carbapenemes por presencia de metalobetalactamasas (MBL) tipo IMP, y resistencia intermedia a vancomicina de aislamientos de Staphylococcus aureus (VISA). Métodos. Se enviaron los siguientes tres aislamientos a los 17 laboratorios participantes del LA-EQAS: Klebsiella pneumoniae OPS-161 productor de KPC, Enterobacter cloacae OPS-166 productor de IMP y S. aureus OPS-165 con resistencia intermedia a vancomicina. Se evaluó la interpretación de las pruebas de sensibilidad y detección del mecanismo de resistencia y el tamaño de los halos de inhibición (método de difusión por discos) o valor de la concentración inhibitoria mínima (CIM). Resultados. La concordancia en la detección de los mecanismos de resistencia fue de 76,4%, 73,3% y 66,7% con respecto a la cepas K. pneumoniae OPS-161, E. cloacae OPS-166 y S. aureus OPS-165, respectivamente. La concordancia entre las zonas de inhibición obtenidas por los laboratorios participantes y los rangos establecidos por el laboratorio coordinador fue aceptable en los tres aislamientos, ya que alcanzó 90,8%, 92,8% y 88,9%, respectivamente, para cada cepa. Conclusiones. La concordancia global en la detección de los mecanismos de resistencia KPC, MBL y VISA fue de 72,1%. Consideramos que los laboratorios nacionales de referencia de América Latina son capaces de reconocer estos mecanismos de resistencia emergentes y se espera que en el futuro la concordancia alcance su nivel máximo.

Objective. To evaluate the capability of 17 national reference laboratories participating in the Latin American Quality Control Program in Bacteriology and Antibiotic Resistance (LA-EQAS) to detect emerging resistance mechanisms— namely: resistance of enterobacteria to carbapenems due to the presence of Klebsiella pneumoniae carbapenemase (KPC) and metallo-beta-lactamase (MBL) type IMP, and intermediate resistance of Staphylococcus aureus isolates to vancomycin (vancomycinintermediate resistant S. aureus—VISA). Methods. The following three isolates were sent to the 17 participating LA-EQAS laboratories: KPC-producing Klebsiella pneumoniae PAHO-161, IMP-producing Enterobacter cloacae PAHO-166, and S. aureus PAHO-165 with intermediate resistance to vancomycin. Performance of each of the following operations was evaluated: interpretation of sensitivity tests, detection of the resistance mechanism, and assessment of either inhibition halo size (disk diffusion method) or minimum inhibitory concentration (MIC). Results. Concordance in the detection of resistance mechanisms was 76.4%, 73.3%, and 66.7% for the K. pneumoniae PAHO-161, E. cloacae PAHO-166, and S. aureus PAHO- 165 strains, respectively. Concordance between the inhibition areas observed by the participating laboratories and the ranges established by the coordinating laboratory was acceptable for all three isolates, at 90.8%, 92.8%, and 88.9%, respectively. Conclusions. Overall concordance in on the detection of KPC, MBL, and VISA resistance mechanisms was 72.1%. We consider the national reference laboratories in Latin America capable of recognizing these emerging resistance mechanisms and expect that maximum levels of concordance will be reached in the future.

Criterios de ensayo, interpretación e informe de las pruebas de sensibilidad a los antibióticos en los bacilos gram negativos no fermentadores de importancia clínica: recomendaciones de la Subcomisión de Antimicrobianos de la Sociedad Argentina de Bacteriología, Micología y Parasitología Clínicas, Asociación Argentina de Microbiología / Antimicrobial susceptibility testing in clinically relevant non-fermenting gram-negative bacilli: recommendations from the Antimicrobial Agents Subcommittee of the Sociedad Argentina de Bacteriología, Micología y Parasitología Clínicas, Asociación Argentina de Microbiología

En este documento se dan a conocer una serie de recomendaciones para el ensayo, la lectura, la interpretación y el informe de las pruebas de sensibilidad a los antimicrobianos para los bacilos gram negativos no fermentadores (BGNNF) que se aíslan en humanos. Se adoptaron como base las recomendaciones internacionales, las de la Subcomisión de Antimicrobianos de la Sociedad Argentina de Bacteriología, Micología y Parasitología Clínicas y las de un grupo de expertos invitados. Se incluye, además, la nomenclatura actualizada de los BGNNF y la descripción de algunas de sus características individuales, de sus resistencias naturales o habituales a los antimicrobianos de uso clínico y de los mecanismos responsables de tales resistencias. También se indican los agentes antimicrobianos que se deberían ensayar frente a las distintas especies, con la especificación de cuáles deberían ser informados, y su ubicación estratégica en las placas de cultivo para poder detectar los mecanismos de resistencia más frecuentes y relevantes. Por último, se detallan los métodos de detección y de confirmación fenotípica de la presencia de b-lactamasas emergentes en Argentina, como las carbapenemasas clases A y B.

This document contains the recommendations for antimicrobial susceptibility testing of the clinically relevant non-fermenting gram-negative bacilli (NFGNB), adopted after conforming those from international committees to the experience of the Antimicrobial Agents Subcommittee members and invited experts. This document includes an update on NFGNB classification and description, as well as some specific descriptions regarding natural or frequent antimicrobial resistance and a brief account of associated resistance mechanisms. These recommendations not only suggest the antimicrobial drugs to be evaluated in each case, but also provide an optimization of the disk diffusion layout and a selection of results to be reported. Finally, this document also includes a summary of the different methodological approaches that may be used for detection and confirmation of emerging b-lactamases, such as class A and B carbapenemases.