Plasmid-Encoded AmpC (pAmpC) in Enterobacteriaceae: epidemiology of microorganisms and resistance markers.

CMY-2 Β-lactamase is an important cause of Β-lactam resistance in Enterobacteriaceae and constitutes the most widespread pAmpC. Although CMY-2 has been previously recognized in our region, the real prevalence and epidemiology of this resistance marker was uncertain. During August-October 2009, we conducted a multicenter, prospective study to determine pAmpC prevalence and to characterize CMY-2 producing Escherichia coli associated plasmids. Plasmid-encoded AmpC prevalence was 0.9 % in enterobacteria in this period, being CMY-2 prevalent and to a lesser extent DHA. Molecular typing of CMY-2- producing Escherichia coli isolates showed several lineages. Moreover, replicon typing of cmy-2- containing plasmids displayed a broad diversity in Inc/cmy-2 links. Therefore, association of cmy-2 with specific transposon elements may be responsible for the spread of this resistance marker in Enterobacteriaceae.

[Evaluation of direct susceptibility testing from blood culture bottles. Clinical usefulness]. / Evaluación del antibiograma directo desde el frasco de hemocultivo con el sistema Vitek 2C: su utilidad en la clínica.

A prospective observational study was conducted in two hospitals of Buenos Aires city (Argentina); 191 clinically significant monomicrobial gram-negative bloodstream infections were included in the study, which combined the Bact-Alert System Blood culture machine and the Vitek 2C System. Organism identification and susceptibility results directly from blood culture bottles were compared with those obtained from cards inoculated with a standardized bacterial suspension obtained following subculture on agar. By comparing the results obtained from pure cultures with those by the Vitek 2C System as reference method, the agreement between the reference method and the direct identification from positive blood cultures was 99 %. By antimicrobial susceptibility testing, the overall categorical accuracy was 99 % (0.22 %, very major errors, 0.17 %, major errors and 0.61 %, minor errors). One hundred and eight (56,8 %) bloodstream infections were treated empirically with adequate antibiotics. After the results obtained directly from the bottles were reported, antimicrobial therapy was changed in 116 (60.7 %) of the episodes.

[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]. / 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.

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.

Multicenter study to assess the in vitro activity of tigecycline by disk diffusion test against clinical isolates from Argentina.

BACKGROUND: Tigecycline is a new antibiotic currently used in healthcare environments where multidrug resistance is prominent. Because there is a constant potential for resistance to emerge, survey studies are needed. METHODS: Isolates collected in 20 clinical laboratories from 4 states of Argentina between November 2005 and October 2006 were tested using the disk diffusion method as described by the CLSI. RESULTS: A total of 3,182 isolates were assessed. Gram-positive cocci represented 43.4% of the total isolates [Staphylococcus aureus (878), coagulase-negative staphylococci (255), Enterococcus spp. (201), Streptococcus spp. (47)], Enterobacteriaceae 39.6% and Acinetobacter spp. 11.1%. Tigecycline proved equally active against methicillin-resistant and methicillin-susceptible staphylococci, as well as against vancomycin-resistant and vancomycin-susceptible enterococci (100% of susceptibility for all Gram-positive bacteria tested). Tigecycline susceptibility for Enterobacteriaceae, other than Proteeae tribe and Serratia spp., ranged from 88 to 100%, including against strains with resistance to third-generation cephalosporins with phenotype of extended spectrum beta-lactamases (extended spectrum beta-lactamase-positive Escherichia coli 17.7% and extended spectrum beta-lactamase-positive Klebsiella pneumoniae 50.5%). Adopting a resistant breakpoint of 16 mm, 92% of the Acinetobacter isolates were susceptible to tigecycline. CONCLUSION(S): Tigecycline was active against a wide variety of bacterial species, including most of the multidrug-resistant Gram-negative and Gram-positive bacteria. Therefore, it could be a suitable option in the treatment of infections caused by these organisms in hospitalized patients.

First report of plasmid-mediated fluoroquinolone efflux pump QepA in Escherichia coli clinical isolate ST68, in South America.

This is the first report of the presence of qepA1 efflux pump gene in Escherichia coli clinical isolate from Argentina, which was associated to other plasmid-mediated quinolone resistance determinants, such as aac(6')-Ib-cr and qnrB10 and also quinolone resistance determining regions mutations.

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.