Mannitol-negative methicillin-resistant Staphylococcus aureus from nasal swab specimens in Brazil.

The isolation of mannitol-negative methicillin-resistant Staphylococcus aureus from nasal swabs is reported. Among the 59 isolates, 9 (15%) isolates were mannitol-negative; all of these isolates were categorized as staphylococcal cassette chromosome mec (SCCmec) type IVa. This report emphasizes that mannitol fermentation on mannitol salt agar should not be used as the sole criterion when screening nasal swab specimens for S. aureus.

Production of metallo-ß-lactamase among Pseudomonas aeruginosa strains isolated in the State of Sergipe, Brazil.

INTRODUCTION: Acquired production of metallo-ß-lactamases is an important mechanism of resistance in Pseudomonas aeruginosa. The objective of this study was to investigate the production of metallo-ß-lactamase and the genetic diversity among ceftazidime-resistant P. aeruginosa isolates from State of Sergipe, Brazil. METHODS: Metallo-ß-lactamase was investigated using the disk approximation test and polymerase chain reaction (PCR). Genetic diversity was evaluated by pulsed-field gel electrophoresis (PFGE). RESULTS: A total of 48 (51.6%) isolates were resistant to ceftazidime. Six (12.2%) of these were positive for metallo-ß-lactamase production. Only two (4.1%) of the ceftazidime-resistant isolates carried the bla SPM-1 gene. CONCLUSIONS: Production of metallo-ß-lactamases was not the main mechanism of resistance to ceftazidime and carbapenems among P. aeruginosa strains in Sergipe, Brazil.

Detection of bla(OXA-23) in Acinetobacter spp. isolated from patients of a university hospital.

INTRODUCTION: Acinetobacter spp. have emerged as notorious pathogens involved in healthcare-associated infections. Carbapenems are important antimicrobial agents for treating infections due to multidrug resistant Acinetobacter spp. Different mechanisms may confer resistance to these drugs in the genus, particularly production of class D carbapenemases. OXA-23-like family has been pointed out as one of the predominant carbapenamases among Acinetobacter. The present work aimed to investigate the occurrence of OXA-23-like carbapenemases among Acinetobacter isolates recovered from patients of a university hospital in Niterói, RJ, Brazil. METHODS: Antimicrobial susceptibility profiles were determined by disk-diffusion. Imipenem resistant isolates were submitted to Modified Hodge Test in order to screen for carbapenemase production, and later to polymerase chain reaction (PCR) to investigate the presence of bla(OXA-23). RESULTS: Imipenem and meropenem resistance rates were 71.4% and 69.7%, respectively. The Modified Hodge Test revealed carbapenemase production among 76 (89.4%) of the 85 imipenem resistant isolates analyzed; according to PCR results, 81 isolates (95.4%) carried the bla(OXA-23) gene. CONCLUSIONS: OXA-23-like enzymes may be an important mechanism of carbapenem resistance among isolates present in the hospital studied.