Molecular characterization of methicillin-resistant Staphylococcus aureus isolated from blood in Rio de Janeiro displaying susceptibility profiles to non-ß-lactam antibiotics

Abstract The distinction between healthcare-associated MRSA (HA-MRSA) and community-associated MRSA (CA-MRSA) infections has become increasingly blurred. We assessed the molecular characterization and antimicrobial resistance profile for MRSA isolates from blood. Most of all (81.9%) isolates are related to known HA-MRSA and CA-MRSA epidemic lineages, such as, USA300, USA400, USA600, USA800 and USA1100. This is the first multicenter study in Rio de Janeiro.

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) applications in bacteriology: brazilian contributions / Aplicações da técnica de espectrometria de massa por ionização e dessorção de matriz com laser em tempo de voo (MALDI-TOF MS) em bacteriologia: contribuições brasileiras

Among its innumerous applications in Bacteriology, the Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS) technique is evolving as a powerful tool for bacterial identification and antimicrobial resistance investigation. Publications have evaluated the MALDI-TOF MS performance in the identification of a series of bacterial pathogens, including the most common severe infectious agents, emergent pathogens involved with outbreaks of healthcare-associated infections, rare pathogens, and those whose isolation in culture media is difficult. As compared to conventional methods of bacterial identification, MALDI-TOF MS has proven to be a fast, accurate and cost-effective technique. Currently, MALDI-TOF MS has been used in antimicrobial resistance studies, since it has shown to be an efficient tool in detecting specific resistance mechanisms in bacteria, such as beta-lactamases production, for example. Here, we describe the advances in this growing field of mass spectrometry applied to Bacteriology, including Brazilian contributions.

Dentre as suas inúmeras aplicações em Bacteriologia, a técnica de "Espectrometria de Massa por Ionização e Dessorção de Matriz com Laser em Tempo de Voo [Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS)]" tem evoluído como uma poderosa ferramenta para a identificação bacteriana e a investigação da resistência bacteriana aos antimicrobianos. Publicações tem avaliado o desempenho de MALDI-TOF na identificação de uma série de patógenos bacterianos, incluindo os agentes mais comuns de infecções graves, patógenos emergentes envolvidos com surtos de infecções associadas à saúde, patógenos raros, e aqueles de difícil isolamento em meios de cultura. Em comparação aos métodos convencionais de identificação bacteriana, MALDI-TOF MS provou ser uma técnica rápida, precisa e rentável. Atualmente, MALDI-TOF MS tem sido utilizado em estudos de resistência antimicrobiana, uma vez que tem mostrado ser uma ferramenta eficiente na detecção de mecanismos especificos de resistência em bactérias, como a produção beta-lactamases, por exemplo. Aqui, nós descrevemos os avanços neste crescente campo da espectrometria de massa aplicada à Bacteriologia, incluindo as contribuições brasileiras.

Molecular epidemiology of CTX-M producing Enterobacteriaceae isolated from bloodstream infections in Rio de Janeiro, Brazil: emergence of CTX-M-15

OBJECTIVE: The present studywas designed to evaluate the molecular epidemiology of CTX-M producing Klebsiella pneumoniae, Enterobacter cloacae and Escherichia coli isolated from bloodstream infections at tertiary care hospitals in the State of Rio de Janeiro, Brazil. MATERIAL AND METHODS: A total of 231 nonduplicate Enterobacteriaceae were isolated from five Brazilian hospitals between September 2007 and September 2008. The antimicrobial susceptibility testing was performed by disk diffusion method according to the Clinical Laboratory Standard Institute. Isolates showing resistance to third-generation cephalosporins were screened for ESBL activity by the double-disk synergy test. The presence of blaCTX-M , blaCTX-M-15 and blaKPC genes was determined by Polymerase Chain Reaction (PCR) amplification andDNA sequencing. The molecular typing of CTX-M producing isolateswas performed by pulsed-field gel electrophoresis (PFGE). RESULTS AND DISCUSSION: Ninety-three isolates were screened as ESBL positive and 85 (91%) were found to carry CTX-M-type, as follows: K. pneumoniae 59 (49%), E. cloacae 15 (42%), and E. coli 11 (15%). Ten isolates resistant for carbapenems in K. pneumoniae were blaKPC-2 gene positive. Among CTX-M type isolates, CTX-M-15 was predominant in more than 50% of isolates for K. pneumoniae, E. coli, and E. cloacae. PFGE analysis of CTX-M producing isolates showed the predominance of CTX-M-15 in 10 of 24 pulsotypes in K. pneumoniae, 6 of 13 in E. cloacae and 3 of 6 in E. coli. CTX-M-15 was also predominant among KPC producing isolates. In conclusion, this study showed that CTX-M-15 was circulating in Rio de Janeiro state in 2007-2008. This data reinforce the need for continuing surveillance because this scenario may have changed over the years.