Desempenho da metodologia por MALDI-TOF MS na identificação de cocos gram-positivos isolados na cidade de Porto Alegre/RS, Brasil/MALDI-TOF MS performance to identify gram-positive cocci clinical isolates in Porto Alegre/RS, Brazil

Resumo

Until recently, gram-positive cocci identification has mainly relied on conventional and time-SCoNuming phenotypic methods. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) has emerged as a rapid alternative for bacterial identification and our study aimed to compare the performance of this methodology with the golden standard method for gram-positive cocci identification. Staphylococcus spp (n=386), Enterococcus sp (n=46), Streptococcus spp (n=18) clinical isolates and reference strains were studied. MALDI-TOF MS methodology yielded agreement identification of 440  strains out of 450 (97.8%) identified by conventional phenotypic method. The species with more disagreements on identification was S. epidermidis (n=5). Some S. haemolyticus isolates displayed two distinct genus identification at the first acquisition by MALDI-TOF MS. Two E. gallinarum were misidentified as E. faecium and one streptococci isolate was erroneously identified by MALDI-TOF (S. gordonii as S. mitis/oralis). Our data suggest that MALDI-TOF MS is fast and reliable, and can be implemented in a clinical microbiology laboratory setting, mostly due to accuracy for gram-positive cocci identification.