Assessment of different methods for the detection of biofilm production in coagulase-negative staphylococci isolated from blood cultures of newborns

Abstract INTRODUCTION: Coagulase-negative staphylococci (CoNS) are a frequent cause of bacteremia, especially in neonates. The major virulence determinant in CoNS is the ability to produce biofilms, which is conferred by the icaADBC genes. This study aimed to assess different methods for the detection of biofilm formation in 176 CoNS isolates from blood cultures of newborns. METHODS: The presence of the icaACD genes was assessed by polymerase chain reaction (PCR), and biofilm formation was assessed on congo red agar (CRA), by the tube method (TM), and on tissue culture plates (TCP). RESULTS: Of the 176 CoNS isolates, 30.1% expressed icaACD and 11.4% expressed icaAD. The CRA assay and TM showed that 42% and 38.6% of the isolates were biofilm producing, respectively. On TCP, 40.9% of the isolates produced biofilms; 21% were weakly adherent and 19.9% were strongly adherent. When compared to the gold standard technique (PCR), the CRAassay showed 79% sensitivity and 84% specificity (kappa = 0.64), TM showed 78% sensitivity and 89% specificity (kappa = 0.68), and TCP showed 99% sensitivity and 100% specificity (kappa = 0.99). CONCLUSIONS: In this study, ~42% of CoNS isolates produced biofilms, and the presence of icaACD was associated with a greater capacity to form biofilms. Compared to the other phenotypic methodologies, TCP is an ideal procedure for routine laboratory use.

Evaluation of carbapenem-resistant Enterobacteriaceae in a tertiary-level reference hospital in Rio Grande do Sul, Brazil

Abstract INTRODUCTION: The rapid global spread of carbapenem-resistant Enterobacteriaceae (CRE) is a threat to the health system. METHODS: We evaluated the antimicrobial susceptibility profiles of 70 CRE isolated in a tertiary hospital in Brazil between August and December 2015, and determined their resistance mechanisms. RESULTS: The most prevalent microorganism was Klebsiella pneumoniae (95.7%); it showed high-level resistance to carbapenems (>98%), with sensitivity to colistin (91.4%) and amikacin (98.6%). The bla KPC gene was detected in 80% of the CRE isolates. CONCLUSIONS: Evaluation of bacterial resistance contributes to an appropriate treatment, and the reduction of morbimortality and dissemination of resistance.