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.

Synergistic antibacterial effect of statins with the complex {[1-(4-bromophenyl)-3-phenyltriazene N 3 -oxide-κ 2 N 1,O 4 ](dimethylbenzylamine-κ 2 C 1, N 4 )palladium(II)}

Abstract The treatment of infections caused by resistant microorganisms represents a big challenge in healthcare due to limited treatment options. For this reason, the discovery of new active substances which are able to perform innovative and selective actions is of great impact nowadays. Statins and triazenes (TZC) have consolidated as a promising class of compounds, characterized by the expressive biological activity, especially antimicrobial activities. The aim of this study was to assess the in vitro synergistic antibacterial effect of the association of statins and a new TZC complex {[1-(4-bromophenyl)-3-phenyltriazene N 3-oxide-κ 2 N 1,O 4](dimethylbenzylamine-κ 2 C 1,N 4)palladium(II)} (Pd(DMBA)LBr) against American Type Culture Collection (ATCC) strains and clinical isolates. The complex and the statins showed bacterial activity of all tested strains and clinical isolates, evidencing that TZC complexion with metals can be promising. Simvastatin showed synergy when associated to the complex (FICI≤0.5), being the minimum inhibitory concentration (MIC) of 16 µg mL-1 found in 6 samples. Thus, it is possible to infer that the association between Pd(DMBA)LBr and simvastatin consists of an alternative to increase the pontential of these compounds, since statins have low toxicity.

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.

Phenotypic methods for screening carbapenem-resistant Enterobacteriaceae and assessment of their antimicrobial susceptibility profile

Abstract INTRODUCTION: In this study, we used phenotypic methods to screen carbapenem-resistant Enterobacteriaceae (CREs) and evaluated their antimicrobial sensitivity profile. METHODS: One hundred and seventy-eight CREs were isolated at a university hospital in south Brazil in a one-year period. Samples were assessed using disk diffusion tests with inhibitors of β-lactamases such as phenylboronic acid (AFB), cloxacillin (CLOXA), and ethylenediaminetetraacetic acid (EDTA). Strains with differences in zone diameters ≥ 5mm for disks supplemented or not were considered producers of carbapenemases. RESULTS: Klebsiella pneumoniae was the most prevalent CRE, which appeared in 80.3% cases (n = 143). Among clinical materials, the rectal swab was responsible for 43.4% of the isolations (n = 62), followed by urine (18.9%; n = 27). Among the CREs identified in this study, the growth of 56.7% (n = 101) isolates, which were putative producers of Klebsiella pneumoniae carbapenemase (KPC), were inhibited by AFB, whereas 7.3% (n = 13) isolates were inhibited by both AFB and CLOXA and were considered as putative producers of plasmid-mediated AmpC; approximately 3.4% (n = 6) were inhibited by EDTA, which possibly produced metallo-β-lactamase. Lastly, 32.6% (n = 58) cases showed negative results for AFB, CLOXA, and EDTA sensitivity, and represented another class of β-lactamases and/or mechanism of resistance. CONCLUSIONS: Phenotypic screening of CREs is important for clinical laboratories that monitor outbreaks of resistant microbes. Phenotypic tests that use carbapenemase inhibitors and enhancers such as AFB, CLOXA, and EDTA are necessary since they are good screening methods for the detection of carbapenemases.