ObjectivesBiofilm formation is one of the important features of Staphylococcus epidermidis, particularly in nosocomial infections. We aimed to investigate the biofilm production by phenotypic methods and the presence of ica genes in S epidermidis.MethodsA total of 41 S epidermidis isolates were recovered from different clinical specimens. Biofilm formation was evaluated by microtiter plate, tube method and Congo red agar method. The presence of icaA and icaD genes was investigated by PCR. Validity of methods (sensitivity and specificity), and metrics for test performance (positive/negative predictive value, and positive/negative likelihood ratio) were determined.ResultsBy both microtiter plate and tube method, 53.6% of S epidermidis isolates were able to produce biofilm, whilst only 24.4% of isolates provided a biofilm phenotype on Congo red agar plates. icaA and icaD genes were found in 100% and 95.1% of isolates, respectively. Biofilm phenotypes accounted for 4.8% by microtiter plate assay, despite the absence of the ica gene. Congo red agar and PCR exhibited a lower sensitivity (18% and 45.5%, respectively) for identifying the biofilm phenotype in comparison to microtiter plate.ConclusionThe microtiter plate method remains generally a better tool to screen biofilm production in S epidermidis. In addition, the ability of S epidermidis to form biofilm is not always dependent on the presence of ica genes, highlighting the importance of ica-independent mechanisms of biofilm formation. The use of reliable methods to specifically detect biofilms can be helpful to treat the patients affected by such problematic bacteria.

Background:One of the most important causes of urinary tract infection (UTI) in the world is uropathogenic Escherichia coli (UPEC). The first necessary step for establishing UTI is the attachment and invasion of UPEC to the urinary tract epithelial cells. Objectives: In this study, we assessed the anti-adhesion activity of the zinc oxide nanoparticles (ZnO NPs) against UPEC in T24 cell cultures and the effect of these particles on the fimH gene expression by real-time PCR method. Methods: Toxicity of ZnO NPs was measured with MTT test and minimum inhibitory concentration (MIC) was assessed by agar dilution method.Results: Minimum inhibitory concentration for the three UPEC strains that were used in this study were 1250 µg.mL -1 . Our results showed that the IC50 of ZnO NPs for the T24-cells was 19.53 µg.mL -1 and 0.3 µg.mL -1 is a nontoxic concentration for this cell line. These low concentrations of ZnO suspensions showed 28.77 to 44.71% decrease in the attachment of UPEC to the T24 cells and also could decrease the expression of fimH gene in UPEC. Conclusions:This study showed the anti-adhesive effect of ZnO suspension against UPEC adhesion to the T24 cells and decreased fimH gene expression are seen in these low concentrations of ZnO suspensions.