Phenotypic evaluation of biofilm producing ability in Methicillin resistant Staphylococ¬cus aureus

Background: Like genomic changes, the ability for biofilm production is considered as one of the antibiotic resistant factors in bacteria which can cause recurrent infections. The infection resulted from Methicillin-resistant staphylococcus aureus is the most common form of such complications manifested as recurrent infections. The aim of this study was to investigate biofilm production ability among isolated Methicillin-resistant Staphylococcus aureus (MRSA) in patients with different types of clinical infection. Material and Methods: Fifty Staphylococcus aureus strains were isolated from different specimens and identified by biochemical and species-specific PCR tests. Methicillin- resistance specificity of isolates was confirmed by disk diffusion method and mecA gene presence; the biofilm- forming ability was evaluated by crystal violet microtiter plate assay and Congo red agar (CRA). Results: Using turbidimetry with no acetic acid, the ability for biofim production was seen at 550 and 492 nm in 34 (68%) and 28 isolates (56%), respectively. In both methods, the most of isolates were weak biofilm producers. In CRA, 94% of isolates were biofilm producers which most (72.3%) of them were moderate producers. Conclusions: While with the consideration of three studied methods high percentages of isolates were biofilm producers and despite the significant correlation seen between their results, there was a higher correlation coefficient between the results obtained from crystalviolet-treated microtiter plates with two reading methods