Phenotypic evaluation of biofilm producing ability in Methicillin resistant Staphylococcus aureus

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 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).
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.
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.