Biofilm Formation and Detection of IcaAB Genes in Clinical Isolates of Methicillin Resistant Staphylococcus aureus

Document Type : Original Article


Microbiology Department, Faculty of Biological Sciences, Shahid Beheshti University, G.C., Evin, Tehran, Iran


Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of nosocomial and community
infections. Biofilm formation, mediated by a polysaccharide intercellular adhesin (PIA) and encoded by the ica operon, is considered to be an important virulence factor in both S. epidermidis and S. aureus. However, the clinical impact of the ica locus and PIA production is less well described in S. aureus. We studied biofilm formation in clinical isolates of MRSA in relation to the presence of the ica operon.
Materials and Methods
Forty five MRSA were studied for biofilm formation by colony morphology on Congo red agar (CRA) and the microtitre plate assay (MtP). Presence of the ica genes was detected by PCR and specific primers.
The results showed that 53.3% of the isolates had the potential to form biofilm by colony morphology of which, 75% carried the ica operon. Weak biofilm production was observed in the MtP assay by 57.8%, of which 53.8% harbored the ica operon. However, about 70% of biofilm non-producers also carried the ica operon.
Overall, there was no agreement between the icaAB gene carriage and biofilm phenotype by either of the two phenotypic methods. However, 91% of biofilm formers on CRA also produced biofilm in the MtP assay.


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