Association of intercellular adhesion gene A with biofilm formation in staphylococci isolates from patients with conjunctivitis

BACKGROUND: There is a great negative impact of biofilm-mediated infection on patient health which necessitates the use of reliable methods for detecting biofilm producers. AIMS: This study was done to determine biofilm-producing ability and the presence of intercellular adhesion gene A in clinical staphylococcal isolates and to assess the reliability of two phenotypic methods used for biofilm detection. MATERIALS AND METHODS: Fifty staphylococcal strains were isolated from 100 conjunctival swabs from patients attended the Ophthalmology Outpatient Department of the Research Institute of Ophthalmology. Two phenotypic methods were used for detection of biofilm production; qualitative congo red agar (CRA); and quantitative microtiter plate. Polymerase chain reaction was used to determine the presence of icaA gene. RESULTS: In Staph aureus, 60% were positive biofilm forming and 40% were negative biofilm forming by both phenotypic methods. All positive biofilm-forming isolates were positive for icaA gene production. In coagulase negative staph, 50% were positive biofilm forming and 50% were negative biofilm forming by both phenotypic methods. All positive biofilm-forming strains were positive for icaA gene. All negative cases by CRA and microtiter plate methods were negative for icaA gene except two isolates. All staphylococcal isolates were subjected to antibiotic susceptibility test to correlate biofilm formation with multidrug resistance in staph. CONCLUSION: There is high significant correlation between icaA gene presence and biofilm forming ability; however, the biofilm-forming ability of some isolates in the absence of icaA gene highlights the importance of further genetic investigations of ica-independent biofilm formation mechanisms.