Detection of biofilm production in blood culture isolates of Staphylococci

Biofilm producing bacteria which are inherently resistant to antibiotics and disinfectants are widely associated with implant associated infections. Staphylococcus is the most commonly associated pathogens with bloodstream infection.

The current study was conducted to detect biofilm production in Staphylococci isolated from blood culture specimens.

70 clinically significant staphylococcal isolates from blood culture were screened for biofilm production by Tissue culture plate (TCP) method, Tube method (TM) and Congo red agar (CRA) method and their antibiotic susceptibility profile was studied.

59 out of 70 staphylococcal isolates were positive by TCP, out of these 21.4% staphylococci were high biofilm producers, 62.8% staphylococci were moderate biofilm producers and 15.8% were non-biofilm producers. Maximum resistance was observed in biofilm producers to cotrimoxazole (74.5%) and erythromycin (62.7%) and none were resistant to vancomycin and linezolid. Out of total 59 biofilm producers, 20.3% (12) were methicillin resistant and all these were S. aureus isolates. 19% (1) out of total 11 biofilm non-producers were methicillin resistant.

Biofilm production was seen to be a major virulence factor in most of the staphylococcal isolates obtained from patients with signs and symptoms of septicaemia. S. aureus was found to be the major pathogen and timely detection of biofilm producing phenotype should be carried out using a simple and reproducible method, TCP which is both qualitative and quantitative.