Prevalence of Biofilm Formation Among Methicillin Resistance Staphylococcus aureus Isolated From Nasal Carriers

Background: Methicillin -resistant staphylococcus aureus (MRSA) is associated with serious infections. Having the ability of biofilm-formation decrease their susceptibility to antibiotics. Objectives: The aim of this study was to determine the prevalence of biofilm formation among MRSA isolated from nasal carriers in the Beheshti Teaching Hospital in Kashan, Iran. Materials and Methods: A cross-sectional study was conducted in 810 patients referred to emergency department in Beheshti Hospital in Kashan. Sterilized nasal swabs were used for collecting nasal bacteria. Nasal specimens were further recognized as S. aureus strains by standard biochemical tests, and MRSA isolates were detected by disk diffusion method. PCR assay was used for detecting mecA gene in MRSA isolates. The susceptibility of MRSA isolates to amikacin, clindamycin, gentamicin, ciprofloxacin, SXT, erythromycin, tetracycline were determined by using disk diffusion method according to recommendation of CLSI. Biofilm formation ability of MRSA isolates were examined by crystal violet microtitre plate assay and Congo red agar (CRA). Results: Two hundred and ninety six (36.5%) out of 810 isolates were S. aureus. Twenty six (8.8%) of all S. aureus isolates were recognized as MRSA. All the MRSA isolates have the ability of biofilm formation which 15.4%, 19.2% and 65.4% of them were strong, medium and weak biofilm producer respectively. The resistance rate of strong biofilm producer were; erythromycin (100%), clindamycin (75%), ciprofloxacin (75%), SXT (75%), gentamycin (50%), tetracycline (0%), amikacin (0%). Conclusions: High rate of MRSA nasal carrier and having the ability of biofilm formation which decrease their susceptibility to antibiotics, is an alarming for public health. Statistically significant correlation between susceptibility to tetracycline and MRSA carrier was observed.