Evaluation of biofilm formation and antibiotic resistance patterns in Staphylococcus epidermidis isolated from food samples in Shahroud, Iran

BACKGROUND AND OBJECTIVESStaphylococcus epidermidis, a member of Coagulase-negative staphylococci group, can contaminate a variety of food products because humans are common carriers of this bacterium and may be related to specific human infections. This study aimed to evaluate phenotypic detection of the biofilm formation was done by the Congo Red Agar (CRA) method and antimicrobial resistant of Staphylococcus epidermidis strains isolated from food samples in shahroud, Iran.MATERIALS AND METHODSIn present study, ۱۰۰ food isolates of S. epidermidis were identified by using conventional microbiological and biochemical standard tests and then were tested for biofilm formation on Congo red agar (CRA) and the antimicrobial resistance testing of each isolate was examined using the disk diffusion method (Kirby-Bauer technique), on Müeller-Hinton agar plates. The following antibiotic disks used were ciprofloxacin (۵μg), SXT (۵μg), erythromycin (۲۵μg), gentamycin (۱۰μg), Cefoxitin (۳۰μg), clindamycin (۲μg), rifampin (۵μg), tetracycline (۳۰μg), Chloramphenicol (۳۰μg)(MAST, Berkshire, U.K.).RESULTS AND DISCUSSIONIn recent decades, S. epidermidis infections are an increasing cause of concern, because of distribution and high spread of antibiotic resistance among the isolates and their persistence on biotic and abiotic surfaces. The ability to attach to indwelling medical devices and food-processing surfaces and subsequently biofilm production is one of the most prevalent virulence factors in Staphylococcus epidermidis- associated infections. This microorganism is more frequent in dairy and meat products and the most predominant causative agents of hospital associated infections. A total of ۱۳۴ food specimens including raw meat (n = ۳۰) and raw chicken (n = ۲۳), creamery cake (n=۳۵), dried whey (n=۱۲), dough (n=۱۲) cheeses (n=۵), and cream (n= ۱۷) were collected. Among ۱۰۰ S. epidermidis isolates examined only ۱۹ (۱۹%) food isolates produced black colonies (biofilm-producing strains) on CRA plates. All S. epidermidis isolated from food samples showed no resistance to linezolid ,ciprofloxacin, and gentamicin. Twenty six (۲۶%) revealed resistance to erythromycin, ۱۶ (۱۶%) to clindamycin, ۱۱ (۱۱%) to tetracycline, ۹ (۹%) to SXT, ۷ (۷%) to rifampin. and ۲ (۲%) to chloramphenicol.CONCLUSION Isolation of Staphylococcus epidermidis isolates with ability to form biofilm and antibiotic resistance from food samples is a warning for us and requires more detailed molecular investigations.

کلیدواژه ها:

Staphylococcus epidermidis ، CRA ، Food samples ، Shahroud