Multilocus variable number tandem repeat analysis and antimicrobial susceptibility pattern of Staphylococcus epidermidis isolates in Tehran, Iran

Objective: Detection of sources of outbreaks caused by coagulase-negative Staphylococcus relies on molecular epidemiology methods. Little is known about the genetic diversity of the Staphylococcus epidermidis isolates isolated from various sources in Iran. We assessed the molecular epidemiology of S. epidermidis isolates collected from clinical and nonclinical sources from Tehran counties during 2014 to 2016 using MLVA (multilocus variable number tandem repeat analysis). Methods: One hundred and three clinical and nonclinical S. epidermidis isolates were collected from two hospitals in Tehran. Antibiotic susceptibility testing of isolates was evaluated for cefoxitin, tetracycline, erythromycin, clindamycin, mupirocin, vancomycin and linezolid according to Clinical and Laboratory Standards Institute, as well as prevalence of mecA gene was evaluated by PCR method. In addition, genetic relatedness of isolates was assessed by MLVA method. Results: Resistant rate to cefoxitin, tetracycline, erythromycin, clindamycin and mupirocin were 64, 36, 72, 44 and 23% in all isolates. All clinical and nonclinical isolates were susceptible to linezolid and vancomycin. In all, 49.5% of S. epidermidis isolates were multidrug resistant. Prevalence of mecA was 64%. The MLVA profile consists of a series of allele numbers, corresponding to the number of repeats at each variable number tandem repeat locus. The results of MLVA showed 64 types among all 103 isolates. There were 16 MLVA types that were common in two hospitals and 15 MLVA types were existed in various sources of S. epidermidis isolates. The diversity index obtained with MLVA was 0.989 (95% confidence interval [0.984–0.993]) for the 103 S. epidermidis isolates. A range of one to six alleles was identified at variable number tandem repeats loci with Simpson's diversity values between 0.526 and 0.781. Conclusion: Our study demonstrated presence of high molecular diversity among S. epidermidis isolates. In addition, the main conclusion was that some MLVA types can be disseminated over the wards and between the hospitals. In other hand, resistance to various antibiotics in S. epidermidis isolates and prevalence of methicillin-resistant S. epidermidis and multidrug resistant S. epidermidis isolates to be increasing.