Molecular Diversity of Methicillin-resistant Staphylococcus aureus Isolates Originated from Patients in Ahvaz Hospitals, Iran

Abstract

Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) strains are among the significant causes of mortality worldwide [1]. The hospital or community-acquired MRSA is the primary cause of skin and bloodstream infections and ventilator-associated pneumonia (VAP) [2]. Knowledge of the origin of MRSA strains can be useful for control and spread of these bacteria [3]. This issue can be more critical when the emergence of multidrug-resistant strains lead to treatment failure [4]. Hence, planning surveillance and monitoring program is necessary for control of these pathogens [5]. Currently, both phenotypic and genotypic approaches are available for the diagnosis of MRSA strains. However, in many countries genotyping methods are increasingly used for identification of MRSA isolates, their origins and distribution pattern in communities and hospitals [6]. The genotypic methods are not affected by laboratory conditions, are reproducible, rapid and culture-independent, and suitable for fastidious bacteria. Also, in comparison with phenotypic methods, genotypic methods are of higher sensitivity for detection of the bacteria and differentiating the strains within a species [7, 8]. PCR-RFLP has shown to be a useful assay for the identification of bacterial strains [9]. This method can analyze large numbers of specimens in a short period and has a broad application for epidemiologic studies. The S. aureus infections might originate from hospitals or communities, and their origin can influence their antibiotic susceptibility pattern and consequently, their response to treatment. Genotypic identification of S. aureus isolates can provide insights about their origin and their relation with other strains [10]. Through molecular typing, it would be possible to reduce the infections caused by these pathogens and prevent outbreaks [11]. Various molecular markers are available for assessment of S. aureus diversity, among which are spa, coa, aroA, and gap genes. The spa gene codes protein A, a superficial and virulence protein in S. aureus. The X region in the C-terminal of this gene contains 24 repeated base pair with high polymorphism among strains, which can differentiate between epidemic and endemic strains [12-14]. The coa gene encodes coagulase, a virulent factor of S. aureus; it has a high heterogeneity at 3 end, which makes it as another candidate for MRSA typing [4, 8]. The aroA gene is another genetic marker for genotyping of S. aureus isolates. This gene codes 5-enolpyrovyl shikimate-3phosphate synthase, a key enzyme in the biosynthesis of aromatics amino acids and folate [15]. Introduction: Staphylococcus aureus is among the primary cause of hospitals and community-acquired infections. The emergence of methicillin-resistant S. aureus (MRSA) strains has resulted in the treatment failure of the infections caused by these bacteria. Hence, regional data on antibiotic resistance of S. aureus strains is necessary to adopt appropriate treatment regimens. This study aims to identify MRSA isolates’ diversities and frequencies by molecular analysis of four genes. Methods: In a crosssectional study, 100 S. aureus isolates from patients hospitalized in two hospitals of Ahvaz, Iran were collected and identified. The MRSA isolates were identified by phenotypic method and amplification of the mecA gene. The diversity of MRSA isolates was investigated by amplification of the coa, spa, aroA, and gap genes followed by RFLP analysis using the AluI, HindIII, TaqI and RsaI restriction enzymes. Results: In this study, we identified 50 MRSA isolates. Based on the analysis of coa gene, 8 types, spa gene 5 types and 17 subtypes, coa gene with AluI 13 types, and spa with HindIII 13 types were identified. Also, the RFLP analysis of gap gene with AluI revealed 3 types, and of aroA gene with TaqI and RsaI, 3 types and 2 subtypes, respectively. Conclusion: Our PCR-RFLP analysis revealed that diversities are present among MRSA isolates originated from clinical samples and showed that this method is simple, reproducible, and cost-effective. J Med Microbiol Infec Dis, 2019, 7 (1-2): 19-28.