Phenotypic and Genotypic Differentiation of MRSA and MRCoNS Strains Isolated from Teaching Hospitals in Southwest of Iran, Shiraz

Background and Objecties:Staphylococcal infection is one of the most important nosocomial infections that cause a broad spectrum of diseases ranging from superficial skin lesions to invasive infections such as osteomyelitis and bacteremia. The aim of this study was to determine the frequency of methicillin resistant staphylococcus aureus (MRSA) isolates and methicillin resistant coagulase negative staphylococcus (MRCoNS) isolates due to increasing frequency of them and increase in their resistance to methicillin and other antibiotics. Also, we aim to determine the presence of pvl gene due to its importance in S. aureus strains which can causes respiratory tract and skin infections. Materials and methods:This cross-sectional study was performed on a total of 221 staphylococci isolates obtained from clinical specimens from two major hospitals of Shiraz, Iran. Antibiotic susceptibility profile was determined by the disc diffusion method according to CLSI guidelines. Presence of intent genes (femA, mecA and pvl) was investigated by PCR method. Results:Among 221 collected isolates 168 isolates (76%) were staphylococcus aureus and 53 isolates (24%) were coagulase negative staphylococci (CoNS). Among S.aureus isolates, 70 isolates were found to be MRSA and of 53 CoNS isolates, 26 isolates (49.5%) were MRCoNS. Molecular tests showed that among whole isolates, 96 isolates (43.4%) were carrying mecA gene, 168 isolates (76%) carrying femA gene and among S.aureus isolates only six isolates had pvl gene. Antibiotic resistance pattern for MRCoNS isolates showed that resistance to erythromycin (70%), gentamicin (69.2%) and chloramphenicol (65%) were the most and for MRSA isolates resistance to chloramphenicol (82.8%), gentamicin (68.5%) and tobramycin (64.2%) were the most. Conclusions:The frequency of CoNS isolates, especially MRCoNS isolates in Shiraz hospitals is increasing significantly. Along attention and control of MRSA isolates, it is necessary to pay attention to MRCoNS isolates as pathogenic agents and as a gene transfer reservoir which can transfer pathogenic genes and antibiotic resistance genes.