Genetic diversity of Staphylocoagulase genes (Coa) among methicillin-resistant Staphylococcus aureus isolates at clinical specimens of blood and urinary infections

Background: Staphylococcus aureus is a common pathogen in human that can be the cause of a wide range of infectious diseases including bacteremia, pneumonia, cellulitis, and osteomyelitis and skin and soft tissue infections. The coagulase enzyme is one of the most important virulence factors of this bacterium. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) Coa pattern is one of the molecular base typing methods. Molecular typing plays an important role in epidemiological studies of nosocomial infection, such as methicillin-resistant Staphylococcus aureus (MRSA) infection. The PCR-RFLP Coa gene technique provides a useful preliminary method to monitor variations in MRSA populations. We were done Coa-RFLP typing according to the method of Hookey et al., with some modifications. Methods: In this cross-sectional study, one-hundred fifty isolates of S. aureus from urine and blood samples of patients that collected from educational hospitals of Imam Hossein and Al Zahra Isfahan University of Medical Sciences, Iran, from February 2018 to October 2018 were analyzed. After bacterial confirmation of isolates by Coa gene in polymerase chain reaction (PCR) technique, to perform coagulase gene typing, the repeated units encoding hypervariable regions of the coagulase gene of S. aureus were amplified by PCR. This was followed by AluI restriction enzyme digestion and analysis of restriction fragment length polymorphism (RFLP) patterns. Results: Of 150 samples, 45 isolated of S. aureus were confirmed by biochemical methods. Of previous positive samples, 36 (80%) isolates carried Coa gene. Two different genotypes of Coa gene were obtained that include bp680 fragment in 20 specimens and bp750 fragment in 16 specimens. After enzymatic digestion by AluI restriction enzyme for RFLP, four different restriction patterns were obtained that including, the 280+400 pattern in 16 specimens (44.4%), 280+470 pattern in 7 specimens (19.4%), 340+340 pattern in 6 specimens (16.6%) and 750 patterns without digestion were in 7 specimens (19.6%). Conclusion: Using the present experiments, it was determined that the PCR-RFLP pattern, 280+400, was the dominant pattern in the Staphylococcus aureus samples isolated in Isfahan.