Background: Staphylococcus aureus is one of the important causes of clinical infections
that can be more destructive by its antibiotic resistant strains.
Objective: This study aimed to determine the antibiotic susceptibility pattern and distribution of
mecA and coa genes in clinical isolates of S. aureus.
Methods: Two hundred seventy-three specimens suspected to S. aureus were taken from hospitals
of Ahvaz, southwest of Iran. Isolates were identified by standard microbiologic tests and confirmed
by the molecular method. Antimicrobial susceptibility testing was carried out by disk diffusion
method. The presence of mecA and coa genes was determined by PCR method.
Results: Of a total of 200 isolates which were tested for coagulase tube test, 143 (71.5%) showed
coagulase positive, and 57 (28.5%) showed a coagulase-negative reaction. Antibacterial susceptibility
pattern of 200 S. aureus isolates showed the highest and lowest susceptibility rate to linezolid
(98%) and ciprofloxacin (42%), respectively. The prevalence of methicillin-resistant S.
aureus (MRSA) by detection of mecA gene was estimated as 47.5 % (95/200), of which the rate of
MRSA in coagulase positive and negative isolates was 35% (50/143), and 65% (45/57), respectively.
Meanwhile, coa gene was detected in 100% of coagulase positive and 28.1% of coagulasenegative
Conclusion: The results of this study showed that the number of atypical CNSA in our area is
high. Since the coagulase test is an essential test for diagnosis of S. aureus, our findings regarding
the emergence of CNSA are a warning about the misdiagnosis and selection of appropriate treatment
approach for S. aureus isolates.