Community-acquired methicillin-resistant Staphylococcus aureus carriage rate and antimicrobial susceptibility in a tertiary center, Iran

Abstract

Background: Tis study was aimed to determine frequency and antimicrobial susceptibility of Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) among colonized patients in outpatient status. Materials and Methods: A total of 2000 nasal nares specimens were collected and inoculated on mannitol salt agar. MRSAs were identified based on mannitol positivity and coagulase test followed by cefoxitin disc diffusion test. Antimicrobial susceptibility of MRSA isolates was performed by E-test method for vancomycin and doxycycline as well as disc diffusion method for sulfamethoxazole-trimethoprim (SMX-TMP), erythromycin, linezolid, and clindamycin. D-test was performed for detection of inducible resistance to clindamycin. Results: Overall, nasal carrier rate of S. aureus and CA-MRSA was estimated 22% and 1.25%, respectively. Out of the 440 S. aureus isolates, 25 isolates were MRSA. All were susceptible to vancomycin and linezolid, and susceptibility rates to SMX-TMP, erythromycin,  levofloxacin, doxycycline, and clindamycin were 68%, 44%, 48%, 40% and 44%, respectively; furthermore, 28.5% of resistant isolates to erythromycin had inducible resistance to clindamycin. Conclusion: It seems susceptibility to clindamycin and SMX-TMP, recommended agents for empirical treatment of suspected CA-MRSA, are not promising.Vancomycin and linezolid are effective and reliable antibiotics for the treatment of S. aureus infections.

Key words: Antimicrobial susceptibility, Community-acquired methicillin-resistant Staphylococcus aureus, nasal carrier