Antibiotic Resistant Patterns in MRSA Isolates from Patients Admitted in ICU and Infectious Ward


1 Department of Infectious Diseases, Loghman Hakim Hospital, Shaheed Beheshti University of Medical Sciences and Health Services,

2 Department of Microbiology, Pasteur Institute of Iran, TEHRAN-IRAN


Background: Methicillin- Resistant Staphylococcus Aureus (MRSA) has become one of the highest – ranking hospital acquired pathogens throughout the world, capable of causing a wide range of hospital infections. Staphylococcus aureus is a major nosocomial pathogen that causes a range of diseases, including endocarditis, osteomyelitis, pneumonia, toxic shock syndrome, food poisoning, carbuncles, and boils. Materials and Methods: One hundred S.aureus isolates recovered from patients in Loghman Hakim hospital were included in this study. Minimum inhibitory concentration (MIC) of strains for methicillin was determined by broth macrodilution method as recommended by NCCLS. Antibiotic susceptibility was tested by using the “disk diffusion technique on Mueller-Hinton Agar”. Nineteen antibiotics were tested including Ampicillin, Penicillin, Cephalexin, Cefepime, Gentamicin, Doxycycline, Erythromycin, Chloramphenicol, Tetracycline, Nitrofurantoin, Kanamycin, Amikacine, Cefotaxime, Clindamycin, Cefazolin, Amoxicillin, Sulfamethoxazole-trimethoprim, Vancomycin, and Ciprofloxacin. Results: The MIC range for methicillin was from 1µg/ml to 1024µg/ml. Ninety percent of the isolated strains had methicillin MIC≥ 16µg/ml and were designated as resistant. Vancomycin and Chloramphenicol were the most effective antibiotics and only 7% and 14% of the isolates were resistant respectively. Forty-four percent hospital acquired MRSA strains were resistant to Co-trimoxazole. The high antibiotic resistance among MRSA strains could be originated due to widespread use of antibiotics. Conclusion: Out of 90 MRSA isolates characterized in this study, approximately half of them displayed resistance to one or more antimicrobial agents, including Penicillin, Cephalosporins, Tetracycline and aminoglycosides. These data are in accord with previous study suggesting use of these drugs was important in the emergence of antimicrobial resistance in MRSA. In addition, 66% of MRSA isolates were sensitive to Trimethoprim-Sulfamethoxazole (Co-Trimoxazole). Since this drug combination is recommended for treating a range of human infections, S.aureus isolates should be monitored for further emergence of Co-Trimoxazole resistance. (Tanaffos 2004;3(11): 37-44)