The Frequency of Antibiotic-resistant <i>Staphylococcus aureus</i>, Isolated From Samples of Hospitalized Patients in the Intensive Care Unit of Hospitals in Ahvaz, Iran

Introduction: Staphylococcus aureus is a highly significant pathogen responsible for infections and fatalities among patients in the intensive care unit (ICU) of hospitals. This study aimed to determine the frequency of antibiotic resistance in S. aureus strains isolated from urine, blood, and wound samples of hospitalized patients in the ICU of hospitals in Ahvaz, Iran. Methods: A total of 113 samples were collected during the sampling process. These samples were cultured on blood agar and eosin methylene blue (EMB) agar, followed by an incubation period at 37° C for 24 hours. The identification of S. aureus was based on the appearance of grayish-white colonies and a series of tests, including Gram stain, catalase, Mannitol salt agar, DNase, and tube coagulase tests. The isolates were analyzed using antibiograms to test for susceptibility to oxacillin, cefoxitin, linezolid, ciprofloxacin, clindamycin, trimethoprim, sulfamethoxazole, rifampicin, penicillin, and erythromycin. Results: The prevalence of S. aureus was highest in blood samples (49.55%) and lowest in urine samples (32.12%). All strains of tested S. aureus were sensitive to the antibiotic linezolid, while 90% of methicillin resistance S. Aureus (MRSA) found in blood samples were sensitive to rifampicin. The highest prevalence of S. aureus was found in Golestan hospital, accounting for 21.23%. The antibiotics with the highest resistance against MRSA in blood culture samples were penicillin (100%), clindamycin (88.9%), ciprofloxacin (81.81%), erythromycin (80.7%), and trimethoprim-sulfamethoxazole (73.52%). The polymerase chain reaction (PCR) results for gene prevalence revealed that 110 isolates contained this gene, while 3 isolates lacked it. Using the national multiplex PCR method for SCC typing, 47 isolates (7.42%) expressed SCC III, and 33 isolates (30%) expressed SCC II. Conclusion: The study findings revealed significant resistance to certain antibiotics in the hospital strains of S. aureus. Likely, the misuse of antibiotics, taken without a physician’s prescription contributes to this complication.