Prevalence of Extended-spectrum β-Lactamase-Producing Genes among MRSA Isolates from Clinical Samples in Baghdad City

Abstract Background: Methicillin-resistant Staphylococcus aureus (MRSA) is an intrusive human pathogen causing community- and hospital-acquired infections worldwide. S. aureus was discovered to be one of the leading sources of hospital infections and drug resistance in Iraq, particularly methicillin resistant. Objective: The study aims to know the extent of gene prevalence and antibiotic resistance in S. aureus isolated from various clinical samples. Materials and Methods: A total of 150 clinical samples (urine, wound swabs, ear swabs, burn, and sputum samples) were collected. Disk diffusion method was used for evaluating the antibiotic susceptibility status, while conventional PCR was applied to detect the presence of diagnostic and resistance genes. Microtiter plate method was subjected to study the biofilm formation among the resistance strains. Results: The antibiotic susceptibility results of S. aureus infections showed full resistance to penicillin and cefoxitin, while full sensitivity against vancomycin was observed. MRSA isolates also showed a resistance rate against some macrolide antibiotics, including azithromycin, clindamycin, and erythromycin. There was no association or correlation between antibiotic resistance and biofilm-producing capacity. All MRSA isolates were screened for mecA , blaZ , blaDHA -1 using conventional PCR. Regarding the β -lactamase detection genes among MRSA isolates harbored, only 4/20 (20%) of MRSA isolates carried blaDHA-1 AmpC genes, while 20/20 (100%) showed bla-Z genes. Only 19/20 (95%) isolates showed positive for mecA gene. The mecA genes usually circulate in phenotypically-identified MRSA isolate, confirming the phenotypically-resistant strain and explaining the mechanism of resistance. Conclusion: The high frequencies of circulating mecA genes and β -lactam genes demonstrate the necessity of policies for overcoming MRSA problems in clinical specimens, although no isolate showed that vancomycin resistance depends on a phenotypic test. Improper using of antibiotics among patients in Baghdad city may play an essential role in the spread and emergence of antibiotic resistance.