Prevalence of Pathogenic Bacteria in Shiraz Hospital Wards and Evaluation of Their Antibiotic Resistance Genes

Background & objectives: Hospital-acquired infections (HAIs) are the most common adverse event in healthcare worldwide. Furthermore, multidrug-resistant organisms are another complication associated with hospital infections. This study aimed to isolate and identify pathogenic bacteria from hospital wards in Shiraz (Namazi and Rajaei) and to evaluate their antibiotic resistance genes.
Materials and Methods: In this cross- sectional study, 50 samples were collected from hospital walls, floors, clothing, beds, endotracheal tubes, and some other areas in Namazi and Rajaei Hospitals between October 2023 to March 2024. The samples were transferred to the laboratory within two hours and cultured on blood agar and Eosin methylene blue agar. The isolates were subjected to determine antibiotic sensitivity using the disk diffusion method to antibiotics viz., gentamicin (30µg), ceftazidime (30µg), chloramphenicol (30µg), tetracycline (30µg), sulfamethoxazole (30µg), and erythromycin (30µg). Molecular identification of the isolates was performed by the 16S rRNA gene, and resistance genes such as AAC1, Ctx-m, cmlA1, tet(W), Sul1, and ermB were examined using Multiplex PCR.
Results: Of 50 samples, 22 pathogenic bacterial strains were isolated and identified as Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Acinetobacter baumannii, Klebsiella pneumoniae, Staphylococcus aureus, and Escherichia coli. The results of Antibiotic resistance tests revealed that the highest percentage of resistance was to ceftazidime (89.5%), followed by gentamicin (87.6%), and less resistance was to sulfamethoxazole (26%). The results obtained from the detection of AAC1, Ctx-m, cmlA1, tet(W), Sul1, and ermB showed that Acinetobacter baumannii carried all 6 antibiotic resistance genes, while the rest of the pathogenic bacterial isolates carried 4 antibiotic-resistant genes.
Conclusion: Our finding showed that high prevalence of antibiotic-resistant bacteria in hospital environments. Although all isolates exhibited resistance characteristics, Acinetobacter baumannii demonstrated the highest level of multidrug resistance.