Hamadan University of Medical Sciences Avicenna Journal of Clinical Microbiology and Infection 2383-0298 10 3 2023 09 29 Genotypic Investigation of Antibiotic Resistant blaOXA-4 Gene in Clinical Isolates of Pseudomonas aeruginosa 95 99 10.34172/ajcmi.3471 EN Milad Gholampour Matin https://orcid.org/0009-0001-4889-7801 Reza Shapouri Mohammadreza Nahaei https://orcid.org/0000-0001-9367-3279 Mojtaba Mohammadi Roknabadi Rasoul Shokri Journal Article 10.34172/ajcmi.3471 2023 07 07 2023 07 28 Background: Pseudomonas aeruginosa, an opportunistic Gram-negative bacterium, is responsible for 10-15% of hospital infections worldwide. The acquisition of resistance genes is one of the important mechanisms that causes the spread of resistance in this bacterium. This study aimed to conduct a phenotypic and genotypic investigation of the blaOXA-4 resistance gene in P. aeruginosa isolated from clinical samples. Methods: In this study, 110 P. aeruginosa strains were isolated from various clinical samples. The disk diffusion method was applied to reveal the resistance pattern in the isolates. Moreover, the combined disk method was used for the phenotypic analysis of extended-spectrum beta-lactamases (ESBL). Finally, the presence of the blaOXA-4 beta-lactamase gene was analyzed genotypically by polymerase chain reactions (PCR) method. Results: The highest sensitivity and resistance of the isolates were related to amikacin (65.45%) and ceftazidime (86.36%), respectively. The phenotypic analysis indicated that 72 isolates (65.45%) of P. aeruginosa are ESBL-producing. Furthermore, the presence of blaOXA-4 was approved genotypically in 33 P. aeruginosa isolates (45.83%). Conclusion: This study revealed a high prevalence of antibiotic-resistant isolates of P. aeruginosa in the East Azerbaijan population that may be associated with the presence of the blaOXA-4 gene. However, further studies are necessary to identify other resistant genes in ESBL-producing isolates and other geographical areas with larger sample size.