Identification of bla OXA-23 gene in resistant Pseudomonas aeruginosa strains isolated from cows and humans in Basra province, Iraq.

Background and aim: Pseudomonas aeruginosa is an infectious agent of great importance for animals and humans. It causes serious infections that show high resistance to antibiotics. This study investigated the molecular detection of bla_OXA-23 gene in antibiotic-resistant P. aeruginosa strains isolated from cows and humans.

Materials and methods: In total, 120 samples, comprised 60 from cows (30 milk and 30 nasal discharge) and 60 from their owners (30 urine and 30 sputum), were individually collected, cultured, and tested for P. aeruginosa through molecular analysis targeting the bla_OXA-23 gene. P. aeruginosa antibiotic-resistant isolates were identified by performing antibiotic susceptibility testing and detecting biofilm formation.

Results: In total, 74.17% positive P. aeruginosa isolates, including 66.67% and 81.67% for cows and humans, respectively. Subsequently, positive cow isolates were detected in 60% of milk samples and 73.33% of nasal discharge samples; while positive human isolates were detected in 76.67% of urine samples and 86.66% of sputum samples. Targeting bla_OXA-23 gene, 58.43% of cultured isolates were positive for P. aeruginosa by polymerase chain reaction. Respectively, positive isolates were detected in 66.67% and 45.46% of cow milk and nasal discharges as well as in 60.87% and 61.54% of human urine and sputum. The antibiotic susceptibility test revealed that all isolates were resistant to all applied antibiotics, particularly imipenem. Results of biofilm formation revealed 67.31% total positives, including 51.43% strong, 34.285% moderate, and 14.285% weak reactions. In addition, although values of the total positive cows and humans differed insignificantly, total positives showed insignificant variation between values of milk and nasal discharges of cows as well as between urine and sputum of humans; however, significant differences were identified in the distribution of strong, moderate, and weak positivity of these samples.

Conclusion: Antibiotic overuse contributes extensively to increasing the prevalence of resistant P. aeruginosa isolates carrying the bla_OXA-23 gene in both cows and humans. Furthermore, studies in other Iraqi areas are necessary to support our findings. The main limitations include that the number of tested samples is relatively low, and there is a need to use a large number of samples from different sources. Also, the current methods for detection of resistant isolates are still culture-based approaches.