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¹ Suez Canal University, Department of Bacteriology, Immunology and Mycology, Faculty of Veterinary Medicine, Ismailia 41522, Egypt
² National Institute of Oceanography and Fisheries, Aquaculture Division, Laboratory of Fish Diseases, Alexandria, 21500, Egypt
³ Suez Canal University, Department of Fish Diseases and Management, Faculty of Veterinary Medicine, Ismailia 41522, Egypt DOI : 10.4194/1303-2712-v20_7_01 Viewed : 6099 - Downloaded : 3467 Pseudomoniasis has become a serious threat not only as a disease but also for the ensuing emergence of antibiotic-resistant bacteria. Thus, a total of 180 Oreochromis niloticus and water samples were collected from three intensive farms located in Ismailia Governorate for physicochemical and biological analysis. All retrieved isolates were tested for the presence of the P. aeruginosa oprL gene and for their sensitivity to commercial antimicrobial agents. Isolates showing multidrug resistance (MDR) were examined for the presence of exoS, toxA, mexA, and mexB. The sensitivity of those isolates and their virulence genes expression profiles were evaluated following treatment with Origanum marjoram and Origanum vulgare. Analyzed water samples showed a high load of total and fecal coliforms and indicated faecal contamination. The prevalence of P. aeruginosa in examined fish was 6.11%. All isolates harboured the oprL gene and showed different sensitivity to the antimicrobial agents. Only four isolates showed MDR and harboured all genes of interest. Both herbal extracts were effective and reduced the expression levels of exoS and toxA genes, even at subinhibitory concentrations. Despite the pathogenicity and antibiotic-resistance patterns of P. aeruginosa, it can be controlled by herbal medication, and thus encourages their use as antibiotic surrogates in aquaculture. Keywords : Pseudomonas aeruginosa, Multidrug resistance, Gene expression, Origanum extracts, Oreochromis niloticus