New insights into the effect of origanum extracts on the gene expression profiles of multidrug-resistant isolates of pseudomonas aeruginosa retrieved from oreochromis niloticus

Abstract

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 sub-inhibitory 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.