Beta-lactamase Genes in Multi-resistant Aeromonas spp. isolated from River and Aquaculture Water Sources in Nigeria

This study examined multi-resistant Aeromonas spp. isolated from river and aquaculture water sources for determinants of resistant genes. These species can provide a reservoir for resistant genes capable of transfer to other water-borne and human pathogens. The isolates were confirmed with API 20NE. Resistance profiles of 206 Aeromonas isolates were determined for 11 antimicrobials by the Kirby-Bauer technique. PCR was used to determine the genetic determinants responsible for the ESBL phenotypes using primers for bIaTpjvi, blaSnv and blacrx beta-lactamase genes. Phenotypic expression of ESBL production was done by the double disk diffusion method and plasmid curing was effected with acridine orange. The Aeromonas spp. comprised of the following: Aeromonas hydrophilia/caviae, A. sobria and A. salmonicida. Isolates expressed high resistant rates (75-100%) to 63.6% of the antimicrobials and moderate resistant rates (53.3-60.0%) to 27.3% of the antimicrobials tested. There were also high occurrences of multiple resistances with 100% of the isolates being resistant to 2 or more anti'niorobials. Aeromonas spp. from river water expressed higher resistant rates than those from aquaculture water samples. Phenotypic screening for carriage or presence of ESBL gene showed that all the isolates tested positive for the presence of ESBL gene and were resistant to amoxicillin/clavulanate. Amongst the 13 isolates analysed for the 3 (3-lactamase genes, the blaTEM was most prevalent with 30.8% of isolates possessing it, while 23.1% and 7.7% possessed blaSHv, and blacrx respectively. Antimicrobial resistance profile, post curing, showed 38% and 100% of isolates remained ESBL producers and inhibitor resistant respectively. The study infers the presence and diversity of ESBL genes in Aeromonas spp. isolated from river and aquaculture water settings in Nigeria.