MOLECULAR CHARACTERIZATION, VIRULENCE PROFILING, AND ANTIMICROBIAL RESISTANCE OF Aeromonas ISOLATES FROM CULTURED Clarias gariepinus: IMPLICATIONS FOR AQUACULTURE AND PUBLIC HEALTH

Abstract

Bacterial pathogens like Aeromonas threaten aquaculture through high fish mortality and pose significant
zoonotic risks to humans due to increasing multidrug resistance. This study aimed to characterize Aeromonas
isolates from cultured Clarias gariepinus in Kwara State, Nigeria, examining their species diversity, virulence
profiles, antimicrobial resistance, and associated public health risks. A total of 119 catfish were sampled across 13
farms; isolates were identified via biochemical tests and 16S rRNA-PCR, followed by screening for virulence
(flaA, aerA/haem) and resistance (TEM, CTX, SHV) genes. Molecular characterization and phylogenetic analysis
of sequenced isolates confirmed species identities with GenBank accession numbers PV364439, PV364441,
PV364438, and PV364443. Findings also revealed 63 of 119 (52.9%) fish tested positive as Aeromonas hosts, with
A. dhakensis (55.7%), A. hydrophila (24.05%), and A. veronii (6.33%) being the primary species identified. All
isolates exhibited multidrug resistance (MAR index > 0.2), including 100% resistance to amoxicillin-clavulanate
(Augmentin) and 98.73% to Amoxycillin. Genetic analysis detected the flaA virulence gene in 44.4% of selected
isolates and resistance genes TEM (50%), CTX (16.7%), and SHV (11.1%). Socio-demographic data highlighted
significant awareness gaps, with 60% of farmers handling fish with bare hands despite having open wounds. The
study concludes that the high prevalence of virulent, multidrug-resistant Aeromonas strains poses a severe threat
to food security and public health. It recommends mandatory veterinary oversight for antibiotic use and improved
farmer education on zoonotic risks to ensure sustainable aquaculture