Carbapenem-Resistant and ESBL-Producing Salmonella in Poultry: A One Health Threat Driven by CTX-M–Mediated Multidrug Resistance in Owerri, Imo – State, Nigeria

The emergence of multidrug-resistant (MDR) and extended-spectrum β-lactamase (ESBL)–producing Salmonella in poultry represents a critical public health threat due to potential food-chain transmission. This study assessed antimicrobial resistance (AMR) patterns, ESBL production, and associated resistance genes in Salmonella isolates recovered from chicken cloacal swabs (n = 50) and fecal samples (n = 50). The isolates exhibited alarmingly high resistance to β-lactam antibiotics, including ampicillin, cefotaxime, and ceftazidime, as well as carbapenems. Cloacal swab isolates showed resistance rates of 98% to ampicillin, 94% to cefotaxime, 72% to ceftazidime, and 76–80% to carbapenems, while fecal isolates demonstrated complete resistance to ampicillin (100%) and markedly higher resistance to imipenem (86%), meropenem (86%), and ertapenem (96%). Fluoroquinolone resistance was substantial, with ciprofloxacin resistance ranging from 68% to 74% and levofloxacin resistance from 36% to 78%. Aminoglycoside resistance was also notable, particularly to gentamicin (54–70%). ESBL production was confirmed in 31 isolates, predominantly from fecal samples 18(29%) compared to cloacal swabs 13(21%). Molecular characterization of representative isolates identified CTX-M as the most prevalent ESBL gene (80%), followed by TEM (60%) and SHV (20%). The high prevalence of MDR and ESBL-producing Salmonella in poultry underscores a significant AMR burden and highlights the urgent need for enhanced surveillance, antimicrobial stewardship, and biosecurity interventions to mitigate zoonotic transmission.