Antimicrobial Susceptibility Profiles, Multidrug Resistance Patterns, and MAR Index Analysis of Campylobacter jejuni and Campylobacter coli Isolated from Poultry and Chicken Handlers in Maiduguri, Northeast Nigeria

Background: Antimicrobial resistance (AMR) in Campylobacter jejuni and Campylobacter coli is an escalating global public health concern, driven by misuse of antibiotics in poultry production. In northeastern Nigeria, AMR surveillance data for Campylobacter from live bird markets (LBMs) are essentially absent. This study characterised antimicrobial susceptibility profiles, multidrug resistance (MDR) patterns, multiple antibiotic resistance (MAR) index values, and resistance gene carriage among Campylobacter isolates from chickens and chicken handlers in Maiduguri Metropolis. Methods: Forty-nine phenotypically and molecularly confirmed Campylobacter isolates from 212 samples (broiler cloacal swabs, local chicken cloacal swabs, and hand swabs) were subjected to disc diffusion testing against ten antibiotics per CLSI (2016) guidelines, supplemented by EUCAST where CLSI breakpoints were unavailable. The MAR index was calculated as the ratio of antibiotics resisted to total antibiotics evaluated. Multiplex PCR detected tetracycline tet(A) (888 bp) and erythromycin erm(A) (190 bp) resistance genes. Exact binomial 95% CIs (Clopper–Pearson) were calculated for all resistance rates. MDR was defined as resistance to ≥1 agent in ≥3 antibiotic classes (Magiorakos et al., 2012). Results: Tetracycline resistance was highest (17/49; 34.7%; 95% CI: 21.3%–49.4%) followed by norfloxacin (11/49; 22.4%; 95% CI: 11.5%–36.4%). All isolates were susceptible to ciprofloxacin and levofloxacin (each 91.8% sensitive; 0% resistant; 95% CI for resistance: 0.0%–7.3%) and no isolate was resistant to erythromycin. MDR was detected in 28/49 (57.1%) isolates across 13 distinct resistance patterns. MAR indices ranged from 0.30 to 0.70 (mean 0.40; median 0.40); 16 isolates (32.7%) had MAR ≥0.40, indicating origin from high antibiotic-use environments. The tet(A) and erm(A) genes were detected by multiplex PCR, corroborating phenotypic resistance findings. Conclusions: The 57.1% MDR rate and the predominance of tetracycline resistance in Campylobacter from Maiduguri's LBMs constitute a public health concern requiring urgent antibiotic stewardship, restriction of over-the-counter antibiotic access in poultry, and routine AMR surveillance. Complete susceptibility to ciprofloxacin, levofloxacin, and erythromycin supports their use as empiric first-line agents pending susceptibility data.