First Report of Biofilm-forming, Multidrug-resistant Coagulase-negative Staphylococci from Butcher Tables in Enugu, Nigeria: A Public Health Awareness

Abstract

Background: Coagulase-negative Staphylococci (CoNS) have evolved from commensals to significant opportunistic pathogens, primarily due to their capacity for biofilm formation and the acquisition of multidrug resistance (MDR) genes. In low-resource settings, meat processing surfaces like butcher tables can serve as unrecognized reservoirs for these pathogens. In Enugu, Nigeria, no data exist on the prevalence, biofilm-forming ability, and resistance profiles of CoNS contaminating butcher tables, representing a critical gap in food safety surveillance. This study provides the first report on the biofilm-forming capacity and antibiotic susceptibility of CoNS isolated from butcher tables in Enugu. Methods: A total of 30 swab samples were aseptically collected from butcher tables across five major abattoirs/markets in the Enugu metropolis. Standard microbiological techniques were used for isolation, including mannitol salt agar and coagulase testing. Biofilm formation was assessed using the Congo Red Agar (CRA) method and the quantitative microtiter plate (MTP) assay. Confirmed CoNS isolates (n=25) were subjected to antibiotic susceptibility testing against 15 antibiotics using the Kirby-Bauer disk diffusion method, and the results were interpreted per CLSI guidelines. The Multiple Antibiotic Resistance (MAR) index was calculated. Statistical analysis was performed using Chi-square tests to determine associations between biofilm formation and resistance phenotypes. Results: Of the 30 butcher table swabs, 25 (83.3%) yielded CoNS. Among these, biofilm formation was detected in 23 isolates (92% of CoNS; 76.7% of total samples) by MTP assay, with 12 (48%) classified as strong biofilm producers. The CRA method showed substantial agreement (κ = 0.64) with the quantitative method. Antibiotic susceptibility testing revealed alarmingly high resistance rates: 100% to amoxicillin-clavulanic acid, cefoxitin, oxacillin, trimethoprim-sulfamethoxazole, chloramphenicol, clindamycin, and vancomycin. High resistance was also observed for erythromycin (92%), imipenem (60%), ceftriaxone (48%), and piperacillin-tazobactam (40%). All isolates remained 100% susceptible to ciprofloxacin, levofloxacin, gentamicin, and meropenem. The overall MAR index was high (mean 0.68 ± 0.06). Statistical analysis showed a significant association between strong biofilm formation and resistance to erythromycin (p = 0.03). Conclusion: This first report demonstrates that butcher tables in Enugu are heavily contaminated with multidrug-resistant, biofilm-forming CoNS. The high prevalence of biofilm producers (92% of CoNS) indicates these surfaces are persistent reservoirs for transmitting resistant pathogens through the food chain. Urgent One Health interventions, including stricter abattoir hygiene and antimicrobial stewardship, are required.