Exploratory Screening of Antimicrobial Inhibitory Activity in Human Urine Samples from Regular Poultry Consumers in Al-Bayda, Libya: A Pilot Study

Abstract

Antimicrobial use in food-animal production raises concerns regarding potential human exposure to antimicrobial substances and antimicrobial-resistance-related effects through the food chain. However, evidence from human biological samples remains limited in Libya. This pilot study evaluated antimicrobial inhibitory activity in urine samples collected from 15 volunteers in Al-Bayda, Libya, who reported regular poultry consumption. Urine samples were screened for antimicrobial inhibitory activity using a microbiological disc-diffusion bioassay with Bacillus subtilis as the indicator organism. In a separate antimicrobial-response procedure, human-derived B. subtilis isolates were evaluated against ciprofloxacin, gentamicin, vancomycin, tetracycline, and trimethoprim. The retained laboratory dataset classified participant–antimicrobial observations according to the original experimental classification system as positive, resistance-associated, or negative. Positive responses were observed in 11/15 observations (73.3%) for vancomycin, 9/15 (60.0%) for gentamicin, 7/15 (46.7%) for ciprofloxacin, and 4/15 (26.7%) for tetracycline. Resistance-associated responses were recorded in 6/15 observations (40.0%) for ciprofloxacin and 3/15 (20.0%) for gentamicin, whereas all 15 observations (100%) were classified as resistance-associated for trimethoprim. Exploratory regression analysis found no statistically significant association between participant age (18–65 years) and antimicrobial-response classification for any agent for which model estimation was possible. These findings should be interpreted as preliminary microbiological screening signals and assay-specific phenotypic responses rather than as evidence of clinically confirmed antimicrobial resistance in the participants or proof of dietary transmission from poultry. No molecular characterization of resistance determinants or compound-specific confirmatory analyses was performed. Larger One Health studies incorporating detailed medication and dietary histories, paired or otherwise source-linked food and human sampling, standardized antimicrobial susceptibility testing, and confirmatory analytical methods are warranted.