Reservoirs of Antimicrobial Resistance: A Comparative Study of Hospital and Community Settings in Calabar, Nigeria

ABSTRACT Background: Antimicrobial resistance represents a critical global health challenge requiring comprehensive surveillance across healthcare and community environments to understand transmission dynamics and resistance patterns. Objective: This study aimed to assess the level of antimicrobial resistance in clinical and environmental Gram-negative bacterial isolates in Calabar, Nigeria and determine their multiple antibiotic resistance indices. Methodology: This comparative study examined 105 clinical samples from two hospitals. Additionally, 210 environmental samples from hospital sources (door handles, sinks, dump sites) and community sources (sachet water, poultry litter, processed meat), with 35 samples per category, were collected. These were analyzed using standard bacteriological procedures, Vitek identification systems and modified Kirby-Bauer antimicrobial susceptibility testing protocols with ten antibiotics from six classes of antibiotics. Results: Twenty-eight (13.3%) gram-negative isolates were recovered from environmental sources, predominantly from poultry litter 14(50%) and dump sites 10(35%), with significant association between sample sources and organism recovery (χ²=14.412, p=0.001). Forty (38.1%) gram-negative isolates were recovered from clinical samples. Escherichia coli emerged as the predominant isolate in both environmental (30%) and clinical (23.3%) samples. Environmental isolates demonstrated variable resistance patterns with Multiple Antibiotic Resistance Index (MARI) values range of 0.1-0.5 (mean 0.3 ± 0.05), while clinical isolates showed higher resistance levels with MARI of 0.2-0.8 (mean 0.4 ± 0.06). Multidrug resistance was prevalent among clinical isolates, with six bacterial species exhibiting 100% MDR rates. Cefuroxime was the most resisted antibiotic with highest resistance rates in both environmental (60%) and clinical (90%) isolates, while meropenem demonstrated superior efficacy with minimal resistance. Conclusion: The study revealed significant antimicrobial resistance reservoirs in both hospital and community settings, with clinical isolates demonstrating higher resistance levels than environmental counterparts. These findings emphasize the urgent need for comprehensive surveillance and targeted intervention strategies.