Antibiotic-resistant Pseudomonas aeruginosa from abattoir and aquaculture environment in Abakaliki, Ebonyi State, southeast Nigeria Pseudomonas aeruginosa résistant aux antibiotiques dans les abattoirs et les environnements d'aquaculture à Abakaliki, État d'Ebonyi, sud-est du Nigéria

Abstract

Background: Pseudomonas aeruginosa is frequently identified as the predominant bacterial pathogen in abattoir and aquaculture settings. In Ebonyi State, Nigeria there has been a lack of thorough investigation on the impact of the organism in the environment on public health. Therefore, it was necessary to investigate the occurrence of P. aeruginosa and determine its resistance characteristics to antimicrobial agents in selected abattoirs and aquaculture facilities in Abakaliki, Ebonyi State, southeast Nigeria.
Methodology: Wastewater samples from randomly selected abattoirs (n=25) and aquaculture (n=25) sites in various locations in Abakaliki, Ebonyi State, Nigeria, were collected into sterile universal bottles and transported to the microbiology laboratory of Ebonyi State University, Abakaliki, for microbiological analysis. For heterotrophic colony count, measured in colony forming unit/ml (CFU/ml), to estimate the microbial load of the samples, a 1- in-10 dilution of the samples were prepared and cultured on nutrient agar, incubated at 37^oC for 24 hours. Colonies from the culture plate were then sub-cultured on Pseudomonas agar and incubated aerobically at 37^oC for 24 hours. Pseudomonas aeruginosa was phenotypically confirmed on the culture plate by conventional morphological characteristics and biochemical tests. Antibiotic susceptibility testing of the P. aeruginosa isolates was performed by the disk diffusion test and results interpreted using the Clinical and Laboratory Standards Institute (CLSI) zone diameter breakpoints. Multiple antibiotic resistance index (MARI) was calculated for each isolate.
Results: The microbial load varied from 3.0±2.8 to 33.4±23.5 x 10⁵ CFU/ml for abattoir samples and 0.00 to 26.0±2.8 x 10⁵ CFU/ml for aquaculture samples. For the abattoir, wastewater samples from the butcher table had the highest frequency of P. aeruginosa (50.0%) isolation, followed by wastewater from the drainage (26.7%), while the lowest frequency was wash water (23.3%). For the aquaculture, wastewater from earth pond had a higher frequency (63.6%) of P. aeruginosa isolation than concrete pond (36.4%). The antibiotic susceptibility result showed that P. aeruginosa exhibited high resistance rate to amoxicillin-clavulanic acid (80.0%) and cefotaxime (80.0%). Additionally, the bacteria showed resistance rate of 50.0% to tobramycin. On the other hand, the isolates demonstrated high sensitivity rates of 90.0% to imipenem and cefepime, while sensitivity rates of 60.0% were observed for meropenem and ceftazidime. The multiple antibiotic resistance index (MARI) ranged from 0.2 to 0.7, with a mean MARI of 0.6.
Conclusion: The results of this study highlight the importance of close monitoring of abattoir and aquaculture settings, as they may serve as major sources for the environmental dissemination of antibiotic resistant bacteria such as P. aeruginosa.