Multidrug-Resistant Bacteria in Aquaculture Systems in Accra, Ghana

Abstract

Background: Antimicrobial resistance (AMR) is an existential global health threat, associated with high mortality, morbidity, and economic impacts. For remedial efforts to be effective, AMR surveillance needs to encompass both human and animal health. However, most AMR surveillance studies, particularly those conducted in sub-Saharan Africa, have usually focused on humans, and rarely on animals. The few that have been conducted on animals have usually focused on poultry, etc., with very little attention given to the aquaculture sector. Aim: To evaluate AMR in bacteria pathogens harboured in marketed reared fish sold in Accra and the pond water from which they originated. Methodology: The study was cross-sectional, involving 160 inland fish marketed to consumers and the corresponding pond water from which the fish were reared. The samples were bacteriologically cultured, and their total viable and coliform counts determined, following standard procedures. The bacterial isolates were identified using MALDI-TOF, and the AMR pattern determination and ESBL screening done via the Kirby-Bauer method. Further, the sequence types, serotypes, and resistance genes of the ESBL isolates were determined via whole genome sequencing. Results: The overall total viable count was 12.4×105 cfu/ml (18.25×105 cfu/ml in the fish and 6.55×105 cfu/ml in the pond water). The overall total coliform count was 0.31×105 cfu/ml (0.35×105 cfu/ml in the fish and 0.27×105 cfu/ml in the pond water). In total, 39 different types of bacteria, totalling 391, were isolated from the fish and ponds – 38 different in the fish (totaling 201) and 34 different in the pond water, totaling 190. As a composite, the top five bacteria were Escherichia coli (17%), Aeromonas veronii (11%), Citrobacter freundii (8%), Bacillus cereus (5%), and Klebsiella pneumoniae (5%). In the fish, the top five bacteria were Escherichia coli (15.4%), Aeromonas veronii (12.4%), Citrobacter freundii (9.5%), Edwardsiella tarda (5.0%), and Klebsiella pneumoniae (4.5%). In the pond water, the top five bacteria were Escherichia coli (19.5%), Aeromonas veronii (8.9%), Bacillus cereus (5.8%), Citrobacter freundii (5.8%), and Proteus mirabilis (5.3%). The AMR rates, respectively for the fish, pond water, and overall, were cefotaxime (29%, 35%, and 32%), gentamicin (1%, 0%, and 1%), ciprofloxacin (4% each), chloramphenicol (19% each), tetracycline (42%, 31%, and 37%), meropenem (0% each), and ertapenem (0% each). The bacterial MDR rates were 13.6% (n = 53) overall, 13.4% (n = 27) for the fish, and 13.7% (n = 26) for the pond water. The bacterial ESBL rates were 1.3% (n = 5) overall, 1.0% (n = 2) for the fish, and 1.6% (n = 3) for the pond water. The sequence types of the ESBL isolates were ST4684 (80%, n = 4) and ST2005 (20%, n = 1), and the serotypes were H34:09 (80%, n = 4) and H7 (20%, n = 1), and the AMR genes were blaCTX-M-15, fosA7, and qnrS1. Conclusion: The fish and the pond water had high microbial contamination, mainly accounted for by Escherichia coli and Aeromonas veronii. The AMR, MDR, and ESBL rates were low to moderate. Moreover, the main sequence type and serotype of the ESBL isolates were ST4684 and H34:09, respectively, and the AMR genes were blaCTX-M-15, fosA7, and qnrS1.