Sunday Emmanuel Olusola¹ , Temitope Deborah Agboola² , Tolulope Martins Ogunmakinwa² , Folasade Damilola Amulejoye¹ , Mariam Iyabo Adeoba³ , Omotola Victoria Ayebidun¹

1 Department of Fisheries and Aquaculture Technology, School of Agriculture, Food and Natural Resources, Olusegun Agagu University of Science and Technology, Okitipupa, Nigeria
2 Department of Biological Sciences (Microbiology Programme), School of Science, Olusegun Agagu University of Science and Technology, Okitipupa, Nigeria
3 Unisa Biomechanics Research Group, Department of Mechanical, Bioresources and Biomedical Engineering, College of Science Engineering and Technology (CSET) University of South Africa, Pretoria, South Africa
Author    Correspondence author
International Journal of Aquaculture, 2026, Vol. 16, No. 3   doi: 10.5376/ija.2026.16.0015
Received: 03 Apr., 2026    Accepted: 31 May, 2026    Published: 25 Jun., 2026

This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Olusola S.E., Agboola T.D., Ogunmakinwa T.M., Amulejoye F.D., Adeoba M.I., and Ayebidun O.V., 2026, Antimicrobial susceptibility, microbial loads and isolation of Plesiomonas shigelloides from African sharptooth catfish (Clarias gariepinus) juveniles and experimental pond water, International Journal of Aquaculture, 16(3): 184-195 (doi: 10.5376/ija.2026.16.0015)

The aim of this study was to investigate the antimicrobial susceptibility, microbial loads and isolation of Plesiomonas shigelloides isolated from African catfish, Clarias gariepinus juveniles and experimental pond water. Microbial loads of pond water and fish tissues (gill, liver, and intestine) were evaluated using standard methods. Isolation and antibiotic susceptibility of the bacterial species were carried out using standard microbiological techniques. Antibiotic susceptibility of the isolates was assessed using a panel of 12 antibiotics by disc diffusion method and standard guidelines. The microbial loads in water from the experimental ponds ranged from 5.60 to 7.00 log₁₀ CFU/mL, while those in gill, liver, and intestine samples ranged from 6.40 to 7.00 log₁₀ CFU/g. The microbial loads were higher than the permissible limits for wastewater and fish tissues. The microscopic cell morphology analysis of presumptive P. shigelloides revealed 40 isolates of round-ended, straight rod shape, which were motile, positive to oxidase, catalase, mannitol, and citrate biochemical test, negative to urease, methyl red, and glucose biochemical test. Antibiotic susceptibility results showed that the presumptive P. shigelloides were 100% resistant to cefuroxime and cefotaxime, 87.5% to meropenem, and 77.5% to ceftazidime. However, the isolates were 0% resistant to gentamicin and amikacin of aminoglycoside derivatives, suggesting that these might be only two out of the 12 panels of antibiotics used that presumptive P. shigelloides might have responded to. The findings highlight the need for routine microbial monitoring, improved pond hygiene, and responsible antimicrobial use in catfish aquaculture. The observed in vitro susceptibility to gentamicin and amikacin may provide useful baseline information for future risk assessment and antimicrobial stewardship.

Antibiotics; Biochemical test; Clarias gariepinus; Microbial loads; Plesiomonas shigelloides