Occurrence and antibiotic susceptibility of fish bacteria isolated from Oreochromis niloticus (Nile tilapia) and Clarias gariepinus (African catfish) in Uganda
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Date
2018
Journal Title
Journal ISSN
Volume Title
Publisher
Fisheries and Aquatic Sciences
Abstract
The intention of this study was to identify the bacterial pathogens infecting Oreochromis niloticus (Nile tilapia) and
Clarias gariepinus (African catfish), and to establish the antibiotic susceptibility of fish bacteria in Uganda. A total of 288
fish samples from 40 fish farms (ponds, cages, and tanks) and 8 wild water sites were aseptically collected and bacteria
isolated from the head kidney, liver, brain and spleen. The isolates were identified by their morphological
characteristics, conventional biochemical tests and Analytical Profile Index test kits. Antibiotic susceptibility of selected
bacteria was determined by the Kirby-Bauer disc diffusion method. The following well-known fish pathogens were
identified at a farm prevalence of; Aeromonas hydrophila (43.8%), Aeromonas sobria (20.8%), Edwardsiella tarda (8.3%),
Flavobacterium spp. (4.2%) and Streptococcus spp. (6.3%). Other bacteria with varying significance as fish pathogens
were also identified including Plesiomonas shigelloides (25.0%), Chryseobacterium indoligenes (12.5%), Pseudomonas
fluorescens (10.4%), Pseudomonas aeruginosa (4.2%), Pseudomonas stutzeri (2.1%), Vibrio cholerae (10.4%), Proteus spp.
(6.3%), Citrobacter spp. (4.2%), Klebsiella spp. (4.2%) Serratia marcescens (4.2%), Burkholderia cepacia (2.1%), Comamonas
testosteroni (8.3%) and Ralstonia picketti (2.1%). Aeromonas spp., Edwardsiella tarda and Streptococcus spp. were
commonly isolated from diseased fish. Aeromonas spp. (n = 82) and Plesiomonas shigelloides (n = 73) were evaluated for
antibiotic susceptibility. All isolates tested were susceptible to at-least ten (10) of the fourteen antibiotics evaluated.
High levels of resistance were however expressed by all isolates to penicillin, oxacillin and ampicillin. This observed
resistance is most probably intrinsic to those bacteria, suggesting minimal levels of acquired antibiotic resistance in fish
bacteria from the study area. To our knowledge, this is the first study to establish the occurrence of several bacteria
species infecting fish; and to determine antibiotic susceptibility of fish bacteria in Uganda. The current study provides
baseline information for future reference and fish disease management in the country.
Description
Keywords
Oreochromis niloticus, Clarias gariepinus, Fish bacteria, Diseases
Citation
Wamala, S. P., Mugimba, K. K., Mutoloki, S., Evensen, Ø., Mdegela, R., Byarugaba, D. K., & Sørum, H. (2018). Occurrence and antibiotic susceptibility of fish bacteria isolated from Oreochromis niloticus (Nile tilapia) and Clarias gariepinus (African catfish) in Uganda. Fisheries and Aquatic Sciences, 21(1), 1-10. DOI 10.1186/s41240-017-0080-x