Microbiota of gills and antibiotic susceptibility patterns of bacteria isolates from Clarias gariepinus in different holding facilities

Gill is a key respiratory and excretory organ in fish as it provides oxygen need for survival and excretes waste products. However, gills can be infected with pathogenic and opportunistic bacteria leading to increasing fish morbidity and mortality. This study was carried out to isolate, estimate and identify bacteria on the gills of Clarias gariepinus reared in different holding facilities. The susceptibility patterns of the bacteria were also studied using 10 antibiotics commonly used in pisciculture in Nigeria. A total of 84 bacteria belonging to 12 genera were isolated from the gills of 75 Clarias gariepinus. Gram-negative bacteria isolated included Salmonella species (3.6%), Pseudomonas species (7.1%), Aeromonas species (2.4%), Escherichia coli (13.1%), Proteus species (11.9%) Klebsiella species (3.6%), Citrobacter species (4.8%), and Shigella species (3.6%). Gram-positive Corynebacterium species (3.6 %), Staphylococcus species (20.3%), Bacillus species (19.0%) and Streptococcus species (7.1%) were also isolated. The result showed varying bacteria species when considering the different holding facilities. Greater than 50 % of Gram-positive and Gram-negative bacteria isolated were resistant to 5 and 6 different antibiotics respectively while greater than 80 % of all the bacteria were resistant to ≥ 3 antibiotics. The presence of these bacteria in fish predict subsequent impediment in pisciculture and may lead to socioeconomic losses, environmental contaminations and high public health risk. This study calls for concern and an urgent intervention on antibiotic stewardship among fish farmers. Keywords: Antibiotics resistance, Clarias gariepinus, Fish farms, Gills microbiota, Kaduna stat