Enumeration, identification, and antibiogram of some pathogenic bacteria recovered from diseased farmed Clarias gariepinus (Burchell, 1822)

Abstract

Prevalent etiological agents and treatment options are essential for diagnosing and managing fish diseases. Therefore, in this study, enumeration and identification of the total bacterial count in water, skin, and gastrointestinal tract of 75 moribund cultured Clarias gariepinus from different culture facilities were investigated using standard microbiological procedures. Following that, the antibiotic susceptibility of the isolated bacteria to eight antibiotics was tested using the Kirby-Bauer disc diffusion method. Various clinical signs and pathological lesions were observed on the sampled moribund fish. Total bacterial count varied significantly (P < 0.05) regardless of the types of culture facilities. Bacteria species from eight different genera were present, comprising three Gram-positive bacteria; Bacillus subtilis, Streptococcus agalactiae, and Staphylococcus aureus; and five Gram-negative bacteria; Aeromonas hydrophila, Citrobacter freundii, Escherichia coli, Pseudomonas aeruginosa and Salmonella enterica were identified in which Gram-negative bacteria (> 70 %) were the most prevalent type of bacteria isolated. There was an association between the bacteria species isolated from the water and the different parts of the fish sampled regardless of the culture facilities. The antibiogram of the bacteria recovered revealed different sensitivity and resistance profiles. More than fifty percent of the Gram-negative bacteria were sensitive to ciprofloxacin, while the Gram-positive bacteria were susceptible to ciprofloxacin and gentamycin (> 40 %). Amoxicillin, ampicillin oxytetracycline, and tetracycline resistance were high in the bacteria isolates. This study confirmed the presence of antibiotic-resistant pathogenic bacteria isolated with a multiple antimicrobial resistance (MAR) index of 0.63 - 0.75, indicating indiscriminate and irrational use of antibiotics.