Multiple antibiotic resistance indices of Aeromonas hydrophila isolates of muscle of catfish (Clarias gariepinus, Burchell 1822) from selected markets in Ibadan, Nigeria

Abstract

The extensive use and misuse of antimicrobials for treatment and prophylaxis in livestock production generally and aquaculture in particular is of great concern to environmental and public health. In Nigeria, regulation and monitoring of aquaculture and other livestock production activities at best is lax. Drug resistance pathogens have therefore been consistently reported in Nigeria.

Ninety-eight adult live fishes weighing an average of 684.88±141.73g were purchased at random from different live-fish selling points fortnightly over a fourteen-week period. Fish were anaesthetized using Tricaine Methane Sulfonate (MS222 and 15g of muscle excised and processed according to standard methods. Growth, isolation and characterization of Aeromonas hydrophila was accomplished using Rimler-Shotts agar medium which had been infused with ampicillin supplement for 24 hours and incubated at 37^oC and appropriate biochemical tests.

Ten positive isolates (AH1-AH10) were subjected to culture and sensitivity test using the disc diffusion method on nutrient agar. Zones of growth inhibition around the colonies were observed, measured and characterized as sensitive, intermediate and resistant based on the Manual of Antimicrobial Susceptibility Testing method. All the isolates had MAR >0.2. Isolate AH9 had the highest MAR index (1). Three of the isolates (AH3, AH5 and AH8) had MAR indices of 0.89, while AH2, AH4 and AH7 had MAR indices of 0.67. This study established the resistance of Aeromonas hydrophila isolates from fish muscle to a wide range of antibiotic. The detection of high MAR A. hydrophila in muscle of fish intended for consumption is significant and could act as a potential source of resistant bacteria for humans. Further investigation into antimicrobial resistance is recommended.