Antibiotic susceptibility of Gram-negative bacteria isolated from freshwater fish hatcheries of West Bengal, India

Abstract

A survey on the use of aquadrugs in freshwater fish hatcheries of West Bengal was conducted and the susceptibility of hatchery bacterial flora to selected antibiotics were studied during June 2006 - July 2007. Aquadrugs such as oxytetracycline, althrocin, ampicillin, sparfloxacin, enrofloxacin, acriflavine, formalin, potassium permanganate, malachite green, tannic acid and herbal extracts were found to be used at varying levels for prophylactic as well as curative purposes. All the bacterial isolates (n = 74) tested were highly susceptible to gentamycin. Majority of the isolates were resistant to oxytetracycline followed by co-trimoxazole and nitrofurantoin. Resistance to chloramphenicol was noticed in few strains of Aeromonas hydrophila (15%), Aeromonas caviae (9%) and Pseudomonas spp. (25%). Multiple antibiotic resistance was observed in 30% and 90% of the Gram-negative bacteria of carp and catfish hatcheries, respectively. The study in general revealed regular use or abuse of aquadrugs in most of the fish hatcheries surveyed, thus raising the risk of antibiotic resistance development and human heath safety.