Bacterial resistance to oxytetracycline in different life stages of Indian freshwater carp aquaculture system

Abstract

In India antibiotics are frequently used for preventing and controlling bacterial pathogens in carp aquaculture system, yet no studies have been performed to evaluate the ecological impact of its intensive and prolonged use. In this work the frequency of oxytetracycline-resistant bacteria from water, palletized feed and different life stages of fish from Indian freshwater carp aquaculture system as well as the level of resistance of selected strains was investigated. Viable as well as antibiotic-resistant bacterial counts were performed by spread plate method in culture media supplemented with the oxytetracycline. Sixty two resistant Gram negative isolates which represented the oxytetracycline-resistant bacterial population, were randomly selected on nutrient agar supplemented with oxytetracycline (50µg/ml) from carp farms and feed pellet samples. Among these bacterial isolates Flavobacterium (21%), Alcaligenes (14.5%), Aeromonas (11%), Pseudomonas (10%) and Enterobacteriace (19%) were the most frequent. The Escherichia, Serratia, Citrobacter, Enterobacter, Shigella and Proteus from Enterobacteriace were recovered. Twelve isolates of oxytetracycline resistant bacteria were mainly dominated in adult fishes by the genus Flavobacterium (23%) and Enterobacteriace(41%). Selected strains exhibited high levels of oxytetracycline resistance with minimum inhibitory concentrations (MICs) ranging from 50 to 600µg/ml.This study shows the presence of an important population of oxytetracycline-resistant bacteria in the microflora of Indian carp aquaculture farms. Therefore the environment of these farms might play important roles as reservoirs of bacteria carrying genetic determinants for high level tetracycline resistance, prompting an important risk to public health.

Antibacterial activity of oxytetracycline on microbial ecology of Nile tilapia ( Oreochromis niloticus ) gastrointestinal tract under laboratory condition

“…Resistant Gram-negative isolates were dominated and increased than control condition. Singh et al (2009) stated that the total bacterial concentration in fish samples were ranged in spawn 1.86 × 10 7 to 3.50 × 10 8 cfu/g, in fry 1.95 × 10 7 to 1.24 × 10 8 cfu/g and in fingerling 1.64 × 10 7 to 1.10 × 10 8 cfu/g. Depaola et al (1995) after OTC treatment in T 2 is possibly related to the initial effect of OTC on the bacterial flora, and bacterial flora tried to resist the antibiotic effect.…”

“…While extensive works had been carried out on the influence of OTC in salmon, catfish, carp and other fish in the different parts of the globe (Miranda & Zemelman, 2002;Petersen et al, 2002;Sarter, Nguyen, Hung, Lazard, & Monte, 2007;Singh et al, 2009;Barros-Becker, Romero, Pulgar, & Feijóo, 2012), little work has been conducted on influence of OTC on tilapia gut microbial ecology. Reda, Ibrahim, El-N, and El-Bouhy (2013) recently conducted a study on growth promoting effect of OTC in tilapia, but they did not study changes in bacterial flora.…”

Application of Outer Membrane Protein-Based Vaccines Against Major Bacterial Fish Pathogens in India

“…Although aquaculture is fast growing in Asian countries such as India, the largest proportion of fish farming is done by low-resource farmers in earthen ponds and floating cages in rivers and lakes whose environmental conditions support the survival of opportunistic pathogenic bacteria that cause disease in fish. Implementation of biosecurity measures is mostly low while the use of antibiotics is high, posing the danger of drug resistance (3)(4)(5). As such, vaccination is considered to be the most effective environmentally friendly disease control strategy.…”