Multiple Antibiotic Resistance pattern of Vibrio harveyi fromLuminous Vibriosis affected cultured Tiger Shrimp, Penaeus monodonin Andhra Pradesh, India

An investigation was undertaken to determine the extent of antibiotic resistance exhibited by Vibrio harveyi, isolated from diseased Penaeus monodon, collected from culture ponds located in East Godavari District of Andhra Pradesh. A total of 159 isolates of Vibrio harveyi, of which 110 are from four Modified-Extensive ponds (ME1, ME2, ME3, ME4) and 49 are from four Semi-Intensive ponds (SIA, SIB, SIC, SID), were screened for their susceptibility to 22 antibiotics. All the isolates from ME and SI ponds were resistant to penicillin G and 100% susceptibility was observed in the case of all the isolates of ME ponds towards Ciprofloxacin and Norfloxacin. The isolates from ME ponds were more resistant than those from SI ponds and the isolates of ME 1 pond exhibited 100% resistance towards eight antibiotics, whereas those of SI ponds were 100% resistant to only one antibiotic. A significant difference was observed in the Multiple Antibiotic Resistance (MAR) of the isolates from ME ponds, whereas the difference was not significant in the case of isolates from SI ponds. MAR against 4 - 10 antibiotics was highest in the isolates from pond ME 4 (90.5%), followed by those from ME 3 (76.7%) and ME 2 (11.4%) and it was highest with 40 % in the isolates from SI D pond. The study revealed the occurrence of highly virulent strains of Vibrio harveyi in shrimp culture ponds, which developed resistance to many antibiotics due to indiscriminate usage of antibiotics.