ANTIBIOTIC SENSITIVITY PATTERN OF BACTERIAL ISOLATES OBTAINED FROM SHRIMP FARMING SYSTEMS OF TAMIL NADU, INDIA

Aquaculture has been progressing rapidly in India during the past few decades. Shrimp farming has been the mainstay of Indian aquaculture financially due to the export earnings and vocational provision to the marginalised shrimp farmers socially. Despite the stringent measures by the implementing authorities against the use of antibiotics in the culture systems, there has been growing incidences of development of antibiotic resistance in the bacterial isolates associated with the aquaculture systems. Due to the global concerns in the development of antimicrobial resistance (AMR) in the bacterial strains and its implication in human health, we have undertaken the current investigation to find out the pattern of AMR in the bacterial strains associated with shrimp farming systems that are normal and those that are infected with pathogens such as white spot syndrome virus (WSSV) and Enterocytozoon hepatopenaei (EHP)

During the current study, we have isolated eighty bacterial strains from shrimp farming systems including animals, water and sediment of normal, infected with WSSV, EHP and combinedly infected with WSSV and EHP. Antibiotic sensitivity of these isolates was tested against 12 antibiotics. Of the 80 isolates, majority (68.75 to 81.25 %) were resistant to Furazolidone, penicillin and erythromycin while less than 6.25 % isolates alone were resistant to ofloxacin, ciprofloxacin, sulphamethizole and chloramphenicol. Multiple antibiotic resistance (MAR) calculated as ratio of resistance to the total number of antibiotics tested, it was found that 33.75 % of the isolates had MAR above the critical value of 0.275 (Fig.1). From the normal shrimp farming systems, only 2.5 % of the isolates were resistant to more than 2 antibiotics while this value was 40, 41.3 and 30.6 % in the isolates obtained from WSSV infected, EHP infected and WSSV and EHP combinedly infected shrimp farms. The present scenario therefore does not augur good for the human health concerns. The increase in the MAR values in the present study points to possible horizontal transfer of AMR genes across the environmental bacterial isolates, which is being investigated separately.