Phenotypic characteristics and antibiotic sensitivity of Vibrio parahaemolyticus strains isolated from diseased groupers (Epinephelus spp.)

Abstract

Bacterial isolations were made from the kidney/blood of diseased groupers (Epinephelus malabaricus and E. tauvina) on thiosulfate citrate bile salt sucrose agar (TCBS) supplemented with 2% NaCl for selective isolation of vibrios. The sucrose non-fermenting isolates obtained on TCBS agar were screened for sensitivity to 10 μg as well as 150 μg 0/129 vibriostatic discs. The presumptive Vibrio parahaemolyticus isolates which were found resistant to 10 μg and sensitive to 150 μg discs were further tested for the detailed phenotypic characteristics. Out of the 10 suspected isolates tested, 9 strains showed typical reactions of V. parahaemolyticus. The phenotypic and biochemical reactions of these V. parahaemolyticus strains were compared with that of a type strain of V. parahaemolyticus (MTCC 451). These strains were also subjected to antibiotic sensitivity studies using 10 different antibiotics. There was wide variation in the antibiotic sensitivity of the strains. Among the various antibiotics tested, chloramphenicol was found to be sensitive to 89% of the V. parahaemolyticus strains used in the study. Streptomycin and nalidixic acid were found sensitive to 67% while neomycin was sensitive to 44% of the strains. All the other antibiotics tested were resistant to most of the strains.