Antibiotic resistance pattern of bacterial isolatesfrom fishes of Andaman and Nicobar Islands

A total of 131 bacteria were isolated from freshwater and marine fishes of Andaman and Nicobar Islands. The percentage of Gram –ve bacteria were 88.52%, while Gram +ve bacteria were 11.47%. The predominating genera identified from fresh water fishes were Aeromonas spp., Pseudomonas spp. and Yersinia spp.; while from marine fishes the predominating bacteria were Edwardsiella spp. and Aeromonas spp. The resistance pattern of Streptomycin, Cephalexin, Rifampicin and Nitrofurantoin were found to be more than 60% both by marine and fresh water bacterial isolates. A high degree of multiple drug resistance patterns has been exhibited by the bacterial isolates from fishes, however the resistance pattern against antibiotics was more in marine bacteria. The high degree of resistance to all the antibiotics by marine and fresh water bacteria may pose a threat to human population by transferring these resistant genes to other bacteria as the consumption of fish food in these islands is very high. Commercial fish farming has been greatly affected by the emergence of disease problems. The most prominent among them are the infectious agents. The infectious diseases due to pathogenic bacteria constitute only a small portion of the total bacterial flora in fish farms but due to over dosage / indiscriminate use of antibiotic therapy, the problem of multiple drug resistance have become a great problem. Most of the fish farms whether freshwater or marine, have a free exchange of water with stream or the ocean water circulation (Knochel, 1989 and De Vicente et al., 1990). Transfer of drug residues to human beings again posses a great health hazard. At this point it is very important to know the bacterial flora of fishes and to study its antibiotic resistance pattern. Therefore, the present work was undertaken. The isolates were identified by employing various biochemical tests and survey was conducted to know the distribution of bacteria in different Islands. The samples were collected from freshwater fishes such as Indian major carps (Cirrrhinus mrigala, Labeo rohita, Catla catla), cat fish and grass carp from experimental fish pond of the Institute and farmer’s ponds in different Islands. Note Indian J. Fish., 53(2) : 231-235, Apr.-Jun., 2006 232 Jai Sunder et al. The marine fishes such as groupers, casrann, triacanthus, bat fish, scorpion fish etc. were obtained from brackish water fish culture ponds of the Institute and fish landing station of different islands. Skin scrapping, gill, liver, kidney, abdominal fluid and intestinal contents were collected and used for microbiological processing. The samples from freshwater fishes were inoculated into, NA (Nutrient agar), BHIA (Brain heart infusion agar) and McCownkey’s agar and for samples from marine fishes zobell agar, TSA, were used. All the samples were processed and inoculated into respective media and incubated for 24 – 48 hrs at room temperature. From each plate, colony showing difference in morphology were randomly selected and transferred to a fresh plate. Streaking and restreaking was continued until a pure culture was obtained. The colony characterizations of all the isolates were noted and the smears were prepared for Gram’s staining. The motility of the organism was checked by using hanging drop slide. Based on Gram’s staining, the isolates were broadly divided into Gram +ve and Gram -ve organisms. Then a series of biochemical and sugar fermentation tests were performed to identify each isolates. (Holt et al., 1994). Muller Hinton agar (MHA) medium was used to grow the bacterial culture. The overnight fresh bacterial cultures were inoculated into the agar plate by disc diffusion method and the antibiotics were tested for its sensitivity by incubating at room temperature for 24 48 hrs. Zone of inhibition was recorded after 24-48 hrs. A clear inhibition zone of 15mm and above was taken as susceptible, more than 10mm but less than 15 mm as moderately susceptible and less than 10mm as resistant. The zones of growth inhibition were measured with the help of calipers/ scale. A total of 134 bacteria were isolated from freshwater and marine fishes. Out of these 91 (67.91%) isolates belong to fresh water fishes and 43 (32.08%) from marine. The Gram’s staining of all the bacteria showed that 116(86.56%) belong to Gram –ve, while only 18(13.43%) were Gram +ve. From fresh water sources a total of 77(84.61%) bacteria were found to be Gram –ve, while only 14(15.38%) were Gram +ve. In case of bacteria isolated from marine sources 39(90.69%) were Gram –ve and only 4(9.30%) were Gram +ve. Out of the total bacteria isolated from fresh water and marine sources the percentage of Gram –ve bacteria (88.52%) outnumbered the Gram +ve bacteria (11.47%).Finally a total of 61 bacteria were identified up to genus level of which 41 were from fresh water fishes (6 Gram +ve and 35 Gram ve) and 20 were from marine water sources (1 Gram +ve and 19 Gram-ve). The most prominent bacteria isolated from freshwater fishes include Yersinia spp., Aeromonas spp. and Pseudomonas spp, while other bacteria viz, Edwardsiella spp., Klebsiella spp., Kurthia spp., Shigella spp., Arizona spp., Bacillus spp., Listeria spp., Staphylococcus spp., Aerogenes spp., and Proteus spp were also isolated from freshwater fishes. In case of marine bacteria Edwardsiella spp. was the most prominent bacteria isolated apart from Aeromonas spp., Shigella spp., Arizona spp., Staphylococcus spp. and Proteus spp. (Table 1). Among Gram +ve bacteria Staphylococcus spp., was predominantly isolated both from fresh water and marine sources. The high percentage of Staphylococcus may be due to the poor quality of water in the pond. Shome et.al., (1998) also reported the high prevalence of Staphylococcus and Pseudomonas spp. from fresh water fishes. Earlier reports from this island also showed the