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Fish serve as an important source of nutrition and also acts as a reservoir for different pathogenic organisms. Sewage pollution in the water bodies is the major source of pathogenic bacteria in seafood. In this study, the presence of Gram negative bacteria in raw fish samples was detected and the antibiotic susceptibility pattern of the isolates was determined.A total of 25 raw fish samples were collected at random from different local markets of Karachi in sterile zip-lock plastic bags. From these samples, a total of 73 Gram negative bacterial strains were isolated. Of these 73 Gram negative isolates, 6 were E. coli, 14 K. pneumoniae, 7 E. aerogenes, 4 E. cloacae, 5 C. freundii, 1 C. koseri, 2 P. vulgaris, 3 P. mirabilis, 7 Salmonella spp., 6 Shigella spp., 2 Serratia spp., 2 Pseudomonas spp., 7 Yersinia spp., 3 Aeromonas spp. and 4 were Vibrio spp. The most abundant species among all the isolated Gram negative bacteria was Klebsiellapneumoniae(19.17%) followed by Enterobacter aerogenes(9.59%), Salmonella spp. (9.59%) and Yersinia spp. (9.59%). Antibiotic susceptibility pattern of all the Gram negative isolates was determined by Kirby-Bauer disc diffusion method in which a panel of eight antibiotics was tested. The incidence of resistance was highest against Cefazolin (93.2%) and lowest resistance was observed against Gentamicin (1.4%). Of the 73 Gram negative isolates, 24 were found to be multi-drug resistant (MDR). In conclusion, the bacteriological analysis of raw fish samples showed that the quality of raw fish was poor as high bacterial load was obtained and enteric bacteria were isolated from most of the samples indicating fecal pollution. This study provides valuable information about the presence of MDR Gram negative pathogens in raw fish sold locally which could be useful in the selection of antibiotics for empirical treatment.
Keywords: Enteric bacteria; Fresh fish; Karachi; Multidrug resistant; Pre-enrichment