Microbial risk assessment of freshwater fish for internal Trade : preliminary study

Abstract

Andhra Pradesh ranks second in inland fish production and almost the entire quantity is channeled to internal markets within the country. A preliminary study was carried out to assess the microbial risks associated with freshwater fish meant for domestic markets. Catla carla and Labeo rohita procured from aquaculture farms and domestic markets in Andhra Pradesh were analysed for bacteriological quality. Total Plate Count (TPC) in the fish samples ranged between lxl03 and 2.3xl07 cfu.g 1 and about one-third of the fish had TPC values above the maximum acceptable limit of 5x I01 cfu.g·1 • Faecal Streptococci was the most frequently encountered faecal indicatorbacteria in the fish samples with prevalence of;::: 90% and counts rangihg between 3x I02 and 5.2x I04 cfu.g·1 • The incidence of sulphite reducing Clostridia was 50% in C. cat/a and 57% in L. rohita with MPN counts ranging from 0.4 to 45 in C. cat/a and from 0.4 to 110 in L. rohita. E.· coli was detected in 28% of L. rohita with counts ranging from 20 to I90 cfu.g·1 and 40% in C. catla with counts ranging from 20 to 1800 cfu.g·1 • One-third of C. carla and one-fifth of L. rohita samples had E. coli counts above the maximum permissible level of 20.g·1 • Fish samples were negative for the presence of Salmonella and Vibrio parahaemolyticus, but Vibrio cholerae was detected in one sample of C. catla and one sample of L. rohita. Antibiotic resistance pattern of E. coli isolates from C. cat/a (17 isolates) and L. rohitu ( 16 isolates) showed no resistance to chloramphenicol, gentamicin and nortloxacin: showed intermediate resistance to amoxycillin (6%). ciprot1oxacin (6% ), co-trimoxazole (9%) and ampicillin (8%) but showed relatively higher resistance to nalidixic acid (24%), tetracycline (30%) and nitrofurantoin (34%). The E. coli isolates from fish samples showed Multiple Antibiotic Index of 0.13. The results of the preliminary study suggest that the microbial risk with respect to human pathogens in freshwater fish was minimum. However, the hygienic quality of freshwater fish needs improvement. The risk associated with the development of resistance in E.coli isolates from freshwater fish to medically important antibiotics was negligible.