Fish Microbiology and Quality Assurance

11. Isolation and identification of Campylobacter from fish and fishery products

Among Campylobacter spp. causing a range of diseases, C. jejuni is frequently involved in acute gastroenteritis in humans upon consumption of contaminated food. This pathogen is naturally associated with several organisms and isolated from water and aquatic animals. Foods of animal origin are the main cause of campylobacter infection. The isolation of this organism involves selective enrichment and plating on selective agar media.

Materials required:
Preston broth/agar

Procedure:
A fish sample (10g) is homogenized using 90 ml of selective enrichment broth (Preston broth) containing antibiotics and incubated at 42⁰ C in water bath overnight. A loopful of the enriched sample is streaked on to selective enrichment agar media (Preston agar), incubated at 42⁰ C for 48 hours, and the translucent discrete colonies are subjected to biochemical tests for confirmation.

Differentiation of food borne Campylobacter

Character	C. jejuni	C. coli	C. laridis
Growth at 30.50C 45.50C Hippurate hydrolysis H2S production Resistance to Nalidixic acid	_ +/- + +/- _	+ + _ _ _	+ + _ + +

Preston broth: