THE USE OF BACTERIAL MEMBRANE FRACTIONS FOR THE DETECTION OF CAMPYLOBACTER SPECIES IN SHELLFISH

Abstract

Selected enrichment broths supplemented with the enzyme Oxyrase a membrane‐bound enzyme derived from E. coli were evaluated for recoveries of Campylobacter under normal atmospheric conditions from shellfish. Results indicate that Oxyrase is useful for the recovery of Campylobacter from shellfish. Effect of Oxyrase on growth of Campylobacter were dependent upon physical parameters such as media volume and surface volume area. For example, in the comparision of growth of Campylobacter sp (low to high levels, 1 × 101 to 6/mL) in various media volumes in Stomacher 400 closure bags and 250 mL and 500 mL screw‐capped Erlenmeyer flasks, no campylobacters were recovered using the closure bags. However, all levels of Campylobacter were recovered in the Erlenmeyer flasks. Oxyrase was useful for the recovery of C. jejuni from Pacific oysters (Crossostrea gigas). In one study, Pacific shellstock oysters were allowed to take up 1 × 106 cells of C. jejuni per mL for a period of 5 to 7 h in an artificial seawater aquarium system. Oysters were removed and stored at 4C for 24 days. Uptake in oysters ranged from 0.4 to 114 cells/g. At intervals, oysters were removed and analyzed for C. jejuni by using the Oxyrase method and the FDA/Bacteriological Analytical Manual standard method. Comparison of these methods showed that the Oxyrase method was as reliable as the official FDA method. Oxyrase was also useful for recovering naturally occurring Campylobacter in market oyster shellstock. To measure reproducibility of the method, an in‐house preliminary collaborative study was conducted in the University of Central Venezuela (Caracas). Participants consisted of 6 groups of three microbiologist each from various countries in Central and South America. All groups were successful in recovering Campylobacter jejuni and Campylobacter coli using Oxyrase. Our results indicate that Oxyrase provides microaerobic conditions for growth of Campylobacter from shellfish.