Enumeration and identification of Campylobacter species in the liver and bile of slaughtered cattle

Abstract

Healthy cattle are considered as reservoirs for a variety of Campylobacter species. To control the bacterial contamination in meat products, quantitative assessment of campylobacters in liver and gallbladder was carried out at an abattoir. Liver and bile samples were collected from 108 healthy beef cattle after evisceration and viable counts of campylobacters were determined by a direct-plating technique using modified Cefoperazone Charcoal Deoxycholate agar (mCCDA). The suspected colonies on the highest dilution plates were subjected to biochemical tests and PCR for identification. Campylobacter species were isolated from 49 (45%) bile and 6 (5%) liver specimens examined. Numbers of campylobacters in bile and liver ranged from log 103 to 7 (median 5) and log 10 1 to 2 (median 1) cfu per ml and per g, respectively. These Campylobacter species were identified as C. fetus, C. jejuni, and C. coli. Multiple infections involving two species were observed in 16 cattle. C. fetus and C. jejuni were the predominant species in bile. Growth of C. fetus, C. jejuni, and C. coli in spiked bile samples revealed an initial exponential growth phase followed by a period with no apparent increase in colony count for 28 days. It appeared that these campylobacters can survive in bile for a long period. To determine transfer route of bacterial cells to the gallbladder, C. jejuni, C. fetus, or C. coli was inoculated intravenously in mice. The inoculated cells were recovered from bile, suggesting that the organism was transferred from the blood stream to bile duct in the liver. From these results, bile in cattle is considered to be an important contamination source of Campylobacter species in processing plants.