Monitoring sentinel mice for Helicobacter hepaticus, H rodentium, and H bilis infection by use of polymerase chain reaction analysis and serologic testing.

BACKGROUND AND PURPOSE: Natural infection of research mice with enterohepatic Helicobacter spp. is common and may confound experimental studies from intercurrent disease. We evaluated a protocol of dirty bedding exposure for transmission of Helicobacter infection from colony mice to female Tac:(SW)fBR sentinel mice over 6 months. METHODS: Cecal scrapings from culled colony mice and associated sentinel mice were tested for H. hepaticus, H. rodentium, and H. bilis using polymerase chain reaction analysis (PCR). These results were correlated with the results of sentinel serum IgG responses measured by ELISA. RESULTS: In 9 colony rooms, 43 of 45 mice were infected with H. hepaticus; in 14 rooms, 58 of 70 mice were infected with H. rodentium; and in 2 rooms, 2 of 10 mice were infected with H. bilis. Concurrence of Helicobacter infection between colony and sentinel mice was 82% for H. hepaticus, 88% for H. rodentium, and 94% for H. bilis. Concurrence of Helicobacter infection status of sentinel cagemates was 98% for H. hepaticus, 86% for H. rodentium, and 95% for H. bilis. Fecal samples pooled by sentinel cage had positive PCR results for H. hepaticus and H. rodentium at 1 month in 60 and 44%, respectively, of the cages that contained test-positive mice at necropsy (6 months). By 3 months, detection rates were 100 and 81% for H. hepaticus and H. rodentium, respectively, and H. bilis was not detected until 4 months. Newly acquired infections with H. rodentium and H. bilis were evident throughout the 6-month study period. Seroconversion was coincident with positive PCR results in sentinel mice, and serum IgG values continued to increase until necropsy. The serum IgG ELISA was 98 to 100% sensitive, but was low in specificity (34 to 44%), most likely attributable to common coinfection with H. hepaticus and H. rodentium. CONCLUSION: Sentinel mice acquire infection with Helicobacter spp. through dirty bedding exposure. Combined use of PCR analysis and serologic testing of sentinel mice was predictive of Helicobacter infection status of mouse colonies used for biomedical research.

Effects of an abrupt diet change from hay to concentrate on microbial numbers and physical environment in the cecum of the pony.

Microbial numbers, pH, fluid volume, and turnover rate in the pony cecum were measured during an abrupt change from an all-forage to an all-concentrate diet, both fed at maintenance energy levels. Concentrate feeding resulted in increased (P less than 0.01) numbers of total viable anaerobic bacteria. The numbers of organisms growing on selective starch medium increased (P less than 0.01) when concentrate was fed, while numbers on xylan and pectin media decreased (P less than 0.025). Seven days after the diet change to concentrate, the number of bacteria growing on lactate medium increased (P less than 0.01), followed by a gradual decline. Cellulolytic bacteria occurred in low numbers, ranging from 1.1 x 10(4) to 4.4 x 10(4) per g of cecal contents. Feeding all concentrate decreased both the number of genera (P less than 0.01) and total protozoan numbers (P less than 0.01) in the cecum. Minimum cecal pH values of 6.4 and 5.8 were obtained when forage and concentrate, respectively, were fed, with the minimum pH occurring 6 h postfeeding. Dry-matter percentage of cecal contents followed a diurnal pattern which was the inverse of the pH curve. During forage feeding, the cecum contained an average of 2.2 liters (1.6 to 3.4 liters), which turned over 3.9 times per day. When concentrate was fed, cecal volume averaged 3.9 liters (0.6 to 8.6 liters), with a mean liquid turnover of 4.2 times per day. Microbial numbers and pH changes in the pony cecum associated with an abrupt change in diet from hay to concentrate resembled those which occur in the rumen under similar feeding conditions.