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

Abstract

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.