Evaluation of Helicobacter hepaticus bacterial shedding in fostered and strategically housed C57BL/6 mice

The murine pathogen Helicobacter hepaticus has important confounding effects on research. Neonatal fostering has been studied in our laboratory for elimination of infection in mice. The purpose of our study was to examine fostering of pups from experimentally infected dams in male-absent parturition, and to determine the significance of gender and time on quantity of bacterial colonization in the cecum and feces of C57BL/6 mice. Approximately 20 C57BL/6 mice were fostered per day from one to four days of age. None of the C57BL/6 pups tested positive by PCR in fecal or cecal samples through four days of age. This data showed that removal of the male C57BL/6 mouse prior to parturition is crucial for extending the fostering period to obtain Helicobacter-free mice. In a second experiment, H. hepaticus infected mice were housed under varying arrangements to determine the effects of gender and housing on fecal and cecal colonization. Neither time or housing group affected bacterial fecal shedding. However, there was a significant overall effect of gender and a significant difference between male and female mice in both fecal and cecal bacterial copy number. Male fecal and cecal samples contained more copies of H. hepaticus than did female samples. Additionally, significant correlations between fecal and cecal H. hepaticus values were found both overall and by gender. Novel predictive algorithms were formulated to predict cecal bacterial colonization levels in fecal pellets. These findings should prove useful in Helicobacter elimination efforts, and in future work to further elucidate the role of H. hepaticus in transmission and disease

Evaluation of Helicobacter hepaticus bacterial shedding in fostered and sex-segregated C57BL/6 mice

Neonatal fostering has been evaluated as a means of eliminating Helicobacter hepaticus infection in laboratory mouse colonies. The purpose of the present study was to evaluate cross-fostering of neonatal C57BL/6 pups from experimentally infected dams after male-absent parturition and to determine the effects of sex and housing strategy on H. hepaticus populations. Approximately 20 C57BL/6 mice (age, 1 to 4 days) were fostered daily. In all fostered mice, fecal samples collected at 21 and 42 days of age and cecal samples collected at 42 days of age tested negative for H. hepaticus by polymerase chain reaction analysis. Our results demonstrate that removal of the male prior to parturition extends the fostering period to yield Helicobacter-free mice. In a second experiment, the effects of time of infection, housing strategy, and sex on fecal H. hepaticus shedding and cecal colonization were evaluated. Neither time nor housing strategy affected bacterial shedding. In contrast, fecal and cecal bacterial loads were higher in male mice versus female mice. A novel predictive algorithm was developed to predict cecal bacterial colonization levels in light of fecal bacterial loads. Our findings likely will prove useful in Helicobacter eradication efforts and in studies designed to further elucidate the role of H. hepaticus in disease