In-vitro and in-vivo characterisation of resistance to colonisation with Clostridium difficile

In hamsters, resistance to colonisation by Clostridium difficile appears to be mediated by micro-organisms that are present in the gut in relatively low concentrations. Small amounts of normal caecal contents inhibited the growth of C. difficile when added to cultures in vitro or given to animals which had been treated with clindamycin. Filtrates of caecal contents, frozen and thawed contents and contents diluted to 0.1% wet weight lost their inhibitory properties. However, caecal contents retained their protective capacity after culture for 7 days in vitro. Antibiotic treatment altered resistance to colonisation by only a few species of clostridia. Faeces of animals treated with ampicillin but not clindamycin recovered colonisation resistance after incubation at 37 degrees C in vitro. Since human faeces could also restore colonisation resistance to hamsters, the hamster model may be useful for the study of resistance to colonisation by C. difficile in man.