Susceptibility of hamsters to human pathogenic Clostridium difficile strain B1 following clindamycin, ampicillin or ceftriaxone administration.

Clindamycin-treated hamsters are predictably susceptible to infection with pathogenic strains of Clostridium difficile. This animal model parallels most of the important aspects of human C. difficile associated disease (CDAD). In humans, almost any antibiotic may precipitate CDAD, but clindamycin, ampicillin and second-and third-generation cephalosporins are implicated most often. We studied the effect of ampicillin and ceftriaxone compared to clindamycin on the susceptibility of hamsters to challenge with C. difficile strain designated B1 by restriction endonuclease typing, an epidemic strain from one hospital. Hamsters were highly susceptible to CDAD following a single dose of clindamycin (30 mg/kg orogastrically) from 1 to 4 days when challenged with 100 colony-forming units (CFU) of spores of epidemic CD strain B1. Ampicillin was given orogastrically at 60 mg/kg to groups of three hamsters that were challenged with 10000 CFU of CD strain B1 spores on days 1-4 following ampicillin. Hundred percent CDAD mortality occurred in all groups on each challenge day. Ceftriaxone, given intraperitoneally at 60 mg/kg, induced susceptibility to CDAD for a more limited time course and at a higher CD inoculum, producing 100% mortality when hamsters were challenged with 10000 CFU of CD strain B1 on day 1 following ceftriaxone, 33% mortality at day 2, and no CDAD when challenged on days 3 and 4 following ceftriaxone. Hamsters are susceptible to CD infection for at least 4 days following ampicillin and clindamycin, but ceftriaxone has a shorter duration of susceptibility.