Unexpected inefficiency of the European pharmacopoeia sterility test for detecting contamination in clostridial vaccines

Three outbreaks of clostridial disease in ruminants were reported in Spain. Out of 202,525 animals in affected herds, 41,767 were infected and 22,189 died. Epidemiological investigation linked these outbreaks with vaccination with three different commercial anti-clostridial vaccines contaminated with Clostridium sordellii. Vaccines were produced by the same manufacturer. Microbiological and molecular genetic analyses confirmed this association, and isolates of C. sordellii with identical biochemical and pulsed-field gel electrophoresis (PFGE) macrorestriction patterns were isolated from both diseased animals and the epidemiologically related vaccines. Contamination of the commercial vaccines was not detected by the sterility test proposed by the European (EU) Pharmacopoeia. However, growth was obtained when the commercial vaccines were inoculated into specific culture media for Clostridium and incubated for up to 60 days.