Changes in the cell wall of Clostridium species following passage in animals.

Morphological changes in clostridial isolates after animal passage with other flora in mixed infections were studied by utilizing a subcutaneous abscess model in mice. We used 26 isolates of 7 clostridial species, and one isolate each of Bacteroides fragilis and Klebsiella pneumoniae. Abscesses were induced by all 7 Clostridium perfringens and 3 Clostridium butyricum isolates and by some of the other isolates. A thick granular wall prior to animal inoculation was shown only in C. perfringens, C. butyricum, and C. difficile. This structure was observed in other clostridia only following their animal passage alone or when co-inoculated with K. pneumoniae or B. fragilis.