Comparative Effects of Osmotic, Sodium Nitrite-Induced, and pH-Induced Stress on Growth and Survival of Clostridium perfringens Type A Isolates Carrying Chromosomal or Plasmid-Borne Enterotoxin Genes

About 1 to 2% of Clostridium perfringens isolates carry the enterotoxin gene (cpe) necessary for causing C. perfringens type A food poisoning. While the cpe gene can be either chromosomal or plasmid borne, food poisoning isolates usually carry a chromosomal cpe gene. Previous studies have linked this association between chromosomal cpe isolates (i.e., C-cpe isolates) and food poisoning, at least in part, to both the spores and vegetative cells of C-cpe isolates being particularly resistant to high and low temperatures. The current study now reveals that the resistance phenotype of C-cpe isolates extends beyond temperature resistance to also include, for both vegetative cells and spores, enhanced resistance to osmotic stress (from NaCl) and nitrites. However, by omitting one outlier isolate, no significant differences in pH sensitivity were detected between the spores or vegetative cells of C-cpe isolates versus isolates carrying a plasmid-borne cpe gene. These results indicate that both vegetative cells and spores of C-cpe isolates are unusually resistant to several food preservation approaches in addition to temperature extremes. The broad-spectrum nature of the C-cpe resistance phenotype suggests these bacteria may employ multiple mechanisms to persist and grow in foods prior to their transmission to humans.