Traditionally, bacteria have been classified as either primary pathogens, that will always cause disease, opportunistic pathogens, that will cause disease under certain predisposing conditions, or commensals, that are harmless to the host. Emerging evidence shows that many species we traditionally considered pathogenic may be carried asymptomatically. One such species of bacteria is Clostridium perfringens, which is an anaerobic, spore-former that has been extensively studied due to its ability to cause many severe diseases, including gas gangrene and food poisoning in humans and enterotoxemic diseases in domestic livestock.
We have recently shown that 40% of babies will be colonised with C. perfringens by the time they are one month old and many studies have identified C. perfringens as a part of the normal human gut microbiota. To understand the genomic composition of C. perfringens and how this composition leads to variation in the ability to cause disease, a bioinformatic approach was taken. A total of 308 whole genome sequences of C. perfringens were collected and analysed to determine phylogenetic relations between strains. From this analysis it was observed that there were very few correlations between toxin type or host and the relatedness of strains. The only correlation was that strains found to cause food poisoning in humans were found to be more genetically similar and had fewer genes in their genomes. The genomes of these strains were also found to have genes that encode for proteins involved in the regulation of sporulation. Therefore, these C. perfringens strains have adapted to regulate their sporulation differently, and this may be allowing them to survive better in food and reach the gastrointestinal system more effectively to cause food poisoning.