Clostridium perfringens

Clostridium perfringens (formerly known as C. welchii, or Bacillus welchii) is a Gram-positive, rod-shaped, anaerobic, spore-forming pathogenic bacterium of the genus Clostridium. C. perfringens is ever-present in nature and can be found as a normal component of decaying vegetation, marine sediment, the intestinal tract of humans and other vertebrates, insects, and soil. It has the shortest reported generation time of any organism at 6.3 minutes in thioglycolate medium. C. perfringens is one of the most common causes of food poisoning in the United States, alongside norovirus, Salmonella, Campylobacter, and Staphylococcus aureus. However, it can sometimes be ingested and cause no harm. Infections due to C. perfringens show evidence of tissue necrosis, bacteremia, emphysematous cholecystitis, and gas gangrene, also known as clostridial myonecrosis. The specific name perfringens is derived from the Latin per (meaning through) and frango (burst), referring to the disruption of tissue that occurs during gas gangrene. The toxin involved in gas gangrene is α-toxin, which inserts into the plasma membrane of cells, producing gaps in the membrane that disrupt normal cellular function. C. perfringens can participate in polymicrobial anaerobic infections. It is commonly encountered in infections as a component of the normal flora. In this case, its role in disease is minor. The action of C. perfringens on dead bodies is known to mortuary workers as tissue gas. It causes extremely accelerated decomposition, and cannot be stopped by normal embalming measures. These bacteria are resistant to the presence of formaldehyde in normal concentrations. C. perfringens has a stable G+C content around 27–28% and average genome size of 3.5 Mb. Genomes of 56 C. perfringens strains have since been made available on NCBI genomes database for the scientific research community. Genomic research has revealed surprisingly high diversity in C. perfringens pangenome, with only 12.6% core genes, identified as the most divergent Gram-positive bacteria reported. Nevertheless, 16S rRNA regions in between C. perfringens strains are found to be highly conserved (sequence identity >99.1%). Although they lack flagella, C. perfringens bacteria are able to glide across surfaces because their bodies are lined with filaments from end-to-end. The hypermotile variants such as SM101, are often found arising on the edges of colonies on agar plates. Video microscopy of their gliding movement suggests that they form long, thin filaments that allow them to move rapidly like bacteria with flagella. Genome sequencing was used to identify the cause(s) of the hypermotile phenotype and their direct derivatives. In comparing them, strains SM124 and SM127, hypermotile derivatives of strains SM101 and SM102, respectively, contained 10 and six nucleotide polymorphisms (SNPs) relative to their parent strains. Mutations in cell division genes is the common feature of the hypermotile strains. Food poisoning in humans is caused by type A strains able to produce the CPE (for Clostridium perfringens enterotoxin). The CPE is a polypeptide of 35.5 kDa that accumulates in the beginning of the sporulation and is excreted to the media when it lysates at the end of the sporulation. It is coded by the cpe gene, present in less than the 5% of the type A strains, and it can be located in the chromosome or in an external plasmid In the United Kingdom and United States, C. perfringens bacteria are the third-most common cause of foodborne illness, with poorly prepared meat and poultry, or food properly prepared, but left to stand too long, the main culprits in harboring the bacterium. The C. perfringens enterotoxin (CPE) mediating the disease is heat-labile (inactivated at 74 °C (165 °F)). It can be detected in contaminated food (if not heated properly), and feces. Incubation time is between 6 and 24 (commonly 10–12) hours after ingestion of contaminated food.