Abstract
Clostridium perfringens causes a wide range of diseases in a variety of hosts, due to the production of a diverse set of toxins and extracellular enzymes. The C. perfringens toxins play an important role in pathogenesis, such that the presence and absence of the toxins is used as a typing scheme for the species. In recent years, several new toxins have been discovered that have been shown to be essential or highly correlated to diseases; these include binary enterotoxin (BecAB), NetB and NetF. In the current study, genome sequence analysis of C. perfringens isolates from diverse sources revealed several putative novel toxin homologs, some of which appeared to be associated with potential mobile genetic elements, including transposons and plasmids. Four novel toxin homologs encoding proteins related to the pore-forming Leukocidin/Hemolysin family were found in type A and G isolates. Two novel toxin homologs encoding proteins related to the epsilon aerolysin-like toxin family were identified in Type A and F isolates from humans, contaminated food and turkeys. A novel set of proteins related to clostridial binary toxins was also identified. While phenotypic characterisation is required before any of these homologs can be established as functional toxins, the in silico identification of these novel homologs on mobile genetic elements suggests the potential toxin reservoir of C. perfringens may be much larger than previously thought.
Highlights
Clostridium perfringens is a pathogen of humans and animals and is responsible for a wide range of enterotoxigenic and histotoxic diseases that vary in both symptoms and severity
Toxin typing does not account for the full toxin repertoire a strain may be capable of producing and lacks the high resolution afforded with whole genome sequencing (WGS)
Single protein clusters corresponded to epsilon toxin (n = 2), enterotoxin (n = 92), and two clusters corresponding to the subunits of iota toxin (n = 1)
Summary
Clostridium perfringens is a pathogen of humans and animals and is responsible for a wide range of enterotoxigenic and histotoxic diseases that vary in both symptoms and severity. The disease capability of particular strains is due to the production of toxins and extracellular enzymes with specialised roles in pathogenesis. C. perfringens isolates into seven different toxin types, A-G (Table 1) [1]. Toxin typing is used as an indicator of disease-causing capability as some toxins are strongly associated with disease in certain animal hosts, such as NetB (type G) and necrotic enteritis in chickens, and enterotoxin (type F) in food poisoning. Toxin typing does not account for the full toxin repertoire a strain may be capable of producing and lacks the high resolution afforded with whole genome sequencing (WGS). The clostridial toxin typing system does not account for strain clonality and is Pathogens 2019, 8, 16; doi:10.3390/pathogens8010016 www.mdpi.com/journal/pathogens
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