Complete Sequencing and Diversity Analysis of the Enterotoxin-Encoding Plasmids inClostridium perfringensType A Non-Food-Borne Human Gastrointestinal Disease Isolates

Abstract

Enterotoxin-producing Clostridium perfringens type A isolates are an important cause of food poisoning and non-food-borne human gastrointestinal diseases, e.g., sporadic diarrhea (SPOR) and antibiotic-associated diarrhea (AAD). The enterotoxin gene (cpe) is usually chromosomal in food poisoning isolates but plasmidborne in AAD/SPOR isolates. Previous studies determined that type A SPOR isolate F5603 has a plasmid (pCPF5603) carrying cpe, IS1151, and the beta2 toxin gene (cpb2), while type A SPOR isolate F4969 has a plasmid (pCPF4969) lacking cpb2 and IS1151 but carrying cpe and IS1470-like sequences. By completely sequencing these two cpe plasmids, the current study identified pCPF5603 as a 75.

Toxin Plasmids of Clostridium perfringens

“…Overlapping PCR surveys and pulsed-field Southern blot analyses established that most type A CPE-associated non-food-borne human GI disease isolates carry either a pCPF5603-like or a pCPF4969-like cpe-carrying plasmid (13,237). These two cpe-carrying plasmid families share a ϳ35-kb conserved region encoding the tcp (transfer of clostridial plasmids) region, which can mediate C. perfringens toxin plasmid transfer, as discussed below.…”

“…The pCPF4969 variable region contains genes encoding two putative bacteriocins and a two-component regulator similar to VirS/VirR, while the pCPF5603 variable region contains the functional cpb2 gene and several metabolic genes. Some isolates carrying a pCPF4969-like plasmid also possess a second plasmid encoding CPB2 (13,20 (13). Each arrow represents an ORF; ORF arrows shown are as follows: red arrows, the conserved tcp locus (note the adjacent dcm ORF); dark blue arrows, other conserved ORFs shared by these plasmids; light purple arrows, tetracycline resistance gene; green arrows, the cpb2 toxin gene; purple arrows, the netB toxin gene; pink arrows, the etx gene; gray arrows, the cpe gene; dark gray arrows, the iota-toxin gene; yellow arrows, plasmid replication region; light blue arrows, regions unique to each plasmid.…”

“…The first sequenced C. perfringens plasmids (Fig. 2) carrying functional toxin genes were the CPE-encoding plasmids from two type A strains causing non-food-borne human gastrointestinal (GI) diseases (13). The 75.3-kb cpe-carrying plasmid (pCPF5603) of type A sporadic diarrhea isolate F5603 was shown to carry both cpe and cpb2 toxin genes, whereas the ϳ70-kb plasmid pCPF4969 from type A sporadic diarrhea isolate F4969 lacks the cpb2 gene.…”

“…It has now become clear that many important C. perfringens toxins are encoded by large plasmids (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24). Other recent studies, described later in this review, have provided important insights into the diversity of C. perfringens toxin plasmids, the critical importance of these plasmids for pathogenesis, and the ability of toxin plasmids to transfer among C. perfringens strains.…”

Clostridium perfringens extracellular toxins and enzymes: 20 and counting

“…With a few important exceptions, these toxins are encoded on large conjugative plasmids 4,10,[12][13][14][15][16][17][18] , which allows for potential toxin gene transfer between different C. perfringens strains in the gastrointestinal tract and may prolong disease 10 . C. perfringens utilises chromosomally encoded toxins, such as alpha-toxin and perfringolysin O, during human histotoxic infections or human food poisoning (C. perfringens enterotoxin, CPE) 3 .…”