Clostridium perfringens is a causative agent of food-borne gastroenteritis for which C. perfringens enterotoxin (CPE) has been considered an essential factor. Recently, we experienced two outbreaks of food-borne gastroenteritis in which non-CPE producers of C. perfringens were strongly suspected to be the cause. Here, we report a novel enterotoxin produced by C. perfringens isolates, BEC (binary enterotoxin of C. perfringens). Culture supernatants of the C. perfringens strains showed fluid-accumulating activity in rabbit ileal loop and suckling mouse assays. Purification of the enterotoxic substance in the supernatants and high-throughput sequencing of genomic DNA of the strains revealed BEC, composed of BECa and BECb. BECa and BECb displayed limited amino acid sequence similarity to other binary toxin family members, such as the C. perfringens iota toxin. The becAB genes were located on 54.5-kb pCP13-like plasmids. Recombinant BECb (rBECb) alone had fluid-accumulating activity in the suckling mouse assay. Although rBECa alone did not show enterotoxic activity, rBECa enhanced the enterotoxicity of rBECb when simultaneously administered in suckling mice. The entertoxicity of the mutant in which the becB gene was disrupted was dramatically decreased compared to that of the parental strain. rBECa showed an ADP-ribosylating activity on purified actin. Although we have not directly evaluated whether BECb delivers BECa into cells, rounding of Vero cells occurred only when cells were treated with both rBECa and rBECb. These results suggest that BEC is a novel enterotoxin of C. perfringens distinct from CPE, and that BEC-producing C. perfringens strains can be causative agents of acute gastroenteritis in humans. Additionally, the presence of becAB on nearly identical plasmids in distinct lineages of C. perfringens isolates suggests the involvement of horizontal gene transfer in the acquisition of the toxin genes.C lostridium perfringens, a spore-forming anaerobic rod, is a member of the normal intestinal flora in humans and animals and a component of soil and sewage microbiota (1-4). C. perfringens is the causative agent of various human diseases, including gas gangrene and food-borne gastroenteritis (5-10). The pathogenicity of C. perfringens is attributed to various toxins produced by the organism, including alpha, beta, epsilon, and iota toxins that classify C. perfringens isolates into five toxin types (A to E), theta toxin, NetB, and C. perfringens enterotoxin (CPE) (10-13).CPE, which is mainly produced by type A C. perfringens, is associated with human gastrointestinal (GI) illnesses, such as food-borne gastroenteritis, antibiotic-associated diarrhea, and sporadic diarrhea (14-16). CPE is a 35-kDa protein, and the cpe gene is located in the chromosome or on a plasmid (17)(18)(19)(20). After orally ingested CPE-positive C. perfringens reaches the GI tract, sporulating C. perfringens produces CPE, and the toxin causes clinical symptoms, such as diarrhea and abdominal cramping. In the clinical diagnosis of gastroente...

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To investigate the dissemination of ESBL/pAmpC-producing E. coli within the food distribution system of Ho Chi Minh City (HCMC), Vietnam, the prevalence of ESBL/pAmpC-producing E. coli strains in chicken meat, pork, beef, and fish/shrimp samples obtained from slaughterhouses, a wholesale market, and supermarkets was examined. Among the total of 330 collected food samples, ESBL/pAmpC-producing E. coli was detected in 150 samples (45.5%). The highest prevalence of these isolates was in chicken meat (76/82, 92.7%), followed by pork (32/92, 34.8%), beef (18/74, 34.3%), and fish/shrimp (24/82, 29.3%). A total of 342 strains of ESBL/pAmpC-producing E. coli were isolated from 150 positive food samples. The most prevalent genes responsible for ESBL or pAmpC activity belonged to the CTX-M-9 (110/342, 31.2%), CTX-M-1 (102/342, 29.8%), and CIT (118/342, 34.5%) groups. To our knowledge, this is the first report of the high occurrence of pAmpC (37.1%) in animal-based food in Vietnam. Among the 342 total ESBL/pAmpC-producing E. coli isolates, 276 (80.7%) were resistant to at least 6 antibiotic agents. Notably, high percentages of resistance to ciprofloxacin and fosfomycin were found in isolates from chicken (80.5% and 50.8%, resp.). These findings demonstrate that animal-based food products in HCMC represent a major reservoir of ESBL/pAmpC-producing E. coli.

Aims:  We compared the efficiency of universal pre‐enrichment broth (UPB), modified Escherichia coli broth containing novobiocin (mEC + n), modified Tryptic Soy Broth (mTSB) and mTSB with novobiocin (mTSB + n) for the enrichment of non‐O157 Shiga‐toxin‐producing E. coli (STEC). Methods and Results:  Freeze‐injured and control non‐O157 STEC (O91, O103, O111, O119, O121, O145 and O165) strains were used to artificially contaminate beef and radish sprout samples, which were then cultivated in each of the four enrichment media. After incubation, STEC strains were detected by loop‐mediated isothermal amplification (LAMP) and plating assays. Enrichment in mEC + n was least effective for facilitating the detection of uninjured STEC strains in radish sprouts, while mTSB + n was least effective for enriching freeze‐injured non‐O157 STEC strains from beef samples for detection by LAMP assay. UPB and mTSB were superior to mEC + n and mTSB + n for the enrichment of non‐O157 STEC from food samples. Conclusions:  The enrichment of non‐O157 STEC was negatively affected by the addition of novobiocin to enrichment broths. Significance and Impact of the study:  Novobiocin should not be added to media used for the enrichment of non‐O157 STEC in food when cell injury is anticipated.