Production Of Heat-stable Enterotoxin Research Articles

Molecular detection of staphylococcus aureus enterotoxin genes

In this work, S. aureus isolates from meat and meat products were examined for frequency, profiles of antibiotic susceptibility, and virulence genes (seb, sea, sec, sed, see, and fme A). Staphylococcal food poisoning is one of the most economically important foodborne diseases in the world. S. aureus is a prominent food-borne pathogen and common food contamination across the world. Some S. aureus strains generate staphylococcal enterotoxins (SEs), which can cause staphylococcal food poisoning (SFP). Staphylococcus aureus (S. aureus) is one of the most frequently studied foodborne bacteria due to its high pathogenicity, production of heat-stable enterotoxins, and its continued development of resistance to multiple antibiotics. Despite enterotoxigenic staphylococci being thermally killed, cooked beef products may still contain staphylococcal enterotoxins SEs since these toxins are thermo persistent and cannot be removed by heat processing. Therefore, this investigation into the frequency of MRSA genes in certain fresh meat and canned meat was done to learn more about the disease. A total of 80 random samples, Twenty meat samples from butchers, and sixty samples each of Luncheon, Tune, Chicken pieces, Minced meat, Grilled meat, Hamburger Fresh meat and Sausage from some supermarkets in Hilla city in Iraq.

Occurrence and Characteristics of Staphylococcus aureus Isolated from Dairy Products

Food, particularly milk and cheese, may be a reservoir of multi-drug resistant Staphylococcus aureus strains, which can be considered an important issue in terms of food safety. Furthermore, foods of animal origin can be a cause of staphylococcal food poisoning via the production of heat-stable enterotoxins (SE). For this reason, we investigated the prevalence of and characterized Staphylococcus aureus strains isolated from milk and fresh soft cheese obtained from farms located in Wielkopolskie and Zachodniopomorskie Provinces in Poland. Overall, 92% of S. aureus isolates were positive for at least one of the 18 enterotoxin genes identified, and 26% of the strains harbored 5 to 8 enterotoxin genes. Moreover, the S. aureus strains contained genes conferring resistance to antibiotics that are critically important in both human and veterinary medicine, i.e., β-lactams (mecA), aminoglycosides (aac(6′)/aph(2″), aph(3′)-IIIa, ant(4′)-Ia) and MLSB (erm(A), msr(A), lun(A)). The antimicrobial susceptibility of S. aureus to 16 antibiotics representing 11 different categories showed that 74% of the strains were resistant to at least 1 antibiotic. Moreover, 28% of the strains showed multidrug resistance; in particular, two methicillin-resistant S. aureus strains (MRSA) exhibited significant antibiotic resistance. In summary, our results show that dairy products are contaminated by S. aureus strains carrying genes encoding a variety of enterotoxins as well genes conferring resistance to antibiotics. Both MRSA strains and MSSA isolates showing multidrug resistance were present in foods of animal origin.

Prevalence and diversity of Staphylococcus aureus in the Zambian dairy value chain: A public health concern

Staphylococcus aureus is an important opportunistic pathogen of both humans and animals. It can cause several diseases, including mastitis, as well as food poisoning by production of heat-stable enterotoxins in food. The aim of this study was to determine the prevalence of S. aureus and the diversity of strains circulating in the Zambian dairy value chain, which have not been studied in detail before. Three provinces were covered by the study (Lusaka, Southern, and Western) and almost 2000 samples along the dairy value chain, covering both the informal and formal market sectors, were taken at two time points (dry and wet season), with a special focus on raw milk. Nearly 300 presumptive S. aureus isolates were confirmed by MALDI-TOF MS and real-time PCR. Raw milk from traditional and smallholder farms was widely contaminated with S. aureus; prevalence was 33–46% depending on the study province. Raw milk from milk collection centres, informal traders, traditional market sellers, and processors were also frequently contaminated with S. aureus. In addition, S. aureus was detected in several milk bucket swabs and nasal and hand swabs of milkers. From industrially processed (heat-treated) milk and dairy products, no S. aureus was isolated. Methicillin-resistant S. aureus (MRSA) were not detected, but around 10% of the S. aureus isolates carried lukS-PV, a marker gene for the virulence factor Pantone-Valentine leucocidin (PVL), which has been associated with severe diseases in human. Molecular typing identified a total of 44 spa types including 13 novel types: t18396, t18397, t18398, t18399, t18400, t18402, t18416, t20459, t20460, t20461, t20462, t20463, and t20464. Furthermore, 12 novel multi-locus sequence types were identified: ST7012, ST7100, ST7101, ST7177, ST7291, ST7304, ST7305, ST7344, ST7596, ST7597, ST7598, and ST7599, of which ST7012, ST7177, and ST7596 fall into the bovine-associated clonal linage CC97. The spa types t084, t267, t355, and the novel type t20464 were common in all three study provinces. The predominant spa type varied depending on the province. Whole genome sequencing (WGS) and core genome multi-locus sequence typing (cgMLST) indicates transmission of strains along the Zambian dairy chain with possible persistence in the chain over time. cgMLST also revealed a very close relatedness between some isolates from milkers and from raw milk or milk buckets. The high prevalence and wide spa type diversity of S. aureus, as well as possible direct or indirect transmission of (potentially highly virulent) S. aureus to humans along the Zambian dairy value chain, are of public health concern, particularly as milk and milk products are often consumed raw by the Zambian population.

516 Late-Breaking: Iturin a Protects the Intestinal Mucosal Integrity Against E. coli Containing the Gene Coding for Heat-stable Enterotoxin B

Abstract Enterotoxigenic E. coli causes severe infectious diarrhea with high morbidity and mortality in weanling pigs mainly through the production of heat-stable enterotoxins. Iturin A, originally isolated from the insect Hyalophora cecropia, exerts strong antibiotic activity against Gram-positive and Gram-negative bacteria. Thus, our study investigated whether iturin A could protect the intestinal epithelium from the insults of E. coli Rosetta containing the gene coding for heat-stable enterotoxin b (STb-Rosetta). Twenty-eight piglets were divided into four groups and were orally administered PBS (control), 0.16 g/kg BW iturin A, 2 × 109 CFU STb-Rosetta, and 0.16 g/kg BW iturin A + 2 × 109 CFU STb-Rosetta respectively for 8 days. The intestinal epithelial morphology and barrier function were assessed by H&E staining and Ussing chamber, and the growth advantage in enteroids derived from jejunal crypts of piglets in each group was used to evaluate the intestinal stem cell (ISC) activity. The results showed that iturin A increased the average daily gain (ADG) and average daily feed intake (ADFI) of piglets exposed to STb-Rosetta (P < 0.05). Meanwhile, STb-Rosetta-induced decrease in jejunum weight and damage to jejunal morphology and barrier function were significantly improved after iturin A supplementation (P < 0.05). Furthermore, the jejunal crypt cells from piglets in the iturin A + STb-Rosetta group had greater growth advantages of ISCs compared with the STb-Rosetta group, including enteroid forming efficiency, surface area, budding efficiency, and branching coefficient (P < 0.05). Our results indicate that iturin A protects against STb-Rosetta-induced intestinal mucosal injury, which provides an intervention strategy that regulates the function of ISCs in the high turnover-rate crypt-villous axis under ETEC infection. This study was supported by the National Natural Science Foundation of China (31872389, 32072777) and Basic and Applied Basic Research Foundation of Guangdong Province (2019B1515210021).

Heat-stable enterotoxin inhibits intestinal stem cell expansion to disrupt the intestinal integrity by downregulating the Wnt/β-catenin pathway.

Enterotoxigenic Escherichia coli causes severe infectious diarrhea with high morbidity and mortality in newborn and weanling pigs mainly through the production of heat-stable enterotoxins (STs). However, the precise regulatory mechanisms involved in ST-induced intestinal epithelium injury remain unclear. Consequently, we conducted the experiments in vivo (mice), ex vivo (mouse and porcine enteroids), and in vitro (MODE-K and IPEC-J2 cells) to explore the effect of STp (one type of STa) on the integrity of the intestinal epithelium. The results showed that acute STp exposure led to small intestinal edema, disrupted intestinal integrity, induced crypt cell expansion into spheroids, and downregulated Wnt/β-catenin activity in the mice. Following a similar trend, the enteroid-budding efficiency and the expression of Active β-catenin, β-catenin, Lgr5, PCNA, and KRT20 were significantly decreased after STp treatment, as determined ex vivo. In addition, STp inhibited cell proliferation, induced cell apoptosis, destroyed cell barriers, and reduced Wnt/β-catenin activity by downregulating its membrane receptor Frizzled7 (FZD7). In contrast, Wnt/β-catenin reactivation protected the IPEC-J2 cells from STp-induced injury. Taking these findings together, we conclude that STp inhibits intestinal stem cell expansion to disrupt the integrity of the intestinal mucosa through the downregulation of the Wnt/β-catenin signaling pathway.

Evaluating the Behavior of Staphylococcus aureus and Bacillus cereus in Dairy- and Non-Dairy–Based Aqueous Slurries during Manufacturing of Table Spreads

High-moisture slurries used in the production of table spreads may permit growth of Staphylococcus aureus and Bacillus cereus and subsequent production of heat-stable enterotoxins. Compliance with the Food Safety Modernization Act (FSMA), specifically 21 CFR Part 117, subpart B and section 117.80 (c)(2) and (c)(3), requires a hazard analysis to determine whether preventive controls are needed. This study estimates the risk of potential growth of S. aureus and B. cereus in eight different dairy- and non-dairy-based slurries during extended storage and use. Mathematical models were used to screen which slurries might support the growth of S. aureus and B. cereus. Samples were individually inoculated with multiple strains of S. aureus and B. cereus to achieve a target level of 102 to 103 CFU/g. Inoculated and uninoculated slurry samples were incubated at typical holding temperatures of 35°C (95°F), 46.1°C (115°F), and 54.4°C (130°F). Samples were removed and tested following inoculation (time zero), after 4 and 12 h, and after 1, 2, 3, 4, 5, 6, 7, and 10 days of incubation at the target temperatures. All experiments were repeated in triplicate. Samples were analyzed for S. aureus and B. cereus using Baird-Parker agar and mannitol yolk polymyxin agar, respectively. Neither S. aureus nor B. cereus exceeded (P < 0.05) proposed food safety limits (105 CFU/g) at the evaluated experimental conditions. The study highlights the role of multiple hurdles (e.g., pH, potassium sorbate and sodium benzoate, salt, and other ingredients) in assuring microbiological safety of in-process dairy- and non-dairy-based slurries used in the production of table spreads. This study also found that mathematical models representative of product composition, intrinsic parameters, and experimental conditions can help risk managers make informed decisions during product development. Finally, the study findings indicate no significant risk of growth of the target pathogens associated with the dairy- and non-dairy-based aqueous slurries used in the routine manufacturing of table spreads.

Heat-Stable Enterotoxins of Enterotoxigenic Escherichia coli and Their Impact on Host Immunity.

Enterotoxigenic Escherichia coli (ETEC) are an important diarrhea-causing pathogen and are regarded as a global threat for humans and farm animals. ETEC possess several virulence factors to infect its host, including colonization factors and enterotoxins. Production of heat-stable enterotoxins (STs) by most ETEC plays an essential role in triggering diarrhea and ETEC pathogenesis. In this review, we summarize the heat-stable enterotoxins of ETEC strains from different species as well as the molecular mechanisms used by these heat-stable enterotoxins to trigger diarrhea. As recently described, intestinal epithelial cells are important modulators of the intestinal immune system. Thus, we also discuss the impact of the heat-stable enterotoxins on this role of the intestinal epithelium and how these enterotoxins might affect intestinal immune cells. Finally, the latest developments in vaccination strategies to protect against infections with ST secreting ETEC strains are discussed. This review might inform and guide future research on heat-stable enterotoxins to further unravel their molecular pathogenesis, as well as to accelerate vaccine design.

Study the Ability of Enterotoxigenic E.coli Antigens To Induce Cellular Immune Response by Erythrocyte-Rosette Formation and Leukocyte Migration Inhibition Factor in Rabbits

Objectives: This study was aimed to investigate the ability of Enterotoxigenic E.coli and their enterotoxins to induce cellular immune response by means of erythrocyte-rosette formation and leukocyte migration inhibition factor tests. Methodology: Total of 30 stool sample was collected of patient with severe diarrhea whom attended to Al-Sadder teaching hospital in Al-Najaf city in period extended of April to June 2013. All bacterial isolates was identified according to morphological and biochemical testes and by API 20 E system, which further conformational tested for heat stable enterotoxin production by Suckling Mice Assay (SMA). three antigens (heat killed bacterial cell, crude enterotoxin and purified heat stable enterotoxin ETECST) was prepared and injected in experimental animals(rabbit) and tested in the level of systemic and mucosa (appendix and duodenum). Statistical analysis was done by least significant difference (LSD). Results: The results showed that 20% (6 isolates) was Enterotoxigenic E.coli and the immune experiments showed significant increase level of E-rosette formation in rabbit injected with heat killed antigen (50.1%, 49.7% and 53.0%) compared with control (23.1%, 31.8% and 29.6%) in blood appendix and duodenum consecutively, while high level appeared in crude enterotoxin and ETECST in appendix (41.3%) and (47.4%) consecutively. The assessment of ETECST LIF in migration percent to sensitizer was showing high significant LIF (54.5%, 47.6% and 43.3%) compared with control (82.0%, 79.5% and 79.5%) in blood appendix and duodenum consecutively. Conclusions: crud and partially purified enterotoxins have ability to induce cellular immune response in blood and mucosa. Recommendation: prepare a carrier molecule model for partially purified enterotoxins to make a vaccine against Enterotoxigenic E.coli .

Yersinia enterocolitica: Mode of Transmission, Molecular Insights of Virulence, and Pathogenesis of Infection

Although Yersinia enterocolitica is usually transmitted through contaminated food and untreated water, occasional transmission such as human-to-human, animal-to-human and blood transfusion associated transmission have also identified in human disease. Of the six Y. enterocolitica biotypes, the virulence of the pathogenic biotypes, namely, 1B and 2–5 is attributed to the presence of a highly conserved 70-kb virulence plasmid, termed pYV/pCD and certain chromosomal genes. Some biotype 1A strains, despite lacking virulence plasmid (pYV) and traditional chromosomal virulence genes, are isolated frequently from humans with gastrointestinal diseases similar to that produced by isolates belonging known pathogenic biotypes. Y. enterocolitica pathogenic biotypes have evolved two major properties: the ability to penetrate the intestinal wall, which is thought to be controlled by plasmid genes, and the production of heat-stable enterotoxin, which is controlled by chromosomal genes.

Characterization of Toxin Genes and Antimicrobial Susceptibility ofStaphylococcus aureusIsolates from Louisiana Retail Meats

Staphylococcus aureus is a leading cause of food poisoning worldwide due to the production of heat-stable enterotoxins. Recently, the isolation of methicillin-resistant S. aureus (MRSA) from food animals and retail meats raised additional food safety concerns. In this study, we characterized 152 S. aureus isolates, including 22 MRSA recovered from Louisiana retail pork and beef meats, for the prevalence of nine enterotoxin and four other exotoxin genes by polymerase chain reaction and antimicrobial susceptibility testing by broth microdilution. Overall, 85% of S. aureus isolates were positive for at least one of six enterotoxin genes identified and 66% harbored two to four enterotoxin genes. The two most predominant ones were seg and sei (66% each), followed by seh (20%), sed (15%), sej (13%), and sea (1%). No isolates harbored enterotoxin genes seb, sec, or see, the toxic shock syndrome toxin 1 gene tst, or the exfoliative toxin genes eta or etb. Three MRSA isolates were the only ones harboring Panton-Valentine leucocidin. Resistances were common to penicillin (71%), ampicillin (68%), and tetracycline (67%), followed by erythromycin (30%), clindamycin (18%), oxacillin with 2% NaCl (14%), ciprofloxacin (13%), levofloxacin (13%), gentamicin (3%), quinupristin/dapfopristin (3%), chloramphenicol (2%), and moxifloxacin (1%). Multidrug resistance was commonly observed among MRSA isolates and S. aureus isolates from pork. This study demonstrated that S. aureus isolates found in Louisiana retail pork and beef meats possessed various enterotoxin genes and antimicrobial resistance profiles. Therefore, vigilant food safety practice needs to be implemented for people who handle raw meat products to prevent foodborne infections and intoxications due to S. aureus contamination.

Production of Yersinia stable toxin (YST) and distribution of yst genes in biotype 1A strains of Yersinia enterocolitica

Two hundred and fifty nine isolates of Yersinia enterocolitica and related species were examined for the production of heat-stable enterotoxin (Yersinia stable toxin; YST) as well as for the prevalence of enterotoxin genes, viz. ystA, ystB and ystC. Under the conventional conditions used for the production of Y. enterocolitica enterotoxin, i.e. in tryptic soy broth (TSB) supplemented with yeast extract at 28 degrees C for 48 h, 77.7 % of clinical isolates and 62.3 % of swine isolates showed enterotoxigenicity in infant mice. All isolates that produced enterotoxin at 28 degrees C also showed enterotoxic activity at 37 degrees C after 48 h incubation under an alkaline pH of 7.5, the pH present in the ileum. All Yersinia intermedia and Yersinia frederiksenii isolates were negative for enterotoxin production. All clinical isolates and 96.3 % of Y. enterocolitica isolates from swine hybridized with a probe for ystB, which indicated that the ystB gene was most prevalent in Y. enterocolitica biotype 1A strains. None of the Y. enterocolitica isolates showed hybridization with oligonucleotide probes for ystA or ystC. The study indicated that YST-b was the major contributor to diarrhoea produced by biotype 1A strains of Y. enterocolitica.

Microbiological Quality Of Sweetmeat With Special Reference To Staphylococci

Safe food production in countries like India is based in the use of preventive measures such as the use of safe raw materials, application of good manufacturing practices, and application of Hazard Analysis of Critical Control point (HACCP) procedures. Adequate consumer protection can be achieved by measuring the microbiological data of end product. To improve the microbiological quality of Sandesh and Kalakand precaution against contamination must be taken at different Critical Control Points (Roy et al., 1998). Some strains of Staphylococcus aureus are gaining entry into milk products and caus acute gastroenteritis via the production of heat stable enterotoxins. Millions of people are the victims of food borne illnesses resulting from toxins produced by Staphylococcus aureus ingested with food. Coliforms have probably got more attention than most other groups of bacteria on account of their importance as indicator organism for predicting unhygienic conditions during production and processing. Among the coliforms, Escherichia coli has attracted much attention as suspected to be associated with outbreaks of gastro-enteritis and food poisoning in human beings. Keeping in view the public health importance of sweetmeat consumers it is needless to say that the product should be prepared hygienically reducing the microbial load present in it. Therefore an attempt was made to research the hygienic measures adopted by the food handlers and makers during sweetmeat preparation and their reflection in the microbiological quality of the sweetmeat.

Production of heat-stable enterotoxin II by chicken clinical isolates of Escherichia coli

Production of heat-stable enterotoxin II by chicken clinical isolates of Escherichia coli

Identification and characterization of heat-stable enterotoxin II-producing Escherichia coli from patients with diarrhea.

Stock strains of Escherichia coli isolated from patients with traveller's diarrhea were examined for production of heat-stable enterotoxin II (STII). Of 400 strains examined, 3 were found to produce STII. The nucleotide sequence of the STII gene of these human strains was shown to be identical to that of porcine strains. Cultured cells of these strains induced fluid accumulation in ligated mouse intestinal loops and the activity was neutralized by anti-STII antiserum. These results suggest that STII-producing enterotoxigenic E. coli can cause human diarrhea.

Production of heat-stable enterotoxin II by chicken clinical isolates of Escherichia coli.

Enterotoxigenic Escherichia coli isolated from diarrhea stools of chickens were examined for production of heat-stable enterotoxin II which is considered to be implicated only in diarrhea of pigs. Seven out of 38 strains examined were found to contain heat-stable enterotoxin II gene, determined by colony hybridization and the polymerase chain reaction. The culture supernatants of these strains caused fluid accumulation in the mouse intestinal loop test. This fluid accumulation activity was not lost by heating at 100 degrees C and was neutralized by anti-heat-stable enterotoxin II antiserum. Purified heat-stable enterotoxin II caused fluid accumulation in the chicken intestinal loop assay. These results indicate that STII-producing E. coli is implicated in chicken diarrhea.

Production and purification of heat-stable enterotoxin b from a porcine Escherichia coli strain

Production of heat-stable enterotoxin b (STb) by porcine Escherichia coli strains belonging to serogroup O115 was evaluated in ligated intestinal segments of adult rats. The conditions for optimal production and detection of STb were studied by using the STb-producing strain 4247. As STb production was similar in complex Trypticase soy broth and minimal Davis medium, the latter was used for the fermentation of strain 4247 and the production of STb in large quantities. STb was then purified to apparent homogeneity by sequential ultrafiltration, ultracentrifugation, and preparative gel electrophoresis. The enterotoxin was purified more than 500-fold and exhibited a molecular weight of approximately 5,000 as determined by urea-sodium dodecyl sulfate gel electrophoresis. Purified STb retained such chemical characteristics as resistance to heating (60 degrees C/30 min) and sensitivity to trypsin. A rabbit polyclonal antiserum was produced against the purified toxin. Numerous booster doses were required to obtain a significant enzyme-linked immunosorbent assay titer, suggesting that STb is a poor immunogen. Nevertheless, the antiserum was used successfully to discriminate between culture supernatants of STb-positive and STb-negative O115 E. coli strains, thus demonstrating the immunogenicity of purified STb.

Enterotoxin Production in Two-Culture Media by Yersinia enterocolitica Isolated from Sausages, Porcine Ceca and Tongues in San Luis, Argentina

Twenty-six strains of Yersinia enterocolitica isolated from fresh sausages, bovine tongues, and porcine ceca and tongues were evaluated for the production of heat-stable enterotoxin (ST, infant mouse test) in trypticase soy broth (TSB) and casamino acids broth (CAB). The gut weight/body weight ratios obtained with the two media were similar. Sixteen strains produced ST in both media; nine strains did not. Strain 23 produced ST in CAB but not in TSB.

Identification and characterization of Yersinia intermedia isolated from human feces.

Since May 1983, our laboratory has, upon request, cultured stools for Yersinia spp. by using direct plating on cefsulodin-irgasan-novobiocin agar and a 3-week cold enrichment procedure. We isolated bacteria identified as Y. intermedia from six adult patients. All isolates were recovered only by the cold enrichment procedure and misidentified as Y. enterocolitica by the API 20E system (Analytab Products, Plainview, N.Y.). Final identification was made on the basis of results obtained with conventional tube biochemical tests. The isolates were tested for the following characteristics associated with virulence in Y. enterocolitica: lack of pyrazinamidase activity, autoagglutinability, presence of a 40- to 50-megadalton plasmid, production of heat-stable enterotoxin, and mouse lethality. All isolates tested had pyrazinamidase activity, and none were autoagglutinable. However, one isolate possessed a 40-megadalton plasmid. None produced enterotoxin or were lethal for mice. Review of the medical histories of the patients revealed that four of the six had diarrhea; however, none had disease typical of that caused by Y. enterocolitica. Our data confirmed the limited pathogenic potential of Y. intermedia and suggested that its isolation was without clinical significance in our patients. Conventional biochemical tests were required for reliable identification of Y. intermedia.

Role of bacterial toxins, bile acids, and free fatty acids in colonic water malabsorption in tropical sprue.

Colonic perfusion studies in 10 southern Indian patients with tropical sprue and nine matched healthy adults revealed a defect of water and sodium absorption from the colon in sprue. Heat-labile and heat-stable enterotoxin production was not detected in coliforms cultured from the feces of any of the 19 subjects. The 24-hr fecal bile acid output was increased in patients with sprue, but fecal aqueous bile acid concentrations remained within normal limits, and these did not correlate with defects in colonic water and sodium absorption. Fecal free fatty acid excretion was markedly increased in sprue. There was a negative correlation between fecal excretion of unsaturated free fatty acids and colonic water and sodium absorption.

Incidence and some characteristics of fimbriae FY and 31A of Escherichia coli isolates from calves with diarrhea in Japan.

Escherichia coli isolates from calves with diarrhea (1 day to 8 weeks old, 140 individuals) were surveyed for the three immunologically distinct fimbrial adhesins FY, 31A, and K99. Of a total of 1,370 strains isolated, 96 (7.0%), 34 (2.5%), 75 (5.5%), and 13 (0.9%) were identified as FY+, 31A+, FY+.31A+, and K99+, respectively. The K99+ strains also manifested heat-stable enterotoxin production (ST+), while FY+, 31A+, and FY+.31A+ strains were ST-. Expression of FY and 31A was repressed at lower temperatures or poor aeration. The FY+ and 31A+ E. coli showed mannose-resistant hemagglutinating activity with bovine erythrocytes. Electron microscopy revealed that FY is a gently curled fimbria with a mean diameter of 4.2 nm, and 31A is a fimbria with a mean diameter of 5.1 nm. The molecular mass of protein subunits was found to be approximately 20 kilodaltons (Kd) and 19 Kd for FY and 31A, respectively. Lethal diarrhea of neonatal calves was induced by challenge with the combination of a K99+.ST+ E. coli strain and either a 31A+ E. coli strain or a 31A+ E. coli strain plus an FY+ E. coli strain under the experimental conditions in which lethal diarrhea was not induced by challenge with a K99+.ST+ E. coli strain alone.