Cytotoxin activity on Vero cells among Escherichia coli strains associated with diarrhea in cats

The role of Escherichia coli as a causative agent of diarrhea in cats was investigated. Isolates of E coli from healthy and diarrheic cats were serotyped and investigated for their biochemical characters, production of cytotoxin activity on Vero cells, heat-labile enterotoxin, heat-stable enterotoxin, and hemagglutination of erythrocytes from other animal species. None of 48 investigated strains produced heat-labile enterotoxin or heat-stable enterotoxin, nor did they agglutinate erythrocytes. Most strains were hemolytic and belonged to O-serotypes 2 and 6. Cytotoxin activity on Vero cells was significantly more common and produced in greater amounts among E coli strains isolated from diarrheic cats, and was neutralized by anti-Shiga-like toxin I serum.     

Enterotoxigenic Escherichia coli in the jejunum of piglets with neonatal diarrhea

Thirty-two Escherichia coli colonies were taken from the primary step of cultivation of the jejunal contents of each of 10 dead piglets which had suffered from diarrhea. The organisms of each colony were examined for the presence of adhesion fimbria (F4 (K88) and F5 (K99)), production of heat-stable and heat-labile enterotoxin and of colicins.The presence of heat-labile enterotoxin in the intestinal content of the necropsied pigs was also tested, and results correlated with enterotoxin production of the isolated E. coli strains. In all but 3 pigs, 50–80 % of the E. coli strains were found to produce one or both of the enterotoxins and to possess the F4 of the F5 antigen. All bacteria producing both heat-labile and heat-stable enterotoxin proved to belong toi O group 149 and to possess the F4 antigen. Strains from 1 pig belonged to O group 64 and possessed the F5 antigen; these bacteria produced heat-stable enterotoxin only. Most of the enterotoxin-producing E. coli also produced colicins.After each subcultivation, the strains produced less heat-labile enterotoxin, some becoming negative when assayed.     

Virulence factors of Escherichia coli isolated from cows with acute mastitis

A total of 184 Escherichia coli isolates recovered from cows with acute mastitis were examined for recognized pathogenic mechanisms and virulence factors commonly found in pathogenic groups of E coli. A modification of the Eng procedure (for detecting complement deficiencies in serum) was used to test for resistance to different animal sera. The Sereny test (for invasiveness), infant mouse test (for heat-stable enterotoxin), and Y-1 adrenal tumor cell assay (for heat-labile enterotoxin) were used. Hemagglutination tests, using rabbit, sheep, and guinea pig RBC, were done with and without added mannose. All of the 184 isolates were serum resistant in all tested sera. None of the isolates was invasive. Only 1 isolate was positive for heat-stable enterotoxin and 2 cultures were positive for heat-labile enterotoxin. Multiple patterns of hemagglutination were observed. The majority of the isolates exhibited both mannose-sensitive and mannose-resistant hemagglutinins with guinea pig and rabbit RBC. A few strains were positive only in mannose-sensitive or mannose-resistant hemagglutination tests. A few strains were negative in all hemagglutination tests. Based on our results, E. coli from cows with acute mastitis lack the virulence factors commonly observed in other E coli groups associated with disease. Serum resistance was the only characteristic that could be related to virulence.     

Enterotoxigenicity,hemagglutination and cell-surface hydrophobicity in Aeromonas hydrophila,A. Sobria and A. Salmonicida

Thirty-one Aeromonas hydrophila, 13 A. sobria and two A. salmonicida strains of diverse sources were tested for enterotoxigenicity, hemagglutination and cell surface hydrophobicity. Although 93% of the culture supernatant fluids of the Aeromonas strains exhibited cytotoxic effects on Y1 adrenal and Chinese hamster ovary (CHO) cells, typical rounding of Y1 adrenal cells was reproducibly observed before cytotoxicity for 80% of the isolates within 1 h of exposure.Twenty-eight strains were positive for delayed permeability factor (DPF) activity in rabbit skin. Culture filtrates of 16 of 20 strains that were positive both in the Y1 adrenal cell test and for DPF activity elicited fluid accumulation in rabbit ileal loops. The DPF and ileal loop activities were neutralizable by cholera antitoxin. All, except two strains each of A. sobria and A. hydrophila, produced a heat-stable, rapid permeability factor (RPF) detected in rabbit skin. Heat-treated culture supernatant fluids of two A. hydrophila and one A. sobria isolate gave positive responses in the infant mouse assay. Nine other strains gave borderline reactions.When A. hydrophila and A. sobria isolates were grown in broth, approximately 90% agglutinated bovine, chicken, human group A and guinea-pig erythrocytes in the presence of mannose at 4°C and/or 20°C. The two A. salmonicida isolates produced mannose resistant hemagglutination (MRHA) of these four blood types.Hydrophobic interaction chromatography indicated adhesive potential in 61% A. hydrophila and 100% A. sobria strains expressing weak to strong hydrophobic cell surface properties. The results of these investigations strongly imply that the Aeromonas strains produce a cytotonic enterotoxin immunologically related to cholera toxin. Adhesive characteristics were commonly found in both clinical and routine isolates.     

Characterization of a new fimbrial antigen present in Escherichia coli strains isolated from calves.

Thirteen Escherichia coli strains isolated from calves with diarrhoea, supposed to carry a common antigen were examined for their hemagglutinating activity and compared by bacterial agglutination, double diffusion in two dimensions and by crossed immunoelectrophoresis (CIE). Two of the strains were examined also in the electron microscope. Most of the strains agglutinated red blood cells of horse, ox, guinea pig and chicken, of which the agglutination of ox erythrocytes was mannose-resistant (MRHA). None of the strains agglutinated human erythrocytes. All strains with MRHA of ox red blood cells, regardless to their O:K:H antigens could be agglutinated in unabsorbed or absorbed antisera produced against cultures C1209 (020:K-:H9) and C1213 (09:K36:H-) when live cells as antigens were used. None of these sera agglutinated reference strains carrying K88, K99, 987P, F41 or FY (Att25) antigen respectively. By the double gel diffusion test and by CIE in extracts (60 degrees C) of the strains a common heat labile antigen, responsible for the MRHA of ox red blood cells was identified. Electron microscopy revealed that this common antigen was represented by thin, long, hair-like fimbriae on cells of E. coli C1213, and that specific homologous antibodies attached to these fimbriae.     

Colonization antigens,antibiotic resistance and plasmid content of enterotoxigenic Escherichia coli isolated from piglets with diarrhoea in galicia (North-Western Spain)

Escherichia coli colonies isolated from 50 diarrhoeic and 29 healthy piglets were investigated for several properties related to pathogenicity, such as production of heat-labile (LT) and heat-stable (STa) enterotoxins, presence of K88 and K99 colonization antigens, mannose-resistant haemagglutinating activity (MRHA), β-haemolysis and antibiotic resistance. The objective was to establish the toxic and adhesive abilities of E. coli strains that cause porcine diarrhoea in Galician farms. Fifty-seven colonies from 14 diarrhoeic piglets formed STa, while no STa⁺ colony was detected from healty piglets. Thirty-four of the 57 STa⁺ colonies were resistant to gentamicin. Sixteen representative STa⁺ strains isolated from the 14 infected piglets were serotyped, investigated for plasmid content and examined by electron microscopy. Of these STa⁺ strains, 15 belonged to serotype 0141:K85ab and carried on their surface the fimbrial antigen P987. The remaining representative STa⁺ strain belonged to serotype 0101:K30 and was K99⁺, being the only STa⁺ strain with MRHA activity. All 15 STa⁺ P987⁺ strains possessed a similar plasmid pattern, with three plasmids ranging in molecular weight from 33 × 10⁶ to 74 × 10⁶; nine of the gentamicin-resistant strains possessed an additional plasmid of molecular weight 16 × 10⁶, which was absent in the six gentamicin-sensitive strains. Strains producing LT or K88 antigen were not detected. Forty-one MRHA⁺ colonies were isolated at similar rates from both diarrhoeic and healthy piglets. Twelve of the 19 non-enterotoxigenic MRHA⁺ strains of which the O-group was established, belonged to serogroups (01, 02, 07, 08, 09 and 075) typical of the human E. coli strains that cause extraintestinal infections. Finally, a statistically significant association between haemolytic and MRHA activities in porcine E. coli was found. In conclusion, it was found that STa⁺E. coli strains belonging to serotype 0141:K85ab:P987 are associated with porcine diarrhoea in Galicia. Additionally, no correlation between the isolation of non-ETEC MRHA⁺ strains and diarrhoea was observed.     

The occurrence of adherence factors in Enterobacteriaceae from bacteriological meat examination and from food hygiene research material

An account is given in this paper of the occurrence of 131 specific adherence factors (CFA 1a, CFA 1b, K88, K99) and 216 unspecific adherence factors (CT I) of Enterobacteriaceae strains from 917 bacteriological carcass inspection samples and of 23 or 87 identical strains recorded from 682 food hygiene samples. Identification was based on mannose-resistant and mannose-sensitive hemagglutination (MRHA and MSHA). Particular consideration was given to 3 aspects, occurrence of Escherichia coli adherence factors in bacteremic dissemination in bacteriological carcass inspection, parallel presence of additional virulence factors, and the hemagglutination spectrum of MSHA.     

Prevalence of fimbrial antigens and enterotoxins in nonclassical serogroups of Escherichia coli isolated from newborn pigs with diarrhea

Ninety-nine nonclassical serogroups isolated from newborn pigs with neonatal diarrhea were tested for fimbrial antigens F4(K88), F5(K99), F6(987P), F41, and F165, and for heat-labile enterotoxin, heat-stable enterotoxin a (STa), heat-stable enterotoxin b, verocytotoxin, and cytolethal-distending toxin. Thirty-two strains, belonging mostly to serogroups O64:K"V142,", O9:K103, and O20:K101, were F5-positive and usually produced STa, although 5 strains produced only heat-stable enterotoxin b. Fifteen strains, belonging mostly to serogroups O64:K"V142" and O20:K101, were F41 positive and usually produced STa. Twenty-three stains, belonging mostly to serogroups O64:K"V142," O9:K103, and O20:K101, were F6-positive and usually produced STa. Several strains produced more than one fimbrial antigen, either F5 and F41, F5 and F6, F6 and F41, F6 and F165, or F5, F6, F41, and F165. None of the strains produced heat-labile enterotoxin, verocytotoxin, or cytolethal-distending toxin. The indirect immunofluorescence test was much more sensitive than was the slide agglutination test for the detection of each of the fimbrial antigens F5, F6, F41, and F165 on strains grown in vitro. The production of F6 by certain strains for which only a low proportion of cells were F6-positive in vitro, as demonstrated by immunofluorescence, was confirmed by experimental infection of newborn pigs.     

Pathogenicity of Escherichia coli O115:K"V165" strains isolated from pigs with diarrhea

Eighteen strains of Escherichia coli serogroup O115:K"V165" isolated from 1- to 8-week-old pigs with diarrhea were tested for toxigenicity, pathogenicity in pigs and mice, serum resistance, mannose-resistant hemagglutination (MRHA), F165 and other surface antigens, colicin V (Col V), aerobactin, and biotype. Twelve strains were positive for heat-stable enterotoxin (STb), MRHA-negative, and F165-negative; 5 strains were enterotoxin-negative, MRHA-positive, and F165-positive; and 1 strain was MRHA-positive, but F165- and enterotoxin-negative. Six of the 12 STb-positive strains moderately colonized the ileum of newborn colostrum-deprived pigs within 24 hours after inoculation. Two of the colonizing strains were able to induce watery diarrhea. All 12 STb-positive strains were nonpathogenic for adult mice and were serum-sensitive; 11 of 12 were Col V-negative, 9 of 12 did not produce aerobactin, and 10 of 12 belonged to biotypes other than 1 or 2. All 6 enterotoxin-negative strains colonized the small and large intestines, associated with peritoneal serosal surfaces, and induced septicemia and polyserositis in newborn colostrum-deprived pigs 1 to 2 days after inoculation. In contrast, 3 STb-positive strains poorly colonized the intestines and did not induce septicemia in pigs at 3 days after inoculation. All 6 enterotoxin-negative strains were Col V-positive, produced aerobactin, and belonged to biotype 1 or 2. Of the 5 enterotoxin-negative, F165-positive strains, only 4 were pathogenic for intraperitoneally inoculated adult mice and were serum-resistant. The enterotoxin-negative, F165-negative strain was neither serum-resistant nor mouse-pathogenic.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of antibiotics on mannose-resistant haemagglutination by K88- and K99-positive Escherichia coli strains

Five E. coli strains carrying K99 antigen isolated from the intestines of calves which had succumbed to diarrhoea and six K88-positive strains isolated from fatal cases of diarrhoea in piglets were examined for their mannose-resistant haemagglutination (MRHA) capacity against pig erythrocytes. The bovine strains showed a geometric mean MRHA-titre of 1/18 and the porcine strains one of 1/45. Similar experiments were carried out after addition of the following antibiotics in doubling dilutions: ampicillin, chloramphenicol, colistin, dihydro-streptomycin, gentamicin, neomycin, polymyxin B and oxytetracycline. Colistin and polymyxin B had a marked concentration-dependent inhibitory effect on MRHA. Neomycin and gentamicin also inhibited MRHA but to a lesser degree. Chloramphenicol, dihydrostreptomycin and oxytetracycline showed no effect. With ampicillin, a trend was found for the ratio values to be inversely proportional to the concentration. This suggests that this antibiotic has an enhancing effect on the haemagglutination.     

Detection of enterotoxin production in bovine Salmonella isolates]

54 Salmonella-strains (7 serovars) of bovine origin isolated from faecal samples, rectal swabs as well as from organs of emergency-slaughtered or dead animals were tested for enterotoxin production (heat-labile and heat-stable) in rabbit-ileal-loop-assay (RILT), skin-permeability-factor-test (HPT), CHO- and Y1-cell-culture-assay and in baby-mouse-test (BMT). The cell-free supernatants (CFS) were used in the tests. The Y1-cells did not respond to the Salmonella toxins. While the RILT was suitable, the CHO-cell-assay proved to be the most sensitive and easy-to-handle system. The results confirm the frequent occurrence of the biological property of enterotoxin production within the species Salmonella enterica. Therefore, this property is in our opinion not useful as an epizootological marker for salmonellae.     

Pathogenicity of Vietnamese enterotoxigenic Escherichia coli strains in colostrum-deprived one-day-old piglets

Preweaning colibacillosis is a major cause of economic loss to the swine industry in Vietnam. The aim of this study was to examine the enteropathogenicity of representative enterotoxigenic Escherichia coli (ETEC) strains obtained during an earlier epidemiologic survey conducted in five provinces in North Vietnam. This included isolates belonging to serotype O8 that produced heat-stable and heat-labile enterotoxins but did not produce any of the recognized fimbriae (F4, F5, F6, F41, F18). In vitro hemagglutination (unique mannose-resistant hemagglutination activity with guinea pig, sheep, human, and chicken red blood cells at 37 degrees C, but not at 18 degrees C) and enterocyte brush border attachment assays suggested that the F- ETEC strains produced an unidentified colonization factor that promoted adherence to the intestinal epithelium. Colostrum-deprived 1-day-old piglets challenged with an F- strain (1-2 x 10(9) bacteria) developed acute watery diarrhea within 4 hours of inoculation and suffered up to 20% weight loss, with comparable severity to piglets challenged with conventional F4 and F5 strains. At necropsy, viable counts and histopathologic examination of intestinal sections demonstrated colonization of the duodenum, jejunum, and ileum by F4-positive strains. In comparison, the F- and F5-positive strains attached exclusively to the ileum. Transmission electron micrographs of negatively stained F- cells grown at 37 degrees C demonstrated the presence of fimbriae. These results confirm the presence of a potentially new pathogenic ETEC fimbrial type in piggeries in Vietnam, with a unique hemagglutination property and attachment characteristics similar to ETEC bearing F5 fimbriae.     

Virulence factors of Escherichia coli associated with colisepticemia in chickens and turkeys.

Four hundred twenty turkey and 80 chicken Escherichia coli isolates from colisepticemic birds were examined for the following properties: heat-labile toxin (LT), heat-stable enterotoxin, verotoxin, colicinogenicity, hemolysin, and hydroxamate/aerobactin production. Twenty-four (5.7%) of the 420 turkey isolates and six (7.5%) of the 80 chicken isolates produced an LT that was cytotoxic for both Vero and Y-1 cells. In contrast, 48 (11.4%) of the turkey isolates and 18 (22.5%) of the chicken isolates produced a distinct LT that was cytotoxic only for Vero cells. In addition, 64 (80.0%) of the chicken isolates and 309 (74.0%) of the turkey isolates produced aerobactin. Colicinogenicity occurred in 51 (64.0%) of the chicken isolates, with 41 (51.0%) producing colicin V. By contrast, 254 (61.0%) of the turkey isolates produced a colicin, of which 176 (42.0%) produced colicin V. None of the chicken and turkey isolates produced hemolysin or heat-stable enterotoxin.     

Virulence factors in Escherichia coli isolated from piglets with neonatal and post-weaning diarrhea in Japan

A total of 567 strains of Escherichia coli were isolated from piglets with neonatal diarrhea (ND) or post-weaning diarrhea (PWD) in Japan. They were investigated for enterotoxigenicity and possession of adhesins and O antigens. There were clear differences between the strains of ND origin and those of PWD origin in the occurrence of enterotoxigenic E. coli (ETEC) strains, type of enterotoxin and frequency of adhesins: ETEC was found in 77 (25.7%) of 300 strains of ND origin and in 137 (51.3%) of 267 strains of PWD origin. ETEC strains producing heat-labile enterotoxin (LT) or heat-stable enterotoxin (STa), alone or in combination were evenly distributed among the strains of PWD origin. In contrast most of the ETEC strains of ND origin produced LT alone. Adhesins appeared in 42 (54.5%) of 77 ETEC strains of ND origin and in 36 (26.3%) of 137 ETEC strains of PWD origin. Adhesins were less common in ETEC strains of PWD origin than in those of ND origin. Some K99-positive ETEC strains of PWD origin produced both LT and STa. There was a similarity in the distribution of O antigens, particularly O149 and O157, between the strains of ND origin and those of PWD origin.     

Detection of the enteroaggregative Escherichia coli heat-stable enterotoxin 1 (EAST1) gene and its relationship with fimbrial and enterotoxin markers in E. coli isolates from pigs with diarrhoea

The presence of the astA gene responsible for production of enteroaggregative Escherichia coli heat-stable enterotoxin 1 (EAST1) was examined in E. coli strains isolated from pigs with postweaning diarrhoea. Two hundred and seven isolates were tested using PCR for the astA marker and for heat-labile I (LTI), heat-stable I (STI), and heat-stable II (STII) enterotoxin genes. Moreover, the isolates were also analysed for their serotypes (O and K antigens) as well as for fimbrial adhesins using agglutination methods. It was shown that 96 (46.4%) of the isolates possessed the astA genetic determinant. The most common EAST1-positive E. coli serotype was O149:K91 and these strains were mostly LTI/STII-positive. A close correlation between the presence of F4 fimbriae and the EAST1 gene was also observed: 88 of 96 (91.7%) astA(+) isolates tested possessed the F4 antigen. Thus, EAST1 enterotoxin may represent an additional virulence determinant playing a role in the pathogenesis of porcine colibacillosis.     

Escherichia coli strains isolated from diarrheic piglets in the Province of Quebec.

During 1972 to 1974, 112 Escherichia coli strains isolated from diarrheic piglets were recieved from different parts of the Province of Quebec, Canada. Fifty-six strains elicited a positive gut loop response in three week old piglets and were then considered as Moon's class 1 enteropathogens, while four of the 56 remaining strains reacted only in ten day old piglets and were classified as class 2 enteropathogens. Forty-eight strains produced both a heat-labile and a heat-stable enterotoxin, while 12 isolates which included the four class 2 enteropathogens produced only a heat-stable enterotoxin. Fifty-one enterotoxigenic strains could be serogrouped using OK antisera against E. coli strains commonly associated with colibacillosis in piglets. The most common serogroups encountered were O157: K "V17"; 88a,c, O149:K91; 88a.c. O157:K"V1c, O149:K91; 88a.c, O157:K"V17"; 88 a,c or a,b and O45:K"E5"; 88a,c. No significant difference was observed in the fermentation patterns, antibiotic susceptibility, colicin production, production of a filterable hemolysin and transferable tetracycline resistance between the enterotoxigenic and the nonenterotoxigenic strains.     

致犊牛腹泻肠毒素大肠杆菌多重PCR检测方法的建立

肠毒素大肠杆菌((Ent erot oxi geni c E.col i,ETEC)是引起犊牛腹泻的主要病原之一。本试验建立了多重PCR检测ETEC毒力因子F41菌毛、K99菌毛和STa、LT肠毒素相关基因的技术方法。试验对影响PCR扩增的dNTP、引物浓度以及退火温度等因素进行优化,确定了多重PCR的特异性和灵敏性。结果表明:所建立的多重PCR方法快速、特异、灵敏,在2.5h-3h内就可以完成,为致犊牛腹泻肠毒素大肠杆菌的快速准确检测提供另一种选择。     

Evaluation of plating media for recovering Salmonella from thermally treated egg albumen

Salmonella spp. present in pasteurized egg albumen are often difficult to recover by direct plating because of thermal injury and the presence of innate iron binding and other antimicrobials in egg white. The literature has reported a multiplicity of selective and nonselective media used to recover heat-injured Salmonella, to measure the proportion of injured cells, or both. This study compared the proficiency of selective and nonselective plating media for supporting colony development or for assessing bacterial injury of heat-stressed Salmonella from egg albumen. A 6-strain composite of Salmonella was added to albumen (pH 9.0), heated at 53.3°C for 3.1 min, and plated on 26 nonselective and 22 selective media. Recovery of heat-injured salmonellae varied little (≤0.52 log cfu/mL) among the nonselective media tryptic soy agar, plate count agar, dextrose tryptone agar, or brain heart infusion agar, regardless of the manufacturer. Selective media that were optimal for recovery of salmonellae from albumen included 3 brilliant green agars, Levine eosin methylene blue agar, and bismuth sulfite agar, which recovered more cells (P ≤ 0.05) than selenite-cystine, tetrathionate, xylose-lysine-tergitol-4, xylose lysine deoxycholate, or Rappaport-Vassiliadis agars. The results of this study may assist in choosing selective or nonselective media to maximize the recovery of Salmonella from thermally treated albumen.     

Identification of serotype by use of serologic assay and detection of the enterotoxin gene of Escherichia coli by means of a polymerase chain reaction assay for isolates from pigs, chickens, and cows

OBJECTIVE: To serotype an enterotoxin gene from Escherichia coli isolated from cows, pigs, and chickens in Korea. SAMPLE POPULATION: Isolates from 37 cows with mastitis, 51 diarrheic pigs, and 5 diarrheic chickens. PROCEDURE: Serogroups and serotypes were identified by slide agglutination testing, using pathogenic E coli sera. Detection of E coli enterotoxins by use of reversed passive latex agglutination and ELISA was compared by proving existence of the gene by polymerase chain reaction (PCR) analysis. RESULTS AND CONCLUSIONS: Detection of E. coli enterotoxin by either method was positive for 1 strain (O20:H10; heat-labile enterotoxin [LT+], heat-stable enterotoxin [STa+]; isolation rate, 2%) and 3 other strains (O111:H10, O119:H9, and O125:H6, STa+; isolation rate, 5.9%) isolated from fecal specimens obtained from diarrheic pigs. The E coli enterotoxin genes were identified by use of PCR analysis in 1 strain containing the 417- and 163-base pair (bp) genes (LT+, Sta+; O20:H10) and in 3 strains containing only the 163-bp gene (STa+; O111:H10, O119:H9, and O125:H6). CLINICAL RELEVANCE: Serotyping of E coli enterotoxin may be used to analyze patterns of transmission among species of domestic animals.     

Enterotoxin production at 4, 22, and 37 degrees C by Yersinia enterocolitica and Yersinia enterocolitica-like bacteria isolated from porcine tonsils and pork products

Altogether, 71 strains of Yersinia enterocolitica and Yersinia enterocolitica-like bacteria from porcine tonsils and pork products were examined for their ability to produce enterotoxin using the infant mouse assay. Of these, 37 strains (52.1 %) produced enterotoxin at 22 °C, 3 were positive at 4 and 22 °C, and 1 was enterotoxigenic at 22 and 37°C. No strain was positive at all 3 temperatures. The highest prevalence of enterotoxin production at 22°C was detected in serotype 0:11 (80.0%), followed by 0:3/ biotype 4 (74.2 %), and 0:12 (66.7 %). Enterotoxin production at 4°C was recorded in 2 (15.4 %) of the Yersinia kristensenii strains (0:11, 0:12) and 1 of the Yersinia enterocolitica strains, (0:3) examined. One Yersinia kristensenii strain (0:11) was enterotoxigenic at 37 °C. The results indicate that enterotoxin production is a common feature of yersiniae isolated from porcine tonsils and pork products in Norway and may represent a possible source of food borne intoxication.