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1.
Forty-five Yersinia enterocolitica strains isolated from aborted fetuses and placentas and from vaginal and rectal swabs of aborting sows were subjected to serotyping, biochemical typing and polymerase chain reaction multiplex analyses to detect the presence of the ail, yst A and ystB genes. The isolates were recovered from the internal organs (tonsil, lung, liver, spleen, kidney, mesentheric lymph nodes, small intestine and rectal intestine) of 18 (18.6%) of 97 aborted fetuses examined, two (8%) of 25 aborted placentas and 27 (15.8%) of 172 examined aborting sows. Serotyping of Y. enterocolitica revealed that only six (13.3%) of the examined isolates belonged to serotype O:3, with a considerable number of isolates (31.1%) having serotype O:5, while biochemical studies showed that as many as 40 of the 45 strains belonged to biotype 1A. As expected, the Y. enterocolitica strains of bioserotype 4/O:3 contained ail and ystA genes, while strains of biotype 1A contained only the ystB gene.  相似文献   

2.
The subject of this study was thirty nine strains of Yersinia enterocolitica, isolated from faeces of humans who showed symptoms typical of intestinal yersiniosis, and seventy strains of Y enterocolitica, four strains of Y. pseudotuberculosis, and one strain of Y. kristensenii from healthy pigs. In the population tested the following serogroups appeared: O3, O9, O2, O5. A PCR was used to detect the presence of pathogenic chromosomal markers, such as myfA and inv genes of the tested Yersinia species. Among Y. enterocolitica strains isolated from humans and belonging to serogroup O3 (thirty four strains) and serogroup O9 (five strains) thirty three Y. enterocolitica O3 strains and four Y. enterocolifica O9 strains, gave a positive reaction to the nmyfA gene, yielding a fragment of 280 base pairs (bp). Among seventy Y. enterocolitica strains isolated from pigs forty strains belonging to serogroup O3 and fifteen strains belonging to serogroup O9 gave a positive reaction to the myfA gene. The presence of 390 bp amplified products, corresponding to the inv gene fragment, was detected in PCR products of three Y pseudotlluberculosis strains from pigs and only in one Y. enterocolitica O3 strain from humans, which had no myfA gene. The results obtained show that the myfA gene is only present in the strains that belong to pathogenic serotypes of Y. enterocolitica. The myfA gene prevailed in the Y. enterocolitica O3 and O9 strains from humans but was less common in the Y. enterocolitica O3 and O9 strains from pigs.  相似文献   

3.
AIMS: To study the adhesion properties of a biotype 4, serotype O:3 (human pathogenic) strain of Yersinia enterocolitica and to determine if adhesion in vitro and colonisation in vivo can be prevented by competition with a biotype 1A, serotype O:6,30 (non-pathogenic) strain. To study interaction between Y. enterocolitica biotype 4, serotype O:3 and cultured epithelial cells using the synthetic tripeptide arginine-glycine-aspartic acid (RGD). METHODS: The human intestinal epithelial (HEp-2) cell line was used for in vitro studies. Inocula of Y. enterocolitica biotype 4, serotype O:3 radiolabelled using tritium were incubated with HEp-2 cells and RGD tripeptide, or with Y. enterocolitica biotype 1A, serotype O:6,30 sequentially or concurrently, then washed and lysed, and radioactivity measured to determine the effect of RGD on adhesion, and competitive exclusion of pathogenic by non-pathogenic bacteria. For in vivo studies, two groups of 5-week-old piglets (n=5/group) were sequentially inoculated orally with 5 x 10(9) colony forming units (cfu) of either a non-pathogenic biotype 1A, serotype O:6,30 strain of Y. enterocolitica followed by a pathogenic biotype 4, serotype O:3 strain, or vice versa. Pigs were monitored for carriage of strains using bacterial culture and a multiplex polymerase chain reaction (PCR). RESULTS: The RGD tripeptide significantly inhibited adherence of the pathogenic Y. enterocolitica strain to cultured epithelial cells, suggesting that adhesion involved the RGD tripeptide sequence. The non-pathogenic biotype 1A, serotype O:6,30 strain of Y. enterocolitica prevented adhesion of the pathogenic strain to cells in vitro when allowed to adhere first. Pathogenic Y. enterocolitica was consistently isolated from rectal swabs from 80-100% of pigs on all sampling occasions but not from oral swabs after 14 days in pigs first inoculated with the non-pathogenic strain or at 26 days in pigs first inoculated with the pathogenic strain. CONCLUSIONS: A non-pathogenic strain of Y. enterocolitica reduced adhesion of a human pathogenic strain in vitro but not in vivo.  相似文献   

4.
In 40 submissions to the Regional Veterinary Laboratory (RVL) Wagga Wagga from sheep in southern New South Wales from 1981 to 1989, 53 isolates of Yersinia sp were recovered from 45 sheep in 37 flocks. Of 53 isolates, 26 were identified as Y. pseudotuberculosis, 20 as Y. enterocolitica, 5 as Y. intermedia and 2 as Y. frederiksenii. Twelve isolates of Y. pseudotuberculosis tested in the slide agglutination test all belonged to serotype III. The 20 Y. enterocolitica isolates were categorised biochemically as biotype 5 strains and, of 6 isolates serotyped, all belonged to serogroup 2,3. Outbreaks of yersiniosis were most common in late winter and early spring and affected flocks often had experienced a change in husbandry. Infection with Yersinia sp was associated with diarrhoea, illthrift and mortality. At necropsy, congestion and occasionally thickening of the intestinal mucosa were observed in affected sheep. Gastrointestinal nematodiasis and coccidiosis often were concurrent findings. The characteristic histological lesion in sheep infected with Y. pseudotuberculosis was acute segmental suppurative erosive enterocolitis. There were no lesions consistently associated with Y. enterocolitica, Y. intermedia or Y. frederiksenii.  相似文献   

5.
An enzyme immunoassay (ELISA) was developed to detect antibodies in pigs against the lipopolysaccharidic antigen of the three serotypes of Yersinia enterocolitica mostly associated with human infections. Recent epidemiological evidence has demonstrated that pigs and pork are important sources of yersiniosis in humans. The purpose of this study was to clarify the use of an ELISA to detect swine carriers of this enteroinvasive bacteria by examining seroconversion and tissue distribution of Y. enterocolitica following experimental infection and then screening pigs at a slaughterhouse by bacterial culture and ELISA. It was observed that seroconversion occurred in animals experimentally inoculated with Y. enterocolitica but not with other enterobacteria. It was also found that 27% of swine at a slaughterhouse carried the bacterium in their tonsils and/or intestinal tract, whereas 66% showed serological evidence of previous infection. About 6% of swine at slaughter were culture-positive, but seronegative. Although, similar numbers of swine showed serological evidence of previous infection by each of the three Y. enterocolitica serotypes tested, virtually all culture isolates belonged to serotype O:3. This ELISA appears as a valuable control tool that can be used, in conjunction with culture, to identify pigs or herds infected by strains of Y. enterocolitica associated with human infections.  相似文献   

6.
A simple colony immunoblotting method using monoclonal antibodies (MAbs) was developed to detect Y. enterocolitica serotype O:3 in pig feces. One of the MAbs studied was able to detect single colonies of the organism in the presence of calculated 3.1 x 10(8) heterologous organisms in pig feces. The MAb was found to be specific for the lipopolysaccharide (LPS) O-antigens of Y. enterocolitica serotype O:3. No significant cross-reactivity was found against a variety of closely related serotypes and Gram-negative organisms. The MAb could also be used in a slide agglutination test and an indirect fluorescence antibody assay for rapid identification of Y. enterocolitica serotype O:3.  相似文献   

7.
Serological types of Pasteurella haemolytica in Kenya   总被引：1，自引：0，他引：1  
The 12 known serotypes of P. haemolytica and two biotypes A and T were found to occur in Kenya. Biotype T was more common in disease conditions than biotype A, which was more common in the nasal passages of healthy animals. Only biotypes A strains were recovered from cattle and the majority were serotypes 1 and 2, but serotypes 4 and 11 were also isolated. All serotypes were found to occur in sheep and goats, but serotypes 3, 4, 6, 8 and 10 were more commonly associated with pneumonia. It was observed that chickens could harbour both biotypes A and T in pathological conditions. Biotype A serotype 2 was isolated from an adult wildebeest, but the prevalence of P. haemolytica in wild animals needs furter investigation.  相似文献   

8.
The biochemical and serological properties of 21 strains of Actinobacillus pleuropneumoniae biotype 2 isolated from haemorrhagic necrotic pleuropneumonia of swine were examined. For serologic typing, the indirect haemagglutination (IHA) and the double gel-diffusion tests were used. On the basis of their soluble surface antigens, our A. pleuropneumoniae biotype 2 isolates could be assigned to two proposed serotypes. Serotype 1 comprised 11 strains and serotype 2 comprised 10 strains. All strains contained two surface antigen components. In the strains belonging to serotype 1, one of the antigens was identical with the serotype-specific antigen of Pasteurella haemolytica T4. Both antigens of serotype 2 strains proved to be type-specific. Four strains received from Switzerland, including the holotype strain of A. pleuropneumoniae biotype 2, and three strains isolated from swine in the G.D.R. belonged to serotype 2. Both the double gel diffusion and the IHA tests detected a 2-way cross-reaction between biotype 1, serotype 2 and biotype 2, serotype 2 strains of A. pleuropneumoniae, which could be eliminated using cross-absorbed sera.  相似文献   

9.
The antigenic differences between strains of serotype 2 of both biotypes I and II of Actinobacillus pleuropneumoniae were studied by using several serological techniques. Monoclonal antibodies (MAbs) against A. pleuropneumoniae biotype I serotype 2 were produced by fusion of spleen cells of BALb/c mice immunized with whole-cell (WC) suspension with SP2/O-Ag14 murine myeloma cells. Desirable MAbs were selected by enzyme-linked immunosorbent assay (ELISA) using WC as antigen. MAbs MK-7 and MK-10 identified multiple bands of lipopolysaccharide in Western-blot. Treatment of WC with proteinase K and sodium periodate indicated that both MAb binding sites were carbohydrates in nature. In both ELISA and Western-blot, MAbs MK-7 and MK-10 recognized only biotype I serotype 2 isolates. Neither MAb MK-7 nor MK-10 reacted with reference strains of remaining serotypes of A. pleuropneumoniae and other Gram-negative bacteria tested. The results obtained with various serological tests showed that strains of serotype 2 biotype I shared antigenic determinants with strain N-282 of serotype 2 biotype II, but not with strain N-273 of serotype 1 biotype II. It is suggested that data obtained from this study may be helpful in the development of specific serotyping and serodiagnostic reagents of A. pleuropneumoniae strains.  相似文献   

10.
Sera from calves immunized with Yersinia enterocolitica serotypes O:9 or O:16 were tested by indirect enzyme linked immunosorbent assay (ELISA) using lipopolysaccharide (LPS) preparations from Brucella abortus or Y. enterocolitica O:9 or O:16 for their antibody content of the IgG1 or IgG2 subclasses. High IgG1 responses were present with the three antigens in both groups although some individual variations between animals were noted. The IgG2 responses were modest and in some cases not above background 'noise'. Thus IgG2 antibody was not measurable in sera from serotype O:9 injected calves when using serotype O:16 LPS or in serotype O:16 injected calves when using B. abortus or serotype O:9 LPSs. A competitive ELISA using B. abortus O-polysaccharide and a monoclonal antibody to B. abortus LPS (initially designed to differentiate the antibody responses of cattle naturally infected with B. abortus from those vaccinated with strain 19) was used on sera from both groups of calves. Using this test, no antibody was detected in the group immunized with serotype O:16 and except for one animal in the serotype O:9 immunized group, only low levels of antibody were transiently in evidence. One animal in this group responded with quite high levels of competing antibody which, however, declined towards the end of the test period. The competitive ELISA may prove a useful serological tool for differentiating vaccinal and field infection titers to B. abortus and also to eliminate cross-reactions observed with Y. enterocolitica serotypes.  相似文献   

11.
An examination of 41 fish pathogenic and 51 environmental strains of Vibrio anguillarum from Danish coastal areas, and of 8 reference strains of Vibrio anguillarum, biotype 1, showed that these strains shared rather broad-spectered activities towards many carbohydrates, amino acids, proteins and lipids.They also exhibited rather uniform growth characteristics, including parameters as salinity (NaCl), temperature, antibiotic resistance, and growth on specific media.A computer analysis of these strains and 3 strains of Vibrio anguillarum, biotype 2 (Vibrio ordalii), showed that the Danish strains all belonged to Vibrio anguillarum, biotype 1, and that no basis existed for setting up new biotypes.Mean values of the G+C content in DNA of strains of the various categories of Vibrio anguillarum, biotype 1, ranged from 45.5 to 46, while the mean value for the Vibrio ordalii strains was 48.9.The biochemically active Vibrio anguillarum seems more suitable for environmental studies than the more fastidious Vibrio ordalii.Key words: Vibrio anguillarum, Vibrio ordalii, biochemical activities, environmental, fish pathogenic, reference strains  相似文献   

12.
The objectives of this study were to determine the carriage rate of Yersinia enterocolitica in the tonsils of slaughter hogs, and to characterize them with regard to phenotypic and virulence-associated properties. Of 202 pigs examined from an abattoir in Prince Edward Island, 85 were culture positive for Y. enterocolitica. Sixty-seven percent of isolates belonged to serotype O:3, and 20% were serotype O:5. All isolates produced urease and 95% of O:3 isolates showed virulence-associated characters of autoagglutination at 37 degrees C and lack of fermentation of esculin and salicin. All isolates were tested for crystal violet binding, calcium dependency, and virulence plasmids. Eight isolates (5 belonging to serotype O:3, 2 belonging to O:5,27, and 1 belonging to O:7,8) were tested in addition for the production of heat-stable enterotoxin (ST), and iron-chelating siderophores. Of the 57 O:3 isolates, 93% were positive for crystal violet binding and calcium dependency and 98% possessed a 40-45 MDa plasmid. Four of the 5 O:3 isolates tested for ST related to Escherichia coli STa in a commercial enzyme immunoassay were positive. Six of the 8 isolates belonging to 3 different serotypes produced large orange halos around the colonies on a chrome-azurol-s agar assay medium, for siderophores. Antimicrobial susceptibility tests of all 85 isolates against 16 drugs showed 100% susceptibility against 12 drugs, including trimethoprim-sulfamethoxazole and tetracycline.  相似文献   

13.
Enteritis in sheep and goats due to Yersinia enterocolitica infection   总被引：1，自引：0，他引：1  
Yersinia enterocolitica biotype 5, serotype 02,3 was isolated from the intestine of 38 sheep and 8 goats submitted to the laboratory for disease diagnosis. Infected animals were usually young, had diarrhoea and were in poor condition or emaciated. A number were moribund or dead when submitted. Characteristic microabscesses were demonstrated in the intestine of 5 of 38 sheep and 3 of 8 goats and no alternative cause of morbidity or mortality was established in these animals. Of the 33 sheep and 5 goats infected with Y. enterocolitica in which microabscesses were not demonstrated, a number of other diagnoses were made, including internal parasitism (18), selenium deficiency or white muscle disease (6) and cobalt deficiency (2), so that morbidity and mortality were possibly unrelated to Y. enterocolitica infection. Five of 6 sheep exposed experimentally by mouth to Y. enterocolitica biotype 5, serotype 02,3 developed an intestinal infection. Although infected sheep showed no clinical evidence of disease and haematological and biochemical indices remained normal, multiple intestinal microabscesses typical of yersiniosis were demonstrated in 3 of 5 infected sheep. It is concluded that Y. enterocolitica biotype 5, serotype 02,3 is an enteropathogen of sheep and goats. Since sheep and goats may be the specific hosts of this bacterium, its virulence for these species is apparently low. Morbidity and mortality may, therefore, be unusual manifestations of infection.  相似文献   

14.
A genomic fragment of Pasteurella haemolytica biotype A coding for a serotype 1-specific agglutinating antigen was used as a probe in a series of hybridization experiments to determine distribution of the fragment in various P. haemolytica serotypes as well as other bacteria. Results showed presence of the fragment in seven out of the 12 serotypes tested, all of which belonged to biotype A. Two other serotypes belonging to biotype A, all three serotypes belonging to biotype T, two Pasteurella multocida isolates and Escherichia coli did not have the fragment in their genome. Thus the expression of the P. haemolytica biotype A serotype 1-specific agglutinating antigen (PHA1SAA) seems to be due to serotype-specific regulation of protein expression rather than to genetic deletion. Differences in methylation of the PHA1SAA-coding fragment was also noted in DpnI and Sau3AI genomic DNA digests from the various serotypes analyzed by Southern blot. However, no apparent correlation was observed between methylation and PHA1SAA expression. E. coli with a recombinant plasmid containing a homologous genomic fragment derived from P. haemolytica serotype 2 also expressed PHA1SAA.  相似文献   

15.
AIMS: To study the adhesion properties of a biotype 4, serotype O:3 (human pathogenic) strain of Yersinia enterocolitica and to determine if adhesion in vitro and colonisation in vivo can be prevented by competition with a biotype 1A, serotype O:6,30 (non-pathogenic) strain. To study interaction between Y. enterocolitica biotype 4, serotype O:3 and cultured epithelial cells using the synthetic tripeptide arginine-glycine-aspartic acid (RGD).

METHODS: The human intestinal epithelial (HEp-2) cell line was used for in vitro studies. Inocula of Y. enterocolitica biotype 4, serotype O:3 radiolabelled using tritium were incubated with HEp-2 cells and RGD tripeptide, or with Y. enterocolitica biotype 1A, serotype O:6,30 sequentially or concurrently, then washed and lysed, and radioactivity measured to determine the effect of RGD on adhesion, and competitive exclusion of pathogenic by non-pathogenic bacteria. For in vivo studies, two groups of 5-week-old piglets (n=5/group) were sequentially inoculated orally with 5x109 colony forming units (cfu) of either a non-pathogenic biotype 1A, serotype O:6,30 strain of Y. enterocolitica followed by a pathogenic biotype 4, serotype O:3 strain, or vice versa. Pigs were monitored for carriage of strains using bacterial culture and a multiplex polymerase chain reaction (PCR).

RESULTS: The RGD tripeptide significantly inhibited adherence of the pathogenic Y. enterocolitica strain to cultured epithelial cells, suggesting that adhesion involved the RGD tripeptide sequence. The non-pathogenic biotype 1A, serotype O:6,30 strain of Y. enterocolitica prevented adhesion of the pathogenic strain to cells in vitro when allowed to adhere first. Pathogenic Y. enterocolitica was consistently isolated from rectal swabs from 80-100% of pigs on all sampling occasions but not from oral swabs after 14 days in pigs first inoculated with the non- pathogenic strain or at 26 days in pigs first inoculated with the pathogenic strain.

CONCLUSIONS: A non-pathogenic strain of Y. enterocolitica reduced adhesion of a human pathogenic strain in vitro but not in vivo.  相似文献   

16.
The aim of the present study was to evaluate the lytic activity of three bacteriophages on Yersinia enterocolitica strains isolated from humans and pigs. The Y. enterocolitica strains tested belonged to 0:3, 0:9 and 0:2 serogroups. The ZD5 phage was obtained from a water sample, but remaining phages were obtained from the lysogenic Y. frederiksenii 7291 and Y. enterocolitica 8684 strains. All the Y. enterocolitica strains tested which belonged to 0:9 serogroup did not show any susceptibility to the bacteriophages used. The bacteriophages tested showed different lytic activity on the Y. enterocolitica 0:3 strains investigated. The phage susceptibility of Y. enterocolitica 0:3 strains revealed 9 different phage patterns. ZD5 phage showed the highest lytic activity, because it produced confluent lysis of the most Y. enterocolitica 0:3 strains tested. The Y. enterocolitica 0:2 strains isolated from pigs showed the similar phage susceptibility. The Y. kristensenii and Y. pseudotuberculosis strains tested were not sensitive to the bacteriophages used.  相似文献   

17.

Background

Pigs are regarded as the main reservoir for human pathogenic Yersinia enterocolitica, which is dominated by bioserotype 4/O:3. Other animals, including sheep, have occasionally been reported as carriers of pathogenic strains of Y. enterocolitica. To our knowledge, this is the first study performed in the Nordic countries in which the presence of Y. enterocolitica in sheep is investigated.

Methods

Tonsils and faecal samples collected from sheep slaughtered on the island Gotland (Sweden) from September 2010 through January 2011 were analysed for presence of Y. enterocolitica. In an attempt to maximize recovery, several cultural strategies were applied. Various non-selective media were used and different temperatures and durations of the enrichment were applied before subculturing on Cefsulodin Irgasan Novobiocin (CIN) agar. Presumptive Y. enterocolitica colonies were subjected to urease, API 20E and agglutination test. Yersinia enterocolitica isolates were biotyped, serotyped, and tested for pathogenicity using a TaqMan PCR directed towards the ail-gene that is associated with human pathogenic strains of Y. enterocolitica.

Results

The samples collected from 99 sheep yielded 567 presumptive Y. enterocolitica colonies. Eighty urease positive isolates, from 35 sheep, were identified as Y. enterocolitica by API 20E. Thirty-four of 35 further subtyped Y. enterocolitica isolates, all from faecal samples, belonged to biotype 1A serotype O:5, O:6. O:13,7 and O:10. One strain was Yersinia mollaretii serotype O:62. No human pathogenic strains of Y. enterocolitica were found in the investigated sheep. Other species identified were Y. kristensenii (n = 4), Y. frederiksenii/intermedia (n = 3), Providencia rettgeri (n = 2), Serratia marcescens (n = 1) and Raoultella ornithinolytica (n = 1).

Conclusions

This study does not support the hypothesis that sheep play an important role in transmission of the known human pathogenic Y. enterocolitica in the studied geographical region. However, because there are studies indicating that some strains of Y. enterocolitica biotype 1A may cause disease in humans, the relative importance of sheep as carriers of human pathogenic strains of Y. enterocolitica remains unclear. Tonsils do not appear to be favourable sites for Y. enterocolitica biotype 1A in sheep.  相似文献   

18.
Faecal samples from clinically normal farmed red deer, wapiti, fallow deer; and feral red deer and white tail deer were examined for members of the genus Yersinia. From 922 samples 176 strains of Y.enterocolitica, 56 strains of Y.frederiksenii, 29 strains of Y.kristensenii, eight strains of Y.intermedia, and seven strains of Y.pseudotuberculosis were isolated. High isolation rates of Yersinia sp. were recorded from some farms. Two herds had isolation rates of 33.3% and 36.8%. Sixteen strains of Yersinia sp. in addition to strains of Y.psuedotuberculosis were found to be Hela cell invasive. The majority of these strains were confined to a single herd and represented Y.enterocolitica biotypes I, II and III, Y.intermedia, Y. fredericksenii, and Y.kristensenii.  相似文献   

19.
A total of 142 strains from different serotypes of Streptococcus suis isolated in Spain from diseased pigs (88 strains) and healthy carrier pigs (54 strains) were studied for the presence of a muramidase released protein (MRP) and an extracellular factor (EF). The following five phenotypes: MRP+EF+, MRP+EF-, MRP-EF+, MRP+EF* and MRP*EF- were detected. A high percentage of S. suis serotype 2 strains isolated from diseased pigs (84 per cent) belonged to phenotype MRP+EF+, but this phenotype has also been noticed in other serotypes (serotypes 1, 1/2 and 14). Both proteins were detected in S. suis serotype 2 strains (26%) isolated from healthy carrier pigs and one of both proteins in serotypes 1 and 14 (phenotype MRP+EF*). The isolation of S. suis strains from healthy pigs which have shown both proteins may support the epidemiological significance of these carriers in the maintenance, transmission and distribution of virulent strains within and between swine farms.  相似文献   

20.
The pathogenicity of Yersinia enterocolitica, a bacterium that has been isolated frequently from healthy swine, was studied in piglets by oral challenge of two litters, one derived by cesarean section and deprived of colostrum, and the other delivered at full-term. Eight cesarean-derived piglets were divided into groups of two and challenged with four serotypes of Y. enterocolitica (O:8, O:21, O:3, O:13). Two deaths occurred and two piglets were killed because of severe illness before termination of the experiment eight days after challenge. Surviving piglets showed no clinical signs of illness. Rectal cultures were consistently positive and all cesarean-derived piglets were colonized in the small intestine and throat at necropsy. Full-term piglets were allowed access for 36 hours to sow colostrum containing low levels of antibody against the challenge strains. Six full-term piglets challenged with three serotypes of Y. enterocolitica (O:8, O:21, O:13) survived for 15 days without any signs of illness. These piglets had fewer positive rectal cultures and showed less extensive colonization of internal organs at necropsy than did cesarean-derived piglets. It is uncertain whether this increased resistance to infection with Y. enterocolitica resulted from colostrum-derived antibody, intestinal colonization with other bacteria, or an improved physical condition which accompanied full-term development. Nevertheless, the results of this challenge experiment suggest that piglets are capable of restricting colonization by Y. enterocolitica to the throat and intestinal tract without development of serious illness.  相似文献   

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