Prevalence and characteristics of Escherichia coli serotype O157:H7 and other verotoxin-producing E. coli in healthy cattle.

From February to July of 1994, 328 faecal samples from 32 herds were collected and verotoxin-producing Escherichia coli (VTEC) found on 84% of the farms. The proportion of animals infected varied from 0-63%. VTEC were recovered from 52 (20%) of 257 cows and from 16 (23%) of 71 calves. Although the VTEC belonged to 25 different serogroups, 7 (O8, O20, O22, O77, O113, O126 and O162) accounted for 46% of strains. Nearly 45% of the strains. Nearly 45% of the 83 bovine VTEC strains belonged to serogroups associated with haemorrhagic colitis and haemolytic uraemic syndrome in humans. However, only 2 (2%) of 83 VTEC strains isolated from cattle belonged to enterohaemorrhagic E. coli (EHEC) serotypes (O26:H11 and O157:H7), and only 8 (10%) were positive for the attaching and effacing E. coli (eae) gene sequence. Polymerase chain reaction (PCR) showed that 17 (20%) of VTEC strains carried VT1 genes, 43 (52%) possessed VT2 genes, and 23 (28%) carried both VT1 and VT2 genes. Characterization of VTEC isolates revelated a heterogeneous population in terms of serogroup and toxin type in the positive herds. This study confirms that healthy cattle are a reservoir of VTEC, but, the absence of eae genes in most bovine VTEC strains suggests that they may be less virulent for humans than eae-positive EHEC.     

Prevalence of bovine verotoxin-producing Escherichia coli in Argentina

Faecal swabs obtained from 126 calves and 118 cows in Argentina were investigated for the presence of verotoxin-producing Escherichia coli (VTEC). VTEC strains were recovered from 10 (23%) of 43 calves with diarrhoea, from 24 (29%) of 83 healthy calves, from 40 (44%) of 91 healthy cows waiting at the slaughterhouse, and from 6 (22%) of 27 healthy grazing cattle. PCR showed that 21 (9%) of animals carried VT1⁺ strains, 49 (20%) VT2⁺ strains and 10 (4%) VT1⁺ VT2⁺ strains. VT1⁺ strains predominated among calves (16% versus 0.8%; p < 0.001). The presence of eae gene was significantly more frequent among VTEC strains isolated from calves (78%; 46/59) than from cows (2%; 1/65) (p < 0.001). Furthermore, eae gene was more prevalent in VT1⁺ strains (97%; 32/33) than in VT2⁺ strains (14%; 10/70) (p < 0.001) and in VT1⁺ VT2⁺ strains (24%; 5/21) (p < 0.001). Sorbitol negative high virulent strains serogroups O157 were not detected. This study indicates that cattle are a reservoir of VTEC strains, and that eae gene is associated with VT1⁺ strains that are predominating among young animals. Fortunately, only adult animals are taken to the slaughterhouse, among which VTEC strains negative for eae gen are predominating.     

Extended phage-typing scheme for Escherichia coli O157:H7

In Canada, the number of human isolates of verotoxigenic (VT + ve) Escherichia coli O157:H7 from diarrhoeal cases and haemolytic uraemic syndrome and haemorrhagic colitis has increased from 25 in 1982 to 2384 in 1989. A total of 3273 VT + ve E. coli O157:H7 strains (3255 strains isolated in Canada and 18 isolates from other countries) were phage typed. The phage typing scheme has been extended from 14 to 62 phage types. Of these, five types occurred exclusively in other countries (type 47 in Japan; and types 49, 50, 51 and 52 in the U.K.). Thirty-five different phage types were identified in Canada; only nine of these (1, 2, 4, 8, 14, 21, 23, 31 and 32), each accounted for more than 1% of the cases from human sources. The same nine types were the only ones observed among the isolates from non-human sources (meat and slaughter houses) suggesting a food-borne transmission in most of the human cases. Phage types 1 (30.5%); 4 (21%); 8 (13.5%); 31 (8.9%) and 14 (8%) were encountered in varying frequencies in most of the provinces; infrequently occurring phage types also showed regional variation. Thirteen different phage types were identified among 151 outbreaks representing 556 isolates of E. coli O157:H7. More than one phage type were encountered in 12 outbreaks whereas in 141 outbreaks, all strains in each, had the same phage type.     

Virulence profiling and disease association of verocytotoxin-producing Escherichia coli O157 and non-O157 isolates in Belgium

Whereas the association of verocytotoxin-producing Escherichia coli (VTEC) O157:H7 with the hemolytic uremic syndrome (HUS) is well established, the medical importance of many non-O157 serotypes remains unclear. Using polymerase chain reaction (PCR), we have investigated the distribution of the pathogenicity island O island 122 (OI-122) and other virulence genes in VTEC belonging to seropathotypes (SPT) A through D, and assessed their association with human disease. Two hundred sixty-five VTEC isolated from human stools comprising 52 O157 (of which 14 associated with HUS) and 213 non-O157 isolates (of which 19 associated with HUS) were studied. A complete OI-122 (COI-122) was detected in all O157, but in only 35 (16.4%) of non-O157 strains. A progressive decrease in the frequency of COI-122 was observed from SPT A through D, with a concomitant increase in the frequencies of incomplete and absent OI-122. We focused on the variable virulence profiles of the non-O157 serotypes and found that COI-122 was also more frequently present in isolates associated with HUS (p=0.001). The individual genes vtx2, eae, espP, as well as the OI-122-associated genes sen, nleB, nleE, and the efa gene cluster were significantly more often present in non-O157 VTEC associated with HUS. Non-O157 isolates carrying the combined virulence profile vtx2-nleE-efa showed the strongest association with HUS (p<0.0001). Molecular risk assessment by determination of virulence profiles of individual isolates may be useful in the identification of highly virulent non-O157 strains. We showed that the detection of a specific gene combination could assist in identifying non-O157 VTEC isolates that pose a serious public health concern.     

Sequence heterogeneity of the eae gene and detection of verotoxin-producing Escherichia coli using serotype-specific primers.

The distribution of the Escherichia coli attaching and effacing (eae) gene in strains of verotoxin-producing E. coli (VTEC) isolated from cattle and humans was studied. The majority of strains isolated from humans with bloody diarrhoea or HUS and cattle with severe diarrhoea were eae positive (82 and 83% respectively). In contrast, 59% of VTEC isolated from asymptomatic cattle were eae negative and of the remaining 41% that were eae positive, the majority were serotype O157. H7. The nucleotide sequence of the 3'' end of the eae gene of enteropathogenic E. coli (EPEC) of serotype O55. H7 was found to be almost identical to that of serotype O157. H7. Specific primers are described which detect the eae sequences of VTEC serotypes O157. H7, O157. H-, and EPEC serotypes O55. H7 and O55. H-. The nucleotide sequence of the 3'' end of the eae gene of serotype O111. H8 differed significantly from that of O157. H7. Primers were developed to specifically identify the eae sequences of VTEC serotypes O111. H- and O111. H8. We conclude that whereas the majority of VTEC associated with disease in cattle and humans possess the eae gene, the gene itself may not be necessary to produce haemorrhagic colitis and HUS. Sequence heterogeneity in the 3'' end of eae alleles of VTEC permits specific identification of subsets of these organisms.     

Prevalence of Escherichia coli O157 in lambs at slaughter in Rome, central Italy

A study on the prevalence of the faecal carriage of Escherichia coli O157 in lambs was performed in the major slaughterhouse in Rome, central Italy, during 2002. A total of 643 animals, consisting of 378 weaned and 265 suckling lambs, were assayed for the presence of E. coli O157. Five O157-agglutinating E. coli strains were isolated (0.8%, 95% CI 0.3-1.9). Only one was positive to PCR specific for the eae gene and produced verocytotoxin VT2, with a VTEC O157 overall prevalence of 0.2% (95% CI 0.0-1.0), whereas one strain possessed the eae gene only. All the other isolates were negative for the presence of all the virulence genes considered. The animals were either from local farms or imported from Eastern Europe. The results suggest an age-specific difference since the microorganism was isolated only from 0.3% (95% CI 0.0-1.7) of weaned lambs, while all samples from suckling lambs tested negative. From this study, the overall risk of human exposure to pathogenic E. coli O157 from lamb meat consumption derived from the major slaughterhouse in Rome can be considered reasonably low, particularly when suckling lamb meat is considered.     

A one year study of Escherichia coli O157 in raw beef and lamb products

Between April 1996 and March 1997 we examined 5093 samples of raw beef and lamb products for the presence of E. coli O157. Samples were purchased from 81 small butchers' shops in south Yorkshire. In March 1997 we also examined five samples of dried mint for the presence of E. coli O157. Strains of E. coli O157 were isolated by enrichment culture in modified buffered peptone water followed by immunomagnetic separation and culture of magnetic beads onto cefixime tellurite sorbitol MacConkey agar. Strains were characterized by phage typing, toxin genotyping and plasmid analysis. Strains of E. coli O157 were isolated from 72 (1.4%) of 5093 samples; it was isolated from 36 (1.1%) of 3216 samples of beef products and from 29 (2.9%) samples of lamb products. The highest prevalence was found in lamb sausages and lamb burgers where E. coli O157 was isolated from 3 (4.1%) of 73 and 18 (3.7%) of 484 samples respectively. Strains of E. coli O157 were isolated most frequently during early summer. Strains of E. coli O157 were also isolated from 2 of 5 samples of dried mint although we did not determine how the mint had become contaminated. All isolates of E. coli O157 were Verocytotoxin-producing as determined by both Vero cell assay and DNA hybridization for the genes encoding Verocytotoxin and all were positive for the eaeA gene. A combination of phage typing, toxin genotyping and plasmid profile subdivided the 72 strains of E. coli isolated into 20 different subtypes, of which 18 were indistinguishable from strains isolated previously from cattle and sheep; of these 18 strains, 8 were indistinguishable from strains isolated from human cases of infection during the study period.     

Phage typing of Vero cytotoxin-producing Escherichia coli O 157 isolated in the United Kingdom: 1989-91.

Between 1989 and 1991 a total of 1092 Vero cytotoxin-producing Escherichia coli O 157 isolated in the United Kingdom were phage typed in the Laboratory of Enteric Pathogens (LEP). Twenty-three phage types was identified, the most frequent being types 2 (36.1%), 49 (29.6%), 1 (10.3%) and 4 (8.9%). Although isolations of O 157 VTEC have increased each year from 1 in 1982 to 532 in 1991, the predominant phage types have remained unchanged although the proportion of strains belonging to types 2 and 49 has increased. O 157 VTEC from 17 outbreaks were phage typed during this period with phage type 49 predominating (7 of 17 outbreaks).     

Characterization and epidemiologic subtyping of Shiga toxin-producing Escherichia coli strains isolated from hemolytic uremic syndrome and diarrhea cases in Argentina

Argentina has a high incidence of hemolytic uremic syndrome (HUS); 12.2 cases per 100,000 children younger than 5 years old were reported in 2002. Shiga toxin (Stx)-producing Escherichia coli (STEC) is the primary etiologic agent of HUS, and STEC O157 is the predominant serogroup isolated. The main objective of the present work was to establish the phenotypic and genotypic characteristics of the STEC strains in general isolated from Argentine children during a prospective study and the clonal relatedness of STEC O157:H7 strains using subtyping techniques. One hundred and three STEC strains isolated from 99 children were included. The phenotypic and genotypic features were established, and a polymerase chain reaction-restriction fragment length polymorphism (PCRRFLP) was performed to determine stx2 variants. The clonal relatedness of E. coli O157 isolates was established by phage typing and pulsed-field gel electrophoresis (PFGE). The 103 STEC strains belonged to 18 different serotypes, and 59% were of serotype O157:H7. Stx2 was identified in 90.3%, and stx1 in 9.7%. Among the 61 STEC O157 strains, 93.4% harbored the stx2/stx2vh-a genes; PT4 (39.3%) and PT2 (29.5%) were the predominant phage types. Using PFGE with the enzyme XbaI, a total of 41 patterns with at least 80% similarity were identified, and seven clusters with identical profiles were established. Some of the clusters were further split by PFGE using BlnI as the second enzyme. Isolates with indistinguishable PFGE patterns were with one exception also indistinguishable by phage typing and stx genotyping. These findings confirmed that some isolates were genetically related. However, no epidemiological linkages were identified. STEC strains with different genotypes and belonging to diverse serotypes were isolated in Argentina. Some STEC O157 strains could not be distinguished by applying subtyping techniques such as PFGE and phage typing.     

Vero cytotoxin-producing Escherichia coli, particularly serogroup O157, associated with human infections in England and Wales: 1992-4.

Investigations were performed by the Laboratory of Enteric Pathogens on Vero cytotoxin-producing Escherichia coli (VTEC) in England and Wales from 1992-4. Bacterial isolates, faeces and sera obtained from patients with diarrhoea, bloody diarrhoea and haemolytic uraemic syndrome were examined. Using serotyping, Vero cytotoxin gene probing and serodiagnostic tests for E. coli O157, evidence of infection was detected in 543, 434 and 491 individuals in 1992, 1993 and 1994 respectively; VTEC of serogroup O157 were isolated from 470, 385 and 411 cases. The O157 VTEC strains belonged to at least 19 different phage types (PT) although 84% belonged to PT2, PT49, PT8, PT1 or PT4. Antibodies to E. coli O157 lipopolysaccharide were detected in 13% of the cases. The average annual rate of infection with O157 VTEC was 0.83/100000 and 12% of the 1458 individuals with evidence of infection with VTEC or E. coli O157 developed haemolytic uraemic syndrome. There were at least 18 general outbreaks and many family outbreaks.     

Investigation of human infections with verocytotoxin-producing strains of Escherichia coli (VTEC) belonging to serogroup O118 with evidence for zoonotic transmission

Twenty verocytotoxigenic Escherichia coli (VTEC) O118 strains isolated between 1996 and 1998 from human patients in Germany were analysed for their serotypes, their virulence markers and their epidemiological relatedness. Three strains were typed as O118:H12, these carried only the VT2d-Ount variant gene and were not associated with diarrhoea or haemolytic uraemic syndrome (HUS). Seventeen strains were serotyped as O118:H16 or O118:non-motile (NM). These carried all the genes for VTI, eae and EHEC-haemolysin. The O118:H16/NM strains were from diarrhoea (13 cases) and HUS (2 cases). Sixteen of the patients were young infants and most infections were associated with a rural environment. Evidence for zoonotic transmission from cattle to humans was found in two cases. The epidemiological relationship between the human and bovine O118:H16/NM isolates was indicated by homogeneous plasmid patterns and by very similar XbaI restriction patterns obtained by pulsed-field gel electrophoresis. VTEC O118:H16/NM are emerging pathogens in Germany and should be classified as new enterohaemorrhagic E. coli (EHEC) types.     

Prevalence of the eaeA gene in verotoxigenic Escherichia coli strains from dairy cattle in Southwest Ontario.

This study determined the prevalence of the eaeA gene and its relationship to serotype and type of verotoxin produced in a collection of 432 verotoxigenic Escherichia coli (VTEC) obtained from the faeces of healthy cows and calves in a systematic random survey involving 80 dairy farms in Southwest Ontario. A PCR amplification procedure involving primer pairs which target the conserved central region of the O157:H7 eaeA gene showed that 151 (35.2%) strains were positive for the eaeA gene. All isolates (9-21 for each O group) of O groups 5, 26, 69, 84, 103, 111, 145 and 157 were positive, whereas all isolates (7-34 for each O group) of O groups 113, 132, and 153 and serotype O156:NM (38 isolates) were negative for eaeA. Seventy-three percent of 130 isolates of eaeA-positive serotypes produced VT1 only compared with 20% of 253 isolates of eaeA-negative serotypes. We conclude that there is a strong association between certain O groups and the eaeA gene, that serotypes of eaeA-positive and eaeA-negative VTEC implicated in human and cattle disease are present at high frequency in the faeces of healthy cattle, that VT1 is more frequently associated with eaeA-positive than with eaeA-negative serogroups, and that the eaeA gene is more frequently found in VTEC from calves compared with VTEC from adult cattle.     

A longitudinal study of Vero cytotoxin producing Escherichia coli in cattle calves in Sri Lanka.

Two cohorts of 10 and 16 calves were followed at weekly or fortnightly intervals from 4-28 and 1-9 weeks respectively to determine whether natural infection by Vero cytotoxin (VT) producing Escherichia coli (VTEC) occurred. Ninety-one of 171 (53%) faecal specimens were VTEC positive and 20-80% of animals at any given time excreted VTEC. Of 104 VTEC strains studied further, 6 different serogroups (O 22.H16; O 25.H5; O 49.H-; O 86.H26; O 88.H25; O 153.H12) and an untypable strain (O? .H21) were identified. All strains belonging to the same serotype had identical profiles of reactivity with DNA probes to toxins VT1 or 2, LTI or II and a probe (CVD419) derived from a plasmid carried by enterohaemorrhagic Escherichia coli O 157.H7. Four of these serotypes were found in the faecal flora of the calves, taken as a group, throughout the 4-month study period. Sixty percent of the strains hybridized with the probe for VT1, 4% with the probe for VT2, and 36% with both probes. Faecal VTEC were significantly associated with overt diarrhoeal illness in animals < 10 weeks of age, but no characteristic profile of markers (serotype or hybridization pattern) in E. coli isolates was associated with diarrhoea. A serological response to VT1 was detected in some animals, but faecal VT1 VTEC excretion persisted in spite of seroconversion. VT1 seroconversion was not associated with diarrhoea. A serological response to VT2 was not detected even in those animals excreting VT2 VTEC in the faeces.     

The prevalence and characterization of verotoxin-producing Escherichia coli isolated from cattle and pigs in an abattoir in Hong Kong

The aim of the study was to define the prevalence of verotoxin-producing Escherichia coli (VTEC) in cattle and pigs in a Hong Kong abattoir. Faecal and carcass samples collected from 986 cattle and 487 pigs from an abattoir were tested for verotoxin (VT) by PCR and cytotoxicity assays. VTEC was isolated from 415 and 1-8% of cattle faecal and carcass samples and from 2.1 and 0.2% of porcine faecal and carcass samples, respectively. Amongst 409 VTEC isolates from cattle, 9 were serotype O157:H7 and eaeA+. The most prevalent vt genotype among bovine VTEC was vtl+vt2 (73.8%) and in porcine VTEC was vt2e+ (30%). None of the porcine VTEC isolates and 9.3% of the bovine VTEC isolates was eaeA+. The non-O157 serogroup VTEC isolates carrying eaeA and EHEC-hlyA belonged to serogroups O172, O15, O84, O91, O110 and O121. The local dietary preference for pork or chicken (rather than beef), the low VTEC carriage in pigs, the rarity of additional virulence factors (caeA) in VTEC isolated from cattle may explain the apparently low incidence of human diarrhoeal disease associated with VTEC in Hong Kong hitherto. However, the presence of non-O157 VTEC strains carrying the eacA virulence marker in cattle highlights the fact that sole reliance on sorbitol-MacConkey agar for screening human VTEC isolates may underestimate the human disease burden. The changing dietary habits of the population in Hong Kong reinforce the need for continued vigilance.     

Phage-typing of Vero-cytotoxin (VT) producing Escherichia coli O157 isolated in the United Kingdom

Vero-cytotoxin (VT) producing Escherichia coli serogroup O157 have been isolated from patients with diarrhoea, haemorrhagic colitis (HC) and haemolytic uraemic syndrome (HUS). A phage-typing scheme developed in Canada has been used to type 155 VT+ E. coli O157 serogroup isolated from sporadic infections in the UK since 1983, and 48 strains from HC or HUS outbreaks. Twelve phage types were identified of which three, types 49, 51 and 52, have not been found in North America. All strains carried a 60 x 10(6) plasmid and most VT1+VT2+ strains also had a 5 x 10(6) plasmid coding for colicin D production. The majority of strains producing both VT1 and VT2 belonged to phage type 1, or the related types 4, 8 and 14. Most strains producing only VT2 belonged to types 2 or 49. Four outbreaks were included in the survey. Three had strains of a single phage type while strains from the fourth outbreak were more variable. The distribution of phage types throughout the UK showed no marked geographical variations.     

Variations in biochemical phenotypes and phage types of Salmonella enteritidis in Germany 1980-92.

The Phene Plate system for typing Salmonella serotypes (PhP-S) is a simple automated typing method based on biochemical fingerprinting. It gives a quantitative value of the metabolism of various substrates by measuring the speed and intensity of each reaction. The ''biochemical fingerprint'' of each isolate is used to calculate similarities among the tested strains with a personal computer program. We used this system to examine a collection of 86 strains of Salmonella enteritidis isolated from human sporadic cases in Germany between 1980 and 1992. Twenty-three biochemical phenotypes (BPTs) consisting of 9 common (C) and 14 single (S) BPTs were identified. BPTs C2 and C4 containing 20 and 36 strains respectively accounted for 65% of the isolates. Strains of BPT C2 were found over a wide period of time whereas strains of BPT C4 were isolated during the period between 1988 and 1992. With phage typing, 11 discrete phage types (PTs) and 18 strains designated as non-specific type (NST) were identified. PTs 4 and 8 with 39 and 17 strains respectively were the dominant PTs. Strains of PT 8 were isolated over a wide period of time whereas all (except one) strains of PT 4 were isolated between 1988 and 1992. Combination of biochemical fingerprinting and phage typing divided the strains into 25 phenotypes (BPT:PTs). Whilst phenotype C2:8 was found over a number of different years, phenotype C4:4 was isolated only between 1988 and 1992. These findings indicate the presence of one persistent and one recently emerged phenotype among S. enteritidis strains in Germany.(ABSTRACT TRUNCATED AT 250 WORDS)     

Asymptomatic carriage of verocytotoxin-producing Escherichia coli O157 in farm workers in Northern Italy

Faecal samples from 350 farm workers on 276 dairy farms and 50 abattoir employees from seven different operations were examined for the presence of Verocytotoxin-producing Escherichia coli 0157 (VTEC O157) by an O157-specific enzyme-linked fluorescent assay followed by immunoconcentration. VTEC O157 was isolated from four (1.1%) of the farm workers. A second stool sample was obtained from the positive farm workers as well as from their household contacts. VTEC O157 was isolated from the wife of one of them. The strains from the same household shared the same Verocytotoxin genes profile, phage type and pulsed-field gel electrophoresis pattern. The VTEC O157-positive subjects had neither intestinal symptoms at the moment of sampling nor a history of bloody diarrhoea or renal failure. Our study seems to confirm the hypothesis that farm residents often develop immunity to VTEC O157 infection, possibly due to recurrent exposure to less virulent strains of VTEC.     

Infection with verocytotoxin-producing Escherichia coli O157 during a visit to an inner city open farm

Two cases of Escherichia coli O157 infection occurred in children after visiting an inner city open farm. Subsequently faecal samples collected from animal pens and samples of composted mixed animal manure and vegetable waste were examined for E. coli O157 by enrichment culture, immunomagnetic separation and culture of magnetic beads to cefixime tellurite sorbitol MacConkey agar. Strains of E. coli O157 were characterized by hybridization with DNA probes for VT1, VT2 and eaeA, plasmid profile analysis, phage typing and pulsed field gel electrophoresis (PFGE). Verocytotoxin-producing E. coli O157 strains were isolated from faecal samples from a cow, a horse, 3 breeds of pigs, 2 breeds of sheep and 2 breeds of goats and from 2 samples of compost which had been processed for 3 months. All strains were phage type 21, hybridized with probes for VT2 and eaeA but not with one for VT1, harboured 92 and 2 kb plasmids and gave indistinguishable banding patterns with PFGE. Although only two culture-confirmed cases of infection had been identified, the farm had over 100,000 visitors per year and so it was closed as a precaution both to allow a thorough investigation and to prevent further cases. The investigation identified many factors which may have contributed to transmission of E. coli O157 infection. Most of these were readily resolved by appropriate corrective measures and as there were no further cases associated with the farm during the ensuing 4 weeks it then re-opened. These cases highlight the risk, especially to young children, of acquiring zoonotic infections during visits to open farms and emphasize the need for adequate guidance and supervision before and during such visits.     

2001年中国食源性致病菌及其耐药性主动监测研究

目的　旨在监测中国食源性致病菌及其耐药性。方法　中国疾病预防控制中心营养与食品安全所建立的全国食品污染物监测网的食源性致病菌监测部分 ,2 0 0 1年在全国 11个省市设点采样并检测了七大类 (生肉、熟肉、生奶、冰激淋、酸奶、水产品和蔬菜 )共 4 0 34份样品。结果　沙门氏菌、大肠杆菌O15 7∶H7和单核细胞增生李斯特氏菌 ,总阳性率 5 5 0 %。其中沙门氏菌 3 32 % ,单核细胞增生李斯特氏菌 1 2 9% ,大肠杆菌O15 7∶H70 82 %。生肉的污染情况最为严重 ,阳性率 12 96 %。共分离出沙门氏菌 137株 ,德比沙门氏菌、阿贡纳沙门氏菌、肠炎沙门氏菌、里定沙门氏菌、鸭沙门氏菌、明斯特沙门氏菌及鼠伤寒沙门氏菌 7种血清型占 80 %。结论　沙门氏菌的血清型分布和耐药性各个省不同。自生、熟肉中分离到O15 7∶H7的强毒株。对分离的沙门氏菌、大肠杆菌检测了 14种抗生素的耐药性 ,结果表明沙门氏菌和大肠杆菌中都有多重耐药株。     

Continuous surveillance of Shiga toxin-producing Escherichia coli infections by pulsed-field gel electrophoresis shows that most infections are sporadic

The purpose of this study was to evaluate the value of real-time molecular typing of Shiga toxin (Verocytotoxin)-producing Escherichia coli (STEC) infections in order to detect possible outbreaks of infections. All laboratory confirmed STEC infections in Denmark from 2003 to mid 2005 were routinely characterized by serotyping, virulence genes characterization, and subtyping by pulsed-field gel electrophoresis (PFGE) using the PulseNet protocol for STEC O157. The study included 312 STEC isolates representing 50 different O groups and 75 O:H-serotypes, and 68% of the isolates belonged to the eight most common O-groups: O157 (26%), O103 (13%), O146 (8%), O26 (8%), O117 (4%), O145 (3%), O128 (3%), and O111 (2%). The remaining O-groups constituted less than 2% each, and 8.1% of the isolates were O-rough. The eae gene was found in 60% of all isolates, and detection of the two main Shiga toxin genes showed that 40% had stx1 only, 31% had stx2 only, and 29% had both stx1 and stx2. A high diversity was seen within all O groups, and for most of the rare O groups, the number of PFGE profiles equaled the number of isolates. However, one outbreak of E. coli O157 was detected by the routine PFGE typing. The value of "real-time' PFGE typing of the infrequent serotypes is limited if the full scheme for O-grouping or O:H-serotyping is used routinely for all STEC isolates. Possible outbreaks can then be detected by the increased number of isolates within a particular serotype. PFGE typing would then be valuable in subsequent steps of the outbreak investigation. However, routine PFGE typing of the three to five most common O groups will enable early recognition of possible outbreaks.