The prevalence of virulence-related genes, eaeA, aggR and astA, of localized and aggregative-adherent Escherichia coli (EPEC and EAggEC) in healthy children and age-matched patients with diarrhea

The prevalence of virulence-related genes of localized- and aggregated-adherent Escherichia coli (EPEC and EAggEC), such as eaeA, aggR and astA was compared between E. coli isolated from 0 to 5 year old children with and without diarrhea in Saga Prefecture. In the case of eaeA, 233 cases in Aichi Prefecture were included. The subjects were 74 diarrheal patients from which no diarrheagenic bacteria were detected besides E. coli. The control subjects were 304 nursery school children without diarrhea, and E. coli was isolated from 278 children in which 105 strains were of 0-serotype. EaeA-positive E. coli was isolated from nine (12.2%) Saga cases, 19 (8.2%) Aichi cases and 6 (5.7%) control subjects; aggR-positive E. coli was isolated from 10 (13.5%) cases and 6 (5.7%) control subjects and astA-positive E. coli from 10 (13.5%) cases and 14 (13.3%) control subjects. No significant difference (p > 0.05) was observed in the prevalence of eaeA, aggR and astA between healthy and diarrheal children, even in age-matched and 0-serotypable E. coli limited comparisons. The pathogenicity of EPEC and EAggEC should be investigated, considering other known or unidentified factors.     

Prevalence of Escherichia coli possessing the eaeA gene of enteropathogenic E. coli (EPEC) or the aggR gene of enteroaggregative E. coli (EAggEC) in traveler's diarrhea diagnosed in those returning to Tama, Tokyo from other Asian countries

To elucidate the importance of enteropathogenic Escherichia coli (EPEC) and enteroaggregative E. coli (EAggEC) as etiological agents in traveler's diarrhea, the detection of the eaeA and aggR gene in E. coli strains isolated from overseas travelers with diarrhea in Tama, Tokyo was carried out using a PCR method. Of 192 travelers who were mostly adults and had visited Asian countries from April 1998 to March 1999, aggR-positive E. coli strains were detected in 26 (13.5%). These strains represent the second predominant enteropathogen following enterotoxigenic E. coli (ETEC), whereas eaeA-positive E. coli strains were confirmed in seven subjects (3.6%). In 13 cases with aggR and four cases with eaeA, the organisms were detected in stool samples of patients as the only potential enteric pathogen. The clinical symptoms of these patients were similar to those in patients with ETEC; however, the severity of illness was milder than that associated with ETEC alone. Three strains with eaeA and five strains with aggR were typed as six different kinds of O serogroups, of which four strains belonged to the classical EPEC serogroups (O55, O114, O119, and O127a). These findings suggest that aggR-positive E. coli (EAggEC) is a significant causative agent in traveler's diarrhea. In addition, it was demonstrated that eaeA-positive E. coli (EPEC) is markedly correlated with diarrhea in adults.     

Molecular investigation of pathogenic factors of suspected-diarrheogenic Escherichia coli isolates from patients feces

One hundred fifty-one O serotypable Escherichia coli strains which were assumed diarrheogenic E. coli among 2,240 strains of E. coli isolated from the in- and outpatients stools with or without gastrointestinal symptoms at Kyorin University Hospital from February 1994 to September 1996 were examined for the relationship between the possession of eight pathogenic factor-related genes and gastrointestinal symptoms of the patients using the polymerase chain reaction (PCR) for these strains. The rate of possession of pathogenic factor-related genes in the E. coli examined was 20.5% (31 strains) and gastrointestinal symptoms were found in all the patients with these strains except one. In the patients without gastrointestinal symptoms, E. coli isolates that possesses these genes was detected in only one case during 61 cases. The respective genes detected were eaeA and astA in each 14 strains, VT1 in 6, VT2 in 5, ST1b in 4, aggR in 3 and LT in 2, ST1a and invE gene was not detected. In particular, the O157 strains were found in 55.6% (5/9 strains) for these genes, and individual strains had VT1, VT2, eaeA and astA genes simultaneously. In contrast, none of these related genes was found in 9 strains of enteroinvasive serotype but enteropathogenic E. coli-related genes were found in 3 strains. The rate of possession of the genes related to enterotoxigenic E. coli, O159 which was most frequently isolated was low as 2.3% (1/43 strains, astA gene) and there were strains showing low correlation to the state of possession of the genes with the O serotype. Since the prevalence of the gastrointestinal symptoms is clearly high for the case which possesses the strain of which the pathogenic factor-related gene was detected, it was suggested that detection of pathogenic factor-related genes in E. coli isolates from feces using the PCR could be an effective means to decide whether the bacteria concerned was a causal bacteria or not in clinical practice.     

The incidence and the valuation of eaeA gene of enteropathogenic Escherichia coli (EPEC) or aggR gene of enteroaggregative E. coli (EAggEC) in the strains isolated from patients in sporadic diarrhea cases

To clarify the pathogenic role of enteropathogenic Escherichia coli (EPEC) or enteroaggregative E. coli (EAggEC), the possession of eaeA gene of EPEC or aggR gene of EAggEC in the strains isolated from 525 patients in sporadic diarrhea cases during 3 years (1998-2000) in Tama, Tokyo was investigated by a PCR method. The eaeA-positive E. coli strains were confirmed from 23 cases including 5 cases detected verotoxin-producing E. coli (VTEC), and those except VTEC strains (18 cases, 3.4%) were the 5th predominant enteropathogen following rotavirus, Campylobacter, adenovirus, and Salmonella. By age, 17 eaeA-positive cases were from children < 10 years of age, and noticeably, of which 9 were from infants < 24 months of age. On the other hand, although aggR-positive E. coli strains were detected from 11 cases (2.1%), of which 6 also were from infants < 24 months of age. Clinical symptoms of patients whom eaeA or aggR gene-positive E.coli was isolated as the only potential enteric pathogen were similar, showing a mild gastroenteritic features. Only one strain of eaeA-positive E. coli and 4 of aggR-strains were typed with the commercial O-antisera, which were O55, and O86, O111 or O126. In antibiotic sensitivity tests for 9 agents, 22% of eaeA-strains and 91% of aggR-strains showed resistant, especially 10 aggR-strains had resistant to ABPC. These findings suggest that these organisms are a significant causative agents of infantile diarrhea and the PCR method is a useful procedure for the diagnosis of EPEC or EAggEC infectious disease.     

Four serotypes highly positive for pathogenic factor-related genes found among Escherichia coli isolates from sporadic diarrheal cases in Fukui Prefecture

To evaluate the prevalence of pathogenic factor-related genes in 964 O-serotype Escherichia coli isolated from sporadic diarrhea cases at 2 hospitals in Fukui during 1997 to 2001, we checked all of these strains for H-serotype and examined them for 4 pathogenic factor-related genes (LT, ST, stx and invE) by PCR. Of these strains, 409 except for most of 9 serotypes which are usually low prevalence of pathogenic factor-related genes, and additional 16 strains isolated from other hospitals in Fukui Prefecture were also examined for 3 pathogenic factor-related genes (eaeA, astA and aggR) by PCR. It was found that 4 serotypes, O6:H16, O25:HNM, O111:H21 and O126:H27, were highly positive for pathogenic factor-related genes; O6:H16 (11/12 strains) positive for LT, ST, astA, O 25:HNM (10/14 strains) positive for ST and astA, O111:H21 (22/22 strains) positive for astA or aggR, and O126:H27 (8/9) positive for astA and aggR genes. According to the drug susceptibility test, these serotypes as O6:H16, O25:HNM, O111:H21 and O126:H27 showed a significant resistance to some drugs in 7/12, 4/14, 21/22 and 9/9 strains, respectively. Such results indicate that both O111 and O126-serotypes are highly positive for pathogenic factor-related genes and also drug-resistant, namely this fact suggests that the O-serotyping as laboratory screening is one of the useful measures of clinical management. Additionally, the pulsedfied gel electrophoresis patterns found in each of the 4 serotypes mentioned revealed that a part of E. coli in Fukui might be derived from the same source of infection.     

The incidences of virulence genes in Escherichia coli strains from sporadic diarrheal children

To investigate the incidence of diarrheagenic Escherichia coli among E. coli strains screened by commercially available O-antigen antisera, we used PCR to isolate 8 virulence genes (eae, bfpA, IpaH, LT, ST, VT1, VT2, and aggR) in 184 E. coli strains sampled from sporadic diarrheal children in our district. eae and bfpA are the localized adherence factor genes of enteropathogenic E. coli (EPEC). IpaH is the invasion antigen gene of enteroinvasive E. coli (EIEC), LT and ST are the toxin genes of enterotoxigenic E. coli (ETEC), VT1 and VT2 are the toxin genes of enterohemorrhagic E. coli (EHEC), and aggR is the adherence factor gene of enteroaggregative E. coli (EAggEC). The results were as follows: eae, 7 (3.8%); bfpA, 0 (0%); IpaH, 0 (0%); LT, 0 (0%); ST, 2 (1.1%); VT, 5 (2.7%); aggR, 8 (4.3%). Seven isolates with eae did not have bfpA, and did not show a localized adherence to HeLa cells. Seven of the 8 isolates with aggR showed aggregative adherence to HeLa cells, while their O-serotypes of them were O111:H21 or O111:HUT. Because of the low incidence of the virulence gene, the commercially available O-antigen antisera was not expected to be useful for the screening of diarrheagenic E. coli, except for EHEC and EAggEC. EAggEC may be important as a pathogen of sporadic diarrhea of children as well as EHEC.     

Presence of the genes regarding adherence factors of Escherichia coli isolates and a consideration of the procedure for detection of diarrheagenic strain

Diarrheagenic Escherichia coli are differentiated from non-pathogenic members with enterotoxin production, enteroinvasiveness and serotyping. However, the serotypic members are rarely sufficient to reliably identify a strain as diarrheagenic on E. coli. Recently, there are many definite articles which the adhesive E. coli strain against intestinal epithelial cells is enterovirulent. In this study, 1,748 E. coli isolates of diarrheagenic and non-diarrheagenic categories which belonged to EHEC, ETEC, EIEC EPEC and non-EPEC were examinated by PCR method for the presence of eaeA, aggR and bfpA regarding adherence factor genes, and astA of EAST1. The strains examined were recognized to variable carrying geno-patterns, and a large number of EHEC, EPEC and non-EPEC had carried either eaeA or aggR genes. In EHEC isolates, a carrying pattern with the most high frequency was only eaeA, and this type was recognized in the isolates of serotype O157, O26 and O111. EPEC and non-EPEC isolates were recognized eaeA or aggR which harboring with astA or not. Of 508 EPEC isolates from human, a total of 137 isolates (27.0%) carried aggR, and a total of 74 isolates (14.6%) had eaeA, while of the 91 isolates from non-human were recognized aggR and eaeA with 2.2% (2 isolates) and 12.1% (11 isolates), respectively. Also, of 266 non-EPEC isolates from human, a total of 16 isolates (6.0%) carried aggR, and a total of 58 isolates (21.8%) had eaeA. On the other hand, 22 (7.0%) of 316 isolates examined from non-human had eaeA, however no isolate had aggR. Thirteen isolates of EIEC and 218 ETEC isolates were screened, and only 6 ETEC isolates had either eaeA or aggR. The astA gene was recognized in the isolates of all categories, and ETEC strains had more frequently. The bfpA gene was recognized with more frequently in a serotype O157: H45, which is obtained from human with diarrhea, however, this strain was not recognized a member of the EPEC serotype. There is no diagnostic system for the strain of E. coli that cause diarrheal diseases, therefore more laboratories are unable to identify them. The authors had confirmed which PCR technique is a useful simple and rapid method for the detection of adherence factor genes on E. coli strains. From the these results, we showed a differentiation method using PCR technique which have relation with adherence factor, enterotoxin-production and invasiveness, and we firmly believe that application of the procedure is a reasonable and useful method for the identification of diarrheagenic E. coli.     

A survey of pathogenic genes from diarrhea stool samples obtained in Nara prefecture

We conducted a survey of diarrhea stool samples in which no virulent agents had previously been detected at clinical laboratories. DNA extracted directly and purified from the diarrhea stool was tested for bacterial pathogenic genes by polymerase chain reaction. The test results for 85 specimens were as follows: one sample was positive for lt, ipaH, and eae; two were positive for aggR; and eight were positive for astA. Inoculation with the stool specimens led to the isolation of a strain of Escherichia coli possessing eae, three strains of E. coli possessing astA, and a strain of Klebsiella possessing astA.     

Localized, aggregative, and diffuse adherence to HeLa cells, plastic, and human small intestines by Escherichia coli isolated from patients with diarrhea.

Adherence of diarrhea-associated Escherichia coli was studied by scanning electron microscopy. Enteropathogenic E. coli (EPEC) adherence factor-positive (EAF+) E. coli of EPEC serotypes (class I EPEC) adhered to plastic and human jejunal and ileal mucosa, similar to case and HeLa cells. Localized adherence, elongation of cell microvilli, and "locking" of the bacterial aggregates by the elongated microvilli were evident after incubation for 20 min. EAF+ E. coli adhered strikingly to mucus but rarely to M cells in Peyer's patch-associated epithelium. Most enteroaggregative E. coli (EAggEC) strains adhered to plastic, similar to HeLa cells. Some diffuse-adhering E. coli (DAEC) strains displayed no adherence to plastic but formed "dimples" on HeLa cells. Both EAggEC and DAEC adhered at lower levels to human small intestines (except M cells) than did EAF+ E. coli. In all cases of EAF+ E. coli, EAggEC, and DAEC, strains were found with atypical characteristics. The data demonstrate the unique adherence characteristics of EAF+ E. coli, EAggEC, and DAEC.     

Examination of diarrheal stools in Hat Yai City, South Thailand, for Escherichia coli O157 and other diarrheagenic Escherichia coli using immunomagnetic separation and PCR method

A total of 493 stool samples from diarrheal patients in Songklanagarind Hospital, in southern Thailand, were examined for Escherichia coli O157 by the culture method combined with an immunomagnetic separation (IMS) technique. E. coli O157 was not found, although the IMS-based method could detect 10(2)-10(3) CFU of artificially inoculated O157/g of stool samples. Polymerase chain reaction was also used for the detection and identification of diarrheagenic E coli from 530 stool samples. The target genes were eae for enteropathogenic E. coli (EPEC), stx for enterohemorrhagic E. coli (EHEC), elt and est for enterotoxigenic E. coli (ETEC), ipaH for enteroinvasive E. coli (EIEC), and aggR for enteroaggregative E. coli (EAggEC). Fifty-eight diarrheagenic E. coli strains were detected in 55 stool samples (10%) from 32 children and 23 adults. These included 31 EAggEC strains (5.8%), 13 ETEC strains (2.5%), 13 EPEC strains (2.5%), and one EIEC strain (0.2%). EHEC was not detected. The diarrheagenic E. coli strains were found mainly in children under 2 years of age (24 of 32 children). EAggEC strains and ETEC strains were susceptible to several antibiotics whereas the EPEC strains exhibited resistance to these antibiotics.     

一起由产气荚膜梭菌和肠聚集性大肠埃希菌共感染导致的聚集性腹泻事件病原学分析

目的 对一起产气荚膜梭菌和肠聚集性大肠埃希菌(PFGE)混合感染导致的腹泻暴发事件进行病原学分析。方法 采集暴发事件的病例粪便样本;病原体筛查使用实时荧光PCR方法;细菌分离使用培养法;菌株毒力基因鉴定使用普通PCR方法;菌株抗生素敏感性测试使用微量肉汤稀释法,菌株分子分型使用脉冲场凝胶电泳方法。 结果 9份粪便样本核酸中,6份肠聚集性大肠埃希菌astA+(+:基因阳性),8份样本产气荚膜梭菌cpa+,5份样本同时检出2种病原体。6份粪便标本分离到肠聚集性大肠埃希菌,均astA+;8份粪便标本分离到产气荚膜梭菌,其中2株cpa+/cpe+,6株cpa+/β2+。6株肠聚集大肠埃希菌分为2种PFGE带型,其中5株同带型,也为同种耐药表型(AMP-CFZ);8株产气荚膜梭菌分为3种PFGE带型,其中6株cpa+/β2+的菌株同带型。 本次腹泻暴发事件可能由2种病原体混合感染导致。     

Tissue culture-adherent Escherichia coli in infantile diarrhea.

To determine the association of tissue culture-adherent Escherichia coli with diarrhea, serotyped E. coli strains isolated in a yearlong case-control study of infantile diarrhea in Bangkok, Thailand, were examined for adherence to HeLa cells and for hybridization with the enteropathogenic E. coli adherence factor, the F1845, and the enteroaggregative E. coli (EAggEC) DNA probes. E. coli that adhered to HeLa cells in a localized adherence (LA) pattern (LA E. coli) was isolated from 26 of 509 infants with diarrhea (cases) and 9 of 509 age-matched controls (P = .006); E. coli with diffuse or aggregative adherence (DA or AA) to HeLa cells or that hybridized with the F1845 or EAggEC probes was not associated with infantile diarrhea. LA E. coli of classical enteropathogenic E. coli (EPEC) serotypes was isolated from 11 cases and 1 control (P = .003). EPEC O44:H18 that adhered to HeLa cells in a DA pattern and hybridized with the F1845 DNA probe was the predominant E. coli (five of five colonies tested) isolated from a 5-month-old girl with diarrhea in whom no other enteric infections were identified. Although LA E. coli was highly associated with infantile diarrhea, the role of DA and AA E. coli was uncertain in this setting.     

Isolation of Escherichia coli O128:HNM harboring stx2f gene from diarrhea patients

Shiga-like-toxin-producing Esherichia coli O128:HNM were isolated from feces of a one-year-old boy with diarrhea and abdominal pain on July, 2002, and a 11-month-old girl with diarrhea and fever on June, 1997. None of other enteropathogenic bacteria including Salmonella were isolated. E. coli O128:HNM isolates from both patients carry stx2f and eaeA gene, but not stx1, stx2, aggR, bfpA, esth, estp, invE, astA, ureC and hlyA gene. As far as we know, this may be the first report indicating that E. coli O128:HNM carrying stx2f gene were isolated from patients in Japan.     

Quantitative biofilm assay using a microtiter plate to screen for enteroaggregative Escherichia coli

The gold standard for identification of Enteroaggregative Escherichia coli (EAEC) remains the HEp-2 cell adherence test, which is time-consuming and requires specialized facilities. We evaluated the usefulness of a quantitative biofilm assay to screen for EAEC from a total of 1,042 E. coli strains from children with diarrhea. Bacteria were incubated overnight in high-glucose Dulbecco's modified Eagle's medium using a polystyrene microtiter plate. The plate was stained with crystal violet after washing, and the biofilm was quantified using an enzyme-linked immunosorbent assay plate reader. The aggR gene was evaluated by a polymerase chain reaction. Forty-eight (77.4%) of 62 strains with an optical density at 570 nm (OD(570)) > 0.2 were identified as EAEC by the HEp-2 adherence test, while no EAEC was found in strains with an OD(570) < or = 0.2. Twenty-one aggR+ and 27 aggR - EAEC strains could be screened by an OD(570) > 0.2 using this assay. Although confirmation by a HEp-2 cell adherence test is needed, this biofilm assay is convenient and useful in screening for EAEC.     

Enteroaggregative Escherichia aoliisolated from Chinese diarrhea patients with high-pathogenicity island of Yersinia''''xs involved in synthesis of siderophore yersiniabactin

AIM: To investigate the distribution of 12 high-pathogenicity island(HPI) genes and the relation between HPI genes and expression of yersiniabactin(Ybt) in enteroaggregative E.coli(EAggEC) isolated from Chinese diarrhea patients. METHODS: The distribution of 12 HPI genes was investigated by PCR and DNA hybridization in two prototype strains of EAggEC, EAggEC 17-2, EAggEC 042, and 6 clinical EAggEC isolates from China. The production of siderophore Ybt in HPI-positive strains was detected by reporter gene bioassay to determine the relation between HPI genes and expression of Ybt. Flow cytometry was used to detect fluorescent signal of the reporter strain that could designate production of Ybt. RESULTS: Seven strains were HPI-positive and one strain was HPI-negative. Six of the seven HPI-positive strains were inserted into asnT-tRNA site. Moreover, seven EAggEC HPI-positive strains revealed enhanced fluorescence signal but the EAggEC HPI-negative strain did not. However, there was a difference in Ybt expression condition and level among these seven EAggEC HPI-positive strains. Although UFT073 strain, the prototype strain of uropathogenic E.coli(UPEC), carried the complete HPI core part, we did not detect the expression of Ybt in it. CONCLUSION: EAggEC HPI-positive strains can express the Ybt system, but the presence of HPI core part does not mean the functional expression of Ybt.     

Enteroaggregative Escherichia coli isolated from Chinese diarrhea patients with high-pathogenicity island of Yersinia is involved in synthesis of siderophore yersiniabactin

AIM: To investigate the distribution of 12 high-pathogenicity island (HPI) genes and the relation between HPI genes and expression of yersiniabactin (Ybt) in enteroaggregative E.coli (EAggEC) isolated from Chinese diarrhea patients. METHODS: The distribution of 12 HPI genes was investigated by PCR and DNA hybridization in two prototype strains of EAggEC, EAggEC 17-2, EAggEC O42, and 6 clinical EAggEC isolates from China. The production of siderophore Ybt in HPI-positive strains was detected by reporter gene bioassay to determine the relation between HPI genes and expression of Ybt. Flow cytometry was used to detect fluorescent signal of the reporter strain that could designate production of Ybt. RESULTS: Seven strains were HPI-positive and one strain was HPI-negative. Six of seven HPI-positive strains were inserted into asnT-tRNA site. Moreover, seven EAggEC HPI-positive strains revealed enhanced fluorescence signal but the EAggEC HPI-negative strain did not. However, there was a difference in Ybt expression condition and level among these seven EAggEC HPI-positive strains. Although UFT073 strain, the prototype strain of uropathogenic E.coli (UPEC), carried the complete HPI core part, we did not detect the expression of Ybt in it. CONCLUSION: EAggEC HPI-positive strains can express the Ybt system, but the presence of HPI core part does not mean the functional expression of Ybt.     

Properties of Vero cytotoxin-producing Escherichia coli of human origin of O serogroups other than O157.

The 48 Vero cytotoxin-producing Escherichia coli (VTEC) examined for properties associated with virulence were of human origin and represented 17 O serogroups other than O157 and O26. Only Vero cytotoxin production was common to all the strains. About 60% produced enterohemolysin and hybridized with the CVD419 probe derived from plasmid sequences of E. coli O157. Thirteen strains gave localized adherence (LA) to HEp-2 cells. All of these hybridized with the E. coli attaching and effacing (eae) gene probe and were positive in the fluorescence actin staining test, properties characteristic of strains that efface intestinal microvilli. A further 5 strains were eae probe-positive but did not give LA. None of the VTEC hybridized with a probe specific for the enteropathogenic E. coli adherence factor. Seven strains adhered to HEp-2 cells in a diffuse or aggregative pattern but did not hybridize with probes for these phenotypes. Non-O157 E. coli strains are diverse in their properties, although some may share virulence mechanisms with other diarrheogenic E. coli.     

Association of patterns of Escherichia coli adherence to HEp-2 cells with acute and persistent diarrhea]

In Brazil diarrhea is the cause of approximately 15% of death among infants. Enteropathogenic E coli is the most important bacterial agent causing acute diarrhea, which is defined as less than 14 days of duration. About 30% of these cases may evolve to persistent diarrhea, defined as lasting more than 14 days. In this work it was carried out a case-control study including 34 children under 2 years of age, and admitted to hospital facilities in S?o Paulo for rehydration therapy. Thirty-four age matched children hospitalized in the same facilities, and presenting no gastrointestinal symptoms were included as controls. Stool samples were analyzed for the presence of bacterial pathogens (diarrheagenic E coli, Shigella, Salmonella, Yersinia, and Campylobacter), protoparasytes, rotavirus, and enteric adenovirus. The E coli strains isolated were analyzed for their ability to adhere to HEp-2 cultured cells, in a 3 h adhesion assay. Search for homology with DNA probes for localized adherence (EAF, eaeA probes), AA (enteroagregative adherence) (AA probe), and diffuse adherence (F1845, AIDA-I probes) was carried out by the colony hybridization method. Twenty-four of the cases were acute diarrhea and 10 persistent diarrhea. Strains with localized adherence were associated with acute and persistent diarrhea. About 23.5% of E coli were associated with typical Enteropathogenic E coli strains (EAF+, eaeA+). Enteroaggregative E coli (EAggEC) (AA+) was isolated only from cases and in similar frequency for acute and persistent diarrhea. Diffusely adherent E coli (DAEC) which did not hybridize with the diffuse adherence probes were isolated among cases and controls. E coli eaeA+ with localized-like adherence was isolated from cases in a frequency three times higher than in controls, suggesting that it may really have a pathogenic potential.     

Drug resistance and adherence to human intestines of enteroaggregative Escherichia coli.

Clinical isolates of enteroaggregative Escherichia coli (EAggEC) were tested for their in vitro susceptibilities to 27 antimicrobial agents. Marked drug resistance was observed with sulfamethoxazole, ampicillin, and chloramphenicol in contrast to such antimicrobial agents as cefixime, sparfloxacin, and ciprofloxacin. One of the EAggEC strains carried a plasmid that conferred on its host resistance to ampicillin, tetracycline, sulfamethoxazole, streptomycin, and spectinomycin and an ability to adhere to child ileal villi or HeLa cells in the characteristic aggregative pattern. This plasmid also mediated D-mannose-resistant hemagglutinin production and bacterial clump formation (autoagglutination). The data demonstrate appearance of marked drug resistance and an intestine-adherence and drug-resistance plasmid in the newest category of diarrheagenic E. coli.     

一个新的TonB依赖的基因岛的分布特征研究

目的 为揭示首次在尿道致病性大肠杆菌CFT073菌株中发现的TonB依赖的基因岛在其他菌属中是否存在及分布特点。方法 根据组成该基因岛的全部基因设计引物，利用PCR方法进行检测分析，并以Southern blot和Dot blot方法予以证实。结果 该基因岛主要存在于多种大肠杆菌和志贺氏菌中，在41株被检测的沙门氏菌、小肠结肠炎耶尔森氏菌、克雷伯氏菌、构橼酸杆菌等其他菌属的标准菌株中均没有完整的该基因岛结构。在33株从腹泻病患者粪便标本分离的包括6种血清型的福氏志贺氏菌株中有30株携带该基因岛。17株ETEC临床分离菌株中仅有1株菌阳性；19株EPEC临床分离株中仅有1株阳性；7株EAEC菌中均为阴性。在183株从腹泻病患者粪便标本分离的不属于已知的五类致泻性大肠杆菌中发现有123株携带该基因岛，阳性率为67．2％，其中130株携带HPI毒力岛的大肠杆菌中有95株携带该基因岛(阳性率为73％)，53株非携带HPI大肠杆菌有28株携带该岛(阳性率为52、8％)。结论 该基因岛的结构比较保守，五个组成基因协同存在，主要分布在亲缘关系较近的大肠杆菌和志贺氏菌属，在大肠杆菌中与HPI毒力岛无明显的协同存在规律。