Serotypes of enterotoxigenic Escherichia coli in Thailand and the Philippines.

The serotypes of 386 enterotoxigenic Escherichia coli (ETEC) isolated from 82 individuals with and without diarrhea in Thailand and the Philippines were determined. The 136 strains producing both heat-labile toxin (LT) and heat-stable toxin (ST) belonged to 12 different O serogroups; however, 83% (113/136) were of one of four serogroups (O6, O8, O25, and O78), and 76% of (104/136) belonged to one of seven O:K:H serotypes. Only 14% (28/196) of LT-only-producing ETEC belonged to serogroups most common among LT and ST strains, and these 196 strains belonged to 35 different O:K:H serotypes. Three O serogroups (O20, O27, and O78) accounted for 94% (52/54) of strains producing only ST. Although only 4% (2/54) of ST-only ETEC belonged to the seven serotypes most commonly found among strains which produced LT and ST, 85% of ETEC belonged to three other serotypes, O20:K?:H21, O27:K?:H7, and O78:H-. A total of 46% (37/80) of ETEC of serotypes O6:H16, O8:H9, O25:H42, and O78:H12 were resistant to two or more antibiotics in comparison to 68% (208/306) of ETEC of other serotypes (P less than 0.001). In Thailand and the Philippines, E. coli which produced LT and ST or ST alone, but not those which produced LT alone, were restricted in their O:K:H serotypes.     

Phenotypic Diversity of Enterotoxigenic Escherichia coli Strains from a Community-Based Study of Pediatric Diarrhea in Periurban Egypt

No past studies of diarrhea in children of the Middle East have examined in detail the phenotypes of enterotoxigenic Escherichia coli (ETEC) strains, which are important pathogens in this setting. During a prospective study conducted from November 1993 to September 1995 with 242 children under 3 years of age with diarrhea living near Alexandria, Egypt, 125 episodes of diarrhea were positive for ETEC. ETEC strains were available for 98 of these episodes, from which 100 ETEC strains were selected and characterized on the basis of enterotoxins, colonization factors (CFs), and O:H serotypes. Of these representative isolates, 57 produced heat-stable toxin (ST) only, 34 produced heat-labile toxin (LT) only, and 9 produced both LT and ST. Twenty-three ETEC strains expressed a CF, with the specific factors being CF antigen IV (CFA/IV; 10 of 23; 43%), CFA/II (5 of 23; 22%), CFA/I (3 of 23; 13%), PCFO166 (3 of 23; 13%), and CS7 (2 of 23; 9%). No ETEC strains appeared to express CFA/III, CS17, or PCFO159. Among the 100 ETEC strains, 47 O groups and 20 H groups were represented, with 59 O:H serotypes. The most common O serogroups were O159 (13 strains) and O43 (10 strains). O148 and O21 were each detected in five individual strains, O7 and O56 were each detected in four individual strains, O73, O20, O86, and O114 were each detected in three individual strains, and O23, O78, O91, O103, O128, and O132 were each detected in two individual strains. The most common H serogroups were H4 (16 strains), 12 of which were of serogroup O159; H2 (9 strains), all of which were O43; H18 (6 strains); H30 (6 strains); and H28 (5 strains); strains of the last three H serogroups were all O148. Cumulatively, our results suggest a high degree of clonal diversity of disease-associated ETEC strains in this region. As a low percentage of these strains expressed a CF, it remains possible that other adhesins for which we either did not assay or that are as yet undiscovered are prevalent in this region. Our findings point out some potential barriers to effective immunization against ETEC diarrhea in this population and emphasize the need to identify additional protective antigens commonly expressed by ETEC for inclusion in future vaccine candidates.     

Relationship among enterotoxigenic phenotypes, serotypes, and sources of strains in enterotoxigenic Escherichia coli.

The relationship among O groups, O:H serotypes and enterotoxigenic phenotypes was examined in 76 Escherichia coli strains isolated in Brazil from different sources. Of the 17 heat-labile and -stable enterotoxin (LT/ST)-producing strains whose O antigens were identified, 15 belonged to serotypes O6:H16 (7 strains), O63:H- (5 strains), and O139:H28 (3 strains). All 11 ST strains were in group OO128PAC, which was represented by four O:H serotypes. The 23 LT strains with the O antigen identified were distributed among serotypes of 14 O groups. Colonization factor CFA/I was not found in any of the LT strains, but it was found in six LT/ST and three ST strains. On the whole, each E. coli O:H serotype had a particular fermentation pattern. LT/ST as well as ST strains were all isolated from patients with diarrhea, whereas LT strains were isolated from patients with diarrhea, normal children, food, and river water.     

Serotypes,genotypes and antimicrobial resistance patterns of human diarrhoeagenic Escherichia coli isolates circulating in southeastern China

Diarrhoeagenic Escherichia coli (DEC) infection is a major health problem in developing countries. The prevalence and characteristics of DEC have not been thoroughly investigated in China. Consecutive faecal specimens from outpatients with acute diarrhoea in nine sentinel hospitals in southeastern China were collected from July 2009 to June 2011. Bacterial and viral pathogens were detected by culture and RT-PCR, respectively. DEC isolates were further classified into five pathotypes using multiplex PCR. The O/H serotypes, sequence types (STs) and antimicrobial susceptibility profiles of the DEC isolates were determined. A total of 2466 faecal specimens were collected, from which 347 (14.1%) DEC isolates were isolated. DEC was the dominant bacterial pathogen detected. The DEC isolates included 217 EAEC, 62 ETEC, 52 EPEC, 14 STEC, one EIEC and one EAEC/ETEC. O45 (6.6%) was the predominant serotype. Genotypic analysis revealed that the major genotype was ST complex 10 (87, 25.6%). Isolates belonging to the serogroups or genotypes of O6, O25, O159, ST48, ST218, ST94 and ST1491 were highly susceptible to the majority of antimicrobials. In contrast, isolates belonging to O45, O15, O1, O169, ST38, ST226, ST69, ST31, ST93, ST394 and ST648 were highly resistant to the majority of antimicrobials. DEC accounted for the majority of bacterial pathogens causing acute diarrhoea in southeastern China, and it is therefore necessary to test for all DEC, not only the EHEC O157:H7. Some serogroups or genotypes of DEC were highly resistant to the majority of antimicrobials. DEC surveillance should be emphasized.     

The role of diarrhoeagenic Escherichia coli in acute diarrhoeal diseases in Bandar-Abbas, Iran

The prevalance of different types of diarrhoea-producing Escherichia coli was measured in 273 patients attending 12 out-patient clinics in Bandar-Abbas, State of Hormozgan, Iran, during March 1984. Enteropathogenic E. coli (EPEC) belonging to 12 different serogroups, of which O128 and O126 were the most common, were found in almost 31% of the patients. Enterotoxigenic strains of E. coli (ETEC) were the next most frequent group (21.9%); among these, 36 (60%) strains produced heat-stable enterotoxin (ST), 14 (23.3%) strains produced both heat-labile enterotoxin (LT) and ST, and 10 (16.7%) strains produced LT only. The same pattern of toxigenicity was observed among the EPEC isolates. Ten of the 12 serogroups encountered in this study contained toxin producers, amongst which strains producing ST were dominant. Enteroinvasive E. coli (EIEC) strains were not isolated. These findings suggest that enterotoxin-producing E. coli may be an important cause of diarrhoea in this part of Iran.     

Comparison of rapid methods for detection of heat-labile (LT) and heat-stable (ST) enterotoxin in Escherichia coli.

Oxoid VET-RPLA, ST-EIA and Pharmacia Phadebact ETEC-LT enterotoxin tests were compared to find a simple but reliable method for detecting enterotoxigenic Escherichia coli (ETEC) in Hungary. In the Oxoid tests, all six reference LT- or ST-producing strains, except one ST-producer, gave positive results. Of 11 reference porcine enterotoxigenic strains, all four LT-producers gave positive reactions for LT but three of 10 ST-producers gave negative reactions for ST. Thirteen of 50 strains from culture collections of H. Steinrück (Germany) were LT+ and nine of 33 were ST+. When 31 isolates were tested simultaneously with the Oxoid and the Pharmacia LT tests, 12 strains were LT+ by the Oxoid LT test but by the Phadebact LT test only seven of these strains were LT+ and, of the remainder, three gave uncertain results and two gave negative results. Of 69 porcine strains, seven were LT+ and three ST+. Of 901 human strains isolated in Hungary, 10 were LT+ and one of 24 tested was ST+. In two cases, ETEC strains were isolated from contacts of travellers returning from Mongolia and Bangladesh. Results of comparative studies with reference strains corresponded well to those of the classical toxin detection tests. The Oxoid test was rapid, sensitive, specific and easy to perform and is recommended for use in screening ETEC isolates.     

Enterotoxigenic Escherichia coli in a population of infants with diarrhea in Chile.

The incidence of enterotoxigenic Escherichia coli (ETEC) was investigated in 95 E. coli strains isolated from 48 infants with diarrhea in Santiago, Chile. By using standard biological assays and DNA-DNA hybridization procedures, ETEC was found in 31.2% of the cases: 14 strains produced heat-stable enterotoxin (ST) only, three strains produced heat-labile enterotoxin (LT) and ST, and two strains produced LT only. DNA probes detected all enterotoxin producers except one ST-producing strain. The ST strains hybridized with one or both of the human ST probes (ST Ib and ST A2). Two of the LT-ST strains hybridized with the ST Ia and ST Ib probes, and the third strain did not hybridize with any of the ST probes. Only the ST group expressed multiple resistance (85.7%) and colonization factor antigen I (CFA I) (92.8%); CFA II was found in two of three LT-ST strains. The O153:H45 serotype was found in 10 of 14 ST strains, and O6:K15:H16 was found in one LT strain and in two LT-ST strains. These findings suggest that ETEC, especially strains that produce ST, may be an important cause of diarrhea among Chilean infants.     

Interleukin-8 Response in an Intestinal HCT-8 Cell Line Infected with Enteroaggregative and Enterotoxigenic Escherichia coli

This study examined the interleukin-8 (IL-8) response of the intestinal adenocarcinoma HCT-8 cell line to infection with enteroaggregative and enterotoxigenic Escherichia coli pathotypes isolated from patients with travelers' diarrhea. Individual diarrheagenic E. coli strains (enteroaggregative E. coli [EAEC]; n = 30), heat-stable enterotoxin (ST)-producing enterotoxigenic E. coli (ETEC ST; n = 11), heat-labile enterotoxin (LT)-producing enterotoxigenic E. coli (ETEC LT; n = 10), and ST- and LT-producing enterotoxigenic E. coli (ETEC ST:LT; n = 8) were coincubated with HCT-8 cells for 3 h. Tissue culture supernatants were assayed for IL-8 content by enzyme-linked immunosorbent assay. Fifty percent of EAEC (72% of those EAEC carrying the virulence factors aggR, aggA, and aspU and 40% of those EAEC not carrying virulence factors) and 64% of ETEC ST elicited IL-8 production. In contrast, 10% of ETEC LT elicited the production of IL-8 above baseline. These results suggest that (i) the HCT-8 cell line infection model can be used as a tool to differentiate proinflammatory E. coli from noninflammatory isolates; (ii) EAEC has a heterogeneous ability to induce the production of IL-8, and this may be associated with the presence of virulence factors; and (iii) ETEC ST can elicit an inflammatory response and helps explain our earlier findings of increased fecal IL-8 in patients with ETEC diarrhea.     

Evaluation of antisera used for detecting enterotoxigenic Escherichia coli in Sao Paulo.

The usefulness of antisera in detecting enterotoxigenic Escherichia coli (ETEC) strains in Sao Paulo was evaluated. Polyvalent antisera detected 49% of ETEC isolates and were more effective in identifying E. coli that produced heat-labile and heat-stable enterotoxins and in strains that produced only heat-stable enterotoxin. ETEC strains not detected by the antisera belonged to different serogroups not isolated in Sao Paulo before; 34% of these strains had undetermined O antigens, and most of them produced only heat-labile toxin. A variation of serogroups over time was especially observed among strains that produced heat-stable toxin. The importance of H-antigen determinations in the effectiveness of ETEC diagnosis by serological methods became evident, as non-ETEC strains were also detected by polyvalent antisera, but their serotypes were different from those of ETEC strains. Although antisera can be used to identify O:H types of ETEC strains with accuracy, serotyping cannot be recommended for routine diagnosis. However, such a procedure may be useful for studying outbreaks of ETEC diarrhea if the involved serotypes are already known.     

Enterotoxigenic Escherichia coli associated with infant diarrhoea in Galicia, north-western Spain

To assess the role of enterotoxigenic Escherichia coli (ETEC) in infantile diarrhoea, 482 children with diarrhoea and 103 healthy controls, from three localities of Galicia, north-western Spain, were investigated between 1985 and 1988. Rotavirus (37.3%) and Salmonella spp. (12.8%) were the most common causal agents, followed by ETEC (3.9%), Campylobacter jejuni (2.3%), Shigella spp. (0.9%) and Yersinia enterocolitica (0.5%). ETEC were significantly more frequently isolated from children with diarrhoea who were under 1 month of age (26.5%) than from older diarrhoeic children (2.2%) (p less than 0.001) or from healthy children who were under 1 month of age (0%) (p less than 0.05). Among children who harboured ETEC, five of the nine children under 1 month of age developed diarrhoea in hospital, whereas none of the 10 children over 1 month of age did so. Seventeen ETEC isolates produced heat-stable enterotoxin (STa) only, four produced only heat-labile enterotoxin (LT), and two produced both toxins. Colonisation factor antigens CFA/I and CFA/II were detected in 11 (55.0%) of the 20 ETEC isolates that remained enterotoxigenic after maintenance in the laboratory. Most ETEC isolates belonged to serotypes O153:K-:H45 (nine STa+ CFA/I+ isolates), O27:K-:H7 (three STa+ isolates) or O6:K15:H16 (two LT+ STa+ CFA/II+ isolates). Our results suggest that ETEC constitute an important cause of neonatal diarrhoea in this part of Spain.     

Incidence of pathogenic Escherichia coli in acute infantile diarrhea in Dakar

We have studied the incidence of enteropathogenic (EPEC), enteroinvasive (EIEC) and enterotoxigenic (ETEC) Escherichia coli associated with infant acute diarrhoeal disease in Dakar during a period of one year. We report 405 strains of Escherichia coli suspected to be the etiologic agent of the diarrhoea and isolated from 405 diarrheic stools of 0-5 years old children. We have isolated 119 pathogenic Escherichia coli with 63 EPEC (15.5%), 3 ETEC (0.7%) and 53 ETEC (13.1%) including 23 strains releasing heat-labile enterotoxin (LT+) and 30 strains releasing heat-stable enterotoxin (ST+). No ST+/LT+ strain was isolated. Escherichia coli with colonization factor antigens were isolated from 62 children. Almost all of them are CFAI+. Only one strain is CFAII+ and another one agglutinates with both CFAI and CFAII antisera. Among these CFA+ strains 5 belong to the EPEC group, 29 are enterotoxigenic (25 ST+ and 4 LT+) and 28 do not belong to any known etiopathologic group. Near 70% of the pathogenic Escherichia coli are from infants less than one year old, with a highest frequency between 7 and 12 months. Prevalence of ETEC is higher during the raining season. The existence of a great number of strains that belong to none of the 3 groups of etiopathologic Escherichia coli emphasis the need to search other factors of pathogenicity.     

Interleukin-8 response in an intestinal HCT-8 cell line infected with enteroaggregative and enterotoxigenic Escherichia coli

This study examined the interleukin-8 (IL-8) response of the intestinal adenocarcinoma HCT-8 cell line to infection with enteroaggregative and enterotoxigenic Escherichia coli pathotypes isolated from patients with travelers' diarrhea. Individual diarrheagenic E. coli strains (enteroaggregative E. coli [EAEC]; n = 30), heat-stable enterotoxin (ST)-producing enterotoxigenic E. coli (ETEC ST; n = 11), heat-labile enterotoxin (LT)-producing enterotoxigenic E. coli (ETEC LT; n = 10), and ST- and LT-producing enterotoxigenic E. coli (ETEC ST:LT; n = 8) were coincubated with HCT-8 cells for 3 h. Tissue culture supernatants were assayed for IL-8 content by enzyme-linked immunosorbent assay. Fifty percent of EAEC (72% of those EAEC carrying the virulence factors aggR, aggA, and aspU and 40% of those EAEC not carrying virulence factors) and 64% of ETEC ST elicited IL-8 production. In contrast, 10% of ETEC LT elicited the production of IL-8 above baseline. These results suggest that (i) the HCT-8 cell line infection model can be used as a tool to differentiate proinflammatory E. coli from noninflammatory isolates; (ii) EAEC has a heterogeneous ability to induce the production of IL-8, and this may be associated with the presence of virulence factors; and (iii) ETEC ST can elicit an inflammatory response and helps explain our earlier findings of increased fecal IL-8 in patients with ETEC diarrhea.     

Evaluation of non-radioactive trivalent DNA probe (LT, ST1a, ST1b) for detecting enterotoxigenic Escherichia coli.

AIMS: To evaluate a digoxigenin-labelled trivalent DNA probe (LT, ST1a, ST1b) for detecting enterotoxigenic Escherichia coli (ETEC), by comparison with a cell culture assay for detecting LT, individual DNA probes for LT, ST1a and ST1b, and an enzyme immunoassay for detecting ST1. METHODS: A 1268 base pair DNA fragment, containing parts of the genes for E coli heat labile enterotoxin (LT) and heat stable enterotoxins (ST1a and ST1b), was random prime labelled with digoxigenin-dUTP. The labelled DNA was used as a probe in colony hybridisation reactions to examine 180 E coli strains of which 92 had previously been shown by a cell culture assay to produce LT. Six LT negative ST1 positive E coli, 34 Verotoxin producing E coli (VTEC), and 84 organisms from other genera were also examined. All organisms other than VTEC were isolated from travellers returning from abroad with diarrhoea. All E coli strains were retested by cell culture for LT, and were tested by enzyme immunoassay (EIA) for ST1, and by the trivalent and individual DNA probes. RESULTS: All 81 isolates, that on retesting by cell culture were positive for LT, also hybridised with the trivalent and LT probes; 27 of these were also enzyme immunoassay (EIA) positive for ST1 of which 24 hybridised with the ST1b probe and three with the ST1a probe. Of 99 isolates, that on retesting by cell culture were negative for LT, all were negative by LT probe and only three were EIA positive for ST1; these three were positive by both trivalent and ST1b probes. Four isolates were positive by the trivalent probe but negative by cell culture and EIA; all four were positive by ST1b probe. Compared with the cell culture assay for LT, the probe had a sensitivity and specificity both of 100%; compared with the EIA for ST1, the probe had a sensitivity of 100% and specificity of 88%. CONCLUSIONS: The trivalent DNA probe is a sensitive, specific, and reliable method for detecting ETEC that should be considered for use by diagnostic microbiology laboratories.     

Genetic control and properties of coli surface antigens of colonization factor antigen IV (PCF8775) of enterotoxigenic Escherichia coli.

Enterotoxigenic Escherichia coli producing coli surface antigen 4 (CS4), CS5, and CS6 of colonization factor antigen IV were examined. This factor was originally called putative colonization factor 8775 (PCF8775). All of the coli surface antigens were plasmid coded and were usually carried on the same plasmid as the genes coding for heat-stable toxin (ST) or heat-labile toxin (LT); thus, CS5-CS6-ST, CS6-ST, and CS6-LT plasmids were found. In strains of serotype O25:H42, the genes coding for CS4 and CS6 were on a plasmid separate from that containing the genes coding for ST and LT. CS4 and CS5 were fimbrial antigens with a subunit molecular mass of about 17.0 and 21.0 kilodaltons (kDa), respectively. CS6 was found as a single polypeptide with a molecular mass of about 14.5 kDa in strains of serotypes O25:H42, O27:H7, and O27:H20 when heated extracts were run on sodium dodecyl sulfate-polyacrylamide gels. CS6-positive extracts of strains of serogroups O148, O159, and O167 showed two bands with molecular masses between 14.5 and 16.0 kDa.     

Unidentified serogroups of enteropathogenic Escherichia coli (EPEC) associated with diarrhoea in infants in Londrina, Parana, Brazil

Digoxigenin-labelled DNA probes were used to characterise enteropathogenic Escherichia coli (EPEC) isolated in Londrina (Brazil) from faeces samples of 102 children with diarrhoea, and the results were compared with those obtained by serogrouping and adherence to HEp-2 cells. The probes employed detect the gene coding EPEC adherence factor (EAF) and the virulence genes for bundle-forming pilus (bfp) and entero-attaching-effacing (eae) factor. Twenty-one isolates hybridised with at least one probe, and 11 of them were classified as typical EPEC because they hybridised with all three probes, showed a pattern of localised adherence (LA) and carried no genes for enterotoxins (ST and LT) or invasion as detected by PCR. Six of the typical EPEC strains belonged to the classical serotype 0119:H6 and one to O111:H6; O antigens could not be determined in four strains with antisera against 01-0173. All typical EPEC strains carried a 70-MDa plasmid plus two other large plasmids. These data showed that typical EPEC virulence traits may be found in strains not belonging to classical serogroups/serotypes and that molecular identification is required for studying the epidemiology of diarrhoea in children.     

Beyond Serotypes and Virulence-Associated Factors: Detection of Genetic Diversity among O153:H45 CFA/I Heat-Stable Enterotoxigenic Escherichia coli Strains

Characterization of enterotoxigenic Escherichia coli (ETEC) has been based almost exclusively on the detection of phenotypic traits such as serotypes and virulence-associated factors: heat-labile (LT) and heat-stable (ST) toxins and colonization factors (CFs). In the present work we show that the analysis of band patterns generated by randomly amplified polymorphic DNA (RAPD) analysis and pulsed-field gel electrophoresis (PFGE) of digested chromosomal DNA can be used to detect genetic diversity among ETEC strains expressing identical phenotypic traits. The study included 29 ETEC isolates from Latin America and Spain expressing the phenotype O153:H45 CFA/I ST plus 1 rough derivative, 2 nonmotile derivatives, and 1 O78:H12 CFA/I ST isolate, and a representative of a genetically distinct ETEC group. The results showed that the O153:H45 CFA/I ST ETEC isolates belong to a single clonal cluster whose isolates share on average, 84% of the RAPD bands and 77% of the PFGE restriction fragments, while the O78:H12 isolate shared only 44 and 4% of the RAPD bands and PFGE fragments, respectively, with the isolates of the O153:H45 group. More relevantly, RAPD and PFGE fingerprints disclosed the presence of different clonal lineages among the isolates of the O153:H45 cluster. Some of the genetic variants were isolated from defined geographic areas, while places like S?o Paulo City in Brazil and the middle-eastern part of Argentina were populated by several genetic variants of related, but not identical, ETEC strains. These results show that molecular biology-based typing methods can disclose strain diversity, which is usually missed in studies restricted to phenotypic typing of ETEC.     

Comparison between O serotyping method and multiplex real-time PCR to identify diarrheagenic Escherichia coli in Taiwan

To compare the diarrheagenic Escherichia coli (DEC) identifications obtained between traditional O serotyping and modern virulence gene detection assays, we developed a multiplex real-time PCR assay by detecting six specific virulence genes for enteropathogenic E. coli (EPEC), enterohemorrhagic E. coli (EHEC), enterotoxigenic E. coli (ETEC), and enteroinvasive E. coli (EIEC). Among 261 clinical diarrheal stool samples, a total of 137 suspected DEC (sDEC) isolates were identified by the use of commercially available antisera. The most prevalent serogroups were O1 (12/137; 8.7%), O25 (9/137; 6.5%), and O44 (9/137; 6.5%). The specific virulence genes for the 137 sDEC isolates were analyzed by the multiplex real-time PCR assay. Fifteen (10.9%) of 137 isolates were confirmed to be true DEC strains, indicating that the serotypic markers did not correlate with the specific virulence genes. ETEC (66.7%) was the most prevalent, followed by EIEC (20%) and EPEC (13.3%). No EHEC strains were identified in the specimens. Four novel serotypes were found in the study: two in EPEC strains (O111:H9 and O63:H6) and two in EIEC strains (O63:H9 and O169:H9). In conclusion, the real-time PCR assay considerably reduces the high false-positive rate from the use of serotyping alone, and thus, it is suggested that serogrouping-based methods are inadequate for the identification of DEC isolates, although they are useful for the identification of a limited number of serogroups. In addition, ETEC, EPEC, and EIEC strains were present in 5.7% (15/261) of the diarrheal patients in northern Taiwan in 2006.     

Phenotypic profiles of enterotoxigenic Escherichia coli associated with early childhood diarrhea in rural Egypt

Enterotoxigenic Escherichia coli (ETEC) causes substantial diarrheal morbidity and mortality in young children in countries with limited resources. We determined the phenotypic profiles of 915 ETEC diarrheal isolates derived from Egyptian children under 3 years of age who participated in a 3-year population-based study. For each strain, we ascertained enterotoxin and colonization factor (CF) expression, the O:H serotype, and antimicrobial susceptibility. Sixty-one percent of the strains expressed heat-stable enterotoxin (ST) only, 26% expressed heat-labile enterotoxin (LT) alone, and 12% expressed both toxins. The most common CF phenotypes were colonization factor antigen I (CFA/I) (10%), coli surface antigen 6 (CS6) (9%), CS14 (6%), and CS1 plus CS3 (4%). Fifty-nine percent of the strains did not express any of the 12 CFs included in our test panel. Resistance of ETEC strains to ampicillin (63%), trimethoprim-sulfamethoxazole (52%), and tetracycline (43%) was common, while resistance to quinolone antibiotics was rarely detected. As for the distribution of observed serotypes, there was an unusually wide diversity of O antigens and H types represented among the 915 ETEC strains. The most commonly recognized composite ETEC phenotypes were ST CS14 O78:H18 (4%), ST (or LTST) CFA/I O128:H12 (3%), ST CS1+CS3 O6:H16 (2%), and ST CFA/I O153:H45 (1.5%). Temporal plots of diarrheal episodes associated with ETEC strains bearing common composite phenotypes were consistent with discrete community outbreaks either within a single or over successive warm seasons. These data suggest that a proportion of the disease that is endemic to young children in rural Egypt represents the confluence of small epidemics by clonally related ETEC strains that are transiently introduced or that persist in a community reservoir.     

The occurence of colonisation factors (CFA/I,CFA/II and E8775) in enterotoxigenicEscherichia coli from various countries in South East Asia

Four hundred and fifty-eight enterotoxigenic strains ofEscherichia coli (ETEC) were examined for the presence of colonisation factor antigens (CFA) I and II, and the putative colonisation factor, E8775, using an immunodiffusion technique with specific antisera. The ETEC strains had been isolated in Thailand, Bangladesh and from travellers returning to Japan from abroad. Approximately 14% of the ETEC strains possessed CFA/I and a further 13% of the strains possessed CFA/II. The E8775 antigen was found on 5% of the strains. CFA/I was found on strains of the serogroups 04, 015, 063, 078, 090, 0110, 0126, 0128, 0153 and 0? CFA/II was found on strains of the serogroups 06, 08, 09, 078, 0115, 0139, 0? and 0 rough. The E8775 antigen was found on strains of the serogroups 025, 0115 and 0167. The results of this study emphasise the need to continue the search for other mechanisms of adhesion used by ETEC strains, and in particular strains of the serogroups 027, 034, 0148 and 0166.     

Evaluation of the Phadebact ETEC-LT test for the heat-labile enterotoxin of Escherichia coli

The Phadebact ETEC-LT is a rapid method of identifying enterotoxigenic Escherichia coli (ETEC), producing the heat-labile enterotoxin (LT). It uses staphylococcal coagglutination as a means of identifying the LT released from ETEC. In this investigation both known strains of ETEC from a variety of sources as well as strains from patients were tested. Good agreement was found between the Phadebact ETEC-LT test and established tests for LT. The test was found easy to use in the clinical laboratory environment, and revealed that LT producing ETEC may be more common causes of diarrhoea in Australia than had been anticipated.