Enterotoxigenic and enteropathogenic Escherichia coli in Galicia (north-west Spain)

Enterotoxigenic and necrotizing Escherichia coli in human diarrhoea in Spain

Enterotoxigenic Escherichia coli (ETEC) strains of serotype 0153: K-:H45 CFA/I+ STa+ were associated with two outbreaks of neonatal diarrhoea that occurred in two different hospitals of Madrid, in one of which several children died. Two other outbreaks were associated with ETEC strains of serotypes 0159: K-:H21 (LT+) and 0159: K-:H4 (LT+ STa+) without CFA/I and CFA/II colonization factors. Necrotizing E. coli (NTEC) strains of serotype 06:K13, producing the cytotoxic necrotizing factor CNF1 and alpha-haemolysin, were also associated with two outbreaks of neonatal diarrhoea that occurred in a hospital in Madrid and in a hospital in Talavera de la Reina. The results of the characterization of some ETEC and NTEC strains isolated from sporadic cases of diarrhoea are also discussed.

Incidence of sporadic infections due to enterotoxigenic Escherichia coli (ETEC) in the population of Hamburg, north Germany

In two studies (1982 and 1985/86), the presence of enterotoxigenic E. coli (ETEC) and other enteropathogenic bacteria was investigated in 779 stool specimens from children and adults with and without diarrhoeal disease. ETEC was isolated from 2% of diseased children and 1.6% of adult patients, but also from 0.5% of asymptomatic persons. Mixed infections with two different ETEC strains or with other enteropathogenic bacteria were identified in 4 of 9 infected persons. The ETEC strains belonged to 10 different serovars, eight of which produced only heat-stable enterotoxin. One infection had been contracted in a tropical country. After Salmonella and Campylobacter, ETEC was more frequently isolated than Yersinia and Shigella; the difference of ETEC infections in diseased and asymptomatic persons was, however, not statistically significant (p greater than 0.05). Analysis of the isolated serovars suggests that most ETEC strains implicated in sporadic cases of diarrhoea in Hamburg are unrelated to those which are widely spread in the developing world.

Prevalence of enterotoxigenic Escherichia coli strains in outbreaks and sporadic cases of diarrhoea in Spain

Escherichia coli strains isolated 1985-1988 in Spain from patients with diarrhoea were examined; 1170 strains were isolated from 582 sporadic cases of diarrhoea in children, and seven strains were associated with seven outbreaks of diarrhoea. Strains positive for STa enterotoxin production in the infant mouse test were also assayed for production of LT enterotoxin on Vero cells and by a coagglutination test. Thirty-one strains were STa positive: 28 were isolated from 16 (2.7%) sporadic cases of diarrhoea and three were responsible for outbreaks. The majority of STa+LT- strains from both outbreaks and sporadic cases were serotype O153:H45 and expressed the CFA/I colonization factor antigen. Enterotoxigenic STa+LT- strains of serotype O27:H7 and STa+LT+ CFA/II+ strains of serotype O6:K15:H16 were also isolated frequently from sporadic cases.

Toxins and serotypes of faecal non-enterotoxigenic and non-enteropathogenic Escherichia coli strains causing mannose-resistant haemagglutination: relation with haemagglutination patterns

Forty-three faecal non-enterotoxigenic and non-enteropathogenic human Escherichia coli strains causing mannose-resistant haemagglutination (MRHA) were tested for production of cytotoxic necrotizing factor (CNF), haemolysis (Hly), Verotoxin (VT) and lethal activity for mice. The serotypes of the strains were also determined. Of the total strains investigated, 49% synthesized CNF, 53% were haemolytic and 40% were lethal for mice. No strain producing VT was detected. Striking differences in the production of Hly and CNF were observed when MRHA strains were grouped according to their lethal or non-lethal activity. Thus, 82% of lethal strains produced Hly and/or CNF whereas only 35% (p less than 0.01) and 27% (p less than 0.01) of non-lethal strains produced Hly and CNF, respectively. The production of toxins was specially associated with strains possessing defined MRHA types. Thus, 100%, 82% and 50% of strains belonging to MRHA types III, IVa and V, respectively, were toxigenic, whereas no toxigenic strains from MRHA types IVb and VI were detected. The majority (77%) of MRHA strains possessed typical O groups usually reported to be present in pathogenic extraintestinal E. coli or in facultatively enteropathogenic E. coli. Furthermore, these O groups were more frequently detected in toxigenic (93%) than in non-toxigenic (47%) strains (p less than 0.01). Our results suggest that faecal non-enterotoxigenic E. coli strains belonging to MRHA types III, IVa and V may be responsible for extraintestinal infections as well as for sporadic intestinal infections, and that certain O groups are specially associated with E. coli strains belonging to particular MRHA types.

Comparison among enterotoxigenic strains of Escherichia coli isolated in Italy and Somalia

Nine strains of ETEC isolated in Italy have been compared with 13 isolates from Somalia with respect to toxin production, serotype and antimicrobial resistance pattern. None of the strains isolated from Italy belonged to any serotype or serogroups found among the strains from Somalia. Remarkable differences between the two groups of isolates were also observed with regard to the susceptibility to antimicrobials and the presence of R-plasmids. These findings suggest that ETEC strains isolated in Italy are not related to the strains widespread in Somalia and, generally, in developing countries.

Relation between antibiotic resistance and number of plasmids in enterotoxigenic and non-enterotoxigenic Escherichia coli strains

We have investigated the relation between antibiotic resistance and the number of plasmids contained in 44 enterotoxigenic (ETEC) and 69 non-enterotoxigenic (non-ETEC) Escherichia coli strains. Both ETEC and non-ETEC strains were resistant to one or more antibiotics at a similar rate, but multiple resistance in resistant non-ETEC strains was higher than in resistant ETEC strains, showing a significant difference (P less than 0.001) when subjected to Student's t test. Among the ETEC strains, those producing both LT and STa enterotoxins were more sensitive to antibiotics than strains producing only a single toxin type. On the other hand, resistant ETEC strains possessed a higher number of plasmids per strain than the resistant non-ETEC strains (P less than 0.05 by Student's t test). Consequently, resistance to antibiotics could not be related to the possession of a higher number of plasmids. Furthermore, our results support the hypothesis that there is a generalized incompatibility process between plasmids which code for antibiotic resistance and plasmids which code for enterotoxin production in ETEC strains, at least in those strains producing both LT and STa enterotoxins.

Toxin production and haemagglutination in strains of Escherichia coli from diarrhoea in Brescia, Italy

Two hundred and ninety-nine different strains of Escherichia coli, isolated from 172 patients with diarrhoea and 113 healthy subjects, were examined for enterotoxin, cytotoxin and haemolysin (Hly) production and for mannose-resistant haemagglutination (MRHA) and invasive properties. Three strains proved enterotoxigenic, none enteroinvasive; cytotoxin and Hly production was shown in 25 strains from patients and in 3 from controls. Ten strains produced the cytotoxic necrotizing factor (CNF), 6 released other factors which kill cell cultures. Hly production was shown in 21 strains, 9 of which were also positive for CNF. MRHA was detected in 26% of strains from diarrhoea compared with 14% of strains from healthy people. A strong association between toxin production and MRHA was demonstrated. Serotyping results showed that the strains exhibiting virulence traits mostly belonged to serogroups commonly involved in extra-intestinal infections. The possible role of strains of E. coli showing one or more virulence factors as opportunistic pathogens in diarrhoeal diseases is discussed.

Colonization antigens and haemagglutination patterns of human Escherichia coli

The haemagglutinating properties of 223 (35 enterotoxigenic and 188 non-enterotoxigenic) Escherichia coli strains with nine erythrocyte types were investigated; 153 strains were also tested for beta-haemolysis and colicin production and for the presence of CFA/I, CFA/II, K88 and K99 antigens. A selected group of strains was also examined by electron microscopy to determine the presence of fimbriae or fibrils and to establish the relationship between these, the haemagglutinating properties and the presence of colonization antigens. Generally, the haemagglutinating patterns yielded by the same strains grown in Mueller Hinton broth and on CFA agar differed considerably. Mannose-sensitive haemagglutinating (MSHA) patterns were more homogeneous than mannose-resistant haemagglutinating (MRHA) patterns. Forty-seven percent of the non-enterotoxigenic MRHA+ strains were haemolytic while only 6% of the remaining strains were (chi2 correction = 34.01; p less than 0.001). CFA/I was only detected in the four enterotoxigenic MRHA+ strains which were positive only with human and calf erythrocytes when grown on CFA agar. CFA/II was detected in three of a total of six enterotoxigenic strains which were MRHA+ only with calf erythrocytes when grown on CFA agar. K88 and K99 antigens were not detected. All strains in which bacteria with fimbriae or fibrils were observed showed haemagglutinating activity. Thus, 18 (66.7%) of the 27 haemagglutinating strains grown on CFA agar showed fimbriae or fibrils while none of the 19 non-haemagglutinating strains did (chi2 correction = 18.10; p less than 0.001).