New surface-associated heat-labile colonization factor antigen (CFA/II) produced by enterotoxigenic Escherichia coli of serogroups O6 and O8

Enterotoxigenic Escherichia coli (ETEC) belonging to serogroups O6 and O8 do not possess the H-10407-type colonization factor antigen (CFA/I). However, these frequently isolated ETEC were found to possess a second and distinct heat-labile surface-associated colonization factor antigen, termed CFA/II. Whereas CFA/I mediates mannose-resistant hemagglutination of human group A erythrocytes, CFA/II does not. CFA/II mediates mannose-resistant hemagglutination of bovine erythrocytes, and mannose-resistant hemagglutination is rapid only at reduced temperature (4 degrees C). Because CFA/II, like CFA/I, is spontaneously lost by many ETEC isolates in the laboratory, it was possible to produce specific anti-CFA/II serum by preparing antiserum against living cells of a prototype strain (PB-176) and adsorbing this serum with living and heat-treated cells of its CFA/II-negative derivative strain PB-176-P. This serum, which neutralized the colonization factor activity of CFA/II-positive strains in infant rabbits, was employed to confirm the presence of CFA/II on ETEC which exhibited mannose-resistant hemagglutination of bovine but not human erythrocytes. CFA/II, like CFA/I, mediates adherence of the bacteria to the mucosal surface of the small intestine, as demonstrated by indirect immunofluorescence. CFA/II appears to be an important virulence factor for humans since CFA/II-positive ETEC are frequently isolated from diarrhea cases, particularly travelers' diarrhea, in Mexico; these ETEC were not uncommon in a collection of isolates from Bangladesh. The O6:H16 strain of ETEC responsible for an outbreak of diarrhea in the United States was also shown to be CFA/II positive. CFA/I and CFA/II were never found on the same serotypes of ETEC, but 98% of the heat-stable and heat-labile enterotoxin-producing ETEC belonging to the frequently isolated serogroups O6, O8, O15, O25, O63, and O78 were positive for either CFA/I or CFA/II.

Role of Escherichia coli colonisation factor antigen in acute diarrhoea

The role of colonisation factor antigen (C.F.A.) in diarrhoea was studied in volunteers who ingested either E. coli H-10407, which possessed C.F.A., or H-10407-P, which lacked C.F.A. In the first study the dose given was 10(6) C.F.A.+ or C.F.A.- E. coli; in the second study the dose was 10(8) of the same organisms. Diarrhoea, with or without other symptoms, occurred only in those who ingested 10(8) C.F.A.+ E. coli. Those volunteers taking the C.F.A.- strain shed the test organism in the stool for only 2 or 3 days whereas those ingesting the C.F.A+ strain shed the organism until the end of the study (7 days). Antibody responses in those ingesting the C.F.A.+ strain were: anti-C.F.A., 7 of 12 volunteers; antitoxin, 6 of 13; and anti-O78 somatic antigen, 11 of 13. No volunteer ingesting the C.F.A. organism seroconverted to any of the antigens. The study showed the importance of C.F.A. in the pathogenesis of human disease due to toxigenic E. coli.

Pregnancy specific beta1 glycoprotein in fetal and maternal compartments

Pregnancy specific beta glycoprotein is produced by the syncytiotrophoblast and secreted into the maternal peripheral circulation reaching levels of approximately 200 m/liter in normal pregnancy at term. In the present study the distribution of this newly defined placental protein was examined in maternal and fetal compartments in 12 patients at delivery.

Differences in serological responses and excretion patterns of volunteers challenged with enterotoxigenic Escherichia coli with and without the colonization factor antigen

Double-blind studies were performed to compare the virulence of enterotoxigenic Escherichia coli with and without the fimbriate colonization factor antigen (CFA), using young healthy adults (mean age, 23 years) as volunteers. In the first study one group of volunteers ingested 1 X 10(6) E. coli H-10407, the CFA-positive strain, and another group ingested 1 X 10(6) E. coli H-10407-P, the CFA-negative spontaneous derivative of strain H-10407. The second study was similar except that the test strains were administered at a dose of 1 X 10(8) viable cells. Three parameters of infection were monitored: (i) diarrhea and associated symptoms; (ii) excretion pattern of test strains; and (iii) humoral antibody response to CFA, somatic antigen, and heat-labile enterotoxin. Significant signs of illness occurred only in six of seven volunteers who ingested E. coli H-10407 at a dose of 1 X 10(8). At both doses, E. coli H-10407-P appeared in the stool on day 1 postchallenge and disappeared by day 4. In contrast, strain H-10407 was persistently excreted from the first to the last day of the study. Also, only those volunteers in the H-10407 challenge groups (12 of 13 analyzed) responded with a fourfold antibody titer rise to CFA, somatic antigen, and/or heat-labile enterotoxin. No reversion of H-10407-P to H-10407 was detected.

Detection and characterization of colonization factor of enterotoxigenic Escherichia coli isolated from adults with diarrhea

The fimbriate colonization factor antigen (CEA) of Escherichia coli strain H-1047 was isolated and used to prepare anti-CFA antiserum. Enterotoxigenic E. coli (ETEC) isolated from 29 adults with diarrhea acquired in Mexico were examined for CFA by using this serum. Retrospectively, it was found that ETEC possessing the H-10407-type CFA were isolated from 25 (86%) of these diarrhea cases as compared with 2 of 11 (18%) from asymptomatic controls from whom ETEC had been isolated. CFA was found onE. coli of various serotypes, as demonstrated by bacterial agglutination by the anti-CFA serum. Heat treating the cells at 65 degress C for 1 h prevented the agglutination. CFA-positive strains did not react with anti-CFA serum when the cultures were grown at a low incubation temperature (18 degrees C). E. coli isolates identified serologically as CFA positive were shown to adhere to the intestinal villous surfaces of infant rabbits. By the indirect immunofluorescence technique, it was found that adhesion occurred preferentially in the upper 20 cm of the small intestine. Also, the ability or inability of various isolates to adhere to intestinal mucosa in vivo correlated with the presence or absence of fimbriae on the cells when grown in vitro. Agglutinability with anti-CFA serum, fimbriae, and adhesiveness were spontaneously lost by many isolates after laboratory passage in a manner previously described with E. coli H-10407. These observations suggest that the H-10407-type CFA plays a role in the virulence of ETEC possessing this antigen.

Hemagglutination of human group A erythrocytes by enterotoxigenic Escherichia coli isolated from adults with diarrhea: correlation with colonization factor

Enterotoxigenic Escherichia coli (ETEC) of several different serotypes isolated from adults with diarrhea and known to possess the colonization factor antigen (CFA) were found to cause mannose-resistant hemagglutination (HA) of human group A erythrocytes. CFA-negative E. coli isolated during the same study did not possess the mannose-resistant hemagglutinin, although some non-ETEC, CFA-negative isolates did exhibit mannose-sensitive HA activity. The mannoseresistant hemagglutinin of ETEC was found to possess many characteristics previously associated with CFA, which is a surface-associated fimbriate heatlabile antigen, and the functionally and morphologically similar K88 and K99 antigens of animal-specific ETEC. Mannose-resistant HA and CFA titers were maximal when ETEC cells were grown on an agar medium (CFA agar) composed primarily of 1% Casamino Acids and 0.15% yeast extract, pH 7.4. Neither CFA nor HA were produced at a growth temperature of 18 degrees C; HA was completely inhibited by pretreatment of CFA-positive cells with the anti-CFA serum. The mannose-resistant hemagglutinin was lost spontaneously and simultaneously with CFA when clinical ETEC isolates were passaged on artificial medium in the laboratory, indicating plasmid control of both entities. The mannose-resistant hemagglutinin of ETEC was shown to be thermolabile, i.e., sensitive to heating at 65 degrees C, as was the CFA. Also, there was correlation between possession of CFA, as detected serologically and by demonstration of biological activity (adherence in the infant rabbit small intestine), presence of CFA-type fimbriae, and the ability of various E. coli isolates to cause mannose-resistant HA of human group A erythrocytes. These results indicate that the mannose-resistant HA of ETEC is another manifestation of CFA.

Bismuth subsalicylate inhibits activity of crude toxins of Escherichia coli and Vibrio cholerae

The inhibition of the activity of enterotoxins by bismuth salts was assessed in laboratory models. In the Y-1 adrenal cell tissue culture system, a commercial preparation containing bismuth subsalicylate reduced the activity of crude toxin from Vibrio cholerae by 10(4)-fold as compared with the activity of controls. Similar results were obtained with use of the adult rabbit ligated intestinal loop model. The preparation failed to affect crude Escherichia coli or cholera toxin activity once these toxins had become bound to intestinal mucosa. Pretreatment of ligated loops with the preparation reduced the fluid accumulation mediated by crude E. coli and cholera toxins by 78% and 91%, respectively. Bismuth subsalicylate and the complex vehicle of the preparation also inactivated toxin; however, bismuth subsalicylate was more effective when combined with the vehicle. Bismuth subcarbonate failed to inhibit fluid accumulation in ligated loops. Preparations containing bismuth subsalicylate may be effective in the prevention of diarrhea mediated by toxigenic E. coli.

Virulence factors of enterotoxigenic Escherichia coli

Further evidence for the role of enterotoxigenic Escherichia coli as an etiologic agent of diarrhea is presented. A retrospective study of 71 cases of diarrhea in Mexican children demonstrated that greater than 40% of them harbored E. coli that produced heat-labile and/or heat-stable enterotoxin. The antigenic surface-associated colonization factor of E. coli strain H-10407 has been further characterized: this pilus-like antigen is produced under conditions of growth that repress the production of common pili of E. coli. The E. coli H-10407-type colonization factor pilus has been identified as one of the antigens possessed by a strain of E. coli that produced only heat-stable enterotoxin and that was responsible for an outbreak of pediatric diarrhea.

Location of food consumption and travelers' diarrhea

Daily food histories for one month were obtained in summer, 1975, from students attending a Mexican university to determine the influence of food consumption on the development and etiology of diarrhea. In newly-arrived students from the U.S. who ate half or more of their meals in the school cafeteria and public restaurants there were significant increases in diarrhea (p less than 0.005); shigella infection (p less than 0.05) and toxigenic E. coli infection (p less than 0.025) compared to the students eating a comparable number of meals in private homes. In the summer U.S. students there was also an association of diarrhea and eating from street vendors (p less than 0.05). In full-time U.S. students who had lived in Mexico a year or longer as well as in Latin American students a relationship between location of meals and occurrence of enteric disease was not apparent. High numbers of enteric bacteria were recovered from food from the school's cafeteria, public restaurants, street vendors and small grocery stores. Shigella were isolated from cooked and uncooked hamburger patties from the school cafeteria. Four shigella carriers were found among kitchen personnel at the school. This study demonstrates that food serves as a major vehicle through which travelers' diarrhea occurs.

Patterns of loss of enterotoxigenicity by Escherichia coli isolated from adults with diarrhea: suggestive evidence for an interrelationship with serotype

Enterotoxigenic Escherichia coli isolates obtained in Mexico from adult subjects with diarrhea and from healthy controls were examined for the production of heat-stable enterotoxin (ST) and heat-labile enterotoxin (LT) after serial passage in the laboratory. Isolates were found to be either stable for the production of ST and LT or unstable with respect to ST, LT, or both. Unilateral loss of either ST or LT production allowed classification of E. coli isolates into four groups according to stability/instability of enterotoxin production. Fewer serotypes, with more representative isolates, were in group I (stable) than in group IV (completely unstable). Isolates from Dacca, Bangladesh, could be similarly classified into stability groups. There is an apparent relationship between serotype, stability of enterotoxin production, particularly LT, and isolation from diarrhea cases as opposed to isolation from healthy controls.

Enteropathogens associated with pediatric diarrhea in Mexico City

Enteropathogens were investigated as possible agents in pediatric diarrhea occurring in Mexico City during the summer of 1975. Pathogens were identified in 47 (76%) of 62 cases. Rotavirus particles were detected in 16 cases. Enterotoxigenic Escherichia coli was detected in 29 cases; 11 were positive for heat-labile enterotoxin and 18 were positive for only the heat-stable form of enterotoxin. Multiple pathogens were found simultaneously in 15 (24%) of the study population. This study indicates that the etiology of pediatric summertime diarrhea in Mexico City is diverse. ETEC and RV were the most frequently encountered pathogens, yet they frequently occurred together and with other pathogens. ST-only strains of toxigenic E. coli were as frequently recovered as LT-E. coli suggesting that both forms of ETEC must be sought in future field studies.

Direct serological assay for the heat-labile enterotoxin of Escherichia coli, using passive immune hemolysis

Sheep erythrocytes sensitized with the heat-labile enterotoxin (LT) of Escherichia coli exhibited passive immune hemolysis (PIH) when exposed to specific antitoxin and complement. Thus, PIH serves as the basis for an in vitro serological assay for LT that is sufficiently specific and sensitive to differentiate LT-positive and LT-negative E. coli isolates. The PIH assay for E. coli LT has been performed with the standard Microtiter system and also by a tube method employing the spectrophotometric determination of hemoglobin release. The spectrophotometric method enhances the sensitivity, accuracy, and objectivity of the PIH assay. The increased sensitivity of the spectrophotometric method also facilitates the identification of LT-positive cultures employing polymyxin "mini-extracts" of whole overnight (18 h) broth cultures of 2.0% Casamino Acid-0.6% yeast extract-salts medium rather than mini-extracts of cells derived from 3.5-h subcultures. Thus, large numbers of E. coli isolates can be individually tested for LT in less than 24 h after broth inoculation by a rapid in vitro assay which requires anti-LT serum as the only specific reagent.

Inhibition of immune hemolysis: serological assay for the heat-labile enterotoxin of Excherichia coli

Sheep erythrocytes sensitized by incubation with the heat-labile enterotoxin (LT) of Escherichia coli are hemolyzed in the presence of anti-LT antiserum and complement. The Microtiter (Cooke Laboratory Products) technique was used to titrate anti-LT antibody in serum by this immune hemolysis reaction. Immune hemolysis was inhibited by preexposure of the anti-LT antiserum to soluble LT before addition of the LT-sensitized sheep cells. E. coli mini-extract preparations were obtained by the polymyxin release technique and assayed for LT by the lysis inhibition test (LIT) and by the adrenal cell assay. All 75 adrenal cell-positive E. coli isolates were positive in the LIT assay. Eight of 318 adrenal cell-negative isolates tested were positive in the LIT assay, possibly indicating the presence of biologically inactive toxin.

Infantile diarrhea produced by heat-stable enterotoxigenic Escherichia coli

Between December, 1974, and August 1975, intestinal illness occurred in 55 of 205 infants admitted to the special-care nurseries of a large children's hospital. Escherichia coli serotype 078:K80:H12, which produced a heat-stable enterotoxin, was isolated from 18 of 25 symptomatic infants as compared with 14 of 55 asymptomatic infants (P less than 0.001). Colistin administered prophylactically to 24 culture-negative asymptomatic infants did not prevent colonization in 10, whereas colonization did occur in 22 of 56 not receiving colistin (P = 1.0). This outbreak provides laboratory and epidemiologic evidence that heat-stable enterotoxigenic Esch. coli is pathogenic in human beings and produces infantile diarrhea.

Purification of the polymyxin-released, heat-labile enterotoxin of Escherichia coli

The heat-labile enterotoxin of Escherichia coli strain H-10407 has been purified by use of a commercially available affinity gel (Affi-Gel 202). This gel possesses a strong and highly specific affinity for the enterotoxin released from intact E. coli cells by polymyxin B. The polymyxin-release technique could be used with fermenter-size batches of E. coli cells grown in a casamino acids-yeast extract medium. With a simple (NH4)2SO4 back-extraction step prior to affinity chromatography, large batches of E. coli enterotoxin could be processed rapidly. Affi-Gel 202-purified E. coli enterotoxin produced a single precipitin band in the presence of several different antisera against crude preparations of the toxin. The same antigen produced a precipitin band in the presence of both cholera antitoxin and antiserum to choleragenoid.

Mechanism of activation adenylate cyclase in vitro by polymyxin-released, heat-labile enterotoxin of Escherichia coli

Heat-labile enterotoxic material released from Escherichia coli by polymyxin B activates the adenylate cyclase of pigeon erythrocyte ghosts in a time- and concentration-dependent manner. The activation requires nicotinamide adenine dinucleotide, adenosine triphosphate, and another component of the erythrocyte supernatant. The active species has a molecular weight of about 23,000-24,000 daltons, is inhibited by antibodies to the toxin of Vibrio cholerae, and is not irreversibly denatured by sodium dodecyl sulfate. Thus in many respects the active species from E. coli behaves the same as peptide A1 of cholera toxin.

Plasmid-controlled colonization factor associated with virulence in Esherichia coli enterotoxigenic for humans

An enterotoxin-producing strain of Escherichia coli isolated from a case of cholera-like diarrhea (E. coli strain H-10407) was found to possess a surface-associated colonization factor. Colonization was manifested as the ability of small inocula (10(5) bacteria) to attain large (10(9)) populations in the infant rabbit intestine with a concomitant diarrheal response. A laboratory-passed derivative of E. coli H-10407, designated H-10407-P, failed to exhibit an increase in population in the infant rabbit and also failed to induce diarrhea. Cell-free culture supernatant fluids of E. coli H-10407 and H-10407-P produced equivalent enterotoxic responses in infant and in adult rabbits. Specific anti-colonization factor antiserum was produced by adsorbing hyperimmune anti-H-10407 serum with both heat-killed and living cells E. coli H-10407-P. This specific adsorbed serum protected infant rabbits from challenge with living E. coli H-10407 although the serum did not possess bactericidal activity. The anti-colonization factor serum did not agglutinate a strain of E. coli K-12 possessing the K88 colonization factor peculiar to E. coli enterotoxigenic for swine. By electron microscopy it was demonstrated that E. coli H-10407, but not H10407-, possessed pilus-like surface structures which agglutinated with the specific adsorbed (anti-colonization factor) antiserum. E. coli H-10407 possessed three species of plasmid deoxyribonucleic acid, measuring 60 X 10(6), 42 X 10(6), and 3.7 X 10(6) daltons, respectively. E. coli H-10407-P possessed only the 42 X 10(6)- and the 3.7 X 10(6)-dalton plasmid species. Spontaneous loss of the specific H-10407 surface-associated antigen was accompanied by loss of the 60 X 10(6)-dalton species of plasmid deoxyribonucleic acid and loss of colonizing ability. Thus, it is concluded that the E. coli colonization factor described here is a virulence factor which may play an important and possibly essential role in naturally occurring E. coli enterotoxic diarrhea in man.

Prevention of tetanus in the wounded

Recommendations for the prevention of tetanus in the wounded have been revised to incorporate the use of human tetanus immunoglobulin, which is now available in the United Kingdom. Surgical toilet is of prime importance for all wounds, and is usually sufficient for tetanus prophylaxis in patients with wounds that are less than six hours old, clean, non-penetrating, and with negligible tissue damage. Human tetanus immunoglobulin should be given to patients with more serious wounds sho have had toxoid injections over 10 years earlier, had an incomplete course, or do not know their immunity status. The importance of active immunization is emphasized. The recommendations should be regarded as guidelines as the circumstances in individual cases will differ.

Travelers' diarrhea and toxigenic Escherichia coli

In a group of 133 United States students studied for 18 days after arriving in Mexico, diarrhea developed in 38 (29 per cent). Diarrhea rarely began before the fourth day, and the mean onset was 13 days after arrival. Symptoms lasted an average of 3.4 days but persisted in 21 per cent of sick students. Heat-labile enterotoxin-producing Escheria coli was found in the stools of 72 per cent of sick and 15 per cent of healthy students. None had heat-labile Esch. coli when they entered Mexico. The incubation period was short, generally 24 to 48 hours, and the carrier state was five days or less in 82 per cent of students surveyed. Entamoeba histolytica was found in 6 per cent of cases of diarrhea, but not salmonella, shigella or penetrating Esch. coli. These studies suggest that approximately 70 per cent of travelers' diarrhea in Mexico is associated with heat-labile toxigenic strains of Esch. coli.