Biomedical subjects

B E Guth

Publications and source records attributed to B E Guth.

24 records · Page 2Linked to original sources

PubMed1986

Variation in chemical properties and antigenic determinants among type II heat-labile enterotoxins of Escherichia coli.

Type II heat-labile enterotoxin (LT-II) from Escherichia coli 41 was purified and compared with prototype LT-II encoded by genes from E. coli SA53. Both toxins were oligomeric proteins consisting of polypeptides A (Mr, 28,000) and B (Mr, 11,800). The A polypeptides were cleaved by trypsin into fragments A1 (Mr, 21,000) and A2 (Mr, about 7,000). These two toxins were shown to belong to two different subclasses of LT-II. We propose to designate the prototype toxin LT-IIa and the new variant LT-IIb. The pI of LT-IIb was between 5.2 and 5.6, significantly lower than the pI of 6.8 for LT-IIa, and the behavior of LT-IIb during purification differed significantly from that of LT-IIa. The toxic dose of unnicked LT-IIb in the Y1 adrenal-cell assay was 94 pg, but trypsin-treated, nicked LT-IIb was toxic at about 3 pg. In contrast, the toxic dose of LT-IIa was previously shown to be 0.5 to 1 pg for several preparations that varied from unnicked to partially nicked, and treatment with trypsin was not required for full toxicity. The titer of LT-II antiserum in neutralization tests was 100-fold greater against LT-IIa than against LT-IIb. In immunodiffusion tests, LT-IIa and LT-IIb gave a reaction of partial identity. In a radioimmunobinding assay, the titer of LT-IIa antiserum against homologous LT-IIa was approximately 10-fold greater than against LT-IIb. The cholera-E. coli family of heat-labile enterotoxins has been divided into serogroup I, which includes cholera toxin and the antigenic variants of E. coli heat-labile toxin designated LTh-I and LTp-I, and serogroup II, which includes LT-IIa and LT-IIb. The type I and type II toxins do not cross-react in neutralization or immunodiffusion tests. By using very sensitive radioimmunobinding assays, it was possible to demonstrate common antigenic determinants between the type I and type II toxins. However, the titers of antibodies in hyperimmune sera that recognized these common determinants were very low.

Antigen-Antibody Complex↗

PubMed1986

Production of type II heat-labile enterotoxin by Escherichia coli isolated from food and human feces.

Escherichia coli strains isolated in Sao Paulo, Brazil, from feces of patients with diarrhea and from food samples produced toxin(s) that was shown to be related both immunologically and genetically to the recently characterized type II heat-labile enterotoxin of E. coli. The new isolates of type II heat-labile enterotoxin-producing E. coli belonged to five different serotypes and did not represent a single clone.

Bacterial Toxins↗

PubMed1985

Enterotoxin production, presence of colonization factor antigen I, and adherence to HeLa cells by Escherichia coli O128 strains belonging to different O subgroups.

Strains of three subgroups of Escherichia coli O128 were studied. Enterotoxin production was observed in 30 (91%) O128ac strains, whereas strains of subgroups O128ab and O128ad were not toxigenic. CFA/I was only found in two serotypes of subgroup O128ac, all of them producing heat-stable enterotoxin except for one which produced both toxins. None of the strains studied produced CFA/II. In a binding test with HeLa cells, localized adherence was found only in strains of subgroup O128ab; diffuse adherence occurred in strains of subgroup O128ac. As flagellar antigens were specific in subgroups ab and ac and toxin production was observed only in subgroup ac, the present results suggest that subgroup and serotype are useful markers for O128 strains that are enterotoxigenic or enteropathogenic.

Antigens, Bacterial↗

PubMed1985

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.

Animals↗

PubMed1982

Frequency of Escherichia coli strains producing heat-labile toxin or heat-stable toxin or both in children with and without diarrhea in São Paulo.

Enterotoxigenic Escherichia coli strains were isolated from 32 (13.4%) of 245 children with diarrhea and from 11 (11.4%) of 96 children of the control group. Strains producing heat-labile toxin were found more frequently in normal children than in children with diarrhea. Strains producing heat-stable toxin and both heat-labile and heat-stable toxins were isolated only from children with diarrhea. Association of these strains with diarrhea was highly significant as shown by statistical analysis. The O:H types and the colonization factors of strains producing heat-stable toxin and both heat-labile and heat-stable toxins are presented.

Bacterial Toxins↗

PubMedDate not supplied

Characterization of enterotoxigenic Escherichia coli by random amplification of polymorphic DNA.

Two enterotoxigenic Escherichia coli (ETEC) strains (H10407 and 4011-1) were characterized by random amplification of polymorphic DNA (RAPD) profiles using 10-mer oligonucleotides with diverse GC content. All tested primers yielded arrays of amplified DNA products ranging in size from 200 to 3000 bp. The effects of annealing temperature, template concentration and GC content of the primers were evaluated and an optimal reaction procedure was established. Application of the RAPD analysis to ten ETEC strains belonging to five different serotypes showed that strains of the same serotype shared identical or almost identical band profiles, suggesting a similar genetic composition. The use of RAPD profiles as a tool in epidemiological analysis of ETEC is discussed.

Child↗