Biomedical subjects

B E Guth

Publications and source records attributed to B E Guth.

At least 19 recordsLinked to original sources

PubMed2001

Diversity of surface structures and virulence genetic markers among enteroaggregative Escherichia coli (EAEC) strains with and without the EAEC DNA probe sequence.

The expression of surface structures and the presence of DNA sequences related to putative virulence factors were investigated in 22 enteroaggregative Escherichia coli strains (EAEC). Fimbria was the most frequent (72.7%) structure identified. Only strains hybridising with the EAEC DNA probe carried aggA, but one strain produced a similar but unrelated bundle-like structure. All probe-positive and 62.5% of the probe-negative strains carried the virulence genes tested; aspU and irp2 prevailed among the former strains. The EAEC probe-positive strains were more diverse, and some of these strains, which promoted cell detachment, also carried the hly and pap sequences, thus suggesting they might represent uropathogenic E. coli.

Adhesins, Bacterial↗

PubMed2000

Enterotoxigenic Escherichia coli--an overview.

Enterotoxigenic Escherichia coli is an important cause of traveler's diarrhea and diarrheal illnesses in children in the developing world. In this presentation we will focus on the main virulence attributes of this pathogenic category of E. coli, and discuss the evolution of studies conducted in our laboratory.

Diarrhea↗

PubMed1999

High occurrence of Shiga toxin-producing Escherichia coli (STEC) in healthy cattle in Rio de Janeiro State, Brazil.

In order to evaluate the prevalence of Shiga toxin-producing Escherichia coli (STEC) strains, 197 fecal samples of healthy cattle from 10 dairy farms, four beef farms and one slaughterhouse at Rio de Janeiro State, Brazil, were examined for Shiga toxin (Stx) gene sequences by polymerase chain reaction (PCR). For presumptive isolation of O157:H7 E. coli, the Cefixime-potassium tellurite-sorbitol MacConkey Agar (CT-SMAC) was used. A high occurrence (71%) of Stx was detected, and was more frequently found among dairy cattle (82% vs. 53% in beef cattle), in which no differences were observed regarding the age of the animals. Dot blot hybridization with stx1 and stx2 probes revealed that the predominant STEC type was one that had the genes for both stx1 and stx2 in dairy cattle and one that had only the stx1 gene for beef cattle. Three (1.5%) O157:H7 E. coli strains were isolated from one beef and two dairy animals by the use of CT-SMAC. To our knowledge, this is the first report of O157:H7 isolation in Brazil. A PCR-based STEC detection protocol led to the isolation of STEC in 12 of 16 randomly selected PCR-positive stool samples. A total of 15 STEC strains belonging to 11 serotypes were isolated, and most of them (60%) had both stx1 and stx2 gene sequences. Cytotoxicity assays with HeLa and Vero cells revealed that all strains except two of serotype O157:H7 expressed Stx. The data point to the high prevalence of STEC in our environment and suggest the need for good control strategies for the prevention of contamination of animal products.

Animals↗

PubMed1999

Characterization of serotypes and outer membrane protein profiles in enteroaggregative Escherichia coli strains.

Twenty-four Escherichia coli strains mainly isolated from children with diarrhea in São Paulo, and showing characteristics of enteroaggregative E. coli (EAEC), were characterized by serotyping and outer membrane protein (OMP) profiles. The relationship between these characteristics was evaluated, as well as the usefulness of OMP profiles in the clonal analysis of EAEC strains. All strains presented aggregative adherence to HeLa cells and were classified in two groups based on their interaction with the EAEC DNA probe. A diversity of serotypes and OMP profiles was observed in both groups studied. Although no significant correlation between serotypes and OMP profiles was observed, unique OMP profiles were identified in 80% of the probe-positive strains which were distributed in only 4 OMP profiles. This result may indicate the presence of a few clones in the probe-positive group. On the other hand, probe-negative strains seem to constitute a more diverse group. In general, the observed heterogeneity in serotypes and OMP profiles described in the present study suggest a great genetic diversity in EAEC isolates of either the same or different serotypes and in strains presenting the same EAEC markers identified in our community.

Bacterial Outer Membrane Proteins↗

PubMed1997

Clonal relationships among Escherichia coli serogroup O6 isolates based on RAPD.

The genetic diversity in a group of Escherichia coli strains belonging to serogroup O6 but expressing different H antigens was investigated by random amplification of polymorphic DNA (RAPD). Isolates of serotypes H16, H1, H31, and non-motile (NM) strains were typed using a set of 3 primers with different G + C contents. The amplified band arrays allowed the identification of 3 main clonal clusters corresponding to each O:H serotype analyzed. Based on their RAPD profiles NM strains could be assigned to either H1 or H31 serotypes. The results indicate that the flagellar antigen and the RAPD fingerprint represent reliable clonal markers in this E. coli group.

DNA Fingerprinting↗

PubMed1997

Virulence properties of Escherichia coli strains belonging to enteropathogenic (EPEC) serogroups isolated from calves with diarrhea.

Nineteen Escherichia coli strains belonging to enteropathogenic (EPEC) serogroups were isolated from calves with diarrhea in Paraná State. Brazil, and studied for virulence markers associated with EPEC or enterohemorrhagic E. coli (EHEC). The 19 isolates belonged to 12 serotypes with isolates of O26:H11, O119:H25 and O114:H- being the most prevalent Localized adherence (LA) was demonstrated for 37% of the isolates, consisting of all four O26:H11, both O114:H- and one O114:H40 isolates. All the LA strains were positive in the fluorescent-actin staining (FAS) test and possessed attaching-effacing E. coli (eae) sequences, but only O114 strains hybridized with the EPEC adherence factor (EAF) probe. None of the strains produced Shiga-like toxins (Verotoxin). Only the O26:H11 strains hybridized with the EHEC plasmid specific (CVD419) probe and were enterohemolytic, properties associated with EHEC strains. This investigation demonstrates that among the bovine strains isolated only those of serogroup O114 behaved as typical EPEC.

Animals↗

PubMed1997

Random amplification of polymorphic DNA reveals serotype-specific clonal clusters among enterotoxigenic Escherichia coli strains isolated from humans.

The genetic diversity of 47 enterotoxigenic Escherichia coli (ETEC) strains of serotypes O6:H16, O27:H7, O29:H21, O128ac:H12, and O153:H45, previously isolated from diarrheic patients in Brazil over a period of 15 years, was investigated by random amplification of polymorphic DNA (RAPD). Informative band arrays were obtained with three 10-mer primers with G+C contents of 50, 60, and 70%. Based on the combination of the band profiles generated by the three primers 22 RAPD types were detected, and 5 major clonal clusters, each one with at least 80% identical bands, were established. The clonal clusters corresponded to strains having the same serotype which, in most cases, also had the same virulence factors (colonization factors and toxin types) and outer membrane protein and lipopolysaccharide sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiles. The results suggested a correlation between phenotypic properties and genetic relatedness of ETEC isolates of human origin and indicated that a reduced number of clonally related strains are found in areas of ETEC endemicity in Brazil. Moreover, the RAPD technique revealed intraserotype-specific variations, undetectable by the combination of several phenotypic typing methods, among the ETEC strains analyzed. These results show that RAPD typing represents a useful tool for population genetics as well as for epidemiological studies of ETEC.

Brazil↗

PubMed1996

Relationship between outer membrane protein and lipopolysaccharide profiles and serotypes of enterotoxigenic Escherichia coli isolated in Brazil.

The electrophoretic profiles of outer membrane proteins and lipopolysaccharide of sixty-five enterotoxigenic Escherichia coli of different serotypes and virulence-associated factors, toxin and colonization factors were determined. A close relationship between serotype and outer membrane protein and lipopolysaccharide patterns could be observed. No correlation could be found between the electrophoretic profiles and the expression of virulence-associated factors. The observed homogeneity of outer membrane protein and lipopolysaccharide profiles suggested the presence of only a few clones in the samples studied, and supported the use of outer membrane protein and lipopolysaccharide analysis as a useful epidemiological tool in the characterization of enterotoxigenic Escherichia coli isolates.

Bacterial Outer Membrane Proteins↗

PubMed1996

Prevalence of invasive ability and other virulence-associated characteristics in Providencia alcalifaciens strains isolated in São Paulo, Brazil.

Providencia alcalifaciens is an invasive enteric pathogen. The present study determined the prevalence of invasive ability in P. alcalifaciens strains isolated in São Paulo, Brazil, mainly from patients with diarrhoea. Invasion of HeLa cells was found in 17 (42%) of 41 strains studied. Most (88%) of the invasive strains were isolated from diarrhoeal stools. The invasive property was identified in 50% of P. alcalifaciens strains isolated as pure cultures or from stool samples where no other enteropathogen was identified. All the invasive strains caused actin condensation in infected cells. Plasmid profile analysis showed the presence of plasmids of 35.8-180 kb in 70% of the strains regardless of their invasive ability, suggesting that invasiveness in P. alcalifaciens is not plasmid related. No homology with a probe for gene sequences for invasion of enteroinvasive Escherichia coli and Shigella strains was identified in colony hybridisation assays. The invasive property of P. alcalifaciens was confirmed in the present study, but this characteristic did not predominate among strains isolated from patients with diarrhoea in São Paulo City. The presence of other virulence mechanisms and the role of non-invasive P. alcalifaciens strains as a cause of diarrhoea remain to be established.

Adult↗

PubMed1996

Diffuse adherence, ST-I enterotoxin and CFA/IV colonization factor are encoded by the same plasmid in the Escherichia coli O29:H21 strain.

Escherichia coli O29:H21 is a human enterotoxigenic serotype that produces heat-stable (ST-I) enterotoxin, adheres diffusely to HeLa cells, and presents colonization factor antigen IV (CFA/IV) composed of CS5CS6 surface antigens. In one strain studied the genes for diffuse adherence and CFA/IV (CS5CS6) production were found to be present in the same plasmid encoding ST-I. The virulence plasmid (Ent) presented two unrelated basic replicons homologous to repFIC and repW. Gene(s) encoding diffuse adherence did not share homology with the probe for F1845 fimbrial adhesin which is responsible for this phenotype in other E. coli strains. Ent plasmids containing genes for diffuse adherence have not been described previously.

Acridine Orange↗

PubMed1995

Comparison of outer membrane protein and lipopolysaccharide profiles of enterotoxigenic Escherichia coli strains isolated in São Paulo, Brazil.

The outer membrane protein (OMP) and lipopolysaccharide (LPS) patterns of 12 strains of serogroups of enterotoxigenic E. coli frequently isolated in São Paulo city were determined by fractionation techniques and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Five O6, three O78 and four O128 serogroup isolates of different serotypes (flagellar antigens) and virulence factors (toxins and colonization factor antigens) showed a high degree of variability in their OMP pattern and at least nine groups could be identified. The analysis of LPS patterns by SDS-PAGE showed a homogeneous profile for the O6 strains and some minor differences for the O128 and O78 strains. The present data indicate that analysis of OMP and LPS by SDS-PAGE may further improve the discriminating ability of extensively used serological techniques or the detection of virulence factors and could be a useful tool in epidemiological studies of enterotoxigenic E. coli (ETEC) strains from this area.

Bacterial Outer Membrane Proteins↗

PubMed1994

Prevalence of colonization factor antigens (CFAs) and adherence to HeLa cells in enterotoxigenic Escherichia coli isolated from feces of children in São Paulo.

Fifty-eight enterotoxigenic Escherichia coli (ETEC) strains, isolated from children with and without diarrhea in São Paulo, were examined for the presence of colonization factor antigens (CFAs) and their ability to adhere to HeLa cells. Antisera to CFA/I, the coli surface (CS) antigens CS1CS3, CS2CS3, and CS2 of CFA/II, CFA/III, and CS5CS6 and CS6 of CFA/IV were used. CFAs were identified in 43% of the ETEC strains: 40% of the CFAs strains with CFAs harbored CFA/I, 24% carried CFA/II (CS1CS3), 24% carried CFA/IV (CS6), and 12% carried CFA/IV (CS5CS6). CFAs occurred mainly among ETEC strains producing only heat-stable (ST-I) enterotoxin and in strains also producing heat-labile toxin (LT-I). No ETEC strains tested expressed CFA/III. A marked change in serotypes of ST-I-producing strains was found in São Paulo between 1979 and 1990. Adherence to HeLa cells was detected in 14% of the ETEC strains. All of them had a diffuse adherence pattern and produced only ST-I, and 88% carried CS6 antigen.

Animals↗

PubMed1994

Survey of cytotoxin production among Escherichia coli strains characterized as enteropathogenic (EPEC) by serotyping and presence of EPEC adherence factor (EAF) sequences.

A total of 108 Escherichia coli strains characterized as enteropathogenic (EPEC) by serotyping and the presence of EPEC adherence factor (EAF) sequences were examined for cytotoxin production by cell line assays and colony hybridization with Shiga-like toxin (SLT) probes. Cytolethal distending toxin (CLDT) production was found in three (2.8%) strains belonging to serotype O86:H34, while one O111ab:NM strain hybridized with a SLT-II probe but did not express any cytotoxic activity. All four strains showed localized adherence to HeLa cells and hybridized to an E. coli attaching-effacing gene (eae) probe. The CLDT-producing strains had multiple plasmids and some were present in all strains, including a plasmid of approximately 54 MDa that hybridized with the EAF probe.

Adhesins, Escherichia coli↗

PubMed1993

Presence of colonization factor antigen IV (CS5CS6) in O29:H21 enterotoxigenic Escherichia coli isolated from children with diarrhea in Brazil.

1. Enterotoxigenic Escherichia coli (ETEC) strains belonging to serotype O29:H21 were analyzed for the presence of colonization factor antigens (CFA). 2. CFA/IV was detected in all twelve strains studied, and immunological analysis demonstrated that it was composed of coli surface antigens 5 (CS5) and 6 (CS6) presenting molecular weights of approximately 21 kDa and approximately 16 kDa, respectively. 3. CS6 antigenic homology was observed between O29:H21 and reference strains E11881C and E17018A. 4. CS6 of the O29:H21 strains was composed of two peptide bands, similar to the reference strain E17018A.

Bacterial Proteins↗

PubMed1991

Enteropathogens associated with acute diarrheal disease in urban infants in São Paulo, Brazil.

To determine the prevalence and epidemiology of enteropathogens in acute infantile diarrhea, 500 infants less than or equal to 12 months of age with diarrhea and 500 age-matched control subjects coming to a São Paulo emergency room were studied. Enteropathogens were identified in 55% of case infants and 10% of controls; enteropathogenic Escherichia coli (EPEC) of classic EPEC serotypes producing EPEC adherence factor (EAF) (26% of case infants), rotavirus (14%), Salmonella species (8%), enterotoxigenic E. coli (7%), and Shigella species (5%) were associated with diarrhea. Isolation of EAF+ classic EPEC decreased with increasing age of cases and peaked in spring, whereas rotavirus was least common in early infancy and peaked in fall and winter. Bloody stool had a 36% positive predictive value for Shigella infection, EAF+ classic EPEC were highly resistant to antimicrobial drugs. Among poor São Paulo infants, EAF+ classic EPEC equaled or exceeded rotavirus throughout the year as a cause of diarrhea bringing children to medical attention.

Acute Disease↗

PubMed1991

Comparison of colony and stool blots for detection of enteropathogens by DNA probes.

DNA probes that identify genes coding for heat-labile type I (LT-I) and heat-stable type 1 (ST-I) enterotoxins, enteropathogenic Escherichia coli adherence factor (EAF), and Shigella-like invasiveness (INV) are used to evaluate the sensitivity and specificity of stool blots in comparison with the sensitivity and specificity of colony blots in detecting enteropathogens. The sensitivities of the probes in stool blots are 91.7% for the LT-I probe, 76.9% for the ST-I probes, 78.9% for the EAF probe, and 45.5% for the INV probe. The specificity of all probes is higher than 95%. In general, the stool blot method identifies as many if not more LT-I-, ST-I-, and EAF-producing E. coli infections than the colony blots.

Adhesins, Escherichia coli↗

PubMed1990

Production of Shiga-like toxin among Escherichia coli strains and other bacteria isolated from diarrhea in São Paulo, Brazil.

An elevated level of Shiga-like toxin I (SLT-I) production was found in 1 of 466 Escherichia coli strains studied. Among the 34 sonic lysates obtained from classical enteropathogenic E. coli, 5 produced SLT-I. The Aeromonas, Citrobacter, Edwardsiella, Enterobacter, Klebsiella, Proteus, Providencia, Pseudomonas, Salmonella, Serratia, Shigella, Yersinia, and Vibrio strains also studied were not SLT producers, except for a Shigella dysenteriae type 1 strain. Although SLT-I-producing E. coli strains were isolated from diarrhea, they seem to be an uncommon cause of disease in children less than 1 year old in our community.

Bacterial Toxins↗

PubMed1989

Virulence factors and biochemical characteristics of serotypes of Escherichia coli serogroup O29.

Escherichia coli strains belonging to serogroup O29 were studied. Invasiveness was the most common virulence factor described in this serogroup, but a few papers also reported production of heat-stable (ST) enterotoxin. In the present study invasive ability was found in O29:H- strains, whereas production of ST-I enterotoxin was observed only in serotype O29:H21 strains, showing that virulence was a characteristic of specific serotypes or bioserotypes within the O29 serogroup. Different serotypes were found among strains that were neither invasive nor toxigenic. Invasive strains were biochemically less active than the toxigenic ones and presented the invasiveness plasmid (pINV) of about 120 to 140 megadaltons, whereas hybridization tests showed that ST-I production was related to a plasmid of about 90 megadaltons. A diffuse adherence pattern to HeLa cells was observed in all ST-I isolates, but the role of this adherence in the pathogenicity of these strains was not determined. Thus, a unique biochemical pattern and plasmid profile may be useful characteristics to distinguish between pathogenic (toxigenic or invasive) and nonpathogenic O29 strains.

Antigens, Bacterial↗