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T G Cleary

Publications and source records attributed to T G Cleary.

At least 37 records · Page 2Linked to original sources
PubMed1992

Concentration of milk secretory immunoglobulin A against Shigella virulence plasmid-associated antigens as a predictor of symptom status in Shigella-infected breast-fed infants.

We conducted a prospective, community-based study of healthy breast-fed Mexican infants to determine the protective effects of anti-Shigella secretory IgA antibodies in milk. Milk samples were collected monthly, and stool culture specimens were obtained weekly and at the time of episodes of diarrhea. Nineteen breast-fed infants were found to have Shigella flexneri, Shigella boydii, or Shigella sonnei in stool samples. Ages of the 10 infants with symptomatic infection and the nine with asymptomatic infection did not differ significantly. Milk samples collected up to 12 weeks before infection were evaluated by enzyme-linked immunosorbent assay for secretory IgA antibodies against lipopolysaccharides of S. flexneri, S. boydii serotype 2, S. sonnei, and virulence plasmid-associated antigens. The geometric mean titers of anti-Shigella antibodies to virulence plasmid-associated antigens in milk received before infection were eightfold higher in infants who remained well than in those in whom diarrhea developed. The significance of milk secretory IgA directed against lipopolysaccharide was less clear. We conclude that human milk protects infants against symptomatic shigella infection when it contains high concentrations of secretory IgA against virulence plasmid-associated antigens.

Antigens, Bacterial↗
PubMed1992

Association between severity of gastrointestinal prodrome and long-term prognosis in classic hemolytic-uremic syndrome.

To determine whether severity of the prodromal gastrointestinal illness is associated with the course and complications of the extraintestinal manifestations of hemolytic-uremic syndrome, we conducted a retrospective review of children (n = 509) hospitalized with hemolytic-uremic syndrome. Those who came to the hospital with colitis and rectal prolapse associated with hemolytic-uremic syndrome (group I, n = 40) were compared with an equal number of time-matched children with hemolytic-uremic syndrome but without prolapse (group II). Children in group I had evidence of more severe colitis than children in group II had, as indicated by increased frequency of bloody diarrhea (p less than 0.001) and longer duration of diarrhea (p less than 0.001). However, they also had more severe extraintestinal manifestations during hemolytic-uremic syndrome, including edema (p less than 0.0001), severe thrombocytopenia (p less than 0.0001), prolonged anuria (p less than 0.001), and seizures (p = 0.036). Long-term prognosis for recovery of renal function was worse for group I than group II. Within group II, patients with bloody diarrhea had milder extraintestinal illness than those with prolapse but more severe extraintestinal illness than those with watery diarrhea. Analysis of Kaplan-Meier survival curves demonstrated a better prognosis for return of normal renal function in the children with watery diarrhea but without prolapse (p = 0.009) than in children with bloody diarrhea or prolapse. These data demonstrate that the severity of the gastrointestinal prodrome reflects the severity of the extraintestinal acute microangiopathic process and the resulting long-term outcome. Widespread vascular damage, often followed by permanent sequelae, is characteristic of patients with the most severe colitis.

Adolescent↗
PubMed1992

Human milk contains the Shiga toxin and Shiga-like toxin receptor glycolipid Gb3.

Human milk antibody and nonantibody factors are thought to be important in protecting infants from diarrheal diseases. The nonantibody factors include host receptor analogues that bind to specific pathogen virulence factors, thereby inhibiting these bacterial products from binding to their intestinal target receptors. Globotriaosylceramide (Gb3), a glycolipid known to bind to both Shiga toxin and Shiga-like toxins, was found to occur in human milk with an average concentration of 73 nM (77 micrograms/L) for Gb3 containing hydroxylated fatty acids and 50 nM (53 micrograms/L) for Gb3 containing nonhydroxylated fatty acids. This human milk Gb3 was found to bind to Shiga toxin, consistent with the hypothesis that Gb3 could contribute to the protective effect of human milk against infantile diarrheas associated with Shiga or Shiga-like toxins.

Bacterial Toxins↗
PubMed1992

The adherence of verocytotoxin-producing Escherichia coli to rabbit intestinal cells.

Verocytotoxin-producing Escherichia coli (VTEC) have been recognised recently as an important cause of human disease. The adherence of VTEC to rabbit intestinal tract and the relationship between adherence and other virulence traits were studied. Twenty clinical isolates of VTEC (O157:H7 and other serotypes) and a control, commensal E. coli strain, were examined. Bacteria were evaluated for the presence of surface fimbriae, plasmid profile and hybridisation with a 3.4 kb DNA probe derived from the 60-MDa plasmid of such strains. Adherence was determined by electronmicroscopy and quantitatively with radio-labelled bacteria. Of the VTEC strains, 12 (60%) had surface fimbriae; all O157:H7 and 10 (70%) of 14 of the non-O157:H7 strains hybridised with the probe. No isolate was negative for both of these virulence traits and there was no correlation between their presence. The plasmid profiles varied among the strains, with no correlation to virulence traits. The adherence of VTEC strains differed significantly, ranging from 0.3 to 34.0 bacteria/intestinal cell. The mean adherence of fimbriate strains was greater than that of non-fimbriate strains (3.9 versus 2.7 bacteria/cell), although marked variability was noted in both groups. This study showed that VTEC strains differed markedly in their adherence capability and that neither the presence of fimbriae nor hybridisation with the 3.4-kb probe was essential for adherence. Several distinct mechanisms probably play a role in VTEC adherence.

Animals↗
PubMed1992

Adherence of enterohemorrhagic Escherichia coli strains to a human colonic epithelial cell line (T84).

Enterohemorrhagic Escherichia coli (EHEC) produce Shiga-like toxins and attach to certain tissue culture cells. T84 cells are human colonic carcinoma cells. Unlike previously studied cell lines, T84 cells grown on collagen-coated surfaces polarize and produce tight junctions and desmosomes, forming a colonic epithelial cell layer in vitro. The purpose of this study was to examine the attachment of EHEC strains to the T84 cell line as a possibly more relevant in vitro model of EHEC adherence. Twelve EHEC strains were grown overnight in Penassay broth, suspended in minimal essential medium with and without 0.5% mannose, and incubated for 1 to 3 h with 5- to 7-day-old T84 cell monolayers grown on collagen-coated coverslips. The bacteria were removed, and attachment was quantitated microscopically. For both E. coli O157:H7 and other EHEC serotypes, there were marked differences in adherence between strains (range of 152 to 3 bacteria per oil immersion field). Mannose partially inhibited the adherence of some EHEC strains. Adherence to the T84 cells appeared to be related to the amount of pili present and not to the serotype. Electron micrographs showed that a highly adherent strain (strain 43-12) tended to form microcolonies in the area of tight junctions on the T84 cell monolayers. In addition, the attachment of these EHEC strains to T84 cells correlated with their ability to adhere to isolated rabbit colonocytes (r = 0.91, P = 0.00004; without mannose) (r = 0.60, P = 0.04; with mannose). These data show that there are EHEC strain-related differences in adherence which can be demonstrated in a human-derived colonic epithelial cell line (T84) and that these cells can be used to study EHEC adherence.

Bacterial Adhesion↗
PubMed1992

Polymerase chain reaction for diagnosis of enterohemorrhagic Escherichia coli infection and hemolytic-uremic syndrome.

Two pairs of oligonucleotide primers were designed to amplify fragments of the genes for Shiga-like toxin I (SLT-I) and SLT-II in a single reaction. A 370-bp segment and a 283-bp segment were amplified for SLT-I and SLT-II, respectively. The specificities of the polymerase chain reaction (PCR) amplification products were confirmed by using radioactively labeled oligonucleotide probes. SLT sequences were amplified from DNA isolated from 13 previously characterized enterohemorrhagic Escherichia coli (EHEC) strains. No amplification product was produced by using DNA from 20 non-EHEC strains. As little as one bacterial genome was detectable. PCR was then applied to DNA isolated directly from stool samples. We had to remove inhibitors of PCR that were present in lysates prepared from stool samples before amplification was achieved. First, we evaluated the sensitivity of PCR for the detection of known numbers of EHEC added to normal stools. Second, three children with SLT in their stools were shown to have SLT sequences in their stools by PCR. Two of these children had hemolytic-uremic syndrome, and a third child was asymptomatic. Stool specimens collected from another 26 asymptomatic children were negative by PCR for SLT sequences. PCR can be used to diagnose EHEC infections without prior culture of stool specimens.

Bacterial Toxins↗
PubMed1992

Ceftibuten and trimethoprim-sulfamethoxazole for treatment of Shigella and enteroinvasive Escherichia coli disease.

In a prospective randomized study at two clinical sites, ceftibuten was compared with trimethoprim-sulfamethoxazole (TMP-SMX), both given orally for a period of 5 days, for the treatment of dysentery. Twenty-two children were found to have bacillary dysentery caused by Shigella and/or enteroinvasive Escherichia coli. All organisms isolated were susceptible to ceftibuten; 6 of 20 Shigella strains and 4 of 5 enteroinvasive E. coli were resistant to TMP-SMX. The diarrhea persisted for a mean (+/- SD) period of 2.4 +/- 1.4 days in the ceftibuten-treated patients vs. 3.4 +/- 1.7 days in the TMP-SMX-treated patients. The duration of fever was similar for both treatment groups. Patients treated with ceftibuten or TMP-SMX had equivalent clinical responses unless the pathogen was found to be TMP-SMX-resistant. Those who were randomized to receive TMP-SMX but who were eventually found to have TMP-SMX-resistant organisms had significantly more stools at days 3, 4 and 5 (P less than 0.02 to less than 0.00006) with more watery consistency for these days (P less than 0.02 to less than 0.005) compared to patients treated with ceftibuten. No clinical relapses were reported and no drug-related side effects were observed. We conclude that ceftibuten is at least as effective as TMP-SMX in the treatment of diarrhea caused by Shigella and enteroinvasive E. coli in children.

Adolescent↗
PubMed1992

Escherichia coli that cause hemolytic uremic syndrome.

Entero-hemorrhagic Escherichia coli (Shiga-like toxin or verotoxin producing E. coli) have been recognized in recent years as an important new group of enteric pathogens. They are the cause of nonspecific diarrhea and hemorrhagic colitis, and in a significant number of patients, these conditions are complicated by the development of microangiopathic hemolytic anemia. In childhood, this complication is called hemolytic uremic syndrome (HUS), and in adults, it is more typically diagnosed as thrombotic thrombocytopenic purpura (TIP). The toxin producing E. coli are the usual etiology of these syndromes when they occur in the setting of a gastrointestinal prodrome with bloody diarrhea.

Escherichia coli↗
PubMed1991

Human milk secretory immunoglobulin A to Shigella virulence plasmid-coded antigens.

Although antibodies to the lipopolysaccharide antigens of Shigella have been demonstrated in human milk, such antibodies do not explain the putative protective effect of breast-feeding against symptomatic Shigella infection. Shigella species do not share related lipopolysaccharides, but they do possess closely related virulence plasmids that code for the proteins essential for cell invasion. We therefore sought to determine the frequency, amount, and duration of excretion of human milk antibodies to these shared virulence plasmid-associated antigens in populations of different rates of Shigella infection frequency (Mexico City, high; Houston, low). Such antibodies were present in the milk of virtually all the Mexican women but also were present in a large proportion of milk samples from the women living in Houston. The amounts of these antibodies were highest in colostrum but after 2 weeks of lactation fell to stable levels. The frequency and persistence of these antibodies in the milk of the women from Houston suggest that the memory and drive for secretion of these antibodies is extremely long lived.

Antibodies, Bacterial↗
PubMed1991

Antibiotic treatment of bacterial gastroenteritis.

Antibiotic treatment is important in certain etiologies of bacterial gastroenteritis, both for clinical improvement and for eradication of the causative organism from stools, which is important epidemiologically. The etiology, however, is seldom known at presentation in sporadic cases of diarrhea. Thus the decision to initiate antibiotic therapy and the choice of the specific antimicrobial agents should be made on a clinical basis, before culture results are available.

Anti-Bacterial Agents↗
PubMed1991

Evidence for long-term memory of the mucosal immune system: milk secretory immunoglobulin A against Shigella lipopolysaccharides.

Although the common mucosal immune system has generally been considered to have only short-term memory, recent data suggest that long-term memory exists for Shigella virulence plasmid antigens. Because such antigens might cross-react with environmental antigens, we investigated milk for the persistence of antibodies to the specific Shigella lipopolysaccharide (LPS) antigens. Enzyme-linked immunosorbent assays to detect secretory immunoglobulin A (sIgA) against Shigella flexneri and Shigella sonnei LPS in milk samples were developed; 15 random milk samples tested on different days correlated from one day to the next (P = 0.0001). Of 18 Mexican mothers, 18 (100%) had one or more milk samples positive for anti-S. flexneri LPS, 14 (78%) had one or more milk samples positive for anti-S. sonnei LPS, and 14 (78%) had one or more milk samples positive for both. Of 27 Houston mothers, 16 (59%) had one or more milk samples positive for anti-S. flexneri LPS, 7 (26%) had one or more milk samples positive for anti-S. sonnei LPS, and 5 (19%) had one or more milk samples positive for both. Mexican mothers were significantly more likely than Houston mothers to have at least one sample with a positive titer for anti-S. flexneri LPS (P less than 0.02) and at least one sample with a positive titer for anti-S. sonnei LPS (P less than 0.002). Although the Houston women had a lower rate of titer positivity for both Shigella species, the rate was too high to be consistent with short-lived mucosal immunity. It is unlikely that 18 of the 27 Houston women had shigellosis during or just prior to lactation. The data suggest that there exists a long-term hormonally driven memory in the secretory immune system for Shigella spp.

Antibodies, Bacterial↗
PubMed1991

The effect of postnatal age on the adherence of enterohemorrhagic Escherichia coli to rabbit intestinal cells.

Enterohemorrhagic Escherichia coli (EHEC) are associated with hemorrhagic colitis and hemolytic uremic syndrome. These illnesses are typically seen in young children, but are rare before 6 mo of age. The cause of this age restriction is unclear. Because bacterial adherence to intestinal mucosa is considered a critical initial event in pathogenesis, we studied the ontogeny of the adherence of EHEC (O157:H7 and other serotypes) isolated from children with diarrhea, hemorrhagic colitis, or hemolytic uremic syndrome. Adherence was quantitatively determined by incubating radiolabeled bacteria with viable rabbit intestinal cells, which were prepared by treating loops of distal ileum and proximal colon with EDTA, DTT, and citrate. Cells obtained from animals of different ages were studied simultaneously. The adherence of the various EHEC strains varied significantly. A non-O157:H7 E. coli strain 43-12 bound best (35 and 32 bacteria/cell to ileal and colonic cells, respectively) with 48-60% inhibition by D-mannose and alpha-methyl mannoside (p less than 0.01) and 20-28% inhibition by L-fucose (p less than 0.05), but no significant inhibition by other carbohydrates. Analysis of variance and polynomial regression showed that postnatal age significantly affected the adherence to ileal and colonic cells. Adherence during the 1st wk of life was 13-19% of that in the adult animal; it increased gradually, reaching the adult level at about 4 wk of age. Our study shows that postnatal age affects the adherence of EHEC to intestinal cells. These findings are compatible with postnatal development of gut receptors and may be relevant to the age-related risk of EHEC disease in children.

Age Factors↗
PubMed1990

Recent advances in understanding the pathogenesis of the hemolytic uremic syndromes.

One of the requirements for an agent to cause hemolytic uremic syndrome (HUS) is its ability to injure endothelial cells. Shiga-like toxin (SLT) can do this. SLT is produced by Escherichia coli and Shigella dysenteriae serotype 1; both have been implicated as causes of typical HUS. Endothelial cells have receptors (GB3) for SLT and the toxin can inhibit eukaryotic protein synthesis, thereby causing cell death. Glomerular endothelial cell injury or death results in a decreased glomerular filtration rate and many of the perturbations seen in HUS. It is no longer certain that hemolysis is the result of a microangiopathy. Cell injury results in release of von Willebrand multimers; if these are ultra-large, thrombosis may ensue. There is also increasing evidence that neutrophils have a role in the pathogenesis of typical HUS. Streptococcus pneumoniae can also cause HUS and care must be taken to avoid giving plasma to patients with S. pneumoniae-associated HUS. There is compelling evidence that types of HUS are inherited by autosomal recessive and autosomal dominant modes. Patients with autosomal recessive HUS may have recurrent episodes. Mortality and morbidity rates are high for the inherited forms.

Bacterial Toxins↗
PubMed1990

The association of Shiga toxin and other cytotoxins with the neurologic manifestations of shigellosis.

The neurologic symptoms in human shigellosis have often been attributed to Shiga toxin, although its exact role has not been determined. By use of a [3H] thymidine-labeled HeLa cell assay, cytotoxic activity was demonstrated in stool but not cerebrospinal fluid or serum from five patients with shigellosis presenting with seizures or encephalopathy. Bacterial isolates produced 16.0-88.2 CD50 (50% cytotoxic dose) of cytotoxin/mg of protein. The toxin activity in stool and the cytotoxic activity of the isolates were not neutralized by antiserum to purified Shiga toxin. DNA hybridization studies showed that Shigella isolates from these patients lacked the structural genes for Shiga toxin. The cytotoxin produced was also distinct from Shiga-like toxins I and II. Sonicates of the Shigella strains injected intraperitoneally into mice caused lethargy and lethality. The toxin activity was heat-labile and sensitive to trypsin, indicating that its active component is protein. Ultrafiltration and gel filtration chromatography showed a molecular mass of 100-125 kDa. Thus Shiga toxin production is not essential for the development of neurologic manifestations of shigellosis; other toxic products may play a role.

Animals↗
PubMed1990

Fucosylated oligosaccharides of human milk protect suckling mice from heat-stabile enterotoxin of Escherichia coli.

Human milk protects suckling mice from the diarrheagenic effects of heat-stabile enterotoxin of Escherichia coli (ST). To identify the human milk fraction responsible for this protection, pooled skimmed, deproteinated milk was passed through charcoal, whereupon lactose was separated from the oligosaccharides. The oligosaccharides contained ST-protective activity; the lactose did not. The neutral, but not the acidic, fraction exhibited protective activity against ST (22% vs. 57% mortality, respectively; P less than .001). The fucosylated, but not the nonfucosylated, subfractions of the neutral fraction contained the factor protective against ST (35% vs. 50% mortality, respectively; P less than .05). An oligosaccharide isolation scheme based on different principles produced confirmatory results. The commercially available neutral fucosylated oligosaccharides of human milk did not significantly protect the mice from the effects of ST. Thus, the protective factor against ST seems to be a minor neutral fucosyloligosaccharide of human milk.

Animals↗