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T G Cleary

Publications and source records attributed to T G Cleary.

At least 19 recordsLinked to original sources
PubMed1998

Shiga toxin 1 elicits diverse biologic responses in mesangial cells.

BACKGROUND: Shiga toxin 1 (Stx1) is a causative agent in hemolytic uremic syndrome (HUS). Its receptor, the glycosphingolipid globotriaosylceramide (Gb3), is expressed on cultured human endothelial and mesangial cells. Mesangial cell injury in HUS ranges from mild cellular edema to severe mesangiolysis and eventual glomerulosclerosis. We hypothesized that, in addition to endothelial cells, mesangial cells are targets of Stx1. METHODS: Human mesangial cells were exposed to Stx1. Protein synthesis was measured using [35S]-methionine/cysteine. Cell viability was measured as the lysosomal uptake of Neutral Red. Monocyte chemotactic peptide (MCP-1) mRNA and protein were analyzed by Northern blotting and ELISA. RESULTS: Stx1 (0.25 to 2500 ng/ml) resulted in a dose-dependent inhibition of protein synthesis. This effect of Stx1 was potentiated by preincubation of the cells with interleukin-1alpha (IL-1alpha; 2 ng/ml) or tumor necrosis-alpha (TNF-alpha; 500 U/ml). Stx1 had little effect on mesangial cell viability during the first 24 hours of exposure to Stx1. However, prolonged incubation with Stx1 for 48 and 72 hours resulted in a 68% and 80% decrease in cell-viability, respectively. Stx1 elicited a dose and time dependent increase in the levels of MCP-1 mRNA, an effect that was potentiated by preincubation with IL-1alpha. CONCLUSION: These data indicate that mesangial cells are susceptible to the effects of Stx1 in vitro. Stx1 exerts a spectrum of biologic effects on mesangial cells ranging from activation of chemokine genes to a lethal toxic injury. Immunoinflammatory cytokines potentiate the effects of Stx1. Thus, glomerular pathology in HUS may also result from a direct effect of Stx1 on mesangial cells.

Bacterial Toxins↗
PubMed1997

Shiga toxin induces medullary tubular injury in isolated perfused rat kidneys.

To investigate the potential direct nephrotoxicity of Shiga toxin, a putative mediator for hemolytic uremic syndrome, purified toxin (10(-11) M) was added to isolated rat kidneys perfused for 160 min with a Krebs-Henseleit acellular medium enriched with albumin and amino acids. Kidney function and morphology were examined after perfusion with the Shiga toxin vs controls. Shiga toxin did not significantly alter renal perfusion flow, glomerular filtration rate, or tubular sodium reabsorption, but it significantly increased urinary protein excretion (from 61 +/- 23 to 169 +/- 28 microg/min, P < 0.01). On renal morphologic study, Shiga toxin did not induce gross glomerular damage but increased markedly the injury to the medullary thick ascending limbs. In conclusion, Shiga toxin is toxic to rat kidneys ex vivo and in the absence of platelets. Renal damage is manifested by proteinuria and medullary tubular injury. The distribution of this injury suggests a possible synergism between local medullary hypoxia and the toxic tubular or endothelial effects of the toxin. These effects may play a pathogenic role in the tubulo-interstitial injury observed in hemolytic uremic syndrome associated with severe renal failure.

Animals↗
PubMed1997

Giardia.

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Animals↗
PubMed1995

Incomplete hemolytic-uremic syndrome in Argentinean children with bloody diarrhea.

Argentina has an exceptionally high frequency of hemolytic-uremic syndrome (HUS). We sought to define prospectively the role of verocytotoxins (Shiga-like toxins [SLTs]) in 254 Argentinean children with grossly bloody diarrhea during spring and summer. Free fecal SLTs (I/II) and/or DNA probe-positive isolates were found in 99 (39%) of the children. During the follow-up period, HUS developed in 6 patients (4 with evidence of recent SLT infection based on stool studies); another 14 patients had some, but not all, of the abnormalities seen in typical HUS. The development of HUS or incomplete HUS in these children was significantly associated with recent SLT-Escherichia coli infection (p = 0.024). The high incidence of SLT-associated bloody diarrhea in Argentina explains, at least partially, the unusually high frequency of HUS. Our data indicate that incomplete forms of HUS may be common in patients with SLT-associated bloody diarrhea.

Argentina↗
PubMed1995

Leukocyte adhesion deficiency mimicking Hirschsprung disease.

An infant had clinical signs suggestive of Hirschsprung disease as the initial manifestation of leukocyte adhesion deficiency. Chromosome studies showed a deletion of the distal third of the long arm of one chromosome 21, and flow cytometric studies confirmed the defective expression of CD18.

CD11 Antigens↗
PubMed1995

Tumor necrosis factor concentrations in hemolytic uremic syndrome patients and children with bloody diarrhea in Argentina.

Hemolytic uremic syndrome (HUS) is thought to be a vascular endothelial injury disease. The mechanism of injury is unknown although verocytotoxins (Shiga-like toxins (SLTs)) are known to be associated with it. Recent evidence suggests that in vitro treatment of some endothelial cells with tumor necrosis factor alpha (TNF-alpha) dramatically increases their susceptibility to SLTs. We studied 25 children with HUS, 63 children with SLT-positive bloody diarrhea, 62 children with bloody diarrhea not associated with SLTs and 39 children admitted for elective surgery, included as an age- and season-matched control group. The TNF-alpha concentrations were found to be significantly elevated in children with HUS (range, 1 to 95 pg/ml; geometric mean, 32.2 pg/ml) compared with the healthy controls (range, 0 to 53 pg/ml; mean, 12.5 pg/ml; P < 0.001). Because it is hypothesized that TNF-alpha elevation might precede development of HUS, we also studied children with blood diarrhea. The TNF-alpha serum concentrations were significantly higher during the first 10 days after onset of bloody diarrhea than after the first 10 days (P < 0.02). Such elevation could be associated with vascular endothelial glycolipid receptor up-regulation and increased susceptibility to the effects of SLTs.

Argentina↗
PubMed1994

Asymptomatic Shigella infections in a cohort of Mexican children younger than two years of age.

The proportion of Shigella infections that occur asymptomatically in young children has not been established. A community-based cohort study of 367 infants was followed prospectively by weekly home visits from January, 1990, through December, 1991. Stool samples were collected weekly and when diarrhea occurred and were tested for Shigella and other enteropathogens. There were 2925 child months of observation and 65 episodes of Shigella infection. There were 3.1 episodes/100 child months during the warm season (May through September) and 0.97 episode/100 child months during the cold season. Shigella infections were rare during the first 6 months of life but increased with age (P < 0.0001). Overall 55% of detected infections were asymptomatic. The proportion of infections that were asymptomatic increased as age increased (P < 0.01). Symptom status was not significantly associated with Shigella species or season. All isolates from symptomatic and asymptomatic children had the 120- to 140-megadalton virulence plasmid. We conclude that infections with virulent strains of Shigella are commonly asymptomatic in Mexican children during the first 2 years of life.

Age Distribution↗
PubMed1994

Infectious disease of public health significance among children and adolescents in Texas.

In the past decade, many infectious diseases in children that were perceived to have been almost eliminated have returned with a vengeance in Texas. Across the state, vaccination rates are exceptionally low, and outbreaks of measles, mumps, and pertussis have been identified. Tuberculosis cases in children increased 77%, and cases of congenital syphilis increased 578% between 1987 and 1991. The new epidemic of HIV infection has placed additional strain on an already overburdened, inadequate public health system in Texas. This article identifies some of the major infections of public health significance among the children of Texas. A common theme for most of these problems is that they are preventable diseases that are not being prevented. Many children in Texas will suffer now and in the future if these public health problems remain ignored.

Adolescent↗
PubMed1993

Susceptibility to hemolytic-uremic syndrome relates to erythrocyte glycosphingolipid patterns.

Hemolytic-uremic syndrome (HUS) is usually preceded by enteric infection by Shiga-like toxin-producing Escherichia coli (SLT-EC), but most children with SLT-EC diarrhea do not develop HUS. SLT toxicity depends on entry into the target cell via its host cell glycolipid receptor, globotriaosylceramide (Gb3). The relationship between differential susceptibility to HUS and erythrocyte Gb3 levels, as measured by high-pressure liquid chromatography, was studied. Erythrocytes of children with histories of HUS had lower nonhydroxylated fatty acyl (NFA) Gb3 levels than did erythrocytes of controls (1.6 vs. 2.0 nmol/mL of packed cells); these erythrocytes had lower ratios of NFA-Gb3 to lactosylceramide (0.16) than did erythrocytes of SLT-EC diarrheal patients without subsequent HUS (0.30; P < .003) or of healthy controls (0.28; P < .001). The lower erythrocyte Gb3 levels associated with HUS may reflect a genetic predisposition for differential outcomes of SLT-EC gastroenteritis.

Child↗
PubMed1993

Multiply resistant nontyphoidal Salmonella gastroenteritis in children.

From January, 1990, to December 31, 1990, 75 children with multiply resistant Salmonella gastroenteritis were studied at the Children's Hospital "Ricardo Gutierrez" of Buenos Aires. These children ranged from 1 month to 15 years of age. Infection was community-acquired in 20 (26.6%), nosocomially acquired in 50 (66.7%) and undetermined in 5. Thirty-nine (52%) had grossly bloody stools. Fever occurred at some point in the clinical course in 61 children (81.3%) with a duration of 1 to 33 days (mean, 6.7 days). The duration of diarrhea (1 to 69 days) was longer in those who developed complications (P < 0.001). Six (8%) developed enterocolitis (2 with bowel perforation), 1 had a pulmonary abscess and 8 (11.4%) had bacteremia; 4 children died (5.3%). Salmonella typhimurium was the most common serovar (85.3%). Ninety percent minimum inhibitory concentration studies demonstrated that all strains were resistant to ampicillin (> 128 micrograms/ml), cephalothin (> 128 micrograms/ml), cefuroxime (> 128 micrograms/ml), nalidixic acid (> 256 micrograms/ml), rifampin (> 256 micrograms/ml), gentamicin (> 256 micrograms/ml) and tobramycin (256 micrograms/ml); 77.3% of strains were resistant to ceftazidime (32 micrograms/ml), 97.6% to netilmicin (> 256 micrograms/ml), 92.8% to amikacin (256 micrograms/ml), 24.4% to isepamicin (32 micrograms/ml), 5.3% to chloramphenicol (4 micrograms/ml) and 2.7% to cefoxitin (2 micrograms/ml). The 90% minimum inhibitory concentration of cefotaxime and ceftazidime was reduced by the addition of clavulanate. Aggressive multiply resistant Salmonella strains are a major pediatric problem in Buenos Aires.

Adolescent↗
PubMed1993

Evaluation of the molecular epidemiology of an outbreak of multiply resistant Shigella sonnei in a day-care center by using pulsed-field gel electrophoresis and plasmid DNA analysis.

Outbreaks of diarrhea in child day-care centers (DCC) are common. This study was undertaken to evaluate the molecular epidemiology of an outbreak of diarrhea due to Shigella sonnei. This outbreak involved 25 of 52 (48%) DCC children and 14 of 132 (11%) teachers and household contacts. S. sonnei isolates from nine children and five contacts were characterized by antimicrobial susceptibility, plasmid content, plasmid DNA restriction fragment pattern, and pulsed-field gel electrophoresis (PFGE) of total genomic DNA; 33 isolates from Houston, Tex., Chicago, Ill., and Mexico City, Mexico, also were studied. All outbreak isolates were resistant to ampicillin and trimethoprim-sulfamethoxazole and shared five to six plasmids ranging from 3.3 to 70 MDa. A total of 8 of 12 temporally associated nonoutbreak Houston isolates had plasmid profiles and restriction fragment patterns similar to those of the outbreak strain, despite possessing different antibiotic susceptibility patterns. PFGE demonstrated identical DNA patterns among outbreak isolates and similar or identical patterns among temporally associated sporadic Houston isolates with plasmid profiles similar to that of the outbreak strain. All other nonoutbreak strains from Houston, Chicago, and Mexico had plasmid profiles, restriction fragment patterns, and PFGE patterns different from those of the outbreak strain. DCC outbreak isolates could be distinguished from most sporadic isolates by antimicrobial susceptibility testing, but plasmid analysis and PFGE could not differentiate common-source isolates from sporadic isolates in the same location during the same time period, indicating that isolates present in the community were genetically similar to those producing outbreaks in the DCC.

Child Day Care Centers↗
PubMed1993

Comparative efficacy of pivmecillinam and cotrimoxazole in acute shigellosis in children.

In a prospective randomized double-blind trial, pivmecillinam was compared with cotrimoxazole (TMP-SMX), both given orally for a period of 5 days, for the treatment of 59 children with shigellosis. 29 patients were treated with pivmecillinam and 30 with cotrimoxazole. 14% of shigella organisms isolated were resistant to pivmecillinam and 21% to TMP-SMX. The diarrhea persisted for a mean (+/- SD) period of 74 +/- 24.8 h in the pivmecillinam-treated patients versus 73.8 +/- 34 h in the TMP-SMX-treated patients. Duration of fever, positive stool culture, visible blood, occult blood, and pus cells in the stools were similar for both treatment groups. Five patients (17%) in the pivmecillinam group and 4 patients (13%) in the cotrimoxazole group fulfilled the clinical criteria that defined treatment failure. One patient (3.4%) in the pivmecillinam group and 2 (6.6%) in the TMP-SMX group evidenced recurrence of the diarrheal symptoms at the follow-up visit. No major drug-related side effects were observed in either group. We concluded that pivmecillinam is equivalent to cotrimoxazole in the treatment of shigellosis in children.

Acute Disease↗
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↗