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Biomedical subjects

M Petric

Publications and source records attributed to M Petric.

At least 91 records · Page 5Linked to original sources
PubMed1990

Clostridium difficile invasion and toxin circulation in fatal pediatric pseudomembranous colitis.

The direct involvement of Clostridium difficile in the lesional tissue of pseudomembranous colitis has not been demonstrated; the organism's effects have been assumed to be strictly toxin mediated. Because C. difficile cytotoxin may be found incidentally in the intestinal lumina of asymptomatic infants, the role of the organism in a variety of pediatric intestinal diseases is uncertain. The authors studied seven cases of fatal pediatric pseudomembranous colitis in which the presence of C. difficile was uniformly demonstrable in lesional tissues with the use of both an intestinal spore stain and a specific immunostain. The patients had either underlying Hirschsprung's disease or hematologic malignancy; the striking pathologic features peculiar to these patients were altered mucosal mucin and immunologic barriers in the former group and neutropenia in the latter. Two patients had demonstrable circulating cytotoxin in serum or ascitic fluid, and C. difficile was identified invading colonic mucosa or submucosa. Such phenomena did not occur in control pediatric patients with multiple other intestinal lesions. Altered host factors may be responsible for the intestinal invasion of C. difficile and its systemic toxin circulation in cases of fatal pediatric pseudomembranous colitis.

Adolescent↗
PubMed1990

The incidence of viral-associated diarrhea after admission to a pediatric hospital.

For determination of the incidence of viral-associated diarrhea after admission to a pediatric hospital, all patients admitted to general pediatrics, cardiology, and neurosurgery wards without diarrhea between January 1 and July 31, 1985 were followed 5 days per week for presence of diarrhea, etiologic agent, and possible risk factors. A total of 1,530 patients were followed for 3,642 days. Of these patients, 69 developed 80 nosocomial diarrhea episodes after 72 hours in hospital for a nosocomial diarrhea rate of 4.5 infected children per 100 admissions. Of 358 patients with an infected roommate, 37 (10.3%) developed nosocomial diarrhea. Etiologic agents recognized included rotavirus (43%), calicivirus (16%), astrovirus (14%), minreovirus (12%), adenovirus (8%), Salmonella sp. (4%), and parvo/picornavirus (3%). The nosocomial diarrhea rate by age was: 0-11 months, 8.8%; 12-35 months, 3.6%; and 36 months or more, 0.6%. The rate by length of stay was: 3-7 days, 8.4%; 8-14 days, 10.4%; 15-21 days, 7.9%; and 22 days or more, 8.8%, and by number of roommates/1,000 patient-days it was: 0-1, 15.7; 2 to 3, 27.7; and 4 or more, 45.2. Patients who acquired diarrhea were more likely to be diapered (9.6% vs. 1.8%, p less than 0.001). Playroom use was not significantly different in the two groups. A total of 64 patients developed diarrhea within 72 hours of admission (community diarrhea rate = 4.2). Nosocomial viral-associated diarrhea is almost exclusively a disease of diapered children less than age 36 months and occurs at any time during hospital stay. It is more common in multibed rooms, but does occur in single-bed rooms.

Age Factors↗
PubMed1990

Six-year retrospective surveillance of gastroenteritis viruses identified at ten electron microscopy centers in the United States and Canada.

To identify the prevalence, seasonality and demographic characteristics of patients with viral gastroenteritis, we reviewed 6 years of retrospective data on viral agents of gastroenteritis screened by electron microscopy at 10 centers in the United States and Canada. From 52,691 individual electron microscopic observations, a virus was detected in 16% of specimens, and the yearly positive detection rate among centers ranged from 8 to 34%. Rotavirus was the agent most commonly observed (26 to 83%), followed by adenoviruses (8 to 27%, respiratory and enteric combined), and small round viruses (SRVs) (0 to 40%) which were second most common at two of the centers. Rotavirus and astrovirus detections occurred more often in the winter but seasonal trends in detection were not apparent for the other viruses. Of all astroviruses detected 64% were found in infants (less than 1 year); unlike the other agents studied SRVs were detected in a large percentage of infants (48%) and older children and adults (20%). Among hospitalized patients a majority of all astroviruses, caliciviruses and SRVs were detected 7 days or more after admission in contrast to both rotaviruses and adenoviruses which were more likely to be detected earlier. The data suggest that SRVs are common agents of gastroenteritis and may be important causes of nosocomial infections. Because of the relative insensitivity of direct electron microscopy as a screening method for SRVs, astroviruses and caliciviruses, these data probably underestimate the true prevalence of disease caused by these agents.

Adenoviruses, Human↗
PubMed1990

Neutralization receptor-based immunoassay for detection of neutralizing antibodies to Escherichia coli verocytotoxin 1.

The NeutRELISA, a modification of the receptor enzyme-linked immunosorbent assay developed for the detection of verocytotoxin 1 (VT1) which permits the rapid detection of neutralizing antibodies (NAb) against this toxin, has been performed. A standard concentration of VT1 was preincubated with VT-immune or nonimmune rabbit serum. The serum-toxin mixtures were then added to microtiter plates coated with deacylated globotriosyl ceramide (lyso-Gb3). The reduction of VT1 binding to lyso-Gb3 in the immune serum-toxin mixtures compared with the VT1-Gb3 binding in the nonimmune serum-toxin mixtures was detected by using mouse monoclonal antibody to VT1. After standardization of the NeutRELISA with rabbit sera, 57 human control serum samples were tested to establish a cutoff value below which NeutRELISA results would be considered positive. Thirty-three single serum samples known to demonstrate NAb to VT1 by biological assay reproducibly demonstrated VT1 NAb when tested by the NeutRELISA. There was a close correlation between the biological VT1 neutralization assay and the NeutRELISA. This assay offers a practical, rapid, and reliable approach for the detection of NAb to VT1 and other verocytotoxins.

Antibodies, Bacterial↗
PubMed1989

Ultrastructural, biochemical and biophysical properties of an erythrocytic virus of frogs from Ontario, Canada.

Frog erythrocytic virus (FEV), one of the largest icosahedral viruses, is enveloped, measures up to 450 nm in diameter, and contains double stranded DNA. The virus is found in the cytoplasm of erythrocytes of Rana catesbeiana, Rana septentrionalis, and Rana clamitans from Algonquin Park, Ontario (Canada). Acidophilic inclusions in infected erythrocytes stained with Giemsa's stain correspond to viroplasms from which FEV buds and forms aggregates of virus particles as seen in the electron microscope. Frog erythrocytic virus appears to acquire its envelope from lamellar membranes which surround the virus particles. The virus is structurally sensitive to cesium chloride, potassium tartrate and glycerol. It is also sensitive at pH 1 to 5 and a temperature of 56 C for 15 min. The virus contains at least 16 proteins which range in relative molecular mass from 19.5 to 91.0 kilodaltons (kDa), with two major proteins of 31.0 and 43.0 kDa. The viral DNA has a buoyant density of 1.690 +/- 0.005 g/ml, guanine plus cytosine ratio of 25 to 36%, and a melting temperature of 82 to 86 C. Data from this study indicate that FEV should be included in the family Iridoviridae.

Animals↗
PubMed1988

Globotriosyl ceramide is specifically recognized by the Escherichia coli verocytotoxin 2.

Two Escherichia coli cytotoxins (verotoxins 1 and 2) have been previously implicated in the cytopathology of the Hemolytic Uremic Syndrome. We have examined the glycolipid binding specificity of verotoxin (VT)2. This toxin specifically binds to globotriosyl ceramide (galactose alpha 1-4 galactose beta 1-4 glucosyl ceramide). Removal, or substitution of the terminal a galactose residue with N-acetyl galactosamine in beta 1-3 linkage, deletes binding activity. The toxin does not recognize similar terminal a galactose residues on a glycoglycerolipid. Thus the binding specificity of VT2 is the same as previously reported for VT1. Liposomes containing globotriosyl ceramide are able to specifically remove VT1 and VT2 cytotoxicity and cell lines selected in vitro for resistance to VT1 are cross resistant to VT2.

Bacterial Toxins↗
PubMed1988

A family outbreak of hemolytic-uremic syndrome associated with verotoxin-producing Escherichia coli serotype O157:H7.

All five siblings (three boys and two girls, aged 1.5-9 years) in a family developed hemolytic-uremic syndrome associated with verotoxin-producing Escherichia coli O157:H7 at a lakeside vacation cottage during the fall of 1985. All five were hospitalized and made a full recovery. Both parents remained asymptomatic, and neither had evidence of this infection. In four children who were investigated prospectively, free verotoxin was still detectable in the stools for between 3 and 7 weeks. The prodromal diarrheal illness in the children occurred over a 10-day period. The epidemic curve was consistent with a point-source outbreak, but continuous exposure or person-to-person transmission could not be ruled out. The source of the infection was not identified.

Bacterial Toxins↗
PubMed1988

Anticomplementary activity in serum of women with a history of recurrent pregnancy loss.

Viral complement fixation tests on women with a history of recurrent pregnancy loss were complicated by the presence of anticomplementary activity. This activity reflects the presence of a factor(s) in a patient's serum that nonspecifically fixes complement. When all patient sera tested were compared, 64.7% of women with recurrent pregnancy loss had anticomplementary activity compared with 22.0% among normal fertile pregnant women (p less than 0.01). In delineating when anticomplementary activity developed, it was found that 41.8% of women with recurrent pregnancy loss compared with 12.9% of normal pregnant women had this activity on entry to the study (p less than 0.01). This was primarily due to the fact that among women with recurrent pregnancy loss 50.0% of the pregnant versus 33.0% of the nonpregnant women had activity (NS). However, 55.2% of the anticomplementary negative women with recurrent pregnancy loss converted to a positive status compared with 15.4% of normal women (p less than 0.05). This was directly influenced by a conversion rate of 78.6% during pregnancy among women with recurrent pregnancy loss who entered the study nonpregnant and with no known cause for loss compared with a 33.3% conversion rate in their pregnant counterparts with recurrent pregnancy loss (p less than 0.025). Conversion to positive anticomplementary status occurred primarily by 20 weeks of gestation and appeared to be transient. Overall there was no association between the presence of anticomplementary activity and cervical colonization with genital mycoplasmas. The data suggest that women with a history of recurrent pregnancy loss develop a serum factor(s), usually by 20 weeks' gestation, that fixes complement. Thus these observations describe an additional anomaly in the immune system of women who experience recurrent pregnancy loss.

Abortion, Habitual↗
PubMed1987

Glycolipid binding of purified and recombinant Escherichia coli produced verotoxin in vitro.

Escherichia coli verotoxin (also known as Shiga-like toxin) has been implicated in the aetiology of the hemolytic uremic syndrome and hemorrhagic colitis. The glycolipid binding specificity of verotoxin purified from E. coli H30 and verotoxin cloned from bacteriophage H19B has been examined. Verotoxin from both sources binds specifically to globotriosyl ceramide containing the carbohydrate sequence galactose alpha 1-4galactose beta 1-4glucose-ceramide. Removal of the terminal galactose or substitution with N-acetylgalactosamine in beta 1-3 linkage deletes toxin binding activity. A ceramide trihexoside species, consistent with a globotriosyl ceramide structure was shown to be the major verotoxin-binding glycolipid of cultured vero cells which are routinely used to measure the cytotoxicity of toxin samples.

Bacterial Toxins↗
PubMed1987

Prevalence of antibody to Chlamydia trachomatis in spontaneous abortion and infertility.

A higher prevalence of Chlamydia trachomatis antibody occurred in 57.6% of women with recurrent abortion, but not in their male partners, compared to 33.7% of normal pregnant women (p less than 0.01) and 44.2% of infertile women (NS). The mean titer for the recurrent abortion group was not significantly elevated, compared to controls. Women with blocked fallopian tubes had the highest prevalence of elevated titers (p less than 0.01) and the highest mean titer (p less than 0.001). Despite multiple testing, no women or men were chlamydia culture-positive. The lack of isolation among patients with antibody could be due to cryptic infection at a site not amenable to culture or to inhibition by secretory IgA. There could also be nonspecific stimulation of chlamydial antibody caused by other infections such as mycoplasma. The presence, though at a low level, of antibody in culture-negative patients suggests chlamydia may not be directly associated with recurrent abortion but reflect previous exposure to chlamydia or an altered immune system.

Abortion, Habitual↗
PubMed1987

Surface properties of the Vero cytotoxin-producing Escherichia coli O157:H7.

Strains of Escherichia coli serotype O157:H7 are Vero cytotoxin-producing enteric pathogens which have been associated with sporadic cases and outbreaks of hemorrhagic colitis and with the hemolytic uremic syndrome in humans. In addition to toxin production, adherence of many pathogenic bacteria to intestinal mucosal surfaces is a critical primary step in the pathogenesis of diarrheal diseases. Although E. coli serotype O157:H7 organisms adhere to intestinal epithelia of orally infected animals in a pattern morphologically identical to that previously described in adherent, effacing E. coli infections, the mechanisms of bacterial adherence are not known. To determine the cell surface adhesins which mediate attachment of E. coli O157:H7 to epithelial surfaces, we evaluated the surface properties of these organisms. Five strains isolated from children with the hemolytic uremic syndrome were grown both in broth cultures and on agar media. Adherence and invasion of E. coli O157:H7 in Intestine 407 and HEp-2 epithelial cell lines was quantitated using an enteroinvasive E. coli strain (serotype O164:NM) as a control. Cell surface properties of E. coli O157:H7 were evaluated by agglutination of a series of erythrocytes, transmission electron microscopy, DEAE-ion-exchange chromatography, and hydrophobic interaction chromatography. E. coli O157:H7 strains adhered to but did not invade either Intestine 407 or HEp-2 cells. Homologous O157:H7 rabbit antiserum blocked attachment of bacteria to tissue culture cells, in contrast to heterologous antiserum and preimmune rabbit serum, which did not inhibit attachment of E. coli O157:H7. None of the five O15:H7 isolates mediated mannose-resistant hemagglutination under any of the in vitro culture conditions. One isolate mediated mannose-sensitive hemagglutination after serial passage in broth cultures. Pili and fibrillae were not visualized by electron microscopy on nonhemagglutinating organisms, but pili were demonstrated on the one isolate which mediated mannose-sensitive hemagglutination. All O157:H7 strains demonstrated high anionic surface charge (DEAE) but low surface hydrophobicity properties (hydrophobic interaction chromatography). The findings suggest that surface structures other than pili can mediate attachment of serotype O157:H7 bacteria to epithelial cells in vitro.

Bacterial Adhesion↗
PubMed1987

Effects of cycloheximide and puromycin on cytotoxic activity of Escherichia coli verocytotoxin (Shiga-like toxin).

Verocytotoxin (VT)-producing Escherichia coli is closely associated with hemorrhagic colitis and hemolytic uremic syndrome. The diagnosis of this infection requires the demonstration of VT activity in fecal filtrates or the isolation of VT-producing E. coli from stools. To improve the sensitivity of the Vero cell assay for detecting VT, we investigated the interaction between this toxin and cycloheximide and puromycin, agents which, like VT and the related Shiga toxin, are protein synthesis inhibitors. Cycloheximide-treated cells were found to be about eightfold more sensitive to VT, this effect being most pronounced when the drug was added before the toxin. In contrast, puromycin treatment had an antagonistic effect in that it decreased the sensitivity of the cells to VT. In assays of VT in fecal filtrates, the addition of cycloheximide (at 4 to 8 micrograms/ml) increased the sensitivity without affecting the specificity of the assays. Likewise, the use of cycloheximide led to an increase in the sensitivity of the serum VT-neutralizing antibody test by a factor of over eightfold.

Animals↗
PubMed1987

Immunochemical analysis of immune response to Chlamydia trachomatis in Reiter's syndrome and nonspecific urethritis.

Chlamydia trachomatis (Ct) has been proposed as a causative agent in Reiter's syndrome (RS) when an infection occurs in a susceptible host. To assess whether this susceptibility is reflected in a characteristic humoral immune response we compared patients with complicated (RS) and uncomplicated courses of nonspecific urethritis (NSU). Geometric mean titres of antibodies to C. trachomatis by immunofluorescence were 89.6 for RS, 80.0 for NSU and 16.0 for normals. 125I-Protein A probing of immunoblotted antigens of C. trachomatis revealed no band unique to RS. 125I-anti-IgA probing of immunoblots demonstrated reactivity with the 59,000 dalton antigen in 11/11 RS and 2/6 NSU. The major outer membrane protein of C. trachomatis (40,000 daltons) bound immunoglobulin nonspecifically. There was no clearly differentiating feature between HLA-B27-positive and B27-negative RS. One sequentially studied patient revealed an augmentation in synovial fluid IgA reactivity during the course of disease. No pattern of humoral immune response to C. trachomatis could be regarded as specific for RS nor for HLA B27-positivity. The study did not identify a Reiter's-specific antigen in C. trachomatis but demonstrates the usefulness of applying blotting techniques to population studies of HLA modulation of immune response to infectious agents.

Adult↗