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Biomedical subjects

H Lior

Publications and source records attributed to H Lior.

At least 19 recordsLinked to original sources
PubMed1999

Molecular typing methods to investigate transmission of Escherichia coli O157:H7 from cattle to humans.

The utility of phage typing, pulsed-field gel electrophoresis (PFGE), and plasmid profile analysis was compared, to differentiate between Canadian Escherichia coli O157:H7 strains of human (n = 27) and cattle (n = 24) origin. The diversity indices for phage typing, plasmid analysis and PFGE were 0.85, 0.69 and 0.93, respectively. PFGE and phage typing were also applied to study the role of direct transmission of E. coli O157:H7 from cattle to humans on isolates collected from two separate farm outbreaks. PFGE showed that more than one E. coli O157:H7 strain with varying PFGE DNA subtype profiles, may be responsible for an outbreak, and that more than one E. coli O157:H7 subtype may be circulating on a particular farm at any one time. To our knowledge, this is one of the first reports where PFGE typing was used to verify the direct transmission of E. coli O157:H7 from cattle to humans.

Animals↗
PubMed1998

Risk factors for infection with verocytotoxigenic Escherichia coli in cattle on Ontario dairy farms.

Risk factors for prevalent infection with verocytotoxigenic Escherichia coli (VTEC) were studied in a random sample of 886 cows and 592 calves under 3 months of age on 80 randomly selected dairy farms in southern Ontario. Fecal-culture supernatants from each animal were screened for verocytotoxicity using a Vero cell assay (VCA) and for verocytotoxin (VT) genes by a polymerase chain reaction (PCR) procedure. Up to 20 F. colt isolates from positive samples were tested for VT production using VCA and PCR. VTEC isolates were serotyped. Farm managers were interviewed using a standardized questionnaire to obtain information on farm- and individual animal-level management practices and characteristics. There was a significant (P < 0.001) positive association between age of calves and their VTEC infection status, and calves were significantly more likely to be infected than cows. The proportion of calves infected on the farm was positively associated with both the use of regular pails for feeding calves (as opposed to nipple bottles or nipple pails) and bringing new animals into the herd in the previous year.

Age Factors↗
PubMed1998

Risk of hemolytic uremic syndrome after sporadic Escherichia coli O157:H7 infection: results of a Canadian collaborative study. Investigators of the Canadian Pediatric Kidney Disease Research Center.

OBJECTIVES: The objectives of this study were to better estimate the age-specific risks of hemolytic uremic syndrome (HUS) and hemolytic anemia after Escherichia coli O157:H7 infection among a representative cohort of both referred and nonreferred children with documented illness from the province of Alberta and to compare this with the rates in children evaluated at referral centers in the rest of Canada. STUDY DESIGN: Children with HUS or E. coli O157:H7 gastroenteritis were eligible if they were < 15 years of age. Hemoglobin, blood smear, urinalysis, and serum creatinine were obtained 8 to 10 days after the onset of diarrhea to ascertain for hemolysis, anemia, thrombocytopenia, and renal injury. Subjects were monitored for 1 month. RESULTS: From June 1991 to March 1994, HUS was diagnosed in 205 children. Of these 77% had evidence of E. coli O157:H7 infection. A further 582 children had E. coli O157:H7 gastroenteritis, of whom 18 had hemolytic anemia. The risk of HUS after E. coli O157:H7 infection in Alberta was 8.1% (95% confidence interval, 5.3 to 11.6) compared with 31.4% in referral centers in the rest of Canada. In Alberta the highest age-specific risk of HUS/hemolytic anemia was 12.9% in those < 5 years of age. CONCLUSIONS: These data will help guide clinical care and provide a basis for estimating the sample sizes required in future treatment trials for the secondary prevention of HUS.

Adolescent↗
PubMed1997

Persistence of Escherichia coli O157:H7 in dairy cattle and the dairy farm environment.

The persistence of Escherichia coli O157:H7 in cattle and the farm environment was investigated on eight Ontario dairy farms positive for E. coli O157:H7 in a longitudinal study commenced one year previously. Faecal samples from cows, calves, humans, cats, rodents, wild birds, a composite fly sample and numerous composite and individual environmental samples were cultured and tested for verotoxin-producing E. coli (VTEC). VTEC isolates were serotyped and E. coli O157:H7 isolates were phage typed. E. coli O157:H7 phage type 34 was isolated from one calf on each of two farms. The same phage type had been isolated on one of these farms 12 months earlier. Most E. coli O157:H7-positive animals and farms became culture-negative within 2 and 3 months, respectively. E. coli O157:H7 was not isolated from any environmental samples, although evidence of VTEC was found in composite samples from calf feeders (19.1%), calf barn surfaces (18%), cow feeders (14.9%), flies (12.5%), cow barn surfaces (11.3%), and individual milk filters (12.5%). VTEC belonging to 21 non-O157 serotypes were isolated from 24 cows (8.2%), 21 calves (18.3%), 2 cow feeder samples (3.0%), and 1 calf feeder sample (4.8%). Shedding of E. coli O157:H7 by infected dairy cattle appears to be transient and persistence of E. coli O157:H7 was not demonstrated from the farm environment sites tested.

Animals↗
PubMed1997

In vitro virulence factors of Arcobacter butzleri strains isolated from superficial water samples.

Eighteen isolates of A. butzleri from river water samples were examined for their biotype, serogroup and putative virulence characteristics. Toxin profiles based on cytotonic, cytotoxic and cytolethal distending factors were determined after analysis responses in Vero and CHO cells Adhesivity and invasivity tests were performed on HeLa and Intestine 407 cells. Six biotypes and five serogroups were determined in our isolates. All strains but one induced cytotoxic effects on cells in culture. The cytotoxic negative strain caused elongation of CHO cells (a cytotonic-like effect). This strain was the only one which adhered to cells in vitro. Invasiveness was never observed. Our results show a phenotypic heterogeneity of arcobacters isolated from environmental sources, and indicate that some strains could be potentially virulent.

Animals↗
PubMed1997

Species, biotype and serogroup of Campylobacter spp. isolated from children with diarrhoea over a ten-year period.

From 1981 to 1990, stool samples from 6403 gastroenteritis cases were examined for the presence of campylobacters as well as Salmonella, Shigella, Aeromonas species and Yersinia enterocolitica. The percentages of isolation were the following: campylobacters 10.8 (86.1% of isolates were C. jejuni and 13.9% were C. coli), Salmonella spp. 8.4, Aeromonas spp 1.4, Yersinia enterocolitica 0.3. Shigella spp. were isolated only occasionally. Predominant biotypes of campylobacters were C. jejuni I (69.5%), C. jejuni II (29.5%) and C. coli I (92.7%). The six most common LIO serogroups-36; 4; 1; 28.53; 11; 2-accounted for 50% ca. of typable strains. Campylobacters are the most common etiological agent of bacterial enteritis in children living in this area of Tuscany. The species and serogroup determination can be useful from an epidemiological point of view.

Aeromonas↗
PubMed1996

Pulsed-field gel electrophoresis indicates genotypic heterogeneity among Campylobacter upsaliensis strains.

To determine the genomic relatedness among a selection of animal and human Campylobacter upsaliensis isolates, macrorestriction profiles were generated for 20 C. upsaliensis strains, among 7 serogroups, using pulsed-field gel electrophoresis (PFGE). XhoI, SalI and SacII restriction enzyme profiles indicated genomic heterogeneity among strains. Using XhoI and SacII restriction enzyme digestion, genomic similarities between some pairs of strains were Lior serogroup specific. The genomic sizes of these isolates varied from 1.74 to 2.09 Mb. These results demonstrate molecular heterogeneity of this species similar to that found among Helicobacter pylori isolates. Among C. upsaliensis strains, PFGE is highly discriminatory and should prove a useful molecular typing method for epidemiological purposes.

Animals↗
PubMed1996

Electrophoretic and immunoblot analysis of Campylobacter fetus lipopolysaccharides.

Proteinase K-digested cell lysates from 25 Campylobacter fetus subspecies fetus and C. fetus subsp. venerealis strains were examined by SDS-PAGE and immunoblotting. Three SDS-PAGE lipopolysaccharide (LPS) profiles were observed. Two profiles were consistent with those previously reported for serogroup A and serogroup B and AB isolates and were distinguished by the relative mobility of bands in the O-chain region and by a strong reaction on immunoblots with homologous antisera. The third profile was similar but had faster migrating O-chain bands. Immunoblot reactions using homologous and heterologous adsorbed antisera showed that the O-antigen of the C. fetus subsp. fetus reference strain and other profile 2-type LPS strains was distinct from the O-antigens of strains with profile 1- or profile 3-type LPS. O-antigens of strains with profile 1- and profile 3-type LPS had shared epitopes. One strain had core components but no detectable O-antigens. Common core LPS antigens appear to be present in all strains and antibodies to common core LPS epitopes may be useful reagents for rapid detection of C. fetus.

Animals↗
PubMed1996

Prevalence of the eaeA gene in verotoxigenic Escherichia coli strains from dairy cattle in Southwest Ontario.

This study determined the prevalence of the eaeA gene and its relationship to serotype and type of verotoxin produced in a collection of 432 verotoxigenic Escherichia coli (VTEC) obtained from the faeces of healthy cows and calves in a systematic random survey involving 80 dairy farms in Southwest Ontario. A PCR amplification procedure involving primer pairs which target the conserved central region of the O157:H7 eaeA gene showed that 151 (35.2%) strains were positive for the eaeA gene. All isolates (9-21 for each O group) of O groups 5, 26, 69, 84, 103, 111, 145 and 157 were positive, whereas all isolates (7-34 for each O group) of O groups 113, 132, and 153 and serotype O156:NM (38 isolates) were negative for eaeA. Seventy-three percent of 130 isolates of eaeA-positive serotypes produced VT1 only compared with 20% of 253 isolates of eaeA-negative serotypes. We conclude that there is a strong association between certain O groups and the eaeA gene, that serotypes of eaeA-positive and eaeA-negative VTEC implicated in human and cattle disease are present at high frequency in the faeces of healthy cattle, that VT1 is more frequently associated with eaeA-positive than with eaeA-negative serogroups, and that the eaeA gene is more frequently found in VTEC from calves compared with VTEC from adult cattle.

Animals↗
PubMed1996

Vero cytotoxigenic Escherichia coli infection in dairy farm families.

Fecal samples from 335 dairy farm residents and 1458 cattle on 80 farms were tested for Vero cytotoxin (VT)-producing Escherichia coli (VTEC). Residents were also tested for antibodies to VT1 and O157 lipopolysaccharide (LPS). Residents and cattle on farms with VTEC-positive persons or E. coli O157:H7-positive cattle were retested. Twenty-one persons (6.3%) on 16 farms (20.8%) and 46% of cattle on 100% of the farms had VTEC in fecal samples. Human VTEC isolates included E. coli O157:H7 and 8 other serotypes, 4 of which were present in cattle on the same farms. More persons had antibodies to VT1 (41%) than to O157 LPS (12.5%). Seropositivity to O157 LPS was associated with isolation of E. coli O157:H7 on the farm (P = .022). Human VTEC infection was negatively associated with age (P < .05) and was not associated with clinical illness. Many dairy farm residents experience subclinical immunizing VTEC infections at a young age, which frequently involve non-O157 VTEC found in cattle.

Adolescent↗
PubMed1996

A selective medium for the isolation of Arcobacter from meats.

A method, including enrichment in Arcobacter Selective Broth (ASB) and isolation on semisolid Arcobacter Selective Medium (ASM) under aerobic conditions at 24 degrees C, is described for the isolation of Arcobacter from retail meat products. Selective agents used in ASB and ASM were cefoperazone, trimethoprim, piperacillin and cycloheximide. Arcobacters were isolated from 53 (24.1%) of 220 poultry meat products and also, at lower incidence from samples of beef and pork. The isolates were identified as A. butzleri or A. butzleri-like and belonged to a wide variety of serotypes and biotypes.

Animals↗
PubMed1996

Restriction fragment length polymorphism of flagellin genes of Campylobacter jejuni and/or C. coli isolates from Egypt.

The conservation of flagellin genes from thermophilic Campylobacter spp. strains isolated in Egypt was evaluated by a restriction fragment length polymorphism (RFLP) assay. The flaA and flaB genes were amplified from 59 independent clinical isolates and digested with EcoRI and PstI, and the resulting patterns were compared with each other and with previously described RFLP groups. The results indicate that the isolates fell into 14 groups for flaA and 11 groups for flaB, 9 of which have been described, and that considerable genetic variability exists among isolates belonging to the same LIO serogroup. In most cases, the flaB gene displayed the same RFLP pattern as that of the flaA gene of the same strain, although some variability was observed. The data suggest that more variability of flagellin genes exists within the LIO serogroups common to Campylobacter field isolates from Egypt than has previously been reported for North American isolates.

Base Sequence↗
PubMed1995

Restriction fragment length polymorphisms among the flagellar genes of the Lior heat-labile serogroup reference strains and field strains of Campylobacter jejuni and C. coli.

Several typing systems have been described for Campylobacter jejuni and C. coli, to assess the complex epidemiology of these important enteric pathogens. In the present study two typing methods, slide agglutination according to the Lior scheme, and the demonstration of restriction-fragment length polymorphisms (RFLP) of flagellar genes, have been used in parallel on a set of 194 strains. This set comprised 118 sero-reference strains of C. jejuni and C. coli of the Lior scheme, as well as 76 clinical isolates. All isolates were serotyped and subjected to PCR for amplification of flagellar genes, and the PCR product was restricted with Alu I. Flagellar genes could be amplified in 152 strains. Among 85 seroreference strains, 74 different RFLP patterns were observed, and among 67 clinical isolates, there were 36 patterns. There was only limited correlation between flagellar RFLP and the Lior serogroup, and the variability of patterns in serogroups HL2 and HL4 were as marked as the variability between serogroups. Flagellar gene RFLP patterns are shown to be stable, highly discriminatory epidemiologic markers.

Animals↗
PubMed1995

A phase I study of chemically synthesized verotoxin (Shiga-like toxin) Pk-trisaccharide receptors attached to chromosorb for preventing hemolytic-uremic syndrome.

A double-blind, placebo-controlled study was conducted to document possible side effects associated with oral consumption of synthetic verotoxin (VT, shiga-like toxin) Pk-trisaccharide receptor sequences attached to Chromosorb (Synsorb-Pk) by healthy adult volunteers. Synsorb-Pk reclaimed from volunteer stool samples was also analyzed to determine if its VT-binding activity was affected by exposure to the pH extremes and digestive processes of the human gastrointestinal tract. No participant reported any Synsorb-Pk-related adverse reactions, and no clinically important trends in laboratory data were evident. Synsorb-Pk recovered from stools retained its ability to absorb VT in polymyxin extracts of VT-producing Escherichia coli and also neutralized VT when mixed in vitro with VT-positive stools from children with hemorrhagic colitis or hemolytic-uremic syndrome (HUS). These results suggest a potential use for Synsorb-Pk in preventing HUS in patients infected with VT-producing E. coli.

Absorption↗
PubMed1995

Prevalence and clinical significance of vero-cytotoxin-producing Escherichia coli (VTEC) isolated from cattle in herds with and without calf diarrhoea.

To determine the clinical significance and prevalence of Vero cytotoxin (VT)-producing E. coli (VTEC) in Swiss cattle, faecal swabs and milk samples of 93 cattle from two farms with calf diarrhoea, and of 54 cattle from two similar farms without clinical problems, were screened for VTEC by PCR and colony-blot hybridization. On average, 21% of all cows were positive for VTEC by PCR, without differences between farms with and without diarrhoea problems. By contrast, VTEC were detected by PCR in 60% of animals younger than 2 years from farms with diarrhoea problems, whereas only 32% of comparable control animals from farms without clinical problems had VTEC. No VTEC were detected in the milk samples. A variety of toxin types, antimicrobial-susceptibility patterns and serotypes were found by colony-blot hybridization, among the VTEC in individual herds. However, there was a significant relationship between the VT1-only toxin type and the presence of antimicrobial resistance and clinical disease in calves. No association could be found between levels of VTEC excretion and the presence of diarrhoea. This is the first study to report systematic quantitative data on numbers of VTEC in faecal samples of cattle positive for VT genes by PCR.

Animals↗
PubMed1995

Evaluation of commercial antisera for Shigella serogrouping.

Shigella serogrouping antisera from six companies (Becton Dickinson, Denka, Difco, Murex, Roach, and Sanofi-Pasteur) intended for the slide agglutination test and those of the Wellcolex Colour Shigella latex agglutination test were evaluated to identify quality products for Shigella identification. Forty-six reference Shigella strains (one for each serotype and species), 50 clinical strains (21 S. flexneri, 21 S. sonnei, 4 S. dysenteriae, 4 S. boydii) representing the most prevalent species and serotypes encountered in Quebec, and 9 non-Shigella strains were tested according to the manufacturers' instructions. A 3+ reaction (> or = 75% agglutination) was considered positive for the slide agglutination tests. Sensitivity varied from 47% (Roach) to 94% (Difco). For the 105 strains tested, accuracy ranged from 53% (Roach) to 91% (Wellcolex). Specificity varied from 97 to 100% for group A antisera, from 96 to 100% for group B antisera, from 88 to 100% for group C antisera, and from 95 to 99% for group D antisera. The costs of reagents required to test one strain varied from $3.50 to $13.20 (in Canadian dollars). In conclusion, Roach reagents proved to be unsatisfactory for Shigella serogrouping. Among those from the remaining companies, the Denka, Difco, and Wellcolex reagents met a performance standard of 90% accuracy.

Agglutination Tests↗