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J F Prescott

Publications and source records attributed to J F Prescott.

At least 19 recordsLinked to original sources
PubMed1996

Streptococcal toxic shock syndrome in dogs.

OBJECTIVE: To determine the clinical, pathologic, and bacteriologic findings in dogs that developed severe invasive infections with group G streptococci (GGS) over a 6-month period in southern Ontario. DESIGN: Prospective case series. ANIMALS: 7 dogs n southern Ontario with severe streptococcal infection during a 6-month period. PROCEDURE: Using pulsed-field gel electrophoresis, molecular typing of streptococcal isolates was performed. Isolates were examined for the M protein gene emm1.0, pyrogenic exotoxin genes speA, speB, speF, hyaluronic acid synthase genes hasA, hasB, and for C5a peptidase gene scpA by use of DNA probes or polymerase chain reaction. RESULTS: 3 dogs with streptococcal shock without necrotizing fasciitis died or were euthanatized within 48 hours of admission, whereas 4 dogs with streptococcal shock and necrotizing fasciitis survived following surgical debridement, supportive medical treatment, and treatment with antibiotics. Of the 6 Lancefield group G streptococcal isolates available for characterization, 5 were Streptococcus canis and 1 had characteristics of group G streptococcal strains of human origin. Results of molecular typing indicated that isolates were unrelated to each other. Examination of the canine isolates for putative virulence genes found in human group A streptococci resulted in identification of the emm1.0 gene only in 1 of the isolates. The canine isolates otherwise lacked virulence genes associated with human group A streptococcal toxic shock infections. CLINICAL-IMPLICATIONS: The development of severe invasive infection in dogs resulting from GGS indicates that a virulent form of GGS has developed in southern Ontario.

Animals↗
PubMed1996

Use of a virulence-associated protein based enzyme-linked immunosorbent assay for Rhodococcus equi serology in horses.

An enzyme-linked immunosorbent assay (ELISA) was developed against Rhodococcus equi using Triton X-114 detergent extracted whole cell material, in which the virulence associated protein (VapA) predominated. Enzymelinked immunosorbent assay titres corresponded to antibody reacting with VapA on Western blots. There was considerable variation in antibody titres of nonimmunised mares and in the time when the colostrally derived antibody of their foals had declined to low or undetectable titres. In general, antibodies in foals declined to their lowest levels at age 4-8 weeks. Seroconversion occurred in foals age 8-10 weeks, but the precise time depended on maternal titre and the month in which the foal was born. Foals reaching age 8 weeks in late summer showed more marked seroconversion than foals born earlier. The ELISA was used to follow the response to immunisation with the same Triton X-114 extracted material. Six mares immunised before parturition with the antigen in aluminium hydroxide adjuvant developed high titres, up to > 102,400 and transferred them to their foals through colostrum. Their foals responded to immunisation with 0.5-1.0 mg antigen 3, 5, 7 and 9 weeks after birth. Antibody titres following immunisation with similar dosage reached up to > 102,400 in a separate group of foals of nonimmunised mares. Nonvaccinated control foals seroconverted at age 6-8 weeks. The VapA based ELISA is useful to follow the course of natural infection with R. equi or immunisation with VapA based antigen.

Actinomycetales Infections↗
PubMed1996

Role of CD4+, CD8+ and double negative T-cells in the protection of SCID/beige mice against respiratory challenge with Rhodococcus equi.

To evaluate the contributions of T-lymphocyte subsets in pulmonary immunity against Rhodococcus equi, C.B-17 SCID/beige mice were adoptively transferred with splenic lymphocytes from congenic BALB/c mice previously infected with R. equi. Spleen cells were enriched for either CD4+ or CD8+ populations before inoculation, Flow cytometry showed that each enriched population contained less than 0.5% cross contamination. Groups of adoptively transferred SCID/beige mice were sacrificed 6 and 13 d after intranasal infection with R. equi. Bacterial clearance was measured in the lungs, liver and spleen. Lesion development was assessed by gross and histopathological score and the fate of transferred cells assessed by flow cytometry and by immunohistochemistry. SCID/beige mice receiving either CD4+ or CD8+ T-cells were able to clear the infection better than control mice. On d 6 post-infection, bacterial numbers were significantly lower in the lungs of CD4+ transferred mice as compared to CD8+ mice. By d 13, both groups had cleared R. equi from all organs. CD4+ cells were however identified in the lung and spleen of CD8+ recipients at d 13 making conclusions about the role of CD8+ cells in R. equi clearance impossible. By contrast, no significant increases in CD8+ lymphocytes were observed in the organs of CD4+ recipients. All mice developed suppurative bronchopneumonia but lesions were most severe in the CD4+ group. Immunohistochemistry and flow cytometry confirmed that CD4+ and CD8+ cells had migrated to the lungs of adoptively transferred mice. Serum antibody against R, equi was not detected by ELISA in the recipients. SCID/beige mice receiving CD4-CD8- cells were unable to clear R. equi. The study supports the suggestion that CD4+ cells have a central role in R. equi clearance in mice.

Actinomycetales Infections↗
PubMed1996

Attempts to find phenotypic markers of the virulence plasmid of Rhodococcus equi.

Four isolates of Rhodococcus equi, from pneumonic foals, and containing the 85 kb virulence plasmid, a porcine isolate containing an 80 kb plasmid, and their plasmid cured derivatives, were examined for 239 phenotypic properties in an attempt to find characters other than the virulence-associated protein (VapA) which might be encoded by the virulence plasmid in organisms grown at 37 degrees C. Tests chosen included those which have previously given variable results for R. equi isolates, since such variability might be attributed to plasmid curing, and characteristics which have been described as properties of plasmids of Rhodococcus species other than R. equi. Tests included cadmium resistance, Congo red binding, resistance to 26 antibiotics, conventional clinical microbiological tests, utilization of 95 different carbon sources, enzymatic activities in API ZYM, fluorogenic assays for exo- and endopeptidase, glycosidase activities, and testosterone degradation. Apart from production of VapA by foal isolates, no phenotypic property was identified in the plasmid-positive isolates. Phenotypic characteristics of R. equi that have not been described before, and might be useful in identification were: metabolism of N-acetyl-beta D-glucopyranoside, alpha- and beta-hydroxybutyric, alpha-ketobutyric and N-acetyl-glutamic acids, of methylpyruvate, heptanoate, nonanoate and stearate esters; exopeptidase activity against alanine-alanine-tyrosine, alanine-phenylalanine-lysine, glycine-arginine, lysine-alanine, and valine-glycine-alanine; endopeptidase activity against arginine and methionine; and hydrolysis of bis-phosphate ester.

Amino Acids↗
PubMed1995

Association with HeLa cells by Rhodococcus equi with and without the virulence plasmid.

HeLa cell association was examined in eight Rhodococcus equi isolates containing 80-85 kb plasmids and their plasmid negative derivatives, and in two other plasmid negative R. equi strains. Seven of the eight plasmid positive strains possessed an 85 kb plasmid and produced the virulence-associated protein (VapA) detected by monoclonal antibody staining in immunoblots; one of the eight had an 80 kb plasmid but did not produce VapA. Curing of the plasmids by repetitive subcultures at 42 degrees C in broth was confirmed by colony and DNA dot blot hybridization with a 7.5 kb BamHI-HindIII plasmid fragment probe, by attempted isolation of plasmid DNA, and by demonstration of lack of VapA. Most strains associated well with HeLa cells and no relationship was found with plasmid status and possession of VapA. Association with HeLa cells was significantly greater for strains with a dry colony type than for those with a mucoid colony, a result which correlated with hydrophobicity of the colonies. HeLa cell association does not correlate with the presence of the virulence plasmid in R. equi.

Actinomycetales Infections↗
PubMed1995

Molecular characterization of a lipid-modified virulence-associated protein of Rhodococcus equi and its potential in protective immunity.

Virulent strains of Rhodococcus equi produce plasmid-mediated 15- and 17-kDa proteins, which are thermoregulated and apparently surface-expressed. We demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) that R. equi produce three antigenically-related virulence-associated proteins, a diffuse 18-22-kDa, a 17.5-kDa and a 15-kDa protein. Phase partitioning of whole cells of R. equi strain 103 with Triton X-114 (TX-114) and labelling with [3H]-labelled palmitic acid showed that the two higher molecular weight proteins are hydrophobic and lipid modified. The 15-kDa protein did not partition into TX-114 and was not lipid modified. Cloning and expression of a fragment of the R. equi virulence plasmid in Escherichia coli showed that the three proteins were expressed from a single gene. Sequence analysis of this gene (designated vapA) revealed a 570-bp open reading frame encoding a polypeptide of 189 amino acids with a calculated molecular mass of 19,175 Da. The mature, nonlipid modified protein had a calculated mass of 16,246 Da. The 17.5- and 18-22-kDa forms of the protein are therefore due to lipid modification. No significant sequence homology of the vapA gene with other reported nucleotide sequences were found. Opsonization of virulent R. equi with an IgG1 mouse monoclonal antibody (MAb103) to the VapA protein significantly enhanced uptake in the murine macrophage cell line IC-21. Intraperitoneal injection of mice with Mab103 enhanced initial clearance from the liver of mice challenged intravenously with R. equi. Immunization of mice with the lipid-modified VapA purified by SDS-PAGE fractionation or with acetone precipitated VapA protein following TX-114 extraction resulted in significantly enhanced clearance from the liver and spleen following intravenous challenge. The VapA protein of R. equi appears therefore to be a protective immunogen.

Actinomycetales Infections↗
PubMed1995

A physical map of the 85 kb virulence plasmid of Rhodococcus equi 103.

A physical map of the 85 kb virulence plasmid pOTS from Rhodococcus equi 103 was constructed. The restriction map contains 2 AsnI, 5 BglII, 9 EcoRI, 4 HindIII, and 3 XbaI sites. The positions of the EcoRI and HindIII of pOTS are identical to that of the 85 kb virulence plasmid of R. equi ATCC 33701 reported recently by others. EcoRI restriction fragment sizes were similar in the 85 kb plasmids isolated from 4 horse derived R. equi but, except apparently for the 28.3 and possibly 2.0 and 1.5 kb fragments, were different in an 80.1 kb plasmid isolated from a pig source R. equi.

Animals↗
PubMed1993

Outer membrane proteins of three pathogenic Leptospira species.

The outer membrane proteins of seven reference strains of pathogenic Leptospira (L. alstoni serovar grippotyphosa, L. borgpetersenii serovar hardjo, and L. interrogans serovars autumnalis, bratislava, canicola, icterohaemorrhagiae, and pomona) were investigated to identify common surface-exposed outer membrane proteins. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of sodium-N-lauroylsarcosinate-insoluble outer membrane enriched fractions of the reference serovars and two field isolates of serovars hardjo and pomona revealed six common protein bands with approximate molecular masses of 77, 66, 42, 35.5, 24, and 18 kDa. At times the 35.5 kDa endoflagellar band resolved into two distinct bands, 35.5 kDa and 34 kDa. Immunoblotting of the same fractions using rabbit leptospiral antibodies showed six bands to be common (66, 59.5, 44, 42, 35.5, and 18 kDa). The 44 kDa band stained poorly with Coomassie blue but prominently by immunoblotting. Four reference strains (serovars bratislava, canicola, icterohaemorrhagiae, pomona), and two field isolates of serovar pomona and one of serovar bratislava were grown in low iron media to which the iron chelators 2,2'-dipyridyl or ethylenediaminehydroxyphenylacetic acid were added. No iron-dependent expression of outer membrane proteins was observed. The only difference observed between the outer membrane proteins when reference serovars of canicola or pomona were grown in dialysis bags in the peritoneum of swine or in vitro was the loss of the 77 kDa band from in vivo grown organisms. Treatment of whole leptospires with proteinase K did not remove the 77, 66, 59.5, or 42 kDa protein; these proteins may not be surface expressed or are inaccessible to the proteinase K. The 44 kDa band could not be evaluated by this method and the 18 kDa band was proteinase K resistant.

Animals↗
PubMed1993

Rhodococcus equi.

This article summarizes recent advances in understanding of the epidemiology, pathogenesis, clinical and laboratory diagnosis, immunology, treatment, and control of Rhodococcus equi infections in foals. Our understanding of these aspects currently is sufficient to ensure control of this problem on affected farms and in infected foals. More information, however, is needed on factors predisposing foals to R. equi pneumonia, in particular, the nature of the naturally occurring cellular immunodeficiency in foals of 2 to 4 months of age, which also predisposes them to severe respiratory infection with certain other intracellular pathogens. In addition, the relative importance of R. equi pneumonia in the context of other causes of lower respiratory tract infection of foals needs to be defined.

Actinomycetales Infections↗
PubMed1993

Clinical and endoscopic study to estimate the incidence of distal respiratory tract infection in thoroughbred foals on Ontario breeding farms.

Respiratory tract infections are prevalent in foals, yet the frequency with which the distal airways are affected in clinical episodes of respiratory tract disease has not been evaluated to our knowledge. The objective of the study was to determine the incidence of distal respiratory tract infection (DRTI) in foals on a sample of Thoroughbred breeding farms (n = 10) in Ontario. In a pilot study, clinical criteria commonly used to select foals for antimicrobial treatment (detection of abnormal lung sounds, plus nasal discharge, cough, fever, tachypnea, and/or lethargy) were found to segregate foals with and without endoscopically confirmed DRTI. Mucopurulent exudate and bronchial erythema were observed more frequently (P < 0.005), bronchial lavage total cell count and neutrophil concentration were significantly (P < 0.005) higher, and intracellular cocci were recovered significantly (P < 0.01) more often from bronchial lavage samples of affected foals (n = 8) than of controls (n = 8). These clinical criteria were used to identify cases in a cohort of Thoroughbred foals (n = 219) from May 1 to October 30, 1991. Case morbidity adjusted for clustering was 82 +/- 5% (95% confidence limits, 72 to 92%). Most (74%) episodes of clinical DRTI were detected in July and August, and equal numbers were detected before (53%) and after (47%) weaning of foals. Of 178 cases, 66 (48%) were selected at random for endoscopy and bronchial lavage. Grade-II pharyngeal lymphoid hyperplasia was observed commonly (60% of foals); auditory tube diverticulum (guttural pouch) discharge was observed in 18 of 86 (21%) foals, and guttural pouch infection was confirmed in 6 of 7 foals examined endoscopically.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Microbiologic changes during antimicrobial treatment and rate of relapse of distal respiratory tract infections in foals.

Despite the high incidence of distal respiratory tract infection of undetermined cause on farms, to our knowledge, the microbiologic effects of conventional antimicrobial treatment for this condition have not been studied. We evaluated the possible pathogenic role of bacterial isolates from the distal airways of foals with clinical respiratory tract disease, by correlating changes in their numbers (increase or decrease) with clinical, endoscopic, and pulmonary cytologic signs of disease resolution during treatment with antimicrobial drugs. We also determined qualitative changes in in vitro antimicrobial susceptibility of bacterial isolates after 7 days of treatment and relapse rate of foals. Significant (P < 0.05) decrease in the numbers of an isolate in the airways was considered strong evidence of a pathogenic role in this disease syndrome. Foals with endoscopically confirmed distal respiratory tract infection (DRTI; n = 65) were selected at random for treatment (n = 56) or nontreatment (n = 9), and bronchial lavage specimens were cultured and evaluated cytologically before and after 7 days of treatment with trimethoprim-sulfamethoxazole (TMS) and a beta-lactam drug (penicillin, ampicillin, or sulbactam-ampicillin), the standard treatment in all foals. The effect of treatment was to abruptly reduce the clinical (nasal discharge, cough, adventitious lung sounds) and cytologic signs of airway infection. Severity of disease in nontreated foals, however, did not change or did worsen over time. Reduction in the frequency and numbers of Streptococcus zooepidemicus isolated during treatment supported a causal role for this organism in the clinical syndrome observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Association of microbiologic flora with clinical, endoscopic, and pulmonary cytologic findings in foals with distal respiratory tract infection.

Undifferentiated distal respiratory tract disease (nasal discharge, cough, pneumonia) in foals (1 to 8 months old) is a burdensome economic problem on breeding farms; yet, the infective agents associated with these episodes have not been well described. Possible causes of these episodes of illness were investigated by culturing specimens of proximal and distal airways of clinically diseased foals (n = 101), prior to any treatment, for aerobic and anaerobic bacteria and viruses (rhinoviruses, equine arteritis virus, equine herpesvirus subtype 1 [EHV-1], influenza virus, and adenovirus). Pairs of sera (n = 47) were examined for antibodies to influenza A virus, equine subtypes 1 and 2, EHV-1, and adenovirus antigens, and sera obtained from foals during acute infection were examined for antibodies (by agar gel immunodiffusion [AGID]) to equi factor antigens of Rhodococcus equi. Viruses were not isolated from the proximal (swab) or distal (bronchial lavage) airway specimens in foals, and only 2 of 47 randomly selected foals seroconverted to EHV-1. Serotiters to the other viruses were low and frequently decreasing between samples, which was compatible with maternally derived antibody. Streptococcus zooepidemicus was the predominant isolate from bronchial lavage specimens (88/101 cases), accompanied by alpha-hemolytic streptococci (8 cases), Bordetella bronchiseptica (13 cases), Staphylococcus epidermidis (9 cases), and other organisms in lesser frequency. Only Str zooepidemicus was recovered significantly (P < 0.05) more often in cases than in controls. The AGID test was found useful to detect foals with presumed exposure to R equi, but positive tests results did not correspond well with bacterial culture results; positive AGID results were recorded in 34% of culture-negative foals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Serodiagnosis of leptospirosis in pigs using an axial filament enzyme-linked immunosorbent assay.

The axial filament (AF) from Leptospira interrogans serovar canicola was isolated by cesium chloride density gradient centrifugation of 2% sarcosyl treated whole cells. Isolation of AF was confirmed by electron microscopic examination, by protein-A immunogold labelling, sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), and immunoblotting. Analysis by SDS-PAGE of the purified preparation showed relatively weak bands of molecular size 41 kDa and 21 kDa, and strong bands of 35 kDa and 34.5 kDa. Immunoblot analysis using antiserum to the AF against sonicated leptospires of a variety of serovars showed prominent reaction against the 41, 35, and 34.5 kDa protein bands, as well as against minor bands of molecular weight 43, 39, and 37 kDa. Antisera prepared against leptospiral serovars also identified minor bands at 33 and 32 kDa. Immunoblots with antiserum to whole cells of serovar bratislava detected the 35 and 34.5 kDa AF bands of Borrelia burgdorferi moderately and of Treponema hyodysenteriae only slightly in comparison to leptospiral AF. Antibody to B. burgdorferi did not detect the leptospiral AF antigen. Immunoblots with antiserum to T. hyodysenteriae showed a marked reaction with a 41 kDa band of B. burgdorferi but only a very minor reaction with leptospiral AF. The AF was tested in an AF-ELISA against sera from 260 pigs, many of which reacted in the microscopic agglutination test (MAT) against one or more leptospiral serovars. A sensitivity of 97.1% and a specificity of 93.1% was determined in comparison to the MAT. Only moderate correlation was observed between titres detected in the AF-ELISA and the MAT (r = 0.4). When sonicated whole cells (WC) of serovar canicola were used in an ELISA (WC-ELISA), high correlation was observed between AF-ELISA and WC-ELISA (r = 0.97). These findings show that the AF-ELISA can be used effectively as a species-specific antigen for the serological diagnosis of leptospirosis in swine and that sonicated whole cells can substitute excellently for purified AF as the antigen source. These findings may be extrapolated to the use of AF in immunodiagnosis of leptospirosis in other species.

Agglutination Tests↗