J A Charles

Victoria University Melbourne, Melbourne, Victoria, Australia

Are you J A Charles?

Claim your profile

Publications (14)22.59 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Escherichia coli (E. coli) is the most commonly isolated infectious agent causing pyometra in bitches. Many E. coli strains isolated from the uteri of infected dogs carry several adhesin genes (fimH, papGIII and sfa). The objective of this study was to investigate the role of each adhesin gene product, acting alone or expressed in combination, in the bacterial binding to canine endometrium. E. coli strain P3, which was isolated from a uterus of a bitch naturally affected with pyometra, was shown by PCR to carry all three known fimbrial adhesin genes fimH, papGIII and sfa. Knockout (KO) mutants of this wildtype (P3-wt) strain were generated using insertional inactivation. Adhesion assays on anoestrous uteri of three post-pubertal bitches were undertaken. Overall, the number of bacteria adhering to canine endometrial biopsies was comparable between strains and no significant difference in the number of bound bacteria was found between the P3-wt strain and the single or double KO-strains. However, the triple knockout strain displayed less binding to the canine endometrium compared with the P3-wt strain. This study shows that a pathogenic E. coli strain (P3) isolated from the uterus of a bitch with pyometra was able to fully compensate for the loss of two of its three known adhesin genes. It was necessary to inactivate all three known adhesin genes in order to see a significant decrease in binding to canine endometrium.
    Veterinary Microbiology 03/2013; · 3.13 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Pyometra, a prevalent infectious uterine disease that affects intact middle-aged bitches, is typically associated with Escherichia coli. Our hypotheses were (i) that bacterial adhesion to canine endometrium differs between different stages of the oestrous cycle and (ii) that the adhesin FimH facilitates this adhesion. Twelve post-pubertal, ovariectomized greyhound bitches were treated with exogenous hormones to simulate different stages of the oestrous cycle. Tissue samples from each uterus were incubated with a pathogenic E. coli strain carrying the fimH gene, but no other adhesin genes (P4-wt)-or an E. coli strain in which fimH was insertionally inactivated (P4-∆fimH::kan)-or with phosphate-buffered saline as a negative control. After washing, tissue samples were homogenized for quantification of adherent bacteria. The differences in binding to canine endometrium at different stages of the oestrous cycle were not significant. However, the mean difference in binding of the P4-wt and the P4-∆fimH::kan across all stages of the simulated oestrous cycle was significant (p < 0.001 by paired t-test on geometric means). Individual differences in numbers of P4-wt bacteria bound between dogs might suggest genetic variations or epigenetic differences in FimH receptor expression by the endometrium, unrelated to the stage of the oestrous cycle.
    Reproduction in Domestic Animals 12/2012; 47 Suppl 6:331-4. · 1.39 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Pyometra is a potentially life-threatening condition in bitches and is often caused by Escherichia coli infection. Both pathogenic and non-pathogenic E. coli strains commonly carry the genes for type 1 fimbriae that mediate bacterial adhesion onto host epithelium. To investigate whether the type 1 fimbrial adhesin, FimH, facilitates the binding of uropathogenic E. coli to canine endometrium, the fimH gene was insertionally inactivated in a pathogenic E. coli strain. The ability of E. coli to bind to canine endometrial epithelial cells was determined in vitro using canine uterine biopsies. Binding of the fimH mutant was only 0.3% of that of the wild type. Complementation of the mutation restored the phenotype to that of the parent. This study has developed an in vitro model that allows quantitative and qualitative assessment of bacterial binding to canine endometrium and has demonstrated that the fimH gene plays a role in adherence of pathogenic E. coli to canine endometrium.
    Comparative immunology, microbiology and infectious diseases 05/2012; 35(5):461-7. · 2.99 Impact Factor
  • B P Landon, L A Abraham, J A Charles
    [Show abstract] [Hide abstract]
    ABSTRACT: To evaluate the efficacy of cellophane banding of single congenital extrahepatic portosystemic shunts in dogs using transcolonic portal scintigraphy. To investigate the portal circulation of those dogs with elevated postoperative shunt fractions to determine the cause of the persistent shunting. Further, to evaluate whether presenting signs, clinical pathology findings and liver histopathology are predictive of outcome. Prospective study of 16 dogs presenting with single congenital extrahepatic portosystemic shunts. Dogs with single extrahepatic portosystemic shunts attenuated by cellophane banding underwent portal scintigraphy and bile acids tolerance testing pre- and post-operatively. Dogs identified with elevated shunt fractions at 10 weeks post-operatively underwent mesenteric portovenography. Qualitative hepatic histopathology from all dogs was reviewed by a veterinary pathologist and assigned a semi-quantitative score to identify any abnormalities that may predict surgical outcome. At 10 weeks post cellophane banding, 10 of 16 cases (63%) had normal shunt fractions, whilst six dogs (37%) had increased shunt fractions and seven dogs (44%) had increased serum bile acids. Of these dogs, mesenteric portovenography revealed incomplete closure of the shunt in three dogs (18.6%) and multiple acquired shunts in three dogs (18.6%). Liver histopathology findings were similar for all dogs, regardless of outcome. Cellophane banding is an efficacious method for complete gradual occlusion of single extrahepatic shunts when the shunt vessel is attenuated to < or = 3 mm. Transcolonic portal scintigraphy is a reliable method for assessment of shunt attenuation and, unlike serum bile acids, is not influenced by other causes of liver dysfunction.
    Australian Veterinary Journal 05/2008; 86(5):169-79; quiz CE1. · 0.92 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Research into risk factors specific for fatality in flat racing should be focused at a regional level as the risk factors may differ among countries and even regions within countries. To identify risk factors for fatality of Thoroughbred racehorses in flat starts on all racecourses in Victoria, Australia between 1989 and 2004. Fatalities comprised all horses that died during or immediately after a flat race or official flat trial, and all horses that were subjected to euthanasia within 24 h of an event in which an injury was sustained. The retrospective study involved 283 case starts and 3307 control starts. Univariable and multivariable backward stepwise logistic regression was used to identify risk factors for fatality at any one start. In the final multivariable model, horse gender, prior racing history, race length, racing year, racecourse location and track rating were associated with fatality. This study identified specific risk factors for fatality. The findings are consistent with the hypothesis that horses accumulating high speed exercise are predisposed to catastrophic injury. The study has also highlighted the need to investigate further the adverse effects of different track ratings on the incidence of injury and subsequent fatality. The results will facilitate the development of effective strategies to improve overall safety of horses and jockeys in flat racing in Victoria, Australia.
    Equine Veterinary Journal 10/2007; 39(5):430-7. · 2.29 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A 9-month-old female Shar Pei cross-bred dog was presented with a history of recurrent rectal prolapse over 7 months. Repeated reduction and anal purse string sutures and subsequent incisional colopexy failed to prevent recurrent rectal prolapse. Digital rectal examination following reduction of the prolapse identified a faeces-filled sac within the ventral wall of the rectum and an orifice in the ventral colonic wall, cranial to the pubic brim. A ventral, communicating tubular colonic duplication was diagnosed by means of a barium enema. Surgical excision of the duplicated colonic tube was performed via a caudal ventral midline laparotomy. At 20 weeks post-operation, there has been no recurrence of rectal prolapse.
    Australian Veterinary Journal 10/2007; 85(9):381-5. · 0.92 Impact Factor
  • L A Abraham, D Tyrrell, J A Charles
    [Show abstract] [Hide abstract]
    ABSTRACT: A 2-year-old female Greyhound was presented for inappetence and lethargy. On referral, results of diagnostic tests indicated renal glucosuria, increased excretion of selected amino acids and abnormal fractional excretion of electrolytes consistent with renal tubular dysfunction. Systemic blood pressure was elevated. Renal biopsy revealed mild proximal renal tubular damage consistent with a subacute toxic or hypoxic insult. Systemic hypertension, renal glucosuria and altered fractional excretion of electrolytes resolved during the 7 day period of hospital treatment. The Greyhound resumed training without recurrence of renal dysfunction.
    Australian Veterinary Journal 12/2006; 84(11):398-401. · 0.92 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Determining the risk of fatality of Thoroughbred horses while racing is essential to assess the impact of intervention measures designed to minimise such fatalities. To measure the risk of racehorse fatality in jump and flat starts on racecourses in Victoria, Australia, over a 15 year period and to determine proportional mortality rates for specific causes of death. All fatalities of Thoroughbred horses that occurred during or within 24 h of a race were identified from a database. The risk of a start resulting in a racehorse fatality in all races and within flat and jump races, proportional mortality rates, population attributable risk, population attributable fraction and risk ratios were calculated along with 95% confidence intervals. Poisson regression was also performed to estimate risk ratios. There were 514 fatalities over the 15 year period; 316 in flat races and 198 in jump races. The risk of fatality was 0.44 per 1000 flat starts and 8.3 per 1000 jump starts (18.9 x greater). The risk of fatality on city tracks was 1.1 per 1000 starts whereas on country tracks it was 0.57 per 1000 starts. Of the 316 fatalities in flat races, 73.4% were due to limb injury, 2.5% to cranial or vertebral injury and 19.0% were sudden deaths. Of the 198 fatalities in jump races, 68.7% were due to limb injury, 16.2% to cranial or vertebral injury and 3.5% were sudden deaths. The risk of fatality in flat starts increased between 1989 and 2004 but the risk in jump starts remained unchanged over the 15 year period. The risk of fatality in flat starts was lower in Victoria than North America and the UK but the risk in jump starts was greater. Catastrophic limb injury was the major reason for racehorse fatality in Victoria but there was a larger percentage of sudden deaths than has been reported overseas. The risk of fatality in jump starts remained constant over the study period despite jump racing reviews that recommended changes to hurdle and steeple races to improve safety. This study provides important benchmarks for the racing industry to monitor racetrack fatalities and evaluate intervention strategies.
    Equine Veterinary Journal 08/2006; 38(4):312-8. · 2.29 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A 3-year-old dog presented with a severe polymyopathy and subsequently developed nodular skin lesions. The disease in this dog was caused by lymphoma, showing cutaneous epitheliotropism as well as infiltration of skeletal muscle in conjunction with polymyositis.
    Australian Veterinary Journal 11/2005; 83(10):612-5. · 0.92 Impact Factor
  • Equine Veterinary Journal 06/2005; 37(3):269-71. · 2.29 Impact Factor
  • L A Abraham, J A Charles, S A Holloway
    [Show abstract] [Hide abstract]
    ABSTRACT: To determine whether oral administration of ursodeoxycholic acid (UDCA) to healthy dogs alters the results of the bile acids tolerance test. UDCA (15 mg/kg once daily) was administered to 16 healthy dogs for 7 days. Health of the dogs was assessed by clinical examination, haematology, serum biochemistry and a bile acids tolerance test. Normal liver structure was confirmed by histopathology at the end of the study. Bile acids tolerance tests were performed before and at the end of the treatment period, with each dog serving as its own control. For the posttreatment bile acids tolerance test, UDCA was administered at the time of feeding. Pretreatment, the fasted serum total bile acid concentrations ranged between 0 and 9 micromol/L. In the majority of dogs, the postprandial total bile acid concentration was greater than the preprandial value, with a range of 0 to 16 micromol/L. The fasted total bile acid concentration was 0 micromol/L in most dogs (93.75%) after treatment with UDCA. Postprandial serum bile acids also remained within the reference range for the majority of dogs (93.75%) after UDCA treatment. A single dog had a postprandial bile acid concentration above the reference range, but the concentration was within the reference range when the assay was repeated the following day without concurrent administration of UDCA. The pre- and postprandial total serum bile acid concentrations were not significantly affected by UDCA treatment. The administration of UDCA does not alter the bile acids tolerance test of normal healthy dogs.
    Australian Veterinary Journal 04/2004; 82(3):157-60. · 0.92 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Five of 10 pregnant, lactating mares, each with a foal at foot, developed neurological disease. Three of them became recumbent, developed complications and were euthanased; of the two that survived, one aborted an equine herpesvirus type 1 (EHV-1)-positive fetus 68 days after the first signs were observed in the index case and the other gave birth to a healthy foal on day 283 but remained ataxic and incontinent. The diagnosis of EHV-1 myeloencephalitis was supported by postmortem findings, PCR identification of the virus and by serological tests with an EHV-1-specific ELISA. At the time of the index case, the 10 foals all had a heavy mucopurulent nasal discharge, and PCR and the ELISA were used to detect and monitor EHV-1 infection in them. The status of EHV-1 infection in the five in-contact mares was similarly monitored. Sera from three of the affected mares, taken seven days after the index case were negative or had borderline EHV-1-specific antibody titres. In later serum samples there was an increase in the titres of EHV-1-specific antibody in two of the affected mares. In contrast, sera from the five unaffected in-contact mares were all EHV-1-antibody positive when they were first tested seven or 13 days after the index case.
    The Veterinary record 11/2003; 153(14):417-23. · 1.80 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Sciatic nerve tumour was diagnosed in a Staffordshire Bull Terrier cross-bred and a Bichon Frise, both presenting with chronic left hind limb lameness. Neurological examination in each case was consistent with left sciatic nerve deficits and this was confirmed by EMG studies. Rectal examination of both dogs revealed a palpable intrapelvic mass that was not apparent on survey radiographs. A sciatic nerve tumour was identified using MRI in each case. Histological examination of tissue taken from the Staffordshire Bull Terrier cross-bred was consistent with a malignant peripheral nerve sheath tumour.
    Australian Veterinary Journal 01/2003; 81(1-2):42-6. · 0.92 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Acromegaly was diagnosed in a 14-year-old domestic short hair cat presented for investigation and management of apparently insulin-resistant diabetes mellitus. Treatment with L-deprenyl and high doses of insulin was commenced. The L-deprenyl did not reduce the requirement for high doses of insulin and did not appear to reduce the clinical signs associated with the disease. The cat was euthanased one year after initial presentation.
    Australian Veterinary Journal 09/2002; 80(8):479-83. · 0.92 Impact Factor