Prior antimicrobial use as a risk factor for resistance in selected Staphylococcus pseudintermedius isolates from the skin and ears of dogs.

BACKGROUND: Antimicrobial resistance within bacteria continues to present therapeutic challenges. One presumed risk factor for increased rates of resistance is prior exposure to antimicrobial drugs. OBJECTIVES: To examine the impact of time since most recent exposure, the number of prior antimicrobial exposures and duration of use on antimicrobial resistance rates in Staphylococcus pseudintermedius isolates. METHODS: Inclusion of a case in the study required laboratory isolation of S. pseudintermedius from a clinical specimen. Antibiograms and information regarding prior antimicrobial exposures were extracted from the medical records of dogs diagnosed with pyoderma or otitis externa. RESULTS: Meticillin resistance (MR) was identified in 48.1% of isolates. Recent use of beta-lactam antimicrobials was associated with increased odds of resistance to meticillin (P < 0.001) and fluoroquinolones (P < 0.001). Antimicrobial therapy within 1 month prior to sampling was also associated with MR (60.7%; P = 0.009) and multidrug resistance (61.9%; P = 0.029). The number of prior exposures to beta-lactams or fluoroquinolones were associated with resistance to these same classes (P = 0.001 and 0.02, respectively) and to other antimicrobial classes (P = 0.016 for resistance to fluoroquinolones following treatment with beta-lactams and P = 0.015 for MR following treatment with fluoroquinolones). Longer treatment duration with beta-lactam drugs was associated with higher proportion of MR (P = 0.004). CONCLUSIONS AND CLINICAL IMPORTANCE: Treatment based upon culture and susceptibility testing is highly recommended for dogs that have received multiple antimicrobial drug exposures or that were treated within the preceding month. This may be especially important when the prior therapeutic regimen included a drug from the beta-lactam or fluoroquinolone classes.

Comparison between point-of-care dermatophyte test medium and mycology laboratory culture for diagnosis of dermatophytosis in dogs and cats.

BACKGROUND: Point-of-care Dermatophyte Test Medium (PoC-DTM) is a diagnostic procedure to rule in/rule out dermatophytosis in veterinary clinics. OBJECTIVE: To evaluate the performance of PoC-DTM in the clinic compared to DTM plate culture in a mycology laboratory and to compare results obtained by general practitioners and referral clinicians. ANIMALS: Hair samples were collected from 47 cats and 54 dogs with suspected dermatophytosis and from nine healthy controls (seven cats and two dogs). METHODS: This was a multicentre blinded study. In one group (65 suspected cases, 9 healthy controls), PoC-DTM results were evaluated by clinicians in a referral clinic (SP group) who examined the colony morphology macroscopically and microscopically. In the other group (36 suspected cases) PoC-DTM results were evaluated by clinicians from general practice for colour change only, with no macroscopic or microscopic examination (GP group). All hair samples were also cultured on DTM plates in a mycology laboratory. Laboratory culture was considered the gold standard for comparison. RESULTS: Agreements between tests were 97% (two false positive; κ = 0.839) and 80.6% (five false positives and two false negatives; κ = 0.466) in the SP and GP groups, respectively. This difference between groups was significant (P = 0.024). CONCLUSION AND CLINICAL IMPORTANCE: When applying macroscopic and microscopic evaluation of the colony, PoC-DTM is accurate for diagnosing dermatophytes with only a 3% chance of error. However, when macroscopic and microscopic examination is not included there is significant (19.4%) chance for an incorrect diagnosis.

Hyperadrenocorticism in 10 dogs with skin lesions as the only presenting clinical signs.

Ten dogs that had skin lesions as the only presenting signs of hyperadrenocorticism (HAC) and as the owners' primary complaint are described. Dogs were included if the initial examination was for skin disease, there were no signs of systemic illness on initial presentation and there was a confirmed diagnosis of HAC by specific screening tests. Dogs were excluded if they had a severe disease that might interfere with screening tests for HAC or if the screening tests were not diagnostic. There were five males and five females; six dogs were intact. Nine dogs were diagnosed at ≥7 years. Eight dogs weighed ≤10 kg. Alopecia was present in nine dogs. Eight dogs had bacterial pyoderma, five had hyperpigmentation, and four had thin skin. One dog had unresolved dermatophytosis. Skin lesions resolved after treatment in eight dogs. One dog was not treated and one was lost to follow-up. This study showed that skin lesions may be the only clinical signs of HAC. The presence of the more common clinical signs of HAC, such as a non-pruritic, truncal alopecia and/or thin skin, without any systemic signs of HAC and/or the presence of poorly responsive skin infections warrant screening for this disease.

Severe ulcerative and granulomatous pinnal lesions with granulomatous sebaceous adenitis in unrelated vizslas.

Granulomatous sebaceous adenitis (GSA) is uncommon in dogs; however, certain breed predilections exist. In this report, three cases of GSA in unrelated vizslas have been described. All cases initially presented with episodes of otitis externa followed by severe inner pinnal lesions. In one case, multifocal coalescing inner pinnal ulceration appeared 4 wk prior to the occurrence of the skin lesions. The other two cases presented with simultaneous pinnal and skin lesions following episodes of bilateral otitis. The pinnae were diffusely erythematous and had multiple coalescing erosions and ulcers. The body lesions consisted of multifocal alopecia, papules, and fine scales. Biopsies of the skin and pinnae confirmed GSA. Two dogs responded to treatment with synthetic retinoids and cyclosporin A, respectively. One dog was not treated, and the owners preferred euthanasia when the ear lesions recurred and did not respond to glucocorticoids. To the best of the authors' knowledge, GSA with multifocal coalescing ulcerative pinnal lesions has not previously been reported.

A Splice Defect in the EDA Gene in Dogs with an X-Linked Hypohidrotic Ectodermal Dysplasia (XLHED) Phenotype.

X-linked hypohidrotic ectodermal dysplasia (XLHED) caused by variants in the EDA gene represents the most common ectodermal dysplasia in humans. We investigated three male mixed-breed dogs with an ectodermal dysplasia phenotype characterized by marked hypotrichosis and multifocal complete alopecia, almost complete absence of sweat and sebaceous glands, and altered dentition with missing and abnormally shaped teeth. Analysis of SNP chip genotypes and whole genome sequence data from the three affected dogs revealed that the affected dogs shared the same haplotype on a large segment of the X-chromosome, including the EDA gene. Unexpectedly, the whole genome sequence data did not reveal any nonsynonymous EDA variant in the affected dogs. We therefore performed an RNA-seq experiment on skin biopsies to search for changes in the transcriptome. This analysis revealed that the EDA transcript in the affected dogs lacked 103 nucleotides encoded by exon 2. We speculate that this exon skipping is caused by a genetic variant located in one of the large introns flanking this exon, which was missed by whole genome sequencing with the illumina short read technology. The altered EDA transcript splicing most likely causes the observed ectodermal dysplasia in the affected dogs. These dogs thus offer an excellent opportunity to gain insights into the complex splicing processes required for expression of the EDA gene, and other genes with large introns.

Use of ImageJ software for histomorphometric evaluation of normal and severely affected canine ear canals.

Morphological studies comparing normal and diseased ear canals use primarily subjective scoring. The aim of this study was to compare normal and severely affected ears in dogs with objective measurements using ImageJ software. Ear canals were harvested from cadavers with normal ears and from dogs that underwent total ear canal ablation for unresolved otitis. Histopathology samples from ear canals were evaluated by semi-quantitative scoring and also by using ImageJ-software for histomorphometric measurements. The normal ears were compared to the severely affected ears using the 2 methods. The 2 methods were significantly (P < 0.0001) correlated for epidermal hyperplasia, ceruminous gland dilation, and hyperplasia and tissue inflammation, which were significantly greater in the severely affected ears (P < 0.0001). This study demonstrated that there is a very high correlation between the 2 methods for the most markedly affected components of otitis externa and that ImageJ software can be efficiently used to measure and evaluate ear canal histomorphometry.

Les études morphologiques comparant les canaux auriculaires normaux à ceux avec une pathologie utilisent principalement une méthode de pointage subjectif. L'objectif de la présente étude effectuée sur des chiens, était de comparer par des mesures objectives en utilisant le logiciel ImageJ, des oreilles normales à des oreilles sévèrement affectées. Des canaux auriculaires ont été prélevés sur des cadavres de chien avec des oreilles normales et sur des chiens qui ont subi une ablation complète du canal de l'oreille suite à des otites non-résolues. Des échantillons des canaux auriculaires ont été évalués en histopathologie et un pointage semi-quantitatif attribué, de même qu'en utilisant ImageJ pour des mesures histomorphométriques. Les oreilles normales ont été comparées aux oreilles sévèrement atteintes en utilisant les deux méthodes. Les deux méthodes étaient corrélées significativement (P < 0,0001) pour l'hyperplasie épidermique, la dilatation des glandes à cérumen, et l'hyperplasie et l'inflammation tissulaire, qui étaient significativement plus marqués dans les oreilles sévèrement affectées (P < 0,0001). Cette étude démontre qu'il y a une très forte corrélation entre les deux méthodes pour les composantes les plus sévèrement affectées lors d'otite externe et que le logiciel ImageJ peut être utilisé de manière efficiente pour mesurer et évaluer l'histomorphométrie du canal auriculaire.(Traduit par Docteur Serge Messier).

Canine spirocercosis: clinical, diagnostic, pathologic, and epidemiologic characteristics.

The nematode Spirocerca lupi is a parasite of dogs with beetles of several species serving as intermediate hosts. The medical records of 50 dogs diagnosed with spirocercosis at the Hebrew University Veterinary Teaching Hospital (HUVTH) in Israel during 1991-1999 were retrospectively reviewed and compared to a control group (n=100). There was a seven-fold increase in the annual number of dogs diagnosed with spirocercosis during these years while the hospital caseload increased by 80%, indicating an emerging outbreak of this infection. Dogs from the greater Tel Aviv area were at the highest risk of being diagnosed with spirocercosis with 74% of the cases originating from this region compared to only 17% of the controls. The disease appeared to have a primarily urban pattern of distribution with a significantly higher percentage (P=0.025) of dogs from cities versus rural areas, as compared to the control group. Sixty-two percent of the cases were diagnosed during the colder months of December through April. The median age of infected dogs was 5 years, with dogs 1 year old or younger at the lowest risk of being diagnosed with spirocercosis. Large breeds were at a higher risk of infection in comparison to small breeds and the Labrador Retriever was significantly over represented (P=0.027) in the study group compared to the control population. The most common signs were vomiting or regurgitation (60%), pyrexia (24%), weakness (22%), respiratory abnormalities (20%), anorexia (18%), melena (18%) and paraparesis (14%). A caudal esophageal mass was identified by radiography in 53% of the dogs and spondylitis of the thoracic vertebrae in 33%. Fecal flotation was positive for S. lupi eggs in 80% of the dogs, and endoscopy was found to be the most sensitive diagnostic procedure and allowed diagnosis in 100% of the examined dogs. Fifty-three percent of the dogs were anemic and creatine kinase (CK) activities were elevated in 54%. Necropsy of 14 dogs revealed esophageal or gastric granulomas in 13 dogs, and an esophageal osteosarcoma in a single animal. Aortic aneurysms were found in six (43%) dogs. Out of 24, 15 dogs (63%) for which follow-up information was available died or were euthanized within 1 month of admission. The case-fatality rate decreased toward the end of the study period when improved therapy with avermectins became available.

Antihistamines in the management of canine atopic dermatitis: a retrospective study of 171 dogs (1992-1998).

Antihistamines were prescribed for 178 of 271 dogs with a diagnosis of atopic dermatitis at the Veterinary Medical Teaching Hospital of the University of California, Davis from 1992 to 1998. Fifty-four percent of 166 dogs given antihistamines responded favorably to these treatments, with 27% of the responses rated as good and 27% rated as moderate. Diphenhydramine and hydroxyzine were the most commonly used antihistamines and were the most frequently effective. Chlorpheniramine and clemastine were administered less frequently and had much lower positive response rates. Responses to antihistamines as a group were significantly better in dogs having onset of clinical signs at younger ages (odds ratios for 1-year increase in age = 0.72, 95% confidence interval = 0.57 to 0.91, P =.005).

Azithromycin pharmacokinetics in the serum and its distribution to the skin in healthy dogs and dogs with pyoderma.

Serum and skin tissue azithromycin (AZM) concentrations were analysed in healthy and pyoderma affected dogs to determine AZM pharmacokinetics and to establish the effect of disease on AZM skin disposition. AZM was administered orally to two groups of healthy dogs: (1) at 7.02 mg/kg (n=7) and (2) at 11.2mg/kg (n=9). A crossover design was used on five of them. Seven dogs with pyoderma were treated with AZM at 10.7 mg/kg. The two groups of healthy dogs received AZM once daily over three consecutive days and dogs with pyoderma received the same treatment repeated twice with an interval of 1 week. AZM concentrations were determined by liquid chromatography-tandem mass spectrometry. AZM was rapidly absorbed and slowly excreted. In healthy dogs, maximum serum concentrations appeared 2h after administration and were (mean ± standard deviation) 0.60 ± 0.25 µg/mL and 1.03 ± 0.43 µg/mL, and the half-lives were 49.9 ± 5.10 and 51.9 ± 6.69 h for doses of 7.02 and 11.2mg/kg, respectively. Clearance (CL0-24/F) was similar in both dosing groups (1.24 ± 0.24 and 1.29 ± 0.24 L/h/kg) and the respective mean residence time (MRT0-24) was 11.1 ± 0.8 and 8.4 ± 2.2h. The skin concentration in healthy dogs was 3.5-6.5 and 5.0-12.0 times higher than the corresponding serum concentration after the two doses and increased after the cessation of AZM administration. The ratio increased significantly in inflamed tissue (9.5-26.2).

Morphometry of skin changes in Newfoundland dogs following coat clipping.

Dog breeds are unique in their coat conformation and quality. Newfoundland dogs have a long and fine hair coat, and clipping may induce changes in newly grown hair. This study examined structural changes in the skin of Newfoundland dogs following clipping. Dogs included in the study had visible coat changes following clipping that appeared as loss of gloss, increased scaling and textural changes. The control groups consisted of two groups of dogs that had never been clipped: Newfoundland dogs served as within-breed controls, and long-haired dogs of other breeds served as between-breed controls. All dogs were healthy with no history of dermatological problems. Two skin biopsies were taken from each dog and evaluated for predetermined parameters. A total of 41 samples were examined: 11 from clipped Newfoundland dogs, 16 from unclipped ones, and 14 from dogs of other breeds. By histopathology, the clipped dogs had a thicker cornified layer (P=0.006) and smaller sebocytes (P=0.022) than the unclipped ones. Newfoundlands had larger and more epitrichial sweat glands than other breeds (P=0.0002, P=0.036, respectively), and those were not affected by clipping. These results suggest that hyperkeratosis and decreased sebocyte size may explain the observed coat changes following clipping in Newfoundland dogs.

In vitro and in vivo effects of lufenuron on dermatophytes isolated from cases of canine and feline dermatophytoses.

Lufenuron is a benzyl-urea phenol compound that inhibits chitin synthesis and is used as an insecticide. Its efficacy in the therapy of dermatophytosis in dogs and cats was evaluated in several clinical studies, with contradictory results. We assessed the in vitro susceptibility of dermatophytes isolated from dogs and cats to lufenuron, and the clinical response of skin lesions to the drug. Dermatophyte cultures isolated from clinical cases were exposed to lufenuron by three different methods: direct application and application of whole blood or subcutaneous tissue samples obtained from a lufenuron-treated healthy dog. No inhibition of dermatophyte growth was observed in any of the samples after 1 week of incubation. Eight dogs and six cats with skin lesions were included in the in vivo survey. Results indicated that six of seven skin lesions that were diagnosed as being caused by dermatophytes did not respond to lufenuron whereas six of seven skin lesions that were not caused by dermatophytes improved. We concluded that lufenuron, in the way it was administered in this study, had no inhibitory activity on dermatophytes in vitro or in vivo and its clinical use as an anti-fungal agent is questionable. An immunomodulatory effect of the drug is, however, possible.

Bilateral ear canal neoplasia in three dogs.

Bilateral ear canal infections are common in dogs. Ear canal neoplasia is usually associated with unilateral problems, and is uncommon in dogs. To the best of the author's knowledge, bilateral aural neoplasia has not been reported in dogs, and only four case reports were found in the human literature. This report presents three dogs that had bilateral tumours in their ear canals. They were presented with bilateral otitis externa. All three dogs exhibited tissue proliferation of both ear canals that did not respond to glucocorticoids. Treatment consisted of total ear canal ablation, and tissues were submitted for histopathological evaluation. Case # 1 (a 10-year-old, male cocker spaniel) was diagnosed as ceruminious gland carcinoma. Cases # 2 and 3 were diagnosed as squamous cell carcinoma. Case # 1 was diagnosed 4 years earlier as having keratinization disorder, which was causing its chronic ear problems. Case # 2 (a 5-year-old, female French bulldog) was diagnosed 4 years earlier as having atopic dermatitis, which did not respond to hyposensitization, and only partially responded to glucocorticoids therapy. Case # 3 (a 9-year-old, male German shepherd) was diagnosed by the referring veterinarian as having unilateral ear canal proliferation 2 months prior to presentation. However, otoscopic examination showed bilateral proliferation that obstructed both canals. In summary, bilateral ear canal neoplasia should be considered in cases of nonresponsive, proliferative aural pathology.

Canine atopic dermatitis: a retrospective study of 266 cases examined at the University of California, Davis, 1992-1998. Part I. Clinical features and allergy testing results.

The medical records of 266 dogs diagnosed as having atopic dermatitis were reviewed. Statistical data were evaluated referable to breed predilections, clinical signs and positive reactions to allergens. Positive reactions were most common to house dust mites (more common with clinical signs in the fall) followed by moulds (more common with clinical signs in the fall and spring). Dogs with positive reactions to moulds, trees or cultivated plants were more likely to have skin and ear yeast infections. Dogs with positive reactions to cultivated plants were more likely to have otitis externa and pedal lesions. Positive reactions to house dust were more common in dogs with early onset of signs and in those tested early in the disease. Dogs had more positive reactions to weeds when allergy tests were performed in the summer and fall. Positive reactions to flea antigen were highly correlated with the clinical diagnosis of flea allergy dermatitis.

Canine atopic dermatitis: a retrospective study of 169 cases examined at the University of California, Davis, 1992-1998. Part II. Response to hyposensitization.

One hundred and sixty-nine dogs were diagnosed with atopic dermatitis, and treated with hyposensitization for at least 1 year based on the results of either intradermal skin tests (IDST) or enzyme-linked immunosorbant serum assays (ELISA). Excellent (i.e. hyposensitization alone controlled clinical signs), good (> 50% improvement), moderate (< 50% improvement) and no (clinical signs were unchanged) responses were seen in 19.5, 32.5, 20.1 and 27.8%, respectively. Age of onset, age when treatment was initiated or the duration of clinical signs had no influence on response to hyposensitization. Dogs having concurrent flea allergy dermatitis were statistically more likely to respond better than dogs with concurrent food allergies. Although not statistically significant, there were trends for Golden Retriever and male dogs to respond better than other breeds and female dogs, respectively. Dogs having more than 21 positive reactions in allergy tests and treated with more than 21 allergens had lower response scores, and a longer time course before achieving beneficial response. Lower response scores were seen in dogs having positive reactions to cultivated plants, grasses, trees or insects. There was no difference in response to hyposensitization whether based on IDST or ELISA results.