Not just in man's best friend: A review of Staphylococcus pseudintermedius host range and human zoonosis.

Staphylococcus pseudintermedius is one species in the commensal staphylococcal population in dogs. While it is commonly carried on healthy companion dogs it is also an opportunistic pathogen associated with a range of skin, ear, wound and other infections. While adapted to dogs, it is not restricted to them, and we have reviewed its host range, including increasing reports of human colonisation and infections. Despite its association with pet dogs, S. pseudintermedius is found widely in animals, covering companion, livestock and free-living species of birds and mammals. Human infections, typically in immunocompromised individuals, are increasingly being recognised, in part due to improved diagnosis. Colonisation, infection, and antimicrobial resistance, including frequent multidrug resistance, among S. pseudintermedius isolates represent important One Health challenges.

Successful resolution of dermatophyte mycetoma following terbinafine treatment in two cats.

Microsporum canis sensitive to itraconazole and terbinafine was isolated from two cats presented with generalized dermatophytosis and dermatophyte mycetoma. Itraconazole therapy was withdrawn through lack of efficacy in one cat (a Persian) and unacceptable adverse effects in the other (a Maine Coon). Both cats achieved clinical and mycological cure after 12-14 weeks therapy with 26-31 mg kg(-1) terbinafine every 24 h per os (PO). Clinical signs in the Maine Coon resolved completely after 7 weeks treatment. Four weeks of therapy with additional weekly washes with a 2% chlorhexidine/2% miconazole shampoo following clipping produced a 98% reduction in the Persian cat's mycetoma, which was then surgically excised. Recurrent generalized dermatophytosis in the Persian cat has been managed with pulse therapy with 26 mg kg(-1) terbinafine every 24 h PO for 1 week in every month. No underlying conditions predisposing to dermatophytosis were found in either cat despite extensive investigation. Terbinafine administration was associated with mild to moderate lethargy in the Persian cat, but no other adverse effects or changes in blood parameters were seen. To the best of the authors' knowledge this is the first report of a dermatophyte mycetoma in a Maine Coon and of successful resolution of this condition in cats following terbinafine therapy.

Thrombo-ischaemic pinnal necrosis associated with fenbendazole treatment in a dog.

An 11-week-old, female West Highland white terrier was presented with necrosis of the distal third of both pinnae. Haematology, biochemistry and urinalysis, Coombs test, antinuclear antibody and cold autoagglutinin antibody tests were normal. A drug reaction to fenbendazole was diagnosed. The necrotic ear tips were surgically removed. Histopathology revealed extensive coagulative necrosis of the epidermis and superficial to mid-dermis, a moderate interstitial neutrophilic infiltrate and complete thrombotic occlusion and necrosis of blood vessels. There was also endothelial cell activation and proliferation with endothelial cell cushions protruding into the vascular lumen. Immunohistochemistry for factor VIII-related antigen confirmed endothelial cell involvement. This case represents an unusual, drug-induced, thrombo-ischaemic necrosis of the pinnae. It is also, to the authors' knowledge, the first report of fenbendazole sensitivity in a dog. The histopathology is similar to previous cases of proliferative thrombovascular pinnal necrosis, suggesting that drug reactions should be considered in this condition.

Peripheral blood mononuclear cell responses to Dermatophagoides farinae in canine atopic dermatitis.

Atopic dermatitis is a chronic inflammatory and pruritic skin disease commonly seen in dogs and humans that is characterised by the presence of allergen-specific IgE. Data from skin tests and serological analysis suggest that the house dust mite Dermatophagoides farinae is the most important allergen in dogs with atopic dermatitis. The aim of this study was to determine if D. farinae specific peripheral blood mononuclear cell (PBMC) responses could be detected in dogs with atopic dermatitis. PBMCs were isolated by the density centrifugation from dogs with atopic dermatitis that were skin test positive for D. farinae, dogs with atopic dermatitis that were skin test negative for D. farinae, and healthy dogs. Cells were cultured with increasing concentrations of the D. farinae extract, no antigen, vaccine antigens or concanavalin A (ConA). There was significantly greater responsiveness of PBMCs from the D. farinae positive dogs than from either the D. farinae negative or healthy dogs (ANOVA, P<0.05). In contrast, no significant differences were observed in the control responses between the three groups. This is the first study to demonstrate that D. farinae specific circulating memory cells are involved in the pathogenesis of canine house dust mite hypersensitivity.

T-helper 1, T-helper 2 and immunosuppressive cytokines in canine atopic dermatitis.

Atopic dermatitis is a common inflammatory skin disease of humans and dogs. Human atopic dermatitis is associated with T-helper (Th) 2 type responses, although Th1 cytokines are present in chronic lesions. This study used semi-quantitative reverse transcriptase polymerase chain reactions to determine the expression of gene transcripts for immunosuppressive cytokines (transforming growth factor beta [TGFbeta] and interleukin [IL]-10), Th2 type cytokines (IL-4 and IL-6) and Th1 type cytokines (interferon gamma [IFNgamma], tumour necrosis factor alpha [TNFalpha], IL-2 and IL-12) in lesional atopic, non-lesional atopic and healthy canine skin. Canine atopic dermatitis was associated with over-expression of IL-4 mRNA and reduced transcription of TGFbeta compared to healthy skin (ANOVA, p<0.05). Higher levels of IFNgamma, TNFalpha and IL-2 mRNA were seen in lesional compared to non-lesional and healthy skin (p<0.05). There were no significant differences in IL-10, IL-6 or IL-12 transcription. This is the first report to demonstrate that canine atopic dermatitis is associated with over-production of IL-4 and under expression of TGFbeta.

Peripheral blood mononuclear cell responses to major and minor Dermatophagoides allergens in canine atopic dermatitis.

Atopic dermatitis is a chronic inflammatory and pruritic skin disease commonly seen in dogs and humans. Most cases involve hypersensitivity to the house dust mites (HDM) Dermatophagoides farinae and Dermatophagoides pteronyssinus. Human atopic dermatitis is associated with the HDM derived allergens Der f 1 and 2, and Der p 1 and 2. Serological data, however, suggest that a 98/104kD protein is the most important allergen in dogs with atopic dermatitis. The aim of this study was to characterise the specificity of circulating T-cells in canine atopic dermatitis for HDM derived allergens. Peripheral blood mononuclear cells (PBMCs) from dogs with atopic dermatitis that were skin test positive for D. farinae and D. pteronyssinus were cultured with crude extracts of D. farinae, D. pteronyssinus and D. microceras, a 98/104kD allergen purified from D. farinae, Der f 1 and Der f 2. There was significantly greater responsiveness of PBMCs to the D. farinae and D. pteronyssinus extracts compared to the D. microceras extract, and similarly to the purified 98/104kD allergen compared to Der f 1 and Der f 2. The close association between serological findings and PBMC proliferation implies that the 98/104kD HDM protein is a major target of immune recognition and that T-cells also participate in the pathogenesis of canine atopic dermatitis by supporting IgE production.

Characterisation of major and minor Dermatophagoides allergens in canine atopic dermatitis.

Atopic dermatitis is a well-recognised chronic inflammatory skin disease of humans and dogs. Most atopic dogs are sensitised to Dermatophagoides mites. The aim of this study was to characterise allergens in different Dermatophagoides species using polyclonal and monoclonal antibodies to canine IgE. Western blots were prepared from crude extracts of D farinae, D pteronyssinus and D microceras, and purified group 1 and 2 allergens under reducing and non-reducing conditions. They were probed with sera from atopic (n = 33) and healthy (n = 27) dogs. There was no significant difference in the sensitivity or specificity between the polyclonal and monoclonal sera in detecting Dermatophagoides -specific IgE. Major allergens common to both D farinae and D pteronyssinus were detected at 97-98 kDa, 103-104 kDa and 134-139 kDa on both reducing and non-reducing blots. Major allergens at 84-85 kDa, 65-69 kDa and 44-45 kDa were only recognised on reducing blots, suggesting that these are fragments of the larger allergens. Only a few sera recognised group 1 or 2 allergens on blots of crude extracts or purified allergens. These results confirm that, in atopic dogs, high molecular weight allergens are the most important Dermatophagoides allergens, rather than the low molecular weight group 1 and 2 proteins.

Retrospective survey of allergen immunotherapy in canine atopy.

The clinical records of 277 cases of canine atopy treated with specific allergen immunotherapy were reviewed. A good response was defined as control with immunotherapy either alone or with topical agents, a partial response as control with immunotherapy and other systemic agents, and a poor response as no perceived benefit and the immunotherapy discontinued. The mean follow-up period was 29.2 months (range 10 to 85 months). Ninety-one cases (33 per cent) were lost to follow-up or failed to comply with the therapeutic protocol. Of the remaining 186 cases, 40 (21.5 per cent) had a good response to immunotherapy, 74 (39.8 per cent) had a partial response, and 72 (38.7 per cent) had a poor response. Immunotherapy was therefore of long-term benefit in 114 dogs (61.3 per cent). No significant differences in response rates were associated with the breed or sex of the dog, or the age of onset of the disease, or with the type or number of allergens included in a vaccine. Dogs which had clinical signs for more than 61 months before immunotherapy had a significantly poorer response rate (23.5 per cent, P < 0.05). In-house cases had a significantly better response rate (95.2 per cent, P < 0.05) than externally managed cases.

Use of ticarcillin in the management of canine otitis externa complicated by Pseudomonas aeruginosa.

Twelve dogs were referred with purulent and proliferative otitis externa. Prior treatment included fluoroquinolones, glucocorticoids and polyvalent ear drops over seven days to five months. In all cases the vertical and horizontal ear canals were inflamed and thickened, with ruptured tympanic membranes in four cases. No abnormalities were seen on radiography of the osseous bullae. Numerous rod bacilli and degenerate neutrophils were seen on cytology. Pseudomonas aeruginosa resistant to fluoroquinolones and gentamicin was cultured in all cases. Treatment was initiated with 1 to 2 mg/kg prednisolone per os once daily, and a cleansing and drying ear cleaner followed by topical administration of injectable ticarcillin solution four times daily. Cases with ruptured tympanae also received 15 to 25 mg/kg ticarcillin three times daily intravenously until the membranes had healed. All cases were anaesthetised for repeated saline ear flushes until no further discharge was evident and no rods were seen on cytology. Topical ticarcillin and the ear cleaner were continued twice daily for 14 days after clinical resolution. The duration of treatment ranged from 14 to 36 days. Treatment was withdrawn in one case which developed a drug reaction. All other cases responded well with no adverse effects.

Methicillin-resistant Staphylococcus aureus in dogs and cats: an emerging problem?

There is concern over transmission of methicillin-resistant Staphylococcus aureus (MRSA) between animals and humans. The spread of hospital-acquired and community-acquired MRSA is a major challenge in human medicine. MRSA is rarely isolated from animals but methicillin resistance occurs in staphylococci that are more prevalent in animals. MRSA infections in animals are uncommon and most are associated with exposure to medical hospitals, extensive wounds, prolonged hospitalisation and immunosuppression. The risk to human health appears to be small but a survey of methicillin-resistant staphylococci in animals is required. Thorough investigation of possible zoonotic infections to establish linkage is encouraged. Medical and veterinary staff should appreciate that animals can carry MRSA, cooperate in eliminating infections and monitor animals in medical environments. Veterinary clinics should implement guidelines for dealing with MRSA. Responsible antibiotic use should minimise the spread of antibiotic resistance but a UK monitoring scheme is desirable.

Successful intravenous human immunoglobulin treatment of drug-induced Stevens-Johnson syndrome in a dog.

A two-year-old, male English springer spaniel developed severe mucocutaneous ulceration following treatment with trimethoprim-potentiated sulphadiazine. The clinical signs were consistent with Stevens-Johnson syndrome (SJS): there were no target or arciform lesions typical of erythema multiforme minor and major; more than one mucosal surface was affected; epidermal detachment affected less than 10 per cent of the body surface area; and there was a clear history of drug exposure. Systemic signs included a severe hepatopathy, dyspnoea, pyrexia and cachexia. Glucocorticoid therapy was associated with secondary infection by Pseudomonas aeruginosa. The clinical signs rapidly resolved following a single intravenous infusion of 0.51 g/kg human immunoglobulin (ivHIG) as a 5 per cent solution. By blocking FAS/FAS ligand (CD95/CD95L) interactions, ivHIG is thought to prevent keratinocyte apoptosis. It also binds to immunoglobulin G Fc receptors, inhibiting cell activation and cytokine synthesis, neutralises autoantibodies and immune complexes, blocks complement activity, is antimicrobial and increases colloid osmotic pressure. To the authors' knowledge, this is the first report of successful treatment of canine SJS using ivHIG, although it has been used to treat erythema multiforme in a cat and toxic epidermal necrolysis in a dog.

Resolution of paraneoplastic alopecia following surgical removal of a pancreatic carcinoma in a cat.

A 13-year-old female neutered domestic longhaired cat was presented with a five-month history of progressive weight loss and bilaterally symmetrical alopecia of the ventrum, limbs and perineum. The alopecic skin had a shiny appearance and hair in the non-alopecic areas was easily epilated. Fine needle aspirate cytology of a palpable cranial abdominal mass revealed it to be of epithelial or glandular origin. A pancreatic mass was excised by left pancreatectomy during exploratory laparotomy, and histopathology and skin biopsies confirmed a diagnosis of pancreatic carcinoma with concurrent paraneoplastic alopecia. No evidence of metastases was found on liver and lymph node biopsies. At re-examination 10 weeks after surgery, the hair had fully regrown. Skin signs recurred after 18 weeks and metastatic spread of the tumour was confirmed on postmortem examination. This case confirms that paraneoplastic alopecia associated with internal malignancies is a potentially reversible process if the internal neoplasm is excised.

Treatment of Trombicula autumnalis infestation in dogs and cats with a 0.25 per cent fipronil pump spray.

To evaluate the efficacy of fipronil in controlling trombiculid infestations, 18 dogs and three cats infested with Trombicula autumnalis larvae were treated monthly from examination to the end of the Trombicula season (range one to four months) with a 0.25 per cent fipronil spray applied to the whole body, with particular emphasis on the feet, face, ears, perineum and tail. No other antiparasite measures were used. Follow-up was by clinical examination and telephone interview until the end of the Trombicula season (range one to four months). No adverse effects were seen. Monthly treatment controlled trombiculids in 15 dogs. In two dogs localised pedal reinfestations were controlled with additional local application of fipronil to the feet every 14 days. In one dog therapy was of no benefit. In the three cats, treatment was initially effective, but generalised infestations recurred after seven to 10 days. Fipronil is a safe and effective treatment for trombiculid infestations in dogs. Residual activity lasts for 14 to 30 days. Further studies are required to examine the apparent short duration of efficacy in cats.

Reduced in vitro adherence of Staphylococcus species to feline corneocytes compared to canine and human corneocytes.

It is apparent that in-contact humans and animals exchange commensal staphylococci. Previous in vitro studies, however, indicate that staphylococci preferentially adhere to corneocytes from host species. This study compared adherence of meticillin-sensitive and -resistant Staphylococcus aureus (MSSA/MRSA), S. intermedius, S. felis and S. hominis to feline, canine and human corneocytes acquired from 10 healthy subjects using adhesive tape discs. Adherent bacteria were counted using an image processing and analysis programme. Mean adherence of MSSA (P = 0.0009), MRSA (P = 0.0162) and S. intermedius (P = 0.0117), but not S. felis or S. hominis, to feline corneocytes was significantly lower than that to canine and human corneocytes. All the isolates had similar adherence to both human and canine corneocytes. S. felis was the most adherent species to feline corneocytes followed by S. intermedius, and then MSSA, MRSA and S. hominis. For dogs and humans, S. intermedius and S. felis were the most adherent, followed by MRSA and MSSA, and then S. hominis. These results do not reveal any preferential adherence of staphylococci to canine or human corneocytes. Poor adherence to feline corneocytes could suggest that cats are relatively resistant to pyoderma and cross-species transmission of staphylococci.

House dust and forage mite allergens and their role in human and canine atopic dermatitis.

This article reviews the literature regarding the role of house dust and forage mite allergens in canine atopic dermatitis. The presence of immunoglobulin E (IgE) to these mites, especially to Dermatophagoides farinae, is common in both normal and atopic dogs. Exposure of dogs to the different mites is described both in the direct environment and in the coat of animals for house dust mites and in the food for forage mites. Allergens causing allergic disease in dogs seem to be different from those in humans. Dogs seem to react to high molecular weight allergens, compared to the low molecular weight group 1 and group 2 proteases that are commonly implicated in humans with atopic diseases. Despite numerous published studies dealing with this subject, a number of questions still need to be addressed to better understand the exact role of these mites in the pathogenesis of canine atopic dermatitis and to improve the quality of the allergens used in practice.

Serum antibodies to Malassezia yeasts in canine atopic dermatitis.

Significant numbers of humans with atopic dermatitis develop Malassezia-specific IgE. Immediate skin-test reactivity to Malassezia has been demonstrated in atopic dogs. The aim of this study was to compare the serum IgG and IgE response to Malassezia in atopic dogs with and without clinical evidence of Malassezia dermatitis and/or otitis, nonatopic dogs with clinical evidence of Malassezia dermatitis and/or otitis and healthy dogs. Cytology was used to diagnose clinically significant Malassezia dermatitis and otitis. Contact plate cultures confirmed the validity of this technique. Reproducible enzyme-linked immunosorbent assays for Malassezia-specific IgG and IgE in canine serum were established. Atopic dogs had significantly higher serum IgG and IgE levels than either healthy dogs or nonatopic dogs with clinical evidence of Malassezia dermatitis and/or otitis. There was no significant difference in IgG and IgE levels between atopic dogs with and without clinical evidence of Malassezia dermatitis and/or otitis. The implications of these findings in the pathogenesis and management of canine atopic dermatitis are discussed.

Expression of Th1, Th2 and immunosuppressive cytokine gene transcripts in canine atopic dermatitis.

BACKGROUND: Atopic dermatitis is a common inflammatory skin disease of humans and dogs. Human atopic dermatitis is associated with Th2-type responses, although Th1 cytokines can be identified in chronic lesions. In contrast, tolerance to environmental allergens in healthy individuals is mediated by regulatory T cells. OBJECTIVE: This study examined the expression of the immunosuppressive cytokines TGF-beta and IL-10, the Th2-type cytokines IL-4 and IL-6, and the Th1-type cytokines IFN-gamma, TNF-alpha, IL-2, IL-12p35 and IL-12p40, in canine atopic dermatitis. MATERIALS AND METHODS: RNA was isolated from lesional atopic, non-lesional atopic and healthy canine skin samples. Semi-quantitative reverse transcriptase polymerase chain reactions (RT-PCRs) were carried out using specific primers and one-way analyses of variance used to compare cytokine expression in each group. RESULTS: Canine atopic dermatitis was associated with over-expression of IL-4 mRNA and reduced transcription of TGF-beta compared with healthy skin (P < 0.05). Higher levels of IFN-gamma, TNF-alpha and IL-2 mRNA were seen in lesional compared with non-lesional and healthy skin (P < 0.05). There were no significant differences in IL-10, IL-6, IL-12p35 or IL-12p40 transcription between the three groups. CONCLUSIONS: This is the first report to demonstrate that canine atopic dermatitis is associated with over-production of IL-4. Clinical tolerance in healthy individuals appears to be associated with TGF-beta, although it is unclear if this reflects an active mechanism or simply non-responsiveness of the immune system. Th1 cytokines may be induced by subsequent self-trauma and secondary infections in atopic skin. We believe that these results better characterize spontaneously occurring canine atopic dermatitis. We further propose that this should be investigated as a possible animal model of human atopic dermatitis.