Search Results (192)

Malassezia spp. are commensal yeasts of canine skin that may act as opportunistic pathogens. The aim of this study was to assess the presence, distribution and numbers of Malassezia spp. on the skin and external ear canal in clinically healthy Golden Retrievers and Bernese Mountain Dogs, to evaluate the influence of breed, age and sex, and to compare the findings with previously published cytological reference values. Fifty clinically healthy Golden Retrievers and 50 Bernese Mountain Dogs were included in the study. Both external ear canals and six body sites (perioral region, chin, axilla, interdigital spaces, inguinal region and dorsum) were sampled. The external ear canals were sampled using a sterile cotton swab, while the skin sites were sampled using the adhesive tape technique. The slides obtained were microscopically examined, and the number of Malassezia spp. was recorded. All data were statistically analyzed. Malassezia spp. were observed in all dogs, with different distributions in ear and skin areas. Malassezia spp. counts were significantly higher in Golden Retrievers than in Bernese Mountain Dogs at all skin sites. No significant difference was observed between breeds in the external ear canal. Forty-nine (98%) Golden Retrievers and 35 (74%) Bernese Mountain Dogs showed a mean skin number of Malassezia spp. per oil immersion field (OIF) above the 1 yeast/OIF literature threshold commonly used in the presence of clinical signs. No relationship was found between the mean value of Malassezia spp. per microscopic field and sex or age in either breed. The results show that Golden Retrievers have higher Malassezia spp. counts across all evaluated skin sites compared with Bernese Mountain Dogs. Whether higher baseline Malassezia spp. populations contribute to clinical yeast overgrowth requires further investigation. No significant difference in external ear canal Malassezia spp. counts was observed between breeds; however, the mean values recorded in both populations exceeded cytological reference values for healthy dogs. These findings indicate that cytological Malassezia spp. counts in clinically healthy dogs may vary according to breed and anatomical site. Diagnostic interpretation should therefore integrate cytological findings with clinical signs, breed, site, and sampling method. Further studies are required to establish normal reference intervals for Malassezia spp. per microscopic field based on breed and anatomical site. Full article

Staphylococcus pseudintermedius is a common opportunistic pathogen in companion animals and a leading cause of skin and soft tissue infections (SSTIs). Despite its clinical relevance, the genomic determinants underlying pathogenicity and the transition from commensal carriage to invasive infection remain poorly understood. This study aimed to identify the genomic determinants of SSTI pathogenic potential in S. pseudintermedius and to determine whether pathogenicity is driven by single, major-effect virulence genes or by polygenic genome-wide genetic architecture. Using accessory gene-based and unitig-based genome-wide association studies (GWASs), employing a linear mixed model, across a genetically diverse collection of S. pseudintermedius isolates spanning multiple phylogenetic clades, we found that disease and carriage isolates showed no phylogenetic clustering. SSTI pathogenicity exhibited high narrow-sense heritability. Surface-associated LPXTG-anchored proteins, particularly spsF, harbored the strongest associations, with additional signals in iron metabolism (narH, sufB) and oxidative stress tolerance (ahpC). Random Forest classification validated GWAS signals. SSTI pathogenicity in S. pseudintermedius reflects a polygenic architecture driven by cumulative variation across surface-associated, metabolic, and stress-response loci, shifting focus from single virulence genes to genome-wide genetic variation. Full article

Intradermal injections of anti-canine immunoglobulin E (IgE) in healthy dogs have been utilized in preclinical drug testing to evaluate the efficacy of anti-allergic drugs used to treat canine atopic dermatitis (AD). However, the molecular effects of established canine anti-allergic drugs on this acute canine IgE-mediated atopic model remain largely uninvestigated. The objective of this study was to characterize the effect of proactive oclacitinib and prednisolone treatments on the immune and skin barrier transcriptome of IgE-mediated late-phase reactions (LPRs) in an acute model of canine AD. Sixteen healthy adult research-bred beagles were randomized to receive either oclacitinib or prednisolone orally for six days, followed by an intradermal anti-canine IgE injection. Biopsies were collected 24 h post-injection for RNA isolation and sequencing; previously analyzed transcriptomes (healthy skin, saline-injected skin, IgE lesions without drug modulation) from the same colony of dogs served as controls. Administration of prednisolone and oclacitinib prior to intradermal anti-IgE injections reduced the number of differentially expressed genes (DEGs) in 24 h samples to 1251 and 1471, respectively. Both treatments resulted in a decrease in expression of several significantly upregulated T helper-(Th)1 (e.g., MX1, OAS1, STAT1), Th2 (e.g., CCL13, CCL8, IL13RA1, IL-33, IL5RA, OSM), chemokine and receptor (e.g., CCL19, CCL2, CCL3, CCR1, CCR3) genes in comparison to the untreated IgE-mediated lesions. Interestingly, only prednisolone treatment significantly reduced IL-13 upregulation, an important gene in the Th2 immune response. In conclusion, both prednisolone and oclacitinib reduced the transcriptomic changes observed in the acute lesions of the canine IgE-induced atopic dermatitis model, with prednisolone inducing a broader inhibitory immune response. Full article

Alterations in the ceramide (CER) profile have been associated with atopic dermatitis in dogs; however, the specific effects of CER subclasses on canine keratinocytes remain unclear. This study aimed to optimize a CER complex and evaluate its effects on cytokine expression, CER synthesis, and skin barrier formation using canine epidermal keratinocyte progenitor (CPEK) cells and a reconstructed canine epidermis (RCE) model. Among various CER combinations tested, only the mixture of CER [NS] and [EOP] significantly reduced proinflammatory cytokine mRNA levels in Staphylococcus pseudintermedius–stimulated CPEK cells. Further optimization revealed that a 4:1 ratio of CER [NS] to [EOP] (cCER complex) markedly decreased CCL17 and CCL22 mRNA expression while upregulating keratin 10, ceramide synthase 3 (CERS3), and ceramide synthase 4, as well as enzymes involved in both de novo and salvage CER biosynthesis pathways. In the RCE model, cCER administration improved stratum corneum organization and increased the expression of loricrin, CERS3, and CER. In vivo application of cCER in dogs accelerated skin barrier repair and improved hair condition. These findings suggest that a CER [NS]/[EOP] mixture represents a promising therapeutic option with anti-inflammatory and skin barrier-enhancing effects for canine atopic dermatitis. Full article

Background/Objectives: The increasing emergence of antimicrobial-resistant Staphylococcus pseudintermedius has limited the effectiveness of conventional therapies for canine pyoderma, highlighting the need for alternative topical strategies. This study aimed to develop hydrogels incorporating essential oils (EOs) from Peumo (Cryptocarya alba) and Tepa (Laureliopsis philippiana) as potential topical treatments against Staphylococcus pseudintermedius skin infections in veterinary medicine. Methods: EOs were obtained by steam distillation, chemically characterized by gas chromatography–mass spectrometry (GC–MS), and evaluated for antibacterial activity against S. pseudintermedius strains. Carbopol^®-based hydrogels incorporating the EOs of C. alba (HCA), L. philippiana (HLP), and a control vehicle (HVE) were formulated and characterized in terms of physicochemical properties, microbiological safety, and stability under accelerated and refrigerated conditions. Preclinical dermal safety was evaluated in BALB/c mice by repeated topical administration for five days. The analysis included clinical observation, skin irritation scoring, and histological analysis. Additionally, a preliminary microbiological evaluation was conducted in client-owned dogs with superficial pyoderma to assess the performance of the formulations in the target species. Skin lesion swabs were collected at baseline and after 21 days of treatment, followed by bacterial culture and automated identification using the VITEK^® system. Bacterial detection and bacterial load were evaluated to determine changes in microbiological status over the treatment period. Results: GC–MS analysis identified sabinene and eucalyptol as the main compounds in CA-EO, and linalool, eucalyptol, and safrole in L. philippiana EO. Both EOs exhibited moderate antibacterial activity against S. pseudintermedius (inhibition zones 4.9–10.8 mm; MIC ≥ 2.048 mg mL⁻¹). The hydrogels were microbiologically safe. Among formulations, HLP demonstrated superior physical stability and comparable rheological properties to the vehicle. In vivo safety evaluation demonstrated no signs of systemic toxicity, behavioral alterations, or skin irritation, and histological analysis confirmed preserved skin architecture without evidence of inflammation or tissue damage. In the preliminary microbiological evaluation in dogs, all animals were positive for Staphylococcus spp. at baseline. On Day 21, bacterial elimination was observed in the active treatment groups, but not in the HVE group, with elimination rates of 50.0% for Inveclor^® and 25.0% for both HCA and HLP. In parallel, HLP showed the highest proportion of dogs reaching minimal bacterial load levels (75%), followed by Inveclor^® (50.0%) and HCA (37.5%), whereas no dogs in the vehicle group reached this category. Conclusions: EOs from C. alba and L. philippiana presented antibacterial activity and were successfully incorporated into microbiologically safe hydrogel formulations. Notably, HLP demonstrated superior stability and a favorable preclinical safety profile, supporting its potential. In the preliminary microbiological evaluation in dogs, numerical differences in bacterial elimination and bacterial load categories were observed among groups; however, these differences were not statistically significant and should be interpreted as exploratory. Full article

Background: Bacterial skin infections in companion animals, particularly those involving multidrug-resistant Pseudomonas aeruginosa and methicillin-resistant Staphylococcus, pose significant therapeutic challenges due to rising resistance and biofilm formation. While Piper betle is well-recognized in human medicine, data on its efficacy against veterinary isolates—and the comparative phytochemistry and potency of its extracts versus essential oils—remains scarce. Objective: This study evaluated the antimicrobial and antibiofilm efficacy of an ethanolic P. betle leaf extract compared to a panel of representative essential oils—including P. betle leaf oil, clove, tea tree, and plai—against 73 feline and canine clinical isolates. Methods: Minimum inhibitory (MIC) and bactericidal (MBC) concentrations were determined via broth microdilution. Biofilm inhibition was assessed using crystal violet staining to determine the minimum biofilm inhibitory concentration (MBIC). Phytochemical profiles were characterized using gas chromatography–mass spectrometry (GC–MS) and liquid chromatography–quadrupole time-of-flight mass spectrometry (LC–MS/MS-QTOF). Results: P. betle leaf extract exhibited superior anti-pseudomonad activity (mean MIC: 1.5 mg/mL; MBC: 1.9 mg/mL), demonstrating significantly greater potency than the tested essential oils. Among the essential oils, clove oil was the most effective against Staphylococcus strains (mean MIC: 0.8 mg/mL; MBC: 1.2 mg/mL). Despite 74.4% of P. aeruginosa and 90.0% of Staphylococcus spp. being strong biofilm producers, the P. betle extract demonstrated the highest inhibitory potency against P. aeruginosa (MBIC: 0.7 mg/mL) and, alongside clove oil, showed superior efficacy against Staphylococcus spp. (MBICs: 0.3 and 0.7 mg/mL, respectively). GC–MS analysis identified chavibetol (confirmed via standard spiking) and hydroxychavicol as the primary extract constituents. LC–MS/MS-QTOF profiling further revealed a prominent phenolic profile, including 2,3-dihydroxybenzoic acid and 3,4-dihydroxybenzaldehyde. Comparative analysis suggests that while clove oil efficacy is primarily driven by high eugenol content, the broad-spectrum potency of the P. betle extract arises from a complex phenolic richness, specifically the synergistic presence of hydroxychavicol and chavibetol. Conclusions: These findings confirm the robust potential of P. betle extract as a promising plant-based antiseptic for managing biofilm-associated infections and mitigating antimicrobial resistance in veterinary medicine. Full article

Canine atopic dermatitis (AD) is a common allergic skin disease for which identifying allergen sensitization via IgE serological or intradermal testing is necessary to implement allergen-specific immunotherapy. Because serum IgE has a short half-life and circulating levels fluctuate with environmental allergen exposure, the timing of blood sampling may influence serological test outcomes. This cross-sectional study assessed seasonal variation in allergen-specific IgE concentrations and seropositivity rates across pollen and mite allergen categories in Scandinavian dogs suspected of allergic disease. PAX multiplex macroarray results from 5014 canine sera submitted by veterinarians across Denmark, Norway, and Sweden over one full year were retrospectively analyzed for 17 allergens, including tree, grass, and weed pollens, house dust mites, and storage mites. Mean sIgE levels showed statistically significant but relatively small seasonal variation. Seropositivity rates, however, showed clearer patterns: seropositivity for tree and weed pollen was highest in spring and summer, and that for house dust mite peaked in autumn and winter, while storage mite sensitization rates showed the opposite trend. These results confirm that IgE serological test results in dogs are affected by the sampling season and emphasize the importance of considering timing when collecting and interpreting IgE serological tests in atopic dogs. Full article

Background: Antimicrobial resistance in Staphylococcus pseudintermedius is an increasing concern in small animal medicine, particularly due to methicillin-resistant strains and associated multidrug resistance. This study aimed to characterize antimicrobial susceptibility patterns in clinical canine isolates, determine the prevalence of methicillin resistance, and assess the presence of mecA and mecC genes. Methods: A total of 243 clinical isolates from canine skin samples collected in Hungary between 2023 and 2025 were analyzed. Minimum inhibitory concentrations (MICs) for 24 antimicrobial agents were determined using broth microdilution in accordance with CLSI guidelines. Isolates were classified as methicillin-resistant or susceptible based on oxacillin MIC values. PCR assays targeting mecA and mecC were performed on oxacillin-resistant isolates. Results: Of the 243 isolates, 47 (19.3%) were methicillin-resistant. High resistance rates were observed for β-lactams, tetracyclines, macrolides, and lincosamides, while rifampicin, amikacin and florfenicol retained good to excellent activity. Methicillin-resistant isolates exhibited substantially higher resistance across multiple antimicrobial classes. Overall, 50.6% of all isolates were classified as multidrug-resistant (MDR) and 17.3% as extensively drug-resistant (XDR), while no pandrug-resistant (PDR) isolates were detected; all methicillin-resistant isolates were at least MDR. The mecA gene was detected in 80.9% of oxacillin-resistant isolates, while mecC was not identified. Conclusions: Methicillin resistance in canine S. pseudintermedius is closely associated with multidrug resistance, limiting therapeutic options. However, selected agents, including rifampicin, amikacin and florfenicol, retained in vitro activity. Partial discordance between phenotypic resistance and mecA detection highlights the importance of combined phenotypic and molecular approaches. These findings have direct implications for empirical antimicrobial therapy and support targeted treatment strategies, while emphasizing the importance of antimicrobial stewardship in small animal practice. Full article

Mast cell tumors are the most common skin neoplasm in dogs and may be influenced by reproductive status. A gonadectomy modifies gonadotropin levels and may affect the expression of hormonal receptors and proliferative factors; however, the evidence for this remains limited. The objective of this study was to evaluate the expression of VEGF, IGF-1, PCNA, Ki-67, c-KIT, LHR, FSHR, and ERα in intact and neutralized female dogs with and without MCTs. Gene expression in the skin samples was quantified by a real-time PCR, and four groups were included: intact controls (n = 10), neutralized controls (n = 10), intact MCT (n = 9), and neutralized MCT (n = 10). Tumor presence was associated with increased expression of LH and FSH receptors and c-KIT, while angiogenic and proliferative factors (PCNA, Ki-67, IGF-1, VEGF, and ERα) showed lower expression. In dogs with MCTs, a gonadectomy was associated with higher c-KIT and VEGF expression but lower LHR mRNA levels. PCNA expression was lower in the neutralized MCT dogs compared to the neutralized controls, whereas no differences were observed in the intact dogs. Additionally, ERα expression was higher in the neutralized control dogs than in the intact controls, with no differences detected in the MCT dogs. These findings suggest that reproductive status is associated with differential regulation of molecular pathways involved in canine MCT biology. Full article

Canine atopic dermatitis is a hereditary chronic inflammatory and pruritic skin disease, which is mediated by T cells and requires long-term, individualized management. In recent years, numerous studies have described a wide range of therapeutic approaches for canine atopic dermatitis, including fast-acting symptomatic treatments, long-term immune-modulating interventions, and strategies to support skin barrier function and microbial balance. This review summarizes the principal treatment modalities currently available, including glucocorticoids, cyclosporine A, mycophenolate, Janus kinase inhibitors, lokivetmab, and allergen-specific immunotherapy, as well as complementary strategies aimed at restoring skin barrier integrity. Emphasis is placed on the importance of a multimodal and personalized approach to optimize long-term disease control and improve quality of life in affected dogs. Providing an integrated overview of current evidence, this article aims to guide clinicians in making informed, evidence-based decisions and to support the safe and effective management of canine atopic dermatitis. Full article

Canine atopic dermatitis is a common chronic inflammatory skin disease characterized by pruritus and recurrent erythema, yet objective blood biomarkers for monitoring disease activity remain limited. In this study, we evaluated serum cytokine profiles and their associations with clinical severity in client-owned dogs with atopic dermatitis. A total of 143 dogs were enrolled, including 28 healthy and 115 dogs with atopic dermatitis. The atopic dermatitis group was further categorized into untreated dogs (n = 27; no systemic therapy for ≥4 weeks) and systemically treated dogs (n = 88). Serum concentrations of IFN-γ, IL-10, IL-13, IL-31, and TGF-β1 were measured using an enzyme-linked immunosorbent assay. Group differences were assessed using the Kruskal–Wallis test with Bonferroni-adjusted post hoc comparisons, and correlations with the pruritus visual analog scale (pVAS) and the Canine Atopic Dermatitis Extent and Severity Index-04 (CADESI-04) were analyzed using Spearman’s rank correlation. Serum IFN-γ, IL-13, and IL-31 concentrations differed significantly among groups (p < 0.001, p = 0.001, and p = 0.004, respectively). IFN-γ and IL-13 concentrations were lower in treated dogs than in healthy dogs and untreated dogs, whereas IL-31 concentrations were higher in dogs with atopic dermatitis than in healthy dogs, regardless of treatment status. In correlation analyses, the pVAS showed a negative correlation with IFN-γ (r = −0.239, p = 0.004) and a positive correlation with IL-31 (r = 0.173, p = 0.039), while CADESI-04 showed a negative correlation with IFN-γ (r = −0.252, p = 0.002). IL-10 and TGF-β1 did not show significant differences among groups or correlations with clinical indices. These findings suggest that serum IL-31 may reflect pruritus-related immune signaling that can persist despite clinical improvement. While IFN-γ may show a weak negative correlation with clinical severity indices, its potential association with chronic dermatologic changes, such as lichenification, requires further investigation in relation to disease chronicity. Together, these results indicate that circulating cytokine profiles and clinical indices do not necessarily change in parallel and that selected cytokines may provide complementary information when interpreting disease activity in canine atopic dermatitis. These profiles should be interpreted while considering the diverse immunomodulatory mechanisms of the systemic therapy administered. Full article

Antimicrobial resistance is an emerging challenge in veterinary medicine, particularly in dogs, where bacterial skin infections are highly prevalent. Honey and its bioactive extracts have emerged as potential natural alternatives to conventional antimicrobials. This study evaluated the antimicrobial activity of methanolic extracts from four honey types collected in Central Chile against multidrug-resistant (MDR) bacterial isolates from canine patients, including Enterococcus faecium, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Pasteurella multocida, and Enterobacter cloacae. Antimicrobial potency was assessed by minimum inhibitory concentration (MIC), and phenolics, flavonoids, and antioxidant capacity were quantified. All extracts inhibited bacterial growth, with E. coli, E. faecium and S. aureus being the most susceptible (MIC 3.13% w/v), while Gram-negative bacteria such a P. aeruginosa, P. multocida, and E. cloacae required higher concentrations (MIC 12.5% w/v). Secondary metabolite analysis revealed seasonal and apiary-related variations, with apiary 2 honey showing significantly higher phenolic (195.58 ± 4.28 mg GAE/100 g) and flavonoid (65.46 ± 4.35 mg QE/100 g) contents in summer. In contrast, antioxidant capacity (FRAP) did not differ significantly. These findings indicate that honey’s antimicrobial properties are closely related to its bioactive composition and influenced by season and floral origin, reinforcing its potential as a sustainable alternative to antibiotics in veterinary medicine under the One Health approach. Full article

Background: Methicillin-resistant Staphylococcus pseudintermedius (MRSP) represents an emerging challenge in veterinary dermatology. Commercially available ozonated oils promise antibacterial activity, but their efficacy under physiologically relevant conditions remains unexplored. Objective: We aimed to evaluate the efficacy of commercial ozonated olive oil product (800 mEq O₂/kg) against MRSP using an established in vitro model and a newly presented ex vivo canine skin model. Materials and Methods: In vitro susceptibility testing determined minimum inhibitory concentrations (MIC) and time–kill kinetics. Subsequently, canine skin samples were mounted in Franz diffusion cells, inoculated with MRSP (~10⁶ colony-forming units [CFU]), and treated for 8 h with ozonated or placebo olive oil. Bacterial viability was assessed by quantitative culture and histopathology. Results: In vitro testing demonstrated antibacterial activity for ozonated oil (MIC < 20% v/v) compared to placebo oil (90% v/v), with ozonation-specific bactericidal effects. However, ex vivo testing showed no MRSP reduction for either oil versus untreated controls, with bacterial localization in superficial dermis unchanged. Conclusions: Despite in vitro activity, this ozonated olive oil failed to reduce MRSP in ex vivo skin, revealing that tissue barriers prevent antibacterial delivery. These findings demonstrate that in vitro screening cannot predict topical efficacy and emphasize the necessity of tissue-based validation before clinical use. Full article

Atopic dermatitis (AD) and canine atopic dermatitis (CAD) are common allergic and pruritic skin diseases characterized by immune dysregulation and epidermal barrier dysfunction. To delineate how Th2 cytokines contribute to CAD pathogenesis, canine primary epidermal organoids (cPEOs) were established from keratinocytes, and exposure to IL-4/IL-13 induced morphologic changes characteristic of CAD. RNA sequencing analysis comparing IL-4/IL-13-treated cPEOs to untreated controls identified 224 differentially expressed genes (DEGs). Further rigorous filtering narrowed this down to 69 key DEGs, with the majority being associated with atopic dermatitis in both dogs and humans. Pathway enrichment analyses demonstrated the activation of immune and inflammatory signalling and suppression of epidermal differentiation, keratinisation, and lipid metabolism, recapitulating key features of atopic skin. Additional Th2-driven alterations included dysregulation of neuro-immune signalling, calcium homeostasis, apoptosis, extracellular matrix remodelling, and metabolic/epigenetic regulations. Together, these findings demonstrate that Th2 cytokines orchestrate multifaceted transcriptomic alterations relevant to AD/CAD. By mapping each key DEG to its known or putative role in AD/CAD, this study also provides a gene-level functional framework to inform future mechanistic studies and targeted therapeutic development. These findings also underscore the value of this model as a comparative tool for investigating both human and canine atopic dermatitis. Full article

Background/Objectives: Streptococcus intermedius, a member of the Streptococcus anginosus group, is characterized by a marked propensity for abscess formation but only rarely causes native-joint septic arthritis. Involvement of the acromioclavicular (AC) joint is particularly uncommon. We describe a case of native AC joint septic arthritis due to S. intermedius in a patient with multiple predisposing factors and highlight diagnostic and management considerations. Methods: We report the clinical course of a 72-year-old man with poorly controlled type 2 diabetes mellitus who presented with progressive right shoulder pain, erythema, and swelling following recurrent minor skin abrasions from a newly adopted dog. Initial management for presumed inflammatory shoulder pathology included brief systemic corticosteroids and an ultrasound-guided intra-articular ketorolac injection. Magnetic resonance imaging (MRI) was performed after symptom progression. The patient underwent operative irrigation and debridement with collection of synovial fluid and deep tissue cultures. Blood cultures and transthoracic echocardiography were obtained to evaluate for systemic involvement. Results: MRI demonstrated multiloculated periarticular abscesses and osteolysis centered on the AC joint. Operative cultures yielded high colony counts of S. intermedius from synovial fluid and deep tissues. Blood cultures and echocardiography were negative. The patient required multiple operative debridements with irrigation, adjunctive local antibiotic therapy, and prolonged targeted β-lactam treatment. Clinical and radiographic improvement was achieved following surgical source control and antimicrobial therapy. Conclusions: Native AC joint septic arthritis due to S. intermedius is rare. Older age, uncontrolled diabetes, recent intra-articular intervention, and possible zoonotic inoculation from canine wound licking may represent contributory risk factors. Early imaging, prompt surgical source control, and guideline-concordant antimicrobial therapy are essential when bone and soft tissue involvement is present. Full article