Cutaneous infiltrates and peripheral blood immune responses in dogs with immunomodulatory‐responsive lymphocytic–plasmacytic pododermatitis

This study characterizes T‐ and B‐lymphocyte responses in the peripheral blood and lesional skin of dogs with immunomodulatory‐responsive lymphocytic–plasmacytic pododermatitis (ImR‐LPP), a term previously proposed to denote a subpopulation of dogs with idiopathic pododermatitis. T‐cell (CD3⁺, CD4⁺ and CD8⁺) and B‐cell (CD21⁺) counts were significantly increased in both the epidermis and dermis of lesional ImR‐LPP skin compared with that in pedal skin from healthy controls. CD3⁺, CD4⁺, CD8⁺ and CD21⁺ cells were commonly observed in perivascular sites in the superficial dermis, periadnexally, beneath the dermal–epidermal (DE) junction and in the epidermis of lesional ImR‐LPP skin. The CD8⁺/CD3⁺ T‐cell ratio in peripheral blood was significantly increased in the ImR‐LPP group (0.42 versus 0.35 in controls). Serum IgA, IgG and IgM concentrations were all significantly elevated in affected dogs. Lymphocyte stimulation indices in ImR‐LPP dogs were comparable with control levels except for a lower response to ionomycin (6.0 versus 11.1). Dogs with ImR‐LPP had a higher incidence and mean (semi‐quantitative) score for IgA, IgG and IgM deposits in the epidermis, and a significantly increased incidence of dermal IgA⁺, IgG⁺ and IgM⁺ mononuclear inflammatory cells. The results indicate that upregulated T‐ and B‐lymphocyte responses may contribute to the pathogenesis of the skin lesions observed in dogs with ImR‐LPP.     

Heterogeneity of Staphylococcus pseudintermedius isolates from atopic and healthy dogs

Staphylococcus pseudintermedius is part of the normal canine flora but frequently causes pyoderma in canine atopic dermatitis (AD). This study aimed to determine whether particular S. pseudintermedius strains were associated with AD and/or pyoderma. Ninety‐six S. pseudintermedius isolates from the ear, nares, perineum and lesions of 21 atopic and 16 healthy dogs were lysed with proteinase K and digested with 40 U SmaI. Restriction products were separated using pulsed‐field gel electrophoresis (PFGE) with an Oxford S. aureus control and lambda‐ladder DNA concatomer markers. A dendrogram was constructed by the unweighted pair group method. All isolates showed a ≥56% similarity coefficient. Nine distinct PFGE clusters were identified, as follows: five from both atopic and healthy dogs; three from atopic dogs only; and one from healthy dogs only. Nine clusters were isolated from the nares, eight from the perineum, five from the ears and six from pyoderma lesions. There were no significant differences in the frequency of isolation from atopic or healthy skin, body sites or infected lesions for any of the clusters. Two of six healthy dogs and 18 of 20 atopic dogs with multiple isolates had closely related isolates (less than three band differences) at more than one sampling site. Isolates from pyoderma lesions were closely related to at least one mucosal isolate in 11 of 16 dogs. Staphylococcus pseudintermedius isolates appear to be heterogeneous, and colonization or infection of atopic skin was not associated with any particular strain or cluster of strains.     

Usefulness of cefovecin disk‐diffusion test for predicting mecA gene‐containing strains of Staphylococcus pseudintermedius and clinical efficacy of cefovecin in dogs with superficial pyoderma

Background –  Cefovecin has been widely used to treat skin infections in dogs. The relationship of the cefovecin disk‐diffusion test results to the presence of the mecA gene and the clinical efficacy of cefovecin have not been fully evaluated. Hypothesis/Objectives –  To determine the usefulness of an in vitro cefovecin disk‐diffusion test in predicting the presence of the mecA gene in Staphylococcus pseudintermedius, as well as the in vivo efficacy of cefovecin therapy in dogs with superficial pyoderma. Methods –  Twenty‐six S. pseudintermedius strains isolated from 22 dogs with pyoderma were used. In vitro disk‐diffusion test results of cefovecin were compared with agar‐dilution test results, the presence of the mecA gene, and the improvement in clinical scores of dogs with superficial pyoderma at 14 days post treatment. Results –  There was a significant linear correlation (r = ?0.83) between the diameter of the obvious zone of inhibition by disk diffusion and the minimal inhibitory concentration for cefovecin (P < 0.0001). Receiver operating characteristic analysis revealed that zone diameters between 25 and 27 mm exhibited better sensitivity (92.9%) and specificity (100.0%) for detection of strains carrying the mecA gene. The mean improvement in clinical scores in dogs carrying cefovecin‐resistant strains was significantly lower than in dogs carrying cefovecin‐susceptible strains (P < 0.01). Conclusions and clinical importance –  The cefovecin disk‐diffusion test with a cut‐off value estimated in this study was valuable for predicting mecA gene carriage in S. pseudintermedius, as well as the in vivo efficacy of cefovecin therapy in dogs with superficial pyoderma caused by S. pseudintermedius.     

Antimicrobial resistance of Staphylococcus pseudintermedius

Staphylococcus pseudintermedius, Staphylococcus intermedius and Staphylococcus delphini together comprise the S. intermedius group (SIG). Within the SIG, S. pseudintermedius represents the major pathogenic species and is involved in a wide variety of infections, mainly in dogs, but to a lesser degree also in other animal species and humans. Antimicrobial agents are commonly applied to control S. pseudintermedius infections; however, during recent years S. pseudintermedius isolates have been identified that are meticillin‐resistant and have also proved to be resistant to most of the antimicrobial agents approved for veterinary applications. This review deals with the genetic basis of antimicrobial resistance properties in S. pseudintermedius and other SIG members. A summary of the known resistance genes and their association with mobile genetic elements is given, as well as an update of the known resistance‐mediating mutations. These data show that, in contrast to other staphylococcal species, S. pseudintermedius seems to prefer transposon‐borne resistance genes, which are then incorporated into the chromosomal DNA, over plasmid‐located resistance genes.     

Prevalence of meticillin-resistant Staphylococcus pseudintermedius (MRSP) from skin and carriage sites of dogs after treatment of their meticillin-resistant or meticillin-sensitive staphylococcal pyoderma

Background – Meticillin‐resistant staphylococci are significant pathogens in veterinary dermatology, yet longitudinal studies of the impact of routine antimicrobial therapy on emergence or resolution of resistance are lacking. Objectives – To determine the prevalence of meticillin‐resistant staphylococci on skin and carriage sites in dogs with bacterial pyoderma and evaluate the prevalence of meticillin‐resistant Staphylococcus pseudintermedius (MRSP) colonization after successful treatment of pyoderma. Animals – One hundred and seventy‐three dogs that presented to a dermatology referral service with pyoderma and 41 healthy control dogs. Methods – Skin, nasal and rectal swabs for bacterial culture were collected at the time of referral and after clinical resolution of the pyoderma. Meticillin resistance was confirmed by demonstration of penicillin binding protein 2a antigen. Results – Initially, skin cultures yielded MRSP in 70 (40.5%) dogs, meticillin‐resistant Staphylococcus aureus (MRSA) in three (1.7%) and meticillin‐resistant Staphylococcus schleiferi ssp. coagulans (MRSScoag) in five (2.9%). Samples collected from the nose and rectum (carriage sites) yielded MRSP in 59 (34.1%) dogs, MRSA in 11 (6.4%) and MRSScoag in seven (4.0%). One hundred and two dogs were available for follow‐up cultures after clinical cure. Of 42 dogs initially diagnosed with MRSP pyoderma, MRSP was isolated at follow‐up from skin in 19 (45.2%) and carriage sites in 20 (47.6%). Of 60 dogs that did not have MRSP pyoderma initially, MRSP was isolated post‐treatment from the skin in 17 (28.3%), and MRSP from carriage sites increased from 7.8% (initially) to 26.7% (P = 0.0022). Conclusions and clinical importance – Colonization by MRSP often persists after resolution of MRSP pyoderma. Acquisition of MRSP during treatment appears to be common.     

Staphylococcus pseudintermedius expresses surface proteins that closely resemble those from Staphylococcus aureus

Staphylococcus pseudintermedius is a commensal of dogs that is implicated in the pathogenesis of canine pyoderma. This study aimed to determine if S. pseudintermedius expresses surface proteins resembling those from Staphylococcus aureus and to characterise them. S. pseudintermedius strain 326 was shown to adhere strongly to purified fibrinogen, fibronectin and cytokeratin 10. It adhered to the α-chain of fibrinogen which, along with binding to cytokeratin 10, is the hallmark of clumping factor B of S. aureus, a surface protein that is in part responsible for colonisation of the human nares. Ligand-affinity blotting with cell-wall extracts demonstrated that S. pseudintermedius 326 expressed a cell-wall anchored fibronectin binding protein which recognised the N-terminal 29 kDa fragment. The ability to bind fibronectin is an important attribute of pathogenic S. aureus and is associated with the ability of S. aureus to colonise skin of human atopic dermatitis patients. S. pseudintermedius genomic DNA was probed with labelled DNA amplified from the serine-aspartate repeat encoding region of clfA of S. aureus. This probe hybridised to a single SpeI fragment of S. pseudintermedius DNA. In the cell-wall extract of S. pseudintermedius 326, a 180 kDa protein was discovered which bound to fibrinogen by ligand-affinity blotting and reacted in a Western blot with antibodies raised against the serine-aspartate repeat region of ClfA and the B-repeats of SdrD of S. aureus. It is proposed that this is an Sdr protein with B-repeats that has an A domain that binds to fibrinogen. Whether it is the same protein that binds cytokeratin 10 is not clear.     

In vitro evaluation of topical biocide and antimicrobial susceptibility of Staphylococcus pseudintermedius from dogs

Background – Staphylococcus pseudintermedius is an important canine pathogen, and the emergence and widespread dissemination of meticillin‐resistant strains (MRSP) is of significant concern. Multidrug‐resistant infections may require alternative approaches, such as the use of topical therapy. There is minimal information about the in vitro susceptibility of meticillin‐susceptible S. pseudintermedius (MSSP) and MRSP to biocides and topical antimicrobials. Hypothesis/Objectives – The hypothesis was that clinical isolates of MSSP and MRSP would not have universal susceptibility to topical biocides and antimicrobials. The goal of this study was to assess the susceptibility of a collection of S. pseudintermedius isolates to selected antimicrobials and biocides. Animals – The study was performed on clinical isolates of MSSP and MRSP from dogs with skin and soft tissue infections collected throughout North America between 2006 and 2008. Methods – The minimal inhibitory concentrations (MICs) of chlorhexidine digluconate, benzalkonium chloride, triclosan, accelerated hydrogen peroxide, geranium oil, tea tree oil and grapefruit seed extract were tested for 25 MRSP and 25 MSSP isolates from dogs using the agar dilution method. The MICs of fusidic acid, bacitracin and mupirocin were determined using Etests. Results – Triclosan demonstrated excellent activity against all bacterial isolates, with no growth at the lowest concentration evaluated (MIC ≤ 0.5 μg/mL). Conversely, grapefruit seed extract did not inhibit growth at the highest concentration tested (MIC > 3.84 μg/mL). All isolates were susceptible to mupirocin, fusidic acid and bacitracin. There were no significant differences noted in the range, MIC₅₀ or MIC₉₀ between MSSP and MRSP isolates. Conclusions and clinical importance – While isolates were susceptible to most of the tested compounds, universal susceptibility to all compounds with potential antimicrobial activity cannot be assumed, and specific testing is required.     

Serum anti‐Staphylococcus pseudintermedius IgE and IgG antibodies in dogs with atopic dermatitis and nonatopic dogs

Background – Dogs and humans with atopic dermatitis (AD) are predisposed to colonization and recurrent infection with Staphylococcus spp. Studies in humans suggest that staphylococcus‐specific immunoglobulin E (IgE) plays a key role in disease pathogenesis. Few such studies have been undertaken in dogs. Hypothesis/Objectives – The aim of this study was to compare levels of staphylococcus‐specific IgE and immunoglobulin G (IgG) in dogs with AD, nonatopic dogs with staphylococcal pyoderma, and nonatopic and noninfected control dogs. Animals – Sera were collected from 108 dogs with AD, 39 nonatopic dogs with staphylococcal pyoderma secondary to different underlying conditions, 67 age‐matched nonatopic control dogs, and nine control dogs reared in minimal disease conditions. Methods – Serum Staphylococcus pseudintermedius‐specific IgE and IgG antibodies were measured by enzyme‐linked immunosorbent assay. Results – Dogs with AD had significantly higher levels of anti‐staphylococcal IgE than nonatopic dogs with staphylococcal pyoderma and the two groups of control dogs. Levels of anti‐staphylococcal IgG were significantly higher in atopic dogs and nonatopic dogs with pyoderma compared with nonatopic control dogs and control dogs reared in minimal disease conditions, but there was no significant difference in levels of anti‐staphylococcal IgG between dogs with AD and nonatopic dogs with pyoderma. Conclusions and clinical importance – A significantly increased IgE response to S. pseudintermedius antigens in atopic dogs suggests an immunopathogenic role for anti‐staphylococcal IgE. The finding of elevated IgE and IgG in atopic dogs is also important as a prelude to studies on antigenic specificity and possible correlations with disease phenotype.     

Case–control study of Staphylococcus lugdunensis infection isolates from small companion animals

Background – Coagulase‐negative Staphylococcus lugdunensis has recently been shown to cause invasive infections of people, which are similar in pathogenic effect to those caused by Staphylococcus aureus. Little is known about the pathogenicity of S. lugdunensis in companion animals. Objectives – To compare potential risk factors for infection, body sites affected, and whether cases and controls had been treated with antimicrobial drugs based upon susceptibility test results. Animals – Thirty‐three cases of S. lugdunensis infection (25 dogs, six cats and two small mammals) were identified between January 2003 and August 2011. Two Staphylococcus pseudintermedius controls, which were identified by the microbiology laboratory immediately before and after each S. lugdunensis case, were host‐species matched to each case. Methods – A retrospective case–control analysis. Results – During the period evaluated, the prevalence of S. lugdunensis infection was 1.3 cases per 10,000 hospital admissions for dogs and 0.95 cases per 10,000 admissions for cats (P = 0.453). In univariate analyses, S. pseudintermedius isolation was significantly associated with skin infections (P < 0.0001), while S. lugdunensis isolation was associated with the respiratory tract (P = 0.03) and other deep tissues (P = 0.005). Cases were less likely than controls to have been treated based upon susceptibility test results (P = 0.02). A conditional logistic regression analysis showed isolation of S. lugdunensis to be associated with recent (≤ 30 days) steroid administration (odds ratio, 17.72; 95% confidence interval, 2.35–132.82; P = 0.005); and in‐patient status (odds ratio, 9.67; 95% confidence interval, 2.18–42.88; P = 0.003). Conclusions – These results suggest that S. lugdunensis may cause invasive infections in companion animals, which should be treated with antimicrobials based upon susceptibility tests when available.     

Comparative assessment of genotypic and phenotypic correlates of Staphylococcus pseudintermedius strains isolated from dogs with otitis externa and healthy dogs

Staphylococcus pseudintermedius is considered a primary pathogen of canine skin and soft tissue infections, and the rapid emergence of methicillin-resistant S. pseudintermedius worldwide is a major issue. In the current study, genotypic and phenotypic correlates associated with S. pseudintermedius causing canine otitis externa were evaluated using 41 S. pseudintermedius strains isolated from dogs with otitis externa (n = 26) and healthy dogs (n = 15). The S. pseudintermedius strains were subjected to a comparative analysis of (i) genotypes (multilocus sequence typing, agr, and spa types), (ii) methicillin resistance and SCCmec types, (iii) multidrug resistance (MDR), (iv) biofilm formation, and (v) susceptibility to canine cathelicidin (K9CATH). A high degree of genetic diversity was observed in both groups of S. pseudintermedius strains, regardless of methicillin resistance. Almost all methicillin-resistant strains (>95%) harbored SCCmec V and displayed MDR. Although there was no difference in biofilm formation, S. pseudintermedius strains derived from otitis externa exhibited enhanced resistance to cationic antimicrobial peptide (K9CATH) compared with strains from healthy dogs. The high degree of heterogeneity in MLST, agr, and spa types prevented the identification of correlations between any specific genotype and virulence phenotype in otitis externa caused by S. pseudintermedius, These findings provide an important basis for monitoring and treating canine skin and soft tissue infections in Korea.     

In vitro antiseptic susceptibilities for Staphylococcus pseudintermedius isolated from canine superficial pyoderma in Japan

Background –  Topical therapy, particularly with chlorhexidine, is becoming increasingly common as a treatment option for canine pyoderma; however, there are limited studies on the susceptibility of Staphylococcus pseudintermedius to chlorhexidine compounds. Objectives –  To determine the in vitro susceptibility of both meticillin‐resistant and meticillin‐susceptible S. pseudintermedius isolates to chlorhexidine and other antiseptic agents and the presence of multidrug efflux pump genes. Samples –  One hundred S. pseudintermedius isolates from 23 initial and 77 recurrent cases of canine pyoderma. Methods –  After bacterial identification and mecA testing, minimal inhibitory concentrations (MICs) of antiseptic agents were determined. Multidrug efflux pump genes, including qacA, qacB and smr, were identified. Results –  Of the 100 isolates, 57 were identified as meticillin‐resistant S. pseudintermedius. The MIC₉₀ of chlorhexidine acetate, chlorhexidine gluconate, acriflavine, ethidium bromide and benzalkonium chloride were 1, 1, 2, 0.5 and 2 μg/mL, respectively. Multidrug efflux pump genes qacA, qacB and smr were not detected in any of the isolates. Conclusions and clinical importance –  The MICs for chlorhexidine and other antiseptics remain low, and multidrug efflux pump genes were not found in the tested isolates.     

Low Rate of Methicillin‐resistant Coagulase‐positive Staphylococcal Colonization of Veterinary Personnel in Hong Kong

Elevated rates of methicillin‐resistant Staphylococcus aureus (MRSA) carriage have been reported in veterinary personnel, suggesting an occupational colonization risk. Hong Kong veterinary personnel (n = 150) were sampled for coagulase‐positive staphylococci (CPS) nasal colonization. Risk factors for colonization were assessed by questionnaire. Isolates were identified and antibiotic susceptibility determined. All CPS isolates were investigated for mecA carriage, SCCmec type and PVL genes. Two subjects were colonized with methicillin‐resistant CPS: one with MRSA (spa type t002 (CC5), SCCmec type II) and one with methicillin‐resistant Staphylococcus pseudintermedius (MRSP) (MLST type ST71, SCCmec type II‐III). MLST type ST71 S. pseudintermedius strain is the predominant MRSP clone circulating in dogs in Europe and in Hong Kong. The low MR‐CPS colonization rate may be associated with low levels of large animal exposure or low rates of MRSA colonization of companion animals in Hong Kong. Colonization with non‐aureus CPS, which may cause human infection, must also be considered in veterinary personnel.     

In vitro adherence of Staphylococcus pseudintermedius to canine corneocytes is influenced by colonization status of corneocyte donors

The current knowledge of in vitro adherence of Staphylococcus pseudintermedius to canine corneocytes is limited to comparative analyses between strains, staphylococcal species or corneocytes collected from different breeds, body sites and hosts. However, the role played by colonization status of corneocyte donors remains unknown. The aim of this study was to evaluate the adherence properties of commensal S. pseudintermedius strains to corneocytes collected from dogs with different colonization status. For this purpose, corneocytes were collected from five dogs that were classified as persistently colonized (D1 and D2), intermittently colonized (D3 and D4) or non-colonized (D5) on the basis of the results of a previous longitudinal study. Adherence to corneocytes originating from each of the five dogs was assessed by an in vitro adhesion assay using four genetically unrelated strains isolated from the colonized dogs (S1 to S4). Irrespective of their host of origin, all strains adhered significantly better to corneocytes from D1 and D2 than to corneocytes from D3, D4 and D5 (P < 0.0001). The mean count of cells adhering to corneocytes from persistently colonized dogs was on average three times higher than the mean count using corneocytes from the other dogs. A significant difference between strains was only observed for one strain-corneocyte combination (S2-D4), indicating that S. pseudintermedius adherence to corneocytes is driven by host factors and only marginally influenced by strain factors. This finding has important implications for understanding and preventing S. pseudintermedius skin colonization and infection.     

Resistance to fluoroquinolones and methicillin in ophthalmic isolates of Staphylococcus pseudintermedius from companion animals

Resistance to fluoroquinolones and methicillin was determined for 49 ophthalmic isolates of Staphylococcus pseudintermedius from dogs with and without ophthalmic disease. Resistance was observed for ciprofloxacin (40.8%), ofloxacin (38.8%), enrofloxacin (38.8%), levofloxacin (34.7%), and moxifloxacin (4.1%). Eighteen isolates, 16 of which were resistant to oxacillin, were mecA-positive. Nine of the 16 oxacillin-resistant mecA-positive S. pseudintermedius isolates were resistant to more than one fluoroquinolone and 2 isolates were resistant to 5 fluoroquinolones. The frequency of mecA gene occurrence and fluoroquinolone resistance was twice as high among S. pseudintermedius isolates derived from dogs with ophthalmic disease compared with isolates for dogs without ophthalmic disease. The high prevalence of methicillin and fluoroquinolone resistance in S. pseudintermedius from dogs with ophthalmic disease is a concern.     

Staphylococcus pseudintermedius exfoliative toxin EXI selectively digests canine desmoglein 1 and causes subcorneal clefts in canine epidermis

Staphylococcal exfoliative toxins are known to digest desmoglein (Dsg) 1, a desmosomal cell–cell adhesion molecule, thus causing intraepidermal splitting in human bullous impetigo, staphylococcal scalded skin syndrome and swine exudative epidermitis. Recently, a novel exfoliative toxin gene (exi), whose sequence shares significant homology with previously identified exfoliative toxins, was isolated from Staphylococcus pseudintermedius. Little is known about the pathogenic involvement of this toxin in canine pustular diseases such as impetigo. The aim of this study was to determine whether EXI, the product of the exi gene, digests canine Dsg1 and causes intraepidermal splitting in canine skin. An exi gene was isolated from chromosomal DNA of an S. pseudintermedius strain obtained from a pustule of a dog with impetigo, and was used to produce a recombinant EXI by Escherichia coli expression. When purified recombinant EXI was injected intradermally into normal dogs, it caused the development of vesicles or erosions with superficial epidermal splitting. In addition, the EXI abolished immunofluorescence for Dsg1, but not for Dsg3, at the injection sites. Moreover, the EXI directly degraded baculovirus‐secreted recombinant extracellular domains of canine Dsg1, but not that of canine Dsg3, in vitro. The EXI also degraded mouse Dsg1α and swine Dsg1, but not human Dsg1, mouse Dsg1β and Dsg1γ. Conversely, recombinant SIET, previously designated as S. intermedius exfoliative toxin, did not cause intraepidermal splitting or degradation of any Dsgs. These findings indicate that EXI has a proteolytic activity that digests canine Dsg1, and this characteristic might be involved in the pathogenesis of intraepidermal splitting in canine impetigo.     

Molecular characterization of community‐associated methicillin‐resistant Staphylococcus aureus from pet dogs

Community‐associated methicillin‐resistant Staphylococcus aureus (MRSA) is a serious public health concern and in Australia, one that disproportionately affects Aboriginal people. Paralleling MRSA in human medicine, methicillin‐resistant S. pseudintermedius (MRSP) is an increasingly prevalent pathogen in veterinary medicine. We aimed to characterize the carriage of MRSA and MRSP in dogs and cats from predominantly Aboriginal communities in a very remote region of New South Wales (NSW), Australia. Pets (303 dogs and 80 cats) were recruited from six communities in western NSW. Three swabs were collected from each animal (anterior nares, oropharynx and perineum) and from skin lesions or wounds (if present) and cultured on selective media for methicillin‐resistant staphylococci. Human host‐adapted community‐associated MRSA representing four multilocus sequence types (ST1‐IV, ST5‐IV, ST72‐IV, ST93‐IV) were isolated from eight dogs (prevalence 2.6%, 95% confidence interval 1.3%–5.1%). Two ST5‐IV isolates from a single dog were phenotypically trimethoprim‐resistant, harbouring trimethoprim‐resistant gene dfrG within the SCCmec type IVo mobile genetic element. MRSA was not isolated from any cats and MRSP was not isolated from any dogs or cats. This study estimated a high prevalence of human host‐adapted community‐associated MRSA carriage in dogs despite an absence of MRSP. This suggests MRSA carried by dogs in remote NSW originate from human hosts. The cycle of transmission between people, dogs and common environmental sources warrants further investigation. To our knowledge, this is the first report of trimethoprim‐resistant ST5‐IV in eastern Australia and the first report of trimethoprim‐resistant ST5‐IV from a dog.     

Evaluation of the bacterial microflora of the conjunctival sac of healthy dogs and dogs with atopic dermatitis

The aim of this case–control study was to evaluate and compare the bacterial microflora from the conjunctival sac of dogs with atopic dermatitis and healthy dogs. Twenty‐one atopic dogs without clinical and/or cytopathological signs of bacterial blepharoconjunctivitis and 21 breed‐matched healthy dogs were enrolled. Under topical anaesthesia, the inferior conjunctival sac of one eye was scraped twice. Material was collected with a Kimura spatula, spread over a slide and stained with a Diff Quick^®‐type stain (Medion Diagnostics GmbH, Düdingen, Switzerland) for cytological examination. An area of 0.5 cm² was examined at ×1000 magnification, and the types and numbers of cells and bacteria were recorded. A bacterial swab was collected and inoculated into culture media for the growth of aerobic bacteria. Before sampling, each atopic dog was evaluated for severity of cutaneous lesions, pruritus and conjunctival inflammation. Significant differences were observed between atopic and healthy dogs for the presence of bacteria on cytology (P = 0.015), keratinized (P = 0.001) and nonkeratinized epithelial cells (P = 0.013), eosinophils (P = 0.019) and lymphocytes (P = 0.008). Bacteria were recovered from 12 atopic dogs and three healthy dogs (P = 0.004). Staphylococcus pseudintermedius was the most commonly isolated species in atopic dogs (seven of 12). In atopic dogs, no significant relation was found between conjunctival bacterial colonization (on cytology and culture) and the severity of any of the clinical parameters. This study suggests differences in conjunctival bacterial colonization and cytological features between atopic and healthy dogs.     

Staphylococcus pseudintermedius in the dog: taxonomy, diagnostics, ecology, epidemiology and pathogenicity

The dog is the natural host of Staphylococcus pseudintermedius. Many research efforts are currently being undertaken to expand our knowledge and understanding of this important canine commensal and opportunistic pathogen. The objective of this review is to summarize the current knowledge of the species, including the latest research outcomes, with emphasis on taxonomy, diagnostics, ecology, epidemiology and pathogenicity. Despite the important taxonomic changes that have occurred over the past few years, the risk of misidentification in canine specimens is low and does not have serious consequences for clinical practice. Staphylococcus pseudintermedius carriage in the dog is more frequent and genetically heterogeneous compared with that of Staphylococcus aureus in man. It appears that these staphylococcal species have evolved separately through adaptation to their respective natural hosts and differ with regard to various aspects concerning ecology, population structure and evolution of antibiotic resistance. Further understanding of the ecology and epidemiology of S. pseudintermedius is hampered by the lack of a standard method for rapid and discriminatory typing and by the limited data available on longitudinal carriage and population structure of meticillin‐susceptible strains. With regard to pathogenicity, it is only now that we are starting to explore the virulence potential of S. pseudintermedius based on genomic and proteomic approaches, and more research is needed to assess the importance of individual virulence factors and the possible existence of hypervirulent strains.     

Genetic relatedness of methicillin-resistant Staphylococcus pseudintermedius (MRSP) isolated from a dog and the dog owner

In the present study four methicillin-resistant Staphylococcus pseudintermedius (MRSP) strains isolated from a dog (n = 3) and the anterior nares of the dog owner (n = 1) were investigated by conventional and molecular methods. The species identity of the four S. pseudintermedius strains was confirmed by conventional methods, by PCR mediated amplification of S. intermedius/S. pseudintermedius specific segments of thermonuclease encoding gene nuc and by restriction fragment length polymorphism analysis of phosphoacetyltransferase encoding gene pta. Investigation of the four S. pseudintermedius for toxinogenic potential revealed that all four strains were positive for the exfoliative toxin encoding gene siet and the leukotoxin encoding genes lukS, lukF. The oxacillin and penicillin resistance of the four S. pseudintermedius strains could be determined by cultivation of the strains on oxacillin resistant screening agar base, ChromID MRSA Agar and Brilliance MRSA Agar and by multiplex PCR detecting the resistance genes mecA and blaZ. The genetic relatedness of the strains was studied by macrorestriction analysis of their chromosomal DNA using pulsed field gel electrophoresis (PFGE). According to PFGE all four S. pseudintermedius strains represent an identical bacterial clone indicating a cross transmission between the dog and the dog owner.     

In vitro miconazole susceptibility of meticillin-resistant Staphylococcus pseudintermedius and Staphylococcus aureus

Background – The emergence and dissemination of meticillin‐resistant staphylococci has created significant treatment challenges in veterinary medicine and increased interest in topical therapy for superficial infections. Concern has been expressed regarding the use of some topical antimicrobials in animals because of the potential for emergence of resistance, and additional options are required. Miconazole has limited antibacterial properties that include antistaphylococcal activity. Hypothesis/Objectives – The objective of this study was to assess the in vitro susceptibility of Staphylococcus pseudintermedius and Staphylococcus aureus to miconazole. Methods – In vitro susceptibility of 112 meticillin‐resistant S. pseudintermedius (MRSP), 53 meticillin‐resistant S. aureus (MRSA) and 37 meticillin‐susceptible S. pseudintermedius (MSSP) to miconazole was assessed using agar dilution. Results – The minimal inhibitory concentration (MIC) range, MIC₅₀ and MIC₉₀ for MRSP were 1–8, 2 and 4 μg/mL, respectively. Corresponding results for MRSA were 1–8, 2 and 6 μg/mL, and for MSSP 1–4, 2 and 2 μg/mL. The MIC for MSSP was a significantly lower MIC than that for both MRSP (P = 0.006) and MRSA (P < 0.001), while the MIC for MRSP was significantly lower than that for MRSA (P = 0.001). Conclusions and clinical importance – These in vitro data suggest that miconazole could be a useful therapeutic option for superficial infections caused by meticillin‐susceptible and meticillin‐resistant staphylococci, but proper clinical investigation is required.