Daniel O. Morris

Screening for skin carriage of methicillin-resistant coagulase-positive staphylococci and Staphylococcus schleiferi in dogs with healthy and inflamed skin

Methicillin resistance rates of 41% for Staphylococcus aureus, 16% for S. intermedius, and 40% for S. schleiferi have recently been reported in canine patients. These were deemed to be reflective of referral and clinician-selection biases, which would imply significantly lower methicillin-resistant staphylococcal carriage rates in less-biased canine populations. In this study, swabs for bacterial culture were collected from five cutaneous sites on each of 50 healthy dogs and 59 dogs with inflammatory skin disease to determine prevalence of carriage and relative frequency of methicillin resistance in coagulase-positive staphylococci and S. schleiferi ssp. schleiferi. These were identified morphologically and by Grams staining, catalase and coagulase testing, and biochemical speciation. Coagulase-positive staphylococci and S. schleiferi ssp. schleiferi were isolated from 88% (52 of 59) of affected dogs. Species identified in the culture-positive dogs were: S. aureus in 12%, S. intermedius (92%), S. schleiferi ssp. schleiferi (10%), and S. schleiferi ssp. coagulans (10%) with methicillin resistance rates of 17%, 8%, 20% and 20%, respectively. Coagulase-positive staphylococci were isolated from 74% (37 of 50) of healthy dogs: S. aureus (16%), S. intermedius (92%) and S. schleiferi ssp. coagulans (5%). Methicillin resistance rates were 0%, 3% and 50%, respectively. Of total methicillin-resistant isolates, 11 of 13 were positive for PBP2a via latex agglutination. Methicillin-resistant S. intermedius and S. schleiferi ssp. schleiferi isolates were all positive for the mecA gene via PCR. There was no significant difference in staphylococcal isolation or methicillin resistance between study groups. While present, methicillin-resistant coagulase-positive staphylococci are significantly less common in these less-biased populations than in the clinical isolates previously reported from this institution which provided the impetus for this study.

Household transmission of meticillin-resistant Staphylococcus aureus and other staphylococci

Although the role of pets in household transmission of meticillin-resistant Staphylococcus aureus (MRSA) has been examined previously, only minor attention has been given to the role of the abiotic household environment independent of, or in combination with, colonisation of pets and human beings to maintain transmission cycles of MRSA within the household. This report reviews published work about household transmission of S aureus and other staphylococci and describes contamination of household environmental surfaces and colonisation of pets and people. Household microbial communities might have a role in transfer of antimicrobial resistance genes and could be reservoirs for recolonisation of people, although additional research is needed regarding strategies for decontamination of household environments. Household-based interventions should be developed to control recurrent S aureus infections in the community, and coordination between medical and veterinary providers could be beneficial.

Malassezia pachydermatis Carriage in Dog Owners

Malassezia pachydermatis is commonly carried on the hands of dog owners and may cause disease in immunocompromised persons.

Malassezia Dermatitis and Otitis

The incidence of dermatitis and otitis resulting from overgrowth of M. pachydermatis is great enough that cytological sampling techniques should be considered a routine part of the dermatological examination. Because most cases of MD and Malassezia otitis cannot be grossly distinguished from bacterial pyoderma and otitis, respectively, efficiency in performing cytology testing of skin and ear canal exudate is essential to the successful diagnosis and management of pruritic skin diseases and otitis. Although Malassezia infections are rarely primary, therapy can be instituted to remove the yeast as a confounding factor while a differential diagnosis is pursued in evaluating the underlying disease process.

The prevalence of carriage of meticillin-resistant staphylococci by veterinary dermatology practice staff and their respective pets

It has been shown that people and pets can harbour identical strains of meticillin-resistant (MR) staphylococci when they share an environment. Veterinary dermatology practitioners are a professional group with a high incidence of exposure to animals infected by Staphylococcus spp. The objective of this study was to assess the prevalence of carriage of MR Staphylococcus aureus (MRSA), MR S. pseudintermedius (MRSP) and MR S. schleiferi (MRSS) by veterinary dermatology practice staff and their personal pets. A swab technique and selective media were used to screen 171 veterinary dermatology practice staff and their respective pets (258 dogs and 160 cats). Samples were shipped by over-night carrier. Human subjects completed a 22-question survey of demographic and epidemiologic data relevant to staphylococcal transmission. The 171 human-source samples yielded six MRSA (3.5%), nine MRSP (5.3%) and four MRSS (2.3%) isolates, while 418 animal-source samples yielded eight MRSA (1.9%) 21 MRSP (5%), and two MRSS (0.5%) isolates. Concordant strains (genetically identical by pulsed-field gel electrophoresis) were isolated from human subjects and their respective pets in four of 171 (2.9%) households: MRSA from one person/two pets and MRSP from three people/three pets. In seven additional households (4.1%), concordant strains were isolated from only the pets: MRSA in two households and MRSP in five households. There were no demographic or epidemiologic factors statistically associated with either human or animal carriage of MR staphylococci, or with concordant carriage by person-pet or pet-pet pairs. Lack of statistical associations may reflect an underpowered study.

Potential for pet animals to harbour methicillin-resistant Staphylococcus aureus when residing with human MRSA patients.

Colonization by methicillin‐resistant Staphylococcus aureus (MRSA) may be persistent in people and is horizontally transmissible. The scientific literature suggests that domestic pets may also participate in cross‐transmission of MRSA within households. The objectives of this study were to evaluate the prevalence of and risk factors for MRSA carriage by pets residing in households with an MRSA‐infected person. From 66 households in which an MRSA‐infected patient resided, we screened 47 dogs and 52 cats using a swab protocol. Isolates from pets and humans were genotyped using two techniques and compared for concordance. Human participants completed a 22‐question survey of demographic and epidemiologic data relevant to staphylococcal transmission. Eleven of 99 pets (11.5%) representing 9 (13.6%) of households were MRSA‐positive, but in only six of these households were the human and animal‐source strains genetically concordant. Human infection by strain USA 100 was significantly associated with pet carriage [OR = 11.4 (95% CI 1.7, 76.9); P = 0.013]. Yet, for each day of delay in sampling the pet after the person’s MRSA diagnosis, the odds of isolating any type of MRSA from the pet decreased by 13.9% [(95% CI 2.6, 23.8); P = 0.017)]. It may be concluded that pets can harbour pandemic strains of MRSA while residing in a household with an infected person. However, the source of MRSA to the pet cannot always be attributed to the human patient. Moreover, the rapid attrition of the odds of obtaining a positive culture from pets over time suggests that MRSA carriage may be fleeting.

Potential Role of Pet Animals in Household Transmission of Methicillin-Resistant Staphylococcus aureus: A Narrative Review

In this narrative review, we found numerous reports suggesting that dogs and cats may play a role in household methicillin-resistant Staphylococcus aureus (MRSA) transmission and recurrent MRSA infection in human contacts. Future work should emphasize elucidating more clearly the prevalence of MRSA in household pets and characterize transmission dynamics of MRSA humans and pet animals.

The shared microbiota of humans and companion animals as evaluated from Staphylococcus carriage sites

BackgroundStaphylococcus aureus and other coagulase-positive staphylococci (CPS) colonize skin and mucous membrane sites and can cause skin and soft tissue infections (SSTIs) in humans and animals. Factors modulating methicillin-resistant S. aureus (MRSA) colonization and infection in humans remain unclear, including the role of the greater microbial community and environmental factors such as contact with companion animals. In the context of a parent study evaluating the households of outpatients with community MRSA SSTI, the objectives of this study were 1) to characterize the microbiota that colonizes typical coagulase-positive Staphylococcus spp. carriage sites in humans and their companion pets, 2) to analyze associations between Staphylococcus infection and carriage and the composition and diversity of microbial communities, and 3) to analyze factors that influence sharing of microbiota between pets and humans.ResultsWe enrolled 25 households containing 56 pets and 30 humans. Sampling locations were matched to anatomical sites cultured by the parent study for MRSA and other CPS. Bacterial microbiota were characterized by sequencing of 16S ribosomal RNA genes. Household membership was strongly associated with microbial communities, in both humans and pets. Pets were colonized with a greater relative abundance of Proteobacteria, whereas people were colonized with greater relative abundances of Firmicutes and Actinobacteria. We did not detect differences in microbiota associated with MRSA SSTI, or carriage of MRSA, S. aureus or CPS. Humans in households without pets were more similar to each other than humans in pet-owning households, suggesting that companion animals may play a role in microbial transfer. We examined changes in microbiota over a 3-month time period and found that pet staphylococcal carriage sites were more stable than human carriage sites.ConclusionsWe characterized and identified patterns of microbiota sharing and stability between humans and companion animals. While we did not detect associations with MRSA SSTI, or carriage of MRSA, S. aureus or CPS in this small sample size, larger studies are warranted to fully explore how microbial communities may be associated with and contribute to MRSA and/or CPS colonization, infection, and recurrence.

Treatment of Severe Adverse Cutaneous Drug Reactions With Human Intravenous Immunoglobulin in Two Dogs

Severe adverse cutaneous reactions were documented in two dogs with acute skin lesions and systemic signs after exposure to several oral and injectable drugs. Because of the high morbidity and mortality rates of many severe cutaneous drug reactions and a poor response to supportive care, wound management, and conventional immunosuppressive therapy, human intravenous immunoglobulin (IVIG) was infused on 2 consecutive days (1 g/kg per day) after informed consent was received. Human IVIG, with supportive care, resulted in rapid resolution of dermatological and systemic signs in both dogs; this treatment may be considered in other cases of severe cutaneous drug reactions.

Genotypic relatedness and phenotypic characterization of Staphylococcus schleiferi subspecies in clinical samples from dogs

OBJECTIVE To assess the degree of biological similarity (on the basis of genotype determined via pulsed-field gel electrophoresis [PFGE]) between isolates of 2 Staphylococcus schleiferi subspecies (S schleiferi subsp coagulans and S schleiferi subsp schleiferi) in clinical samples obtained from dogs. SAMPLE POPULATION 161 S schleiferi isolates from 160 canine patients. PROCEDURES A commercial microbiology identification system was used to identify each isolate as S schleiferi. Isolates underwent slide and tube coagulase testing and antimicrobial susceptibility testing. A mecA PCR assay and a latex agglutination test for penicillin-binding protein 2a (PBP2a) were also performed on each isolate. Clonal clusters with a similarity cutoff value of 80% were identified via PFGE. RESULTS Of the 161 isolates, 61 (38%), 79 (49%), and 21 (13%) were obtained from cutaneous sites, ears, and other sites, respectively; 110 (68%) were coagulase negative, and 51 (32%) were coagulase positive. Among the coagulase-negative and coagulase-positive isolates, 65% (71/110) and 39% (20/51) were oxacillin resistant, respectively. All oxacillin-resistant isolates yielded positive results via mecA PCR assay and PBP2a latex agglutination testing. Via PFGE, 15 major clusters and 108 individual pulsed-field profiles were identified. Oxacillin-resistant and oxacillin-susceptible isolates clustered separately. Clonal clusters were heterogeneous and contained representatives of both subspecies. CONCLUSIONS AND CLINICAL RELEVANCE Coagulase-positive and coagulase-negative isolates were not genotypically distinct and may represent a single S schleiferi sp with variable coagulase production, rather than 2 biologically distinct subspecies. Further studies are needed to characterize clinical or epidemiological differences associated with infections with coagulase-positive and coagulase-negative S schleiferi in dogs.