Surveillance of healthy cats and cats with inflammatory skin disease for colonization of the skin by methicillin-resistant coagulase-positive staphylococci and Staphylococcus schleiferi ssp. schleiferi

In this study, bacterial cultures were collected from five sites on each of 50 healthy cats and 48 cats with inflammatory skin disease (ISD), to determine prevalence of carriage and relative frequency of methicillin resistance in coagulase-positive staphylococci and Staphylococcus schleiferi ssp. schleiferi. Latex agglutination testing for penicillin-binding protein 2a (PBP2a) and pulsed field gel electrophoresis (PFGE) were performed on all methicillin-resistant (MR) isolates. Polymerase chain reaction (PCR) for the mecA gene was performed on MR S. intermedius and S. schleiferi isolates. Staphylococcal chromosomal cassette (SCCmec) typing was performed on all MR S. aureus isolates. Coagulase-positive staphylococci and S. schleiferi ssp. schleiferi were isolated from 24 of 48 cats with ISD: Staphylococcus aureus (14 of 24, 58%), Staphylococcus intermedius (11 of 24, 46%), Staphylococcus schleiferi ssp. schleiferi (1 of 24, 4%), and Staphylococcus hyicus (1 of 24, 4%). Prevalence of MR was 7% for S. aureus, 0% for S. intermedius, 100% for S. schleiferi ssp. schleiferi, and 0% for S. hyicus. Coagulase-positive staphylococci were isolated from 17 of 50 healthy cats: S. aureus (10 of 17, 59%), S. intermedius (11 of 17, 65%), and S. schleiferi ssp. coagulans (1 of 17, 6%). Prevalence of MR was 20% for S. aureus, 18% for S. intermedius, and 0% for S. schleiferi ssp. coagulans. All MR isolates were positive for PBP2a via latex agglutination. Methicillin-resistant S. intermedius and S. schleiferi ssp. schleiferi isolates were also positive for the mecA gene via PCR. Methicillin-resistant S. aureus isolates were identified as SCCmec type II. Results of PFGE indicated heterogeneity among isolates. There was no significant difference in staphylococcal isolation or methicillin resistance between study groups. While present, MR coagulase-positive staphylococci are significantly less common in these study populations.     

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.     

Distribution of staphylococcal species on clinically healthy cats

Among 827 isolates derived from 113 clinically healthy cats, 12 species of staphylococci were identified. Staphylococci were isolated from each cat and from 54.9% of the anatomic sites evaluated. A mode of 6 (range = 2 to 11) of the 11 anatomic sites evaluated per cat yielded staphylococci. A mode of 8 (range = 2 to 12) isolates were found per cat. Staphylococcus simulans was the most isolated (43.9% of total) coagulase-negative species. Moreover, S simulans was the most isolated species from each of the 11 sites evaluated and, except for the mouth and haircoat, comprised greater than 50% of the isolates from each site. Staphylococcus intermedius was the most isolated (13.5% of the total) coagulase-positive species. Three other species (S epidermidis, S xylosus, and S aureus) comprised 32.2% of the isolates, and 7 species (S haemolyticus, S hominis, S hyicus, S capitis, S warneri, and S saprophyticus) comprised 10.4% of the isolates. Six species (S intermedius [96 of 112 isolates], S haemolyticus [20 of 22], S sciuri [17 of 18], S warneri [10 of 13], S hyicus [10 of 10], and S capitis [7 of 8]) were isolated primarily from household cats. Only 1 species, S xylosus (75 of 87), was isolated primarily from cattery cats. Haircoat specimens (n = 452) yielded 508 isolates (61.4% of the total) distributed among all 12 staphylococcal species and included greater than 50% of the isolates of all species other than S simulans and S sciuri. A more heterogeneous population of staphylococci was isolated from household cats than was isolated from cattery cats.     

Frequency and antimicrobial susceptibility of Staphylococcus species isolated from canine pyodermas

Specimens obtained from pyogenic skin lesions of 210 dogs were culturally examined for staphylococci. A total of 215 isolates of staphylococci were biotyped, using the biochemical tests contained in a commercial staphylococcal identification system. Of 201 coagulase-positive isolates, 197 were identified as Staphylococcus intermedius, 3 as S aureus, and 1 as S hyicus. Of 14 coagulase-negative isolates, 5 were identified as S epidermidis, 5 as S xylosus, 3 as S simulans, and 1 as S hominis. Antimicrobial susceptibility tests were done on all staphylococcal isolates, using the standard disk-diffusion method. Staphylococcus intermedius isolates were susceptible to cephalothin, methicillin, and gentamicin. Resistance to ampicillin, penicillin G, and tetracycline was frequent. Antibiotic resistance was not associated with the depth of skin infection. Resistance to ampicillin, penicillin, tetracycline, and trimethoprim-sulfamethoxazole was not associated with previous antibiotic use. Increased resistance to chloramphenicol, clindamycin, and erythromycin was associated with previous antibiotic therapy. Antimicrobial susceptibilities of the other Staphylococcus species isolated are reported, but the small numbers of these species precluded making meaningful comparison with S intermedius.     

Methicillin resistance among staphylococci isolated from dogs

OBJECTIVE: To determine whether methicillin-resistant staphylococci from dogs expressed the mecA gene and to determine what proportion of canine staphylococcal isolates positive for the mecA gene were resistant to oxacillin and other antibiotics. SAMPLE POPULATION: 25 methicillin-resistant (10 coagulase-positive and 15 coagulase-negative) and 15 methicillin-susceptible (8 coagulase-positive and 7 coagulase-negative) staphylococci isolated from dogs. PROCEDURE: All strains were tested for methicillin resistance by use of oxacillin agar screening and identified by use of standard techniques. Minimum inhibitory concentrations of 16 antibiotics were determined for all 40 isolates. A polymerase chain reaction method targeting a 533-basepair fragment of the mecA gene was used to detect mecA gene expression. RESULTS: 23 of the 25 methicillin-resistant isolates and none of the methicillin-susceptible isolates possessed the mecA gene. For 10 of 16 antibiotics, the proportion of mecA-positive isolates that were resistant or of intermediate susceptibility was significantly higher than the proportion of mecA-negative isolates that were resistant or of intermediate susceptibility. Only 1 methicillin-resistant coagulase-positive isolate was identified as Staphylococcus intermedius; the other 9 were identified as S. aureus. CONCLUSIONS AND CLINICAL RELEVANCE: Results confirm that staphylococci isolated from dogs may have methicillin resistance mediated by the mecA gene. Isolates positive for the mecA gene were more likely to be resistant to various antibiotics than were isolates negative for the mecA gene. Results suggest that in dogs, infections caused by staphylococci that have the mecA gene may be difficult to treat because of resistance to antibiotics.     

Comparison of susceptibility to antimicrobials of bacterial isolates from companion animals in a veterinary diagnostic laboratory in Canada between 2 time points 10 years apart

The susceptibility to antimicrobials of bacterial species most frequently isolated from companion animals in a veterinary teaching diagnostic laboratory was evaluated retrospectively. A significant decrease between 1990-1992 and 2002-2003 was noted in the susceptibility of dog isolates to the following antimicrobials: Escherichia coli to cephalothin (86% to 61%, P < 0.001); E. coli to ampicillin (85% to 67%, P < 0.001); Proteus spp. to ampicillin (92% to 71%, P < 0.01); coagulase-positive staphylococci (Staphylococcus aureus and Staphylococcus intermedius) to enrofloxacin (99% to 95%, P < 0.01). Significantly increased susceptibilities were also noted as follows: coagulase-positive staphylococci to erythromycin (78% to 90%, P < 0.001) and tetracycline (61% to 77%, P < 0.001). Despite a limited number of results available for cats, a significant increase in susceptibility was noted for Pseudomonas spp. to gentamicin (40% to 100%, P < 0.05) and for E. coli to tetracycline (59% to 80%, P < 0.05). Regular updates on the resistance to antimicrobials used in veterinary medicine are required.     

Temporal study of staphylococcal species on healthy dogs

During a 1-year period, specimens were obtained monthly from 5 hair coat and 7 mucous membrane sites of 11 healthy dogs. Among 804 isolates of staphylococci, 13 species were identified. Staphylococcus intermedius was the most frequently isolated (40.2% of total isolates) coagulase-positive species, and S xylosus was the most frequently isolated (17.3%) coagulase-negative species. Moreover, S intermedius was the most frequently isolated species from the 12 sites evaluated and was isolated persistently from 8 of the 9 dogs that completed the 1-year study. On the basis of a commercial identification system, 14 profile numbers were identified for isolates of S intermedius. However, 2 profile numbers accounted for a majority (70.9%) of the isolates. Specific S intermedius biotypes identified on the basis of hemolysis, coagulase production, beta-lactamase activity, and antimicrobial susceptibility patterns were found repeatedly in 3 dogs. Seemingly, S intermedius was a resident of the normal bacterial microflora of these dogs; however, the inability to isolate S intermedius from 1 dog during the study year indicated that not all dogs harbor S intermedius as a resident microorganism.     

Species of Staphylococcus isolated from animal infections

One hundred randomly selected clinical strains of staphylococci were identified by species using a commercial micromethod system. Eight species of staphylococci were identified. Staphylococcus intermedius was the most frequent (n = 74) species identified and accounted for 70/74 (94.6%) of the coagulase-positive strains and 70/79 (88.6%) of the total isolates from dogs. Other species identified, in order of their frequency, included S. epidermidis (8), S. aureus (7), S. simulans (4), S. sciuri (2), S. xylosus (2), S. hyicus (2) and S. saprophyticus (1). These results show that at least 8 different species of staphylococci can be recovered from animal infections and that coagulase-positive species such as S. intermedius may be more common than S. aureus. The relative significance of these other species in animal infections needs to be assessed.     

Frequency and antimicrobial susceptibility of Staphylococcus spp isolated from feline skin lesions

Swab specimens obtained from skin lesions of 45 cats were cultured bacteriologically for staphylococci. Thirty-two staphylococcal isolates were recovered from 30 cats and were biotyped, using biochemical tests contained in a staphylococcal identification system. Of 23 isolates considered coagulase-positive, 16 were identified as Staphylococcus aureus, 5 as S intermedius, and 2 as S hyicus. Of 9 isolates considered coagulase-negative, 6 were identified as S simulans, 2 as S epidermidis, and 1 as S xylosus. Antimicrobial susceptibility tests were done on all staphylococcal isolates, using a disk-diffusion method. Staphylococcal isolates were susceptible to clavulanic acid-amoxicillin, cloxacillin, cephalothin, chloramphenicol, gentamicin, erythromycin, and trimethoprim-sulfamethoxazole. Resistance to penicillin G, ampicillin, and tetracycline was frequent.     

Methicillin resistance of staphylococci isolated from the skin of dogs with pyoderma

OBJECTIVE: To determine the methicillin-resistant profile of staphylococcal isolates from the skin of dogs with pyoderma. ANIMALS: 90 dogs with pyoderma. PROCEDURE: Staphylococci isolated from dogs with pyoderma were tested for susceptibility to methicillin by use of a standard disk diffusion test with oxacillin disks. The DNA extracted from the isolates was tested for the mecA gene that encodes the penicillin-binding protein 2a (PBP2a) by use of a polymerase chain reaction (PCR) assay. The expression of PBP2a was determined with a commercial latex agglutination assay. Species of staphylococcal isolates were identified by use of morphologic, biochemical, and enzymatic tests. RESULTS: Most of the isolated staphylococci were methicillin-susceptible, coagulase-positive Staphylococcus intermedius isolates. Whereas only 2 of 57 S. intermedius isolates were resistant to methicillin, approximately half of the isolates had the mecA gene and produced PBP2a. Staphylococcus schleiferi was the second most common isolate. Widespread resistance to methicillin was found among S. schleiferi isolates. More coagulase-negative S. schleiferi isolates were identified with mecA gene-mediated resistance to methicillin, compared with coagulase-positive S. schleiferi isolates. CONCLUSIONS AND CLINICAL RELEVANCE: The latex agglutination assay for the detection of PBP2a expression coupled with the PCR assay for the mecA gene may provide new information about emerging antimicrobial resistance among staphylococcal isolates.     

Treating Animal Bites: Susceptibility of Staphylococci from Oral Mucosa of Cats

Infected wounds determined by cats’ bites represent high costs to public health, and their adequate treatment relies on the knowledge of the antimicrobial susceptibility of bacterial agents found in the oral microbiota. Members of the genus Staphylococcus sp. belong to the microbiota of the oral mucosa of cats and are frequently involved in secondary infections of these wounds. This study aimed to evaluate the antimicrobial susceptibility of Staphylococcus species isolated from oral mucosa of cats. Samples were collected from 200 clinically healthy cats and processed by standard bacteriological methods and tested for susceptibility to a panel of 16 antimicrobials. A total of 212 staphylococci isolates were obtained from 141 of the 200 cats (70.5%), and more than one colony was recognized in 53 cases. Coagulase‐negative species were most frequently found (89.6%) distributed among Staphylococcus xylosus (50.9%), Staphylococcus felis (27.4%), Staphylococcus simulans (6.1%) and Staphylococcus sciuri (5.2%). Coagulase‐positive species (10.4%) were distributed among Staphylococcus aureus (4.7%) and Staphylococcus intermedius group (SIG) (5.7%). Regarding to antimicrobial resistance, 178 isolates (83.9%) were resistant to at least one antimicrobial, and rifampicin showed the best results with 100% of sensitive strains. Conversely, high rates of resistance were observed for penicillin and tetracycline (56.1%). The 212 staphylococci isolates and 30 (14.1%) strains were resistant to methicillin (on the disc susceptibility test) and may be preliminarily considered as methicilin‐resistant staphylococci. In conclusion, this study reports important rates of antimicrobial resistance among the species of Staphylococcus isolated from clinical specimens of cats, which must be considered for the treating of cats’ bites in humans.     

What’s happened to Staphylococcus intermedius? Taxonomic revision and emergence of multi‐drug resistance

Staphylococcus intermedius has been the predominant coagulase-positive Staphylococcus isolated from canine skin and mucosae and the most commonly reported staphylococcal pathogen in small animal practice for the last 35 years. Although microbiological tests have historically indicated variability in biochemical characteristics amongst S. intermedius isolates from animals, an acceptable level of diagnostic accuracy for clinical purposes was readily achievable with routine phenotypic testing. However, three recent developments have changed our understanding of the term "S. intermedius" and have challenged veterinary bacteriologists to ensure correct species identification of pathogenic staphylococci from small animals. First, the increasing recognition of meticillin-resistant Staphylococcus aureus in small animal practice and its human health implications demand accurate species identification. Secondly, the application of molecular techniques to analysis of staphylococcal isolates has led to a revised taxonomy and canine isolates of S. intermedius being re-named S. pseudintermedius. Thirdly, the recent, rapid emergence of meticillin- and multi-drug-resistant strains of Staphylococcus pseudintermedius (MRSP) has become a major therapeutic challenge in veterinary practice worldwide, including the UK. This article discusses the background of the recent taxonomic changes within the genus Staphylococcus and reviews the key features of MRSP and its implications for day-to-day laboratory diagnosis and small animal practice.     

Identification of coagulase-positive staphylococci isolated from bovine milk

A total of 414 coagulase-positive staphylococcal strains obtained at the mastitis laboratory, National Veterinary Institute, Uppsala, Sweden, were studied. One hundred and seventy seven strains were used for a frequency study. Ninety-seven per cent were identified as Staphylococcus aureus, 2% as Staphylococcus intermedius and 1% as Staphylococcus hyicus. Two hundred and thirty seven strains with atypical hemolysis reactions on bovine blood agar were randomly selected, with the aim to increase the number of S. intermedius and S. hyicus strains available for testing. Eight different characteristics, including physiological, enzymatical and biochemical properties, were used to identify the coagulase-positive Staphylococcus species. The results of this study suggest that the following tests should be included for correct identification of the 3 different species of coagulase-positive staphylococci: P agar supplemented with acriflavin, beta-galactosidase and hemolytic reaction on chocolate agar. These 3 tests are simple and quick to perform and enable accurate for easy differentiation of the 3 coagulase-positive Staphylococcus species.     

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 Gram's 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.     

Species distribution and properties of staphylococci from canine dermatitis

The occurrence and phenotypic, and genotypic properties of 24 Staphylococcus isolates from canine dermatitis were investigated. The predominant staphylococcal species was Staphylococcus intermedius. The other species such as Staphylococcus chromogenes, Staphylococcus sciuri, Staphylococcus aureus, Staphylococcus saprophyticus, Staphylococcus epidermidis, and Staphylococcus capitis were only occasionally isolated. The study showed low level biochemical diversity among S. intermedius isolates. Resistance to antibiotics was frequently observed, with 87.5% of the isolates showing resistance to at least one drug. The most active antimicrobial agents against all staphylococci were amoxicillin/clavulanic acid, cephalexin and gentamicin. Resistance to carbenicillin, amoxicillin, ampicillin, cephadroxil, erythromycin, clinadmaycin and neomycin was common. No correlation was observed between antibiotic resistance and plasmid profile. PFGE analysis revealed a high degree of genetic polymorphism of S. intermedius, even among isolates collected in a restricted area over a short time.     

Fluoroquinolone resistance in Staphylococcus intermedius

Four canine isolates of S. intermedius resistant to enrofloxacin were isolated amongst a total of 429 screened. Two of these were shown to exhibit resistance also to marbofloxacin and ciprofloxacin. Whilst molecular studies have shown the mechanism of resistance to these quinolone antibiotics to be similar in a number of staphylococcal species, it was not possible to confirm this mechanism in Staphylococcus intermedius .     

Molecular epidemiology and genetic linkage of macrolide and aminoglycoside resistance in Staphylococcus intermedius of canine origin

A collection of 77 Staphylococcus intermedius isolates from dogs and cats in Switzerland was examined for resistance to erythromycin. Resistance profiles for 14 additional antibiotics were compared between erythromycin-resistant and susceptible isolates. A resistance prevalence of 27% for erythromycin was observed in the population under study. Complete correlation between resistance to erythromycin, and to spiramycin, streptomycin, and neomycin was observed. The erythromycin-resistant isolates all had a reduced susceptibility to clindamycin when compared to the erythromycin-susceptible isolates. Both constitutive and inducible resistance phenotypes were observed for clindamycin. Ribotyping showed that macrolide-aminoglycoside resistance was randomly distributed among unrelated strains. This suggests that this particular resistance profile is not related to a single bacterial clone but to the horizontal transfer of resistance gene clusters in S. intermedius populations. The erythromycin-resistant isolates were all carrying erm(B), but not erm(A), erm(C), or msr(A). The erm(B) gene was physically linked to Tn5405-like elements known as resistance determinants for streptomycin, streptothricin, neomycin and kanamycin. Analysis of the region flanking erm(B) showed the presence of two different groups of erm(B)-Tn5405-like elements in the S. intermedius population examined and of elements found in Gram-positive species other than staphylococci. This strongly suggests that erm(B) or the whole erm(B)-Tn5405-like elements in S. intermedius originate from other bacterial species, possibly from enterococci.     

Antimicrobial susceptibility of coagulase-positive staphylococci isolated from Louisiana dogs

Disk diffusion susceptibility tests were done on 1,178 clinical strains of coagulase-positive staphylococci (CPS) isolated from dogs during a 7-year period. Relative decreases of 7% to 33% were found in the percentages of CPS sensitive to 8 antimicrobics. Relative percentages of CPS sensitive to 9 other antimicrobics were increased or decreased less than 5%. Sensitivity to the beta-lactam antibiotics showed the least relative change. Regression analysis demonstrated that the greatest change in percentage sensitivity of CPS occurred to gentamicin and cephalothin and the least change occurred to penicillin and ampicillin. Recent canine clinical isolates of CPS, specifically identified as Staphylococcus intermedius (n = 109), were uniformly sensitive to novobiocin, amikacin, tobramycin, spectinomycin, and amoxicillin-clavulanic acid. Twenty-two isolates were also sensitive to 17 other antimicrobics. Eighty-seven isolates were resistant to 1 or more antimicrobics tested. Resistance was most common to sulfonamides, penicillin G, ampicillin, tetracycline, and streptomycin. Differences in susceptibility results between S intermedius and unspecified CPS were not statistically significant.     

Prevalence of oxacillin- and multidrug-resistant staphylococci in clinical samples from dogs: 1,772 samples (2001-2005)

OBJECTIVE: To determine whether resistance to oxacillin and other antimicrobials in 3 Staphylococcus spp commonly isolated from dogs increased from 2001 to 2005. DESIGN: Retrospective case series. SAMPLE POPULATION: 1,772 clinical samples of various types obtained from dogs examined at the University of Tennessee Veterinary Teaching Hospital or at regional veterinary hospitals and submitted to the bacteriology and mycology laboratories associated with the teaching hospital. PROCEDURES: Samples were submitted by attending veterinarians to the bacteriology and mycology laboratories for routine aerobic microbial culture. Identification and antimicrobial susceptibility procedures were performed on all isolates. Susceptibility reports for each antimicrobial and Staphylococcus spp were determined from aggregate electronically archived test results. Oxacillin and multidrug resistance for Staphylococcus intermedius was analyzed by reviewing disk diffusion zone measurements. RESULTS: Oxacillin resistance increased among S. intermedius isolates during the past 5 years, and the increase was associated with multidrug resistance. In 2005, 1 in 5 Staphylococcus spp isolates from canine clinical samples was resistant to oxacillin. The most common staphylococcal species isolated were S. intermedius (n = 37), Staphylococcus schleiferi (21), and Staphylococcus aureus (4), and frequencies of oxacillin resistance in isolates of these species were 15.6%, 46.6%, and 23.5%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Veterinarians should be aware of the potential for empiric drug treatment failures in instances where Staphylococcus spp infections are common (eg, pyoderma). Judicious use of bacterial culture and susceptibility testing is recommended.     

Screening of Staphylococcus aureus, Staphylococcus intermedius, and Staphylococcus schleiferi isolates obtained from small companion animals for antimicrobial resistance: a retrospective review of 749 isolates (2003-04)

Companion animal staphylococcal isolate antibiograms were screened retrospectively to determine the frequency of methicillin-resistant (MR) infection by Staphylococcus aureus, Staphylococcus intermedius, and Staphylococcus schleiferi. Rates of MR were: S. aureus 35%, S. intermedius 17%, and S. schleiferi 40%. Frequency of isolation of methicillin-resistant S. aureus (MRSA) from dogs and cats was similar, whereas methicillin-resistant S. intermedius (MRSI) and methicillin-resistant S. schleiferi (MRSS) were significantly more common in dogs. MRSS was more commonly associated with superficial (skin and ear canal) infections, whereas MRSA was more commonly associated with deep infections. The MR strain resistance pattern to other classes of antibiotics was also investigated. MRSA was resistant to the most classes of antibiotics, followed by MRSI, while MRSS maintained the most favourable susceptibility profile. MR staphylococci may pose a significant risk to animal and public health. Therefore, to avoid selecting for resistant strains in cases of suspected staphylococcal infection, clinicians should consider culture and susceptibility testing early in the course of treatment.