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.     

Methicillin-resistant coagulase-negative staphylococci isolated from healthy horses in Japan

OBJECTIVE: To determine patterns of methicillin-resistant staphylococci isolated from apparently healthy horses. SAMPLE POPULATION: 44 horses from 8 riding clubs in Japan. PROCEDURE: Methicill in-resistant staphylococci were isolated from the skin or nares, using a selective medium containing a beta-(symboric) lactam antibiotic, ceftizoxime. Clonality of isolates was determined by use of pulsed-field gel electrophoresis. Detection of mecA, mecl, and mecR1 genes was accomplished by use of polymerase chain reactions. RESULT: Of the 44 horses, 13 (29.5%) yielded 15 isolates of methicillin-resistant staphylococci. The 15 isolates were identified as 6 species (Staphylococcus epidermidis, S lentus, S saprophyticus, S xylosus, S sciuri, and S haemolyticus). However, methicillin-resistant S aureus was seldom isolated. Each isolate contained the mecA gene and had a high resistance to beta-lactam antibiotics. Some isolates also were resistant to other antibiotics such as erythromycin and kanamycin. CONCLUSIONS AND CLINICAL RELEVANCE: Methicillin-resistant coagulase-negative staphylococci that were highly resistant to various antibiotics were isolated from apparently healthy horses in Japan. These organisms must be considered a potential threat to horses and veterinarians who care for them.     

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.     

Sensitivity to various antibiotics of coagulase-negative staphylococci isolated from samples of milk from Dutch dairy cattle

During recent years the prevalence of coagulase-negative staphylococci in milk samples from Dutch dairy cows has increased. In 1999 16.2% of the bacteria isolated from milk collected from cows with subclinical mastitis were coagulase-negative staphylococci. In 2004 this proportion was 42.2%. The proportion of coagulase-negative staphylococci of the bacteria isolated from milk samples from cows with clinical mastitis was 7.3% in 1999 and 14.1% in 2004. In this study, the susceptibility of 108 coagulase-negative staphylococci to oxacillin, cefquinome, streptomycin, neomycin, penicillin, and the combination of nafcillin, penicillin, and streptomycin was tested. The isolates were cultured from milk collected from cows with mastitis and typed using the Api-Staph system. Eight species were identified. Staphylococcus chromogenes was the predominant species (41.7%), followed by Staphylococcus xylosus (15.7%) and Staphylococcus simulans (10.2%). With the agar dilution method all strains proved to be sensitive to cefquinome and 90% to oxacillin. Three isolates (2.8%) were mecA-positive. Despite the agar dilution results, these three isolates should be considered resistant to all beta-lactam antibiotics (penicillins, penicillins combined with a beta-lactamase inhibitor and all generations of cephalosporins). In the agar diffusion test, all isolates proved to be sensitive to the combination of nafcillin-penicillin-streptomycin, 99% were sensitive to neomycin and 1% intermediate sensitive, and 95% were sensitive to streptomycin, 4% resistant, and 1% intermediate sensitive. The coagulase-negative staphylococci were highly resistant to penicillin (37.4%), although the level of resistance varied between species, from 0% for Staphylococcus simulans to 100% for Staphylococcus saprophyticus. Because coagulase-negative staphylococci are resistant to several antibiotics, sensitivity testing is important for targeted treatment of mastitis.     

The prevalence of methicillin-resistant staphylococci in healthy horses in the Netherlands

Two hundred healthy horses housed at 23 different farms and one clinic and 42 persons in close contact with these horses were screened for the presence of methicillin resistant staphylococci. Samples were taken from the nose and the pastern of the horses and from the nose and throat of the humans and incubated in selective media. Isolates were identified by standard techniques and their susceptibilities were tested using an agar diffusion method. Methicillin-resistant strains were tested for the presence of the mecA gene by PCR. In 45 horses (22.5%) and 15 humans (35.7%) mecA positive staphylococci were found. All isolates were coagulase negative staphylococci, except for one methicillin-resistant Staphylococcus aureus isolated from a veterinarian. Staphylococcus sciuri was the predominant species found among the methicillin resistant staphylococci (MRS) in the horses, whereas S. epidermidis predominated in the humans. From the horses, often more than one species of MRS could be isolated, resulting in a total of 175 mecA positive equine isolates. The equine isolates were predominantly susceptible to most antimicrobials tested, whereas the human isolates showed more resistance. In conclusion, no methicillin-resistant Staphylococcus aureus was found in healthy horses in the Netherlands, but methicillin-resistant coagulase negative staphylococci were found frequently. Further studies are needed in order to investigate whether horses can be a reservoir for MRS or the mecA gene for humans.     

Staphylococci isolated from animals and food with phenotypically reduced susceptibility to beta-lactamase-resistant beta-lactam antibiotics

The antibiotic resistance pattern of 1921 Staphylococcus strains isolated from animals and food within the last two years were examined using diffusion tests. Among them there were only 35 strains of S. aureus having an inhibition zone diameter of 15 mm or less, and 4 strains of coagulase-negative staphylococci (CNS) having a zone diameter of 18 mm or less to 1-microg oxacillin disk. These 39 strains were examined also by E-test to oxacillin and for the detection of the mecA gene by PCR in order to determine whether they might be real methicillin-resistant staphylococci. Among the 39 strains there were only two that were susceptible to penicillin by disk diffusion method; however, further examination by the penicillinase test showed that they produced beta-lactamase. While 19 (15 S. aureus, 4 CNS) strains were resistant and 7 strains were intermediate to oxacillin in disk diffusion test, the E-test gave 8 resistant and 5 intermediate results. Six out of the 8 oxacillin-resistant strains examined by disk diffusion and E-test harboured the mecA gene. Thus only 6 out of the examined 1921 strains proved to be mecA positive. These methicillin-resistant, mecA-positive strains (5 of the S. aureus strains and 1 of the S. epidermidis) originated from two dairy herds. The results prove that methicillin-resistant S. aureus (MRSA) strains in animals are really rare in Hungary. Eighteen strains were chosen and screened for minimal inhibitory concentration (MIC) of oxacillin with or without clavulanic acid or sulbactam, and three of them produced methicillinase enzyme.     

Methicillin-resistant staphylococci isolated from animals

Staphylococci isolated from animals (n=311) were screened for methicillin resistance by oxacillin agar screening. Oxacillin-resistant strains were tested for the presence of the mecA gene by PCR. Isolates were identified by standard techniques and 16S rDNA analysis, and their antimicrobial susceptibilities were tested using an agar diffusion method. MecA-positive strains were further analyzed using pulsed-field gel electrophoresis (PFGE). From 11 multidrug-resistant staphylococci, 6 were mecA-positive: 2 methicillin-resistant Staphylococcus aureus (MRSA) and 4 Staphylococcus haemolyticus. Screening of 300 staphylococci (100 S. aureus, 100 S. intermedius and 100 coagulase-negative staphylococci (CNS)) randomly chosen from the strain collection of the Veterinary Microbiological Diagnostic Center yielded five oxacillin-resistant coagulase-negative staphylococci, four of which were mecA-positive. PFGE showed that all mecA-positive staphylococci isolated from animals had distinct patterns. However, one MRSA isolated from a flank fistula of a dog showed homology to a human epidemic MRSA cluster, suggesting that transfer of MRSA between humans and dogs might occur.     

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.     

兽医临床凝固酶阴性葡萄球菌分离株的耐药性及耐药基因检测

采用微量肉汤稀释法和D-试验法检测64株凝固酶阴性葡萄球菌（CNs）对10种抗菌药物的耐药性,并用PCR方法分别检测头孢西丁耐药菌株和红霉素耐药菌株中mecA基因以及erinA、ermB、ermC和msrA基因的携带情况。结果表明,所有菌株均对万古霉素和甲氧苄啶／磺胺甲恶唑敏感;泰妙菌素为耐药率（65．6％）最高的抗菌药物,其次是红霉素、氧氟沙星和β-内酰胺类药物。28株（43．8％）CNS对青霉素耐药,其中26株对头孢西丁耐药（MRS）并且均携带mecA基因。30株（46．9％）CNS对红霉素耐药,其中24株为MLSB耐药表型,主要由ermB基因介导。总之,兽医临床CNs分离株对常用抗菌药物的耐药性不同,mecA基因和ermB基因的携带分别是兽医临床MRS和MLSB表型产生的主要原因。     

Antimicrobial resistance of feline staphylococci in south-eastern England

Staphylococcus aureus is reported as the predominant feline staphylococcal pathogen. There is concern that cats may transfer resistant staphylococci to humans. In this study, staphylococci were obtained from skin and mucosae of 20 domestic cats, 9 with lesions, and 10 healthy feral cats. Species were identified by DNase and API ID32 Staph tests. Of 187 isolates, 21.4% were coagulase-positive and predominately from lesional cats; 90% of these were Staphylococcus intermedius . Coagulase-negative species were isolated equally in all three groups. All isolates were susceptible to coamoxiclav, cephalexin and bacitracin. Twenty-two, including 18 coagulase-negative isolates, showed some resistance to cotrimoxazole, lincomycin, enrofloxacin or oxytetracycline. Two isolates were resistant to more than one antibiotic. More resistant isolates were obtained from feral cats ( P < 0.01). The results suggest that S. intermedius is the principal coagulase-positive species. Antibiotic resistance is generally low amongst feline staphylococci. Higher resistance amongst feral cats suggests exposure to environmental antibiotics.     

A real-time PCR assay to detect the Panton Valentine Leukocidin toxin in staphylococci: screening Staphylococcus schleiferi subspecies coagulans strains from companion animals

Recent reports suggest that methicillin-resistant strains of Staphylococcus schleiferi subspecies coagulans are now commonly isolated from dogs. Given the association of a potentially mobile SCCmec type IV element with lysogenic phage-encoded Panton Valentine Leukocidin (PVL) toxin genes in community-acquired methicillin-resistant Staphylococcus aureus strains we hypothesized that methicillin-resistant S. schleiferi ssp. coagulans strains may also encode PVL toxin genes. Forty S. schleiferi ssp. coagulans strains isolated from companion animals were studied. Susceptibility to oxacillin was determined by broth microdilution and all isolates were screened by PCR for the presence of the mecA gene. SCCmec typing was performed on 14 isolates. A real-time PCR assay was developed for the detection of the PVL genes using a SmartCycler. Pulsed-field gel electrophoresis (PFGE) was performed to determine whether S. schleiferi ssp. coagulans strains were homogeneous. Twenty-eight of the 40 isolates (70%) were resistant to oxacillin and 26/28 possessed the mecA gene by PCR. SCCmec IV was identified in seven strains; the other seven isolates were not typable by this technique. All 40 strains were negative for the PVL toxin gene. PFGE showed a heterogeneous population and 13 different profiles were determined. In conclusion, this study showed that PVL toxin genes were not detected in a heterogeneous population of methicillin-resistant S. schleiferi ssp. coagulans strains isolated from companion animals.     

Isolation of Staphylococcus schleiferi from dogs with pyoderma

OBJECTIVE: To determine frequency with which Staphylococcus schleiferi could be isolated from dogs with pyoderma and antimicrobial susceptibility patterns of isolates that were obtained. DESIGN: Prospective study. ANIMALS: 54 dogs with a first (n = 14) or recurrent (40) episode of pyoderma. PROCEDURE: Specimens were obtained and submitted for bacterial culture. Isolates were identified as S schleiferi on the basis of growth and biochemical characteristics. Two isolates were submitted for DNA sequencing to confirm identification. Methicillin susceptibility was determined by means of disk diffusion with oxacillin-impregnated disks. RESULTS: 3 of 14 dogs examined because of a first episode of pyoderma and 12 of 40 dogs examined because of a recurrent episode of pyoderma were receiving antimicrobials at the time of specimen collection. Staphylococcus schleiferi was not isolated from any dog with first-time pyoderma but was isolated from 5 dogs with recurrent pyoderma that were not receiving antimicrobials at the time of specimen collection and 10 dogs with recurrent pyoderma that were receiving antimicrobials. Nine isolates were identified as S schleiferi subsp schleiferi, and 6 were identified as S schleiferi subsp coagulans. All S schleiferi subsp schleiferi isolates were resistant to methicillin, but only 2 S schleiferi subsp coagulans isolates were. Two methicillin-resistant isolates were also resistant to fluoroquinolones, and 1 isolate had intermediate susceptibility to fluoroquinolones. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that S schleiferi subsp schleiferi and S schleiferi subsp coagulans may be isolated from dogs with recurrent pyoderma. Although isolates from dogs with pyoderma were frequently resistant to methicillin, multiple drug resistance was uncommon.     

Prevalence of methicillin-resistant Staphylococci on a farm: staff can harbour MRS when animals do not

The aim of this work was to establish the prevalence of methicillin-resistant Staphylococci (MRS) in the animals and staff of a teaching and research farm. Samples of dairy cattle (36), beef cattle (26), sheep (19), horses (21), pigs (23), goats (23) and humans (13) were collected and screened for the presence of MRS. The detection of mecA gene was performed by PCR to determine the resistance of the samples to methicillin. Antimicrobial-resistance testing to penicillin, meropenem, ceftriaxone, cephalothin, oxacillin, levofloxacin, enrofloxacin, chloramphenicol, ciprofloxacin, gentamicin, clindamycin, erytromycin, linezolid, sulfamethoxazole/trimethoprim, tetracycline, doxycycline and vancomycin was performed on the mecA+ isolates. From the 161 samples, four methicillin-resistant coagulase-negative Staphylococci (MRCoNS) were isolated from human beings (31%), whereas none was isolated from animals (0%). No methicillin-resistant Staphylococcus aureus (MRSA) were isolated. All of the MRCoNS isolates from this work presented different antimicrobial resistance patterns. MRCoNS may be present in humans associated with animals while not present in the animals. Selective pressure outside of the farm and a lack of MRCoNS transmission between humans and animals may be responsible for this lack of correlation.     

牛源耐甲氧西林金黄色葡萄球菌的检测

本研究旨在了解甘肃地区奶牛乳房炎金黄色葡萄球菌的耐药性和耐甲氧西林金黄色葡萄球菌的感染情况,为奶牛乳房炎的防制提供理论依据。采用KB纸片扩散法,检测17株金黄色葡萄球菌对8种不同抗菌药物的敏感性;再用琼脂稀释法检测了苯唑西林、万古霉素对金黄色葡萄球菌的最小抑菌浓度(MICs);头孢西丁纸片扩散法和PCR扩增特异性mecA耐药基因对所有受试菌株进行全面的耐甲氧西林金黄色葡萄球菌检测。结果表明,菌株对青霉素、磺胺异恶唑具有较强抗性,而对环丙沙星、头孢唑啉、万古霉素和苯唑西林全敏感;头孢西丁纸片扩散法未能检测出表型为MRSA的阳性菌株,而PCR方法却检测出8株mecA基因阳性菌株,且这些菌株的苯唑西林MIC均小于2 μg/mL。菌株的耐药情况较严重,对甲氧西林敏感而携带mecA基因的菌株高频存在于被调查地区的奶牛场中。     

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.     

Prevalence of antibiotic resistance genes in staphylococci isolated from ready-to-eat meat products

Prevalence of mecA, blaZ, tetO/K/M, ermA/B/C, aph, and vanA/B/C/D genes conferring resistance to oxacillin, penicillin, tetracycline, erythromycin, gentamicin, and vancomycin was investigated in 65 staphylococcal isolates belonging to twelve species obtained from ready-to-eat porcine, bovine, and chicken products. All coagulase negative staphylococci (CNS) and S. aureus isolates harbored at least one antibiotic resistance gene. None of the S. aureus possessed more than three genes, while 25% of the CNS isolates harbored at least four genes encoding resistance to clinically used antibiotics. In 15 CNS isolates the mecA gene was detected, while all S. aureus isolates were mecA-negative. We demonstrate that in ready-to-eat food the frequency of CNS harboring multiple antibiotic resistance genes is higher than that of multiple resistant S. aureus, meaning that food can be considered a reservoir of bacteria containing genes potentially contributing to the evolution of antibiotic resistance in staphylococci.     

Molecular characterization of methicillin-resistant Staphylococcus aureus strains from pet animals and veterinary staff in China

The aim of this study was to determine the epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) isolates from pet animals and veterinary staff and the characteristics of these isolates. A total of 22 MRSA isolates were isolated from nasal swabs from dogs, cats and veterinary staff in six pet hospitals in six cities, and examined for antimicrobial susceptibility, the presence of resistance genes, Panton-Valentine leukocidin gene lukF-lukS, staphylococcal chromosomal cassette (SCC) mec typing, spa tying, pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing. Of 22 MRSA isolates, 21 were recovered from pet animals, and one was isolated from a member of sstaff. All 22 MRSA strains were resistant to penicillin, oxacillin, azithromycin, clindamycin and ceftriaxone, and harboured mecA, ermB and linA genes. The lukF-lukS gene was not detected in any of the MRSA isolates. Eighteen MRSA strains from Qingdao belonged to ST59-MRSA-IV-spa t437. Of four MRSA isolates from Beijing, one belonged to ST398-MRSA-V-spa t034, and three belonged to ST239-MRSA-III-spa t030 profiles. Two PFGE types (A and B) were identified. Two isolates originating from dogs and one isolate originating from a staff member in Beijing shared similar PFGE patterns. Our cumulative data suggested that cross-transmission of MRSA may have occurred between pet animals and veterinary staff.     

Evaluation of methicillin resistance in Staphylococcus intermedius isolated from dogs

Methicillin and multi-drug resistance were investigated in 136 Staphylococcus intermedius strains of canine origin. The large majority of isolates were found to be mecA-negative by polymerase chain reaction, whereas only four strains were positive for the mecA gene. All mecA-positive strains were confirmed as methicillin-resistant by complementary tests, except for oxacillin disk diffusion, which yielded one false-negative result. A significantly higher resistance to fusidic acid, lincosamides, and cotrimoxazole was observed in methicillin-resistant S. intermedius (MRSI) compared with methicillin-susceptible strains. Although the prevalence of MRSI in dogs appeared to be low, methicillin resistance was confirmed to be associated with multi-drug resistance, suggesting the importance of antimicrobial susceptibility testing of canine S. intermedius strains.     

Occurrence, species distribution, antimicrobial resistance and clonality of methicillin- and erythromycin-resistant staphylococci in the nasal cavity of domestic animals

beta-Lactams and macrolides are important antibiotics for treatment of staphylococcal infections in both humans and animals. The aim of the study was to investigate the occurrence, species distribution and clonality of methicillin- and erythromycin-resistant staphylococci in the nasal cavity of dogs, horses, pigs, and cattle in Denmark. Nasal swabs were collected from a total of 400 animals, including 100 individuals of each species. Methicillin- and erythromycin-resistant staphylococci were isolated on selective media, identified by 16S rDNA sequencing, and typed by pulsed field gel electrophoresis (PFGE). Methicillin-resistant coagulase-negative staphylococci (MRCoNS) harbouring mecA were isolated from horses (50%) and dogs (13%), but not from food animals. The species identified were S. haemolyticus (n=21), S. vitulinus (n=19), S. sciuri (n=13), S. epidermidis (n=8), and S. warneri (n=2). mecA-mediated methicillin resistance in S. vitulinus was described for the first time. Methicillin-resistant S. aureus was not detected. PFGE analysis revealed the presence of specific MRCoNS clones in samples originating from the same veterinary hospital or equine farm. Erythromycin-resistant S. aureus (ERSA) was detected in 38% of pigs and all isolates harboured a constitutively expressed erm(C) gene. The vast majority (37/38) of pigs carrying ERSA originated from a farm characterized by frequent use of macrolides. Most ERSA isolates (28/38) displayed indistinguishable or closely related PFGE patterns, indicating clonal distribution within the farm. Based on the analysis of data on antimicrobial consumption, the occurrence of MRCoNS in companion animals and that of ERSA in pigs reflected national and local patterns of antimicrobial usage.     

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.