Macrococcus canis and M. caseolyticus in dogs: occurrence, genetic diversity and antibiotic resistance Kerstin Cotting*, Christian Strauss*, Sabrina Rodriguez-Campos*, Ana Rostaher†, Nina M. Fischer†, Petra J. Roosje‡, Claude Favrot† and Vincent Perreten* *Institute of Veterinary Bacteriology, Department of Infectious Diseases and Pathobiology, University of Bern, L€ anggassstrasse 122, Bern, CH- 3001, Switzerland †Clinic for Small Animal Internal Medicine, Dermatology unit, Vetsuisse Faculty University of Zurich, Winterthurerstrasse 260, Zurich, CH-8057, Switzerland. ‡Division of Clinical Dermatology, Department of Clinical Veterinary Medicine, University of Bern, L€ anggassstrasse 128, Bern, CH-3001, Switzer- land Correspondence: Vincent Perreten, Institute of Veterinary Bacteriology, Department of Infectious Diseases and Pathobiology, University of Bern, L€ anggassstrasse 122, CH-3001 Bern, Switzerland. E-mail: vincent.perreten@vetsuisse.unibe.ch Background – The discovery of a new Macrococcus canis species isolated from skin and infection sites of dogs led us to question if Macrococcus spp. are common in dogs and are resistant to antibiotics. Hypothesis/Objectives – To evaluate the occurrence of Macrococcus spp. in dogs, determine antibiotic resis- tance profiles and genetic relationships. Animals – One hundred and sixty two dogs (mainly West Highland white terriers and Newfoundland dogs) were screened for the presence of Macrococcus, including six dogs with Macrococcus infections. Methods – Samples were taken from skin, ear canal and oral mucosa using swabs. Macrococci were identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry, 16S rRNA sequencing and nuc- PCR. Minimal inhibitory concentrations of 19 antibiotics were determined using broth microdilution. Resistance mechanisms were identified by microarray and sequencing of the fluoroquinolone-determining region of gyrA and grlA. Sequence type (ST) was determined by multilocus sequence typing. Results – Out of the 162 dogs, six harboured M. caseolyticus (n = 6) and 13 harboured M. canis (n = 16). Six isolates of M. canis and one of M. caseolyticus were obtained from infection sites. The 22 M. canis strains belonged to 20 different STs and the seven M. caseolyticus strains to three STs. Resistance to antibiotics was mostly associated with the detection of known genes, with mecB-mediated meticillin resistance being the most frequent. Conclusion and clinical importance – This study gives some insights into the occurrence and genetic charac- teristics of antibiotic-resistant Macrococcus from dogs. Presence of M. canis in infection sites and resistance to antibiotics emphasized that more attention should be paid to this novel bacteria species. Introduction Macrococcus is a Gram-positive coccoid bacterium that is coagulase negative and catalase positive which may be misidentified as a coagulase negative Staphylococcus species thus needing further differentiation. It was origi- nally placed into the Micrococcus genus, then the Staphy- lococcus genus and in 1998 it was assigned to its own Macrococcus genus. 1 The genus Macrococcus currently contains eight species (M. caseolyticus, M. carouselicus, M. equipercicus, M. bovicus, M. brunensis, M. hajekii and M. lamae) including M. canis found in dogs. 1–3 All Macrococcus belong primarily to the microbiota of mam- mals and M. caseolyticus was also found in milk and meat. 1 An association of Macrococcus with infections has rarely been reported: so far there is only one history of abscesses in lambs with M. caseolyticus, and a few cases of rhinitis, dermatitis, mastitis and otitis in dogs with the novel M. canis species. 3–5 Little is known about this novel bacterium and other Macrococcus in general, prompting us to investigate further the occurrence, genetic relationship and antibiotic resistance profile of Macrococcus species in West Highland white terriers and Newfoundland dogs. Although the study was limited to two breeds and was not representative of the dog popula- tion, it aimed to raise awareness of the presence of a potential new opportunistic skin pathogen and to provide baseline information for further studies of Macrococcus infections in dogs. Material and methods Identification of the strains Samples were obtained within the framework of two projects study- ing the bacterial flora of 147 West Highland white terriers and 15 Newfoundland dogs. Samples were taken using swabs (Transwab â , Accepted 16 June 2017 Source of funding: This study was financed by grant no. 320030_152686 from the Swiss National Science Foundation. Conflict of interest: No conflicts of interest have been declared. © 2017 ESVD and ACVD, Veterinary Dermatology 1 Vet Dermatol 2017 DOI: 10.1111/vde.12474