SN ANDREIS¹, V PERRETEN¹, N WOHLWEND², S SCHWENDENER<sup>1

1</sup>Institute of Veterinary Bacteriology, Vetsuisse Faculty, University of Bern, Bern, Switzerland, ²labormedizinisches zentrum Dr Risch, Bern-Liebefeld, Switzerland

Staphylococcus arlettae is a coagulase-negative Staphylococcus (CoNS) which belongs to the normal flora of humans and animals. It is also sporadically associated with mastitis in cows. S. arlettae M1670 was isolated from bovine mastitis milk in Switzerland and analysed for antibiotic resistances by minimal inhibitory concentration (MIC) measurement, PCR and microarray. Strain M1670 exhibited resistance to erythromycin (MIC >8µg/ml), clindamycin (MIC 2µg/ml), fusidic acid (MIC >4µg/ml) and penicilline (MIC 0.5µg/ml). However, no known resistance genes were detected. Whole genome sequencing using Illumina MiSeq revealed the presence of a msr(A)-like gene which shares 87% nucleotide sequence identity with the msr(A) gene from S. epidermidis strain 968. It encodes a Msr(A)-like protein of 488 amino acids that contains the ATP-binding cassettes (ABC) transporter signature pattern and two ABC domains typical for class 2 ABC proteins. The msr(A)-like gene was located downstream of a putative virulence factor encoding a lipase. Comparative sequence analysis of the M1670 draft genome with the genome of S. arlettae strain CVD059 indicated that the msr(A)-like variant and lipase are inserted into the accessory region of the S. arlettae chromosome. This discovery shows that diverse genomic fragments containing msr(A)-like macrolide resistance genes are present in S. arlettae from animal origin.