MLST-Based Analysis and Antimicrobial Resistance of Staphylococcus epidermidis from Cases of Sheep Mastitis in Greece

SIMPLE SUMMARY: Data regarding Staphylococcus epidermidis in the multi-locus sequence typing (MLST) database are appraised. Further, work on the association with the resistance of Staphylococcus epidermidis, isolated from cases of sheep mastitis in Greece, to antibiotics is presented. The database includes 1593 isolates from 46 countries, most (76%) of human origin. Of the isolates of animal origin, 72% are from cases of mastitis, among which there were differences between isolates of bovine or ovine origin. Of the isolates from sheep mastitis in Greece, in 58%, resistance to antibiotics was found. There was no association between MLST types and resistance to antibiotics, but antibiotic resistance was more frequent among isolates from flocks being hand- than machine-milked. ABSTRACT: Staphylococcus epidermidis is an important causal agent of ovine mastitis. A literature search indicated a lack of systematic studies of causal agents of the infection by using multi-locus sequence typing (MLST). The objectives were to analyse MLST-based data and evaluate the antimicrobial resistance of S. epidermidis isolates from ovine mastitis in Greece. The database included 1593 isolates from 46 countries: 1215 of human, 195 of environmental and 134 of animal origin, distributed into 949 sequence types (STs) and cumulatively with 450 alleles therein. Among mastitis isolates, bovine isolates were distributed into 36 different STs and ovine ones into 15 STs. The 33 isolates from ovine mastitis in Greece were in 15 different STs, 6 of these (ST677, ST678, ST700, ST 709, ST710, ST711) assigned for the first time; in addition, 5 alleles (65 for arcC, 59 for aroE, 56 and 57 for gtr and 48 for tpiA) were identified for the first time. The spanning tree of these isolates included 15 nodes and 14 edges (i.e., branches). Among these isolates, 19 showed resistance to antimicrobial agents (tetracycline, penicillin, fucidic adic, erythromycin, clindamycin, cefoxitin). Resistance-related genes (tetK, tetT, msrA, tetM, tetS, ermC, mecA) were detected. There was no association between STs and resistance to antimicrobial agents. Isolates with antimicrobial resistance were recovered more often from flocks where hand-milking was practised.