title: Genetic characterization of antimicrobial resistance in coagulase-negative staphylococci from bovine mastitis milk.
abstract: Coagulase-negative staphylococci (CNS; n=417) were isolated from bovine milk and identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Nineteen different species were identified, and Staphylococcus xylosus, Staphylococcus chromogenes, Staphylococcus haemolyticus, and Staphylococcus sciuri were the most prevalent species. Resistance to oxacillin (47.0% of the isolates), fusidic acid (33.8%), tiamulin (31.9%), penicillin (23.3%), tetracycline (15.8%), streptomycin (9.6%), erythromycin (7.0%), sulfonamides (5%), trimethoprim (4.3%), clindamycin (3.4%), kanamycin (2.4%), and gentamicin (2.4%) was detected. Resistance to oxacillin was attributed to the mecA gene in 9.7% of the oxacillin-resistant isolates. The remaining oxacillin-resistant CNS did not contain the mecC gene or mecA1 promoter mutations. The mecA gene was detected in Staphylococcus fleurettii, Staphylococcus epidermidis, Staph. haemolyticus, and Staph. xylosus. Resistance to tetracycline was attributed to the presence of tet(K) and tet(L), penicillin resistance to blaZ, streptomycin resistance to str and ant(6)-Ia, and erythromycin resistance to erm(C), erm(B), and msr. Resistance to tiamulin and fusidic acid could not be attributed to an acquired resistance gene. In total, 15.1% of the CNS isolates were multidrug resistant (i.e., resistant to 2 or more antimicrobials). The remaining CNS isolates were susceptible to antimicrobials commonly used in mastitis treatment. Methicillin-resistant CNS isolates were diverse, as determined by mecA gene sequence analysis, staphylococcal cassette chromosome mec typing, and pulsed-field gel electrophoresis. Arginine catabolic mobile element types 1 and 3 were detected in both methicillin-resistant and methicillin-susceptible Staph. epidermidis and were associated with sequence types ST59 and ST111. Because this study revealed the presence of multidrug-resistant CNS in a heterogeneous CNS population, we recommend antibiogram analysis of CNS in persistent infections before treatment with antimicrobials.
authors: Institute of Veterinary Bacteriology, Vetsuisse Faculty, University of Bern, CH-3012 Bern, Switzerland.
authors: Yvonne
authors: Y
authors: Frey
authors: Institute of Veterinary Bacteriology, Vetsuisse Faculty, University of Bern, CH-3012 Bern, Switzerland.
authors: Joan Peña
authors: JP
authors: Rodriguez
authors: Institute of Veterinary Bacteriology, Vetsuisse Faculty, University of Bern, CH-3012 Bern, Switzerland.
authors: Andreas
authors: A
authors: Thomann
authors: Institute of Veterinary Bacteriology, Vetsuisse Faculty, University of Bern, CH-3012 Bern, Switzerland.
authors: Sybille
authors: S
authors: Schwendener
authors: Institute of Veterinary Bacteriology, Vetsuisse Faculty, University of Bern, CH-3012 Bern, Switzerland. Electronic address: vincent.perreten@vetsuisse.unibe.ch.
authors: Vincent
authors: V
authors: Perreten
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D002417:Cattle; D003030:Coagulase; D004269:DNA, Bacterial / Q000302:isolation & purification; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D018432:Drug Resistance, Multiple; D005260:Female; D005838:Genotype; D008414:Mastitis, Bovine / Q000382:microbiology*; D016106:Methicillin Resistance / Q000235:genetics; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics; D008826:Microbial Sensitivity Tests; D008892:Milk / Q000382:microbiology*; D013203:Staphylococcal Infections / Q000382:microbiology*; D013210:Staphylococcus / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D003030:Coagulase; D004269:DNA, Bacterial