title: Species distribution and in vitro antimicrobial susceptibility of coagulase-negative staphylococci isolated from bovine mastitic milk.
abstract: BACKGROUND
  Coagulase-negative staphylococci (CoNS) are the most common bovine mastitis causing bacteria in many countries. It is known that resistance for antimicrobials is in general more common in CoNS than in Staphylococcus aureus but little is known about the antimicrobial resistance of specific CoNS species. In this study, 400 CoNS isolates from bovine mastitic milk samples were identified to species level using ribotyping and MALDI-TOF MS, and their antimicrobial susceptibility was determined using a commercially available microdilution system. The results were interpreted according to the epidemiological cut-off values by the European Committee on Antimicrobial Susceptibility testing.
  
  
  RESULTS
  The most common CoNS species were S. simulans, S. epidermidis, S. chromogenes and S. haemolyticus. Penicillin resistance was the most common type of antimicrobial resistance. Staphylococcus epidermidis was the most resistant among the four major species. Almost one-third of our S. epidermidis isolates were resistant to >2 antimicrobials and close to 7 % were multidrug resistant. The majority of S. epidermidis isolates were resistant to benzylpenicillin. On the contrary, only few S. simulans isolates were penicillin-resistant. Phenotypic oxacillin resistance was found in all four main species, and 34 % of the isolates were oxacillin resistant. However, only 21 isolates (5 %) were positive for the mecA gene. Of these, 20 were S. epidermidis and one S. sciuri. mecC positive isolates were not found.
  
  
  CONCLUSIONS
  Staphylococcus epidermidis differed from the three other major CoNS species as resistance to the tested antimicrobials was common, several isolates were multidrug resistant, and 19 % of the isolates carried the mecA gene encoding methicillin resistance.
authors: Department of Production Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Paroninkuja 20, 04920, Saarentaus, Finland. suvi.taponen@helsinki.fi.
authors: Suvi
authors: S
authors: Taponen
authors: Finnish Food Safety Authority Evira, Mustialankatu 3, 00790, Helsinki, Finland. suvi.nykasenoja@evira.fi.
authors: Suvi
authors: S
authors: Nykäsenoja
authors: Finnish Food Safety Authority Evira, Mustialankatu 3, 00790, Helsinki, Finland. tarja.pohjanvirta@evira.fi.
authors: Tarja
authors: T
authors: Pohjanvirta
authors: Finnish Food Safety Authority Evira, Mustialankatu 3, 00790, Helsinki, Finland. anna.pitkala@helsinki.fi.
authors: Anna
authors: A
authors: Pitkälä
authors: Department of Production Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Paroninkuja 20, 04920, Saarentaus, Finland. satu.pyorala@helsinki.fi.
authors: Satu
authors: S
authors: Pyörälä
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002417:Cattle; D003030:Coagulase / Q000032:analysis; D005260:Female; D005387:Finland / Q000453:epidemiology; D008414:Mastitis, Bovine / Q000453:epidemiology / Q000382:microbiology*; D008826:Microbial Sensitivity Tests / Q000662:veterinary; D008892:Milk / Q000382:microbiology*; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D013210:Staphylococcus / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000502:physiology*
chemical_list: D000900:Anti-Bacterial Agents; D003030:Coagulase