Abstract
BackgroundCoagulase-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.ResultsThe 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.Conclusion 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s13028-016-0193-8) contains supplementary material, which is available to authorized users.
Highlights
Coagulase-negative staphylococci (CoNS) are the most common bovine mastitis causing bacteria in many countries
Reports on mastitis causing CoNS species and their antimicrobial susceptibility have since been published by some authors [5, 6, 14]
The unidentified isolates may represent a new Staphylococcus species or one of the few CoNS species, like S. devriesei, which were not included in the ribotype and MALDI-TOF MS comparison databases at the time of the analyses
Summary
Coagulase-negative staphylococci (CoNS) are the most common bovine mastitis causing bacteria in many countries. Prevalence of mastitis in dairy cows and distribution of mastitis-causing bacteria has regularly been monitored in Finland [1, 2] These surveys have reported antimicrobial in vitro susceptibility of different bacterial species, including coagulase-negative staphylococci (CoNS). Reliable genotypic identification has enabled studying frequency of different CoNS species and species-specific antimicrobial susceptibility. Only few studies have used epidemiological cut-off values (ECOFF) of the European Committee on Antimicrobial Susceptibility testing to determine proportions of resistant isolates [15], which has made comparisons difficult. Studies on genetic mechanisms for resistance of bovine CoNS species have been published, with different panels of resistance genes [5, 16, 17]. Knowledge on the antimicrobial susceptibility of different CoNS species is necessary
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
