Abstract
Simple SummaryStaphylococcus aureus is a major, prevalent mastitis pathogen, representing a real issue for bovine udder health, with unquestionable importance in human and veterinary medicine. The present study thus aimed to determine the antimicrobial resistance and the diversity of S. aureus recovered from transient and persistent intramammary infections and from extramammary niches (e.g., nares/muzzles) in dairy cows. We found that a large proportion of S. aureus strains exhibited multidrug resistance to antimicrobials, including resistance to antimicrobials that are critically important to human health. S. aureus isolates from transient and persistent IMIs did not differ, suggesting that the persistence of bovine intramammary infections (IMIs) was mainly determined by host factors, although S. aureus isolated from extramammary niches are not an important source of S. aureus intramammary infections. Furthermore, a discrepancy in antimicrobial resistance between S. aureus strains isolated from nares/muzzles and intramammary infections was observed.In the present study, we aimed to determine the antimicrobial resistance and molecular typing of Staphylococcus aureus recovered from transient and persistent intramammary infections and nares/muzzles in dairy cows. We investigated the antimicrobial resistance of 189 S. aureus strains using a broad antimicrobial susceptibility profile. Furthermore, 107 S. aureus isolates were strain-typed using staphylococcal protein-A (spa) typing. A large proportion of strains exhibited multidrug resistance to antimicrobials, including resistance to critically important antimicrobials, although no methicillin-resistant S. aureus strains were found. Our study did not strengthen the idea that extramammary niches (i.e., nares/muzzles) are an important source of S. aureus for bovine mastitis. A discrepancy in the antimicrobial resistance between S. aureus strains isolated from nares/muzzles and milk samples was observed. Furthermore, S. aureus isolates from transient and persistent intramammary infections (IMIs) did not differ by spa typing, suggesting that the persistence of bovine IMIs was determined by cow factors. Thus, the high level of multidrug-resistant S. aureus found in the two herds, considered together with the predominance of a well udder-adapted S. aureus strain, may contribute to our knowledge of the history of the high prevalence of mastitis caused by S. aureus, which is of great concern for animal and public health.
Highlights
Bovine mastitis is the most prevalent and costly disease that affects dairy farming
MALDI-TOF MS resulted in the identification of Staphylococcus chromogenes (n = 87, 54.72%), Staphylococcus haemolyticus (n = 21; 13.21%), Bacillus pumilus (n = 12; 7.55%), Staphylococcus hyicus (n = 10; 6.29%), S. aureus (n = 9; 5.66%), Staphylococcus xylosus (n = 3; 1.89%), Corynebacterium efficiens (n = 3; 1.89%), Enterococcus casseli (n = 2; 1.26%), Enterococcus faecium (n = 2; 1.26%), Staphylococcus saprophyticus (n = 1; 0.63%), Staphylococcus warneri (n = 1; 0.63%), Staphylococcus nepalensis (n = 1; 0.63%), Macrococcus caseolyticus (n = 1; 0.63%), Enterococcus mundtii (n = 1; 0.63%), Arthrobacter gandavensis (n = 1; 0.63%), Arthrobacter koreensis (n = 1; 0.63%), Arthrobacter protophormiae (n = 1; 0.63%), Bacillus subtilis (n = 1; 0.63%), and Cellulosimicrobium cellulans (n = 1; 0.63%)
Our results showed that 46.56% (n = 88) of S. aureus isolates were not susceptible to at least three distinct classes of antimicrobials
Summary
Bovine mastitis is the most prevalent and costly disease that affects dairy farming. It has great implications for milk production, the quality of milk and dairy products, antimicrobial usage, animal welfare, the environment, and the image of the dairy sector. Staphylococcus aureus is a major, prevalent mastitis pathogen, which represents a significant issue for bovine udder health, with unquestionable importance in human and veterinary medicine [1]. Antibiotic treatment is widely used to fight bovine mastitis, S. aureus resistance to antimicrobials complicates antimicrobial treatment, and represents a huge challenge for public health and food security, as cows are the major reservoir for the emergence of S. aureus human epidemic clones [2]. The growing spa typing database developed by Harmsen et al [4] is the largest database for typing S. aureus, surpassing that of multilocus sequence typing
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