Submitted:
04 September 2020
Posted:
05 September 2020
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Abstract
In the present study, we aimed to determine the antimicrobial resistance and genetic structure of a population of S. aureus recovered from transient and persistent intramammary infections and nares/muzzles. 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. Here, a great 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 for S. aureus. A discrepancy in the antimicrobial resistance between S. aureus strains isolated from nasal/muzzles and milk samples was observed. Furthermore, S. aureus isolates from transient and persistent 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 studied together with the predominance of a well udder-adapted S. aureus strain may contribute to the history of the high prevalence of mastitis caused by S. aureus, leading to great animal and public health concerns.
Keywords:
intramammary infection
; spa typing
; antimicrobial susceptibility
; dairy cow
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