Distribution of non-aureus staphylococci from quarter milk, teat apices, and rectal feces of dairy cows, and their virulence potential

Abstract

Non-aureus staphylococci (NAS) are predominantly isolated from bovine milk samples of quarters suffering from subclinical mastitis. They are also abundantly present on dairy cows' teat apices and can be recovered from bovine fecal samples, as recently described. Differences in ecology, epidemiology, effect on udder health, and virulence or protective traits have been reported among the species within this group. The objectives of this study were (1) to describe the species-specific distribution of NAS in 3 bovine-associated habitats, namely quarter milk, teat apices, and rectal feces, and (2) to evaluate the virulence potential of NAS by comparing their distribution in contrasting milk sample strata and the presence of selected virulence genes. A cross-sectional, systematic sampling procedure was followed in 8 dairy herds that participated in the local Dairy Herd Improvement program in Flanders, Belgium. Quarter milk samples (n = 573) were collected from 144 lactating cows in 8 herds. In 5 of the 8 herds, teat apex swabs (n = 192) were taken from 15 lactating cows, before and after milking, and from 18 dry cows. In the same 5 herds, rectal feces were sampled from 80 lactating cows (n = 80), taking into account that a cow could only serve as the source of one type of sample. In addition, milk samples of all clinical mastitis cases were continuously collected during the 1-yr study period from March 2017 to March 2018 in the 8 herds. In total, 1,676 Staphylococcus isolates were phenotypically identified and subjected to MALDI-TOF mass spectrometry. Thirty-three, 98, and 28% of all quarter milk, teat apex, and rectal fecal samples were NASpositive, respectively, reaffirming the presence of NAS in rectal feces. The overall predominant species in the 3 habitats combined were Staphylococcus haemolyticus, Staphylococcus chromogenes, and Staphylococcus hominis. Four, 16, and 12% of the healthy quarters (quarter milk somatic cell count ≤50,000 cells/mL of milk), quarters with subclinical mastitis (quarter milk somatic cell count >50,000 cells/mL of milk), and quarters with clinical mastitis, respectively, were NAS-positive, suggesting that the potential to cause (mild) clinical mastitis is present among NAS. This was substantiated by comparing the presence of virulence genes of NAS isolates originating from contrasting milk sample strata (healthy quarters and quarters with clinical mastitis).

Colonization and local host response following intramammary Staphylococcus chromogenes challenge in dry cows

“…The phenotypically different Gram-positive, catalasepositive cocci found between D-35/D-21 and L6 that were stored at -80 °C, were identified at the species level by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) MS (MALDI Biotyper, Bruker Daltonics, Bremen, Germany) [39]. A score value ≥ 2.000 was considered reliable at species level for most species although this was lowered to 1.700 for the species-level identification of NAS isolates as previously described [39,40], and a validated and updated bovine NAS library was used [5]. If isolates could not be reliably identified by MALDI-TOF MS, 16S rRNA sequencing was carried out [41].…”

“…Non-aureus staphylococci (NAS) are the most frequently isolated bacteria from bovine mammary quarters either with or without subclinical mastitis [1][2][3][4][5] and have been detected in dry quarter secretions as well [6,7]. Differences in ecology, epidemiology and relevance for bovine udder health in this heterogeneous group of bacteria are present both at the species level and within species [8][9][10][11][12][13].…”

Antimicrobial resistance and virulence characteristics in 3 collections of staphylococci from bovine milk samples

“…De Visscher, 2 * T. L'Abee-Lund, 1 C. Ngassam Tchamba, 3 J. G. Mainil, 3 D. Thiry, 3 S. De Vliegher, 2 and Y. Wasteson 1 † samples is described in several studies; however, the results are not directly comparable due to a variety of study designs. A recent study from Belgium concluded that the 5 most prevalent NAS species recovered from quarter milk samples were Staphylococcus chromogenes, Staphylococcus haemolyticus, Staphylococcus equorum, Staphylococcus hominis, and Staphylococcus cohnii (Wuytack et al, 2020). In Norway, Staphylococcus epidermidis and Staph.…”

“…The NAS species lack the aggressive potential of Staph. aureus, and less is known about the virulence of these species (Becker et al, 2014;Naushad et al, 2019;Wuytack et al, 2020). Knowledge regarding virulence of both Staph.…”

Randomized controlled field trial comparing quarter and cow level selective dry cow treatment using the California Mastitis Test

“…together and treated them as a single group. While there is an increasing body of evidence to suggest that all NAS are not equal (Valckenier et al, 2020;Wuytack et al, 2020), we took this approach to facilitate comparison with earlier research in the area. A more detailed analysis of the outcomes and potential roles of the individual NAS spp.…”