Molecular characterization of non-aureus Staphylococcus spp. from heifer intramammary infections and body sites

Abstract

The purpose of this study was to investigate non-aureus Staphylococcus spp. intramammary infections (IMI) in periparturient heifers and determine the relationship of precalving body site isolation with precalving IMI and postcalving IMI using molecular speciation and strain-typing methods. Primiparous heifers were enrolled at approximately 14 d before expected calving date. Precalving mammary quarter secretions and body site swabbing samples (teat skin, inguinal skin, muzzle, and perineum) were collected. Postcalving, mammary quarter milk samples were collected for culture and somatic cell counting. Precalving body site samples were cultured, and up to 10 staphylococcal colonies were saved for characterization. Staphylococcal isolates were speciated using matrix-assisted laser/desorption ionization time-of-flight mass spectrometry or sequencing of rpoB or tuf. Pulsed-field gel electrophoresis was used to strain type a subset of isolates. Overall, Staphylococcus chromogenes, Staphylococcus agnetis, and Staphylococcus simulans were the most common species identified in precalving mammary secretions, whereas S. chromogenes, Staphylococcus xylosus, and S. agnetis were the most common species found in postcalving milk samples. The most common species identified from body site samples were S. chromogenes, S. xylosus, and Staphylococcus haemolyticus. Mammary quarters that had a precalving mammary secretion that was culture positive for S. agnetis, S. chromogenes, or Staphylococcus devriesei had increased odds of having an IMI with the same species postcalving. A S. chromogenes IMI postcalving was associated with higher somatic cell count when compared with postcalving culture-negative quarters. Among heifers identified with a non-aureus Staphylococcus spp. IMI either precalving or postcalving, heifers that had S. agnetis or S. chromogenes isolated from their teat skin had increased odds of having the same species found in their precalving mammary secretions, and heifers with S. chromogenes, S. simulans, and S. xylosus isolated from their teat skin precalving were at increased odds of having an IMI with the same species postcalving. Overall, 44% of all heifers with a S. chromogenes IMI around the time of parturition had the same strain isolated from a body site. Based on pulsed-field gel electrophoresis, a high level of strain diversity was found.

Fecal non-aureus Staphylococci are a potential cause of bovine intramammary infection

“…Some NAS species tend to be more relevant for the udder health, e.g. S. chromogenes [8,37,38]. This was substantiated in the current study as in herd 1, only milk samples from quarters with a SCC > 50 000 cells/mL milk and clinical signs harbored S. chromogenes.…”

“…Non-aureus staphylococci (NAS), a heterogeneous group of bacteria, are the most frequently identified bacteria in bovine milk samples worldwide [1][2][3][4]. They are also colonizing the teat apex of both lactating and dry cows [5,6] as well as the teat canal [7] and other body parts [8]. We recently reported that Staphylococcus (S.) agnetis, S. auricularis, S. chromogenes, S. cohnii, S. epidermidis, S. equorum, S. haemolyticus, S. hominis, S. kloosii, S. rostri, and S. xylosus can also be isolated from rectal feces [9], indicating cows are shedding NAS into the environment which could eventually give rise to the establishment of intramammary infection (IMI), most likely after colonization of the teat apices.…”

Cross-sectional study to identify staphylococcal species isolated from teat and inguinal skin of different-aged dairy heifers

“…This finding has also been demonstrated for other host-adapted staphylococcal species, specifically Staphylococcus aureus (Roberson et al, 1994). Furthermore, in one study, 44% of all heifers with a S. chromogenes IMI around the time of parturition had the same strain of S. chromogenes isolated from a body site, with many originating from the teat skin (Adkins et al, 2018). Although S. chromogenes IMI has been linked to elevated milk SCC and persistent IMI (Supré et al, 2011;Fry et al, 2014), isolation of S. chromogenes from the prepartum teat end has been associated with an SCC of <200,000 cells/ mL and may protect against IMI in early lactation (De Vliegher et al, 2003).…”

“…Identification of some staphylococcal species on the teat end has been found to be associated with IMI. Specifically, finding S. chromogenes on the teat skin of late-term heifers has been shown to significantly increase the odds of S. chromogenes IMI around the time of parturition (De Visscher et al, 2016a;Adkins et al, 2018). This finding has also been demonstrated for other host-adapted staphylococcal species, specifically Staphylococcus aureus (Roberson et al, 1994).…”

“…Recent research using molecular identification methods has demonstrated diversity among NAS species that can be found on the dairy farm as well as differences between species with regard to IMI, associated mammary inflammation, persistence of IMI, and ecological niches on and off the cow (Piessens et al, 2011;Supré et al, 2011;De Visscher et al, 2014;Fry et al, 2014). Staphylococci have been found in abundance in various extramammary sites (defined as any site not inside the mammary gland) including environmental sites such as floor samples, air samples, and used bedding samples as well as bovine Cross-sectional study to identify staphylococcal species isolated from teat and inguinal skin of different-aged dairy heifers body sites including the perineum, udder skin, and teat skin (Taponen et al, 2008;Piessens et al, 2011;De Visscher et al, 2016b;Adkins et al, 2018).…”