Association of coagulase-negative staphylococcal species, mammary quarter milk somatic cell count, and persistence of intramammary infection in dairy cattle

Abstract

This study was conducted to evaluate the association between subclinical intramammary infection (IMI) with coagulase-negative staphylococci (CNS), mammary quarter milk somatic cell count (SCC), and persistence of IMI in dairy cattle. Convenience samples of CNS isolates harvested from milk samples of subclinically infected mammary quarters collected between 4 and 2wk before drying-off, between 2wk before drying-off and the day of drying-off, within 24h after calving, between 1 and 2wk after calving, and during lactation were evaluated. Isolates were obtained from the Canadian Bovine Mastitis Research Network culture bank and were identified to the species level using rpoB gene sequencing. Cow and quarter-level data were obtained from the Canadian Bovine Mastitis Research Network database and used for statistical analyses. In addition, for mammary quarters that had more than one isolation of the same CNS species at different time points, the isolates were evaluated using pulsed-field gel electrophoresis to identify persistent IMI. Milk SCC was compared between mammary quarters infected with different CNS species and to a cohort of uninfected mammary quarters. A total of 877 isolates from 643 mammary quarters of 555 cows on 89 Canadian dairy farms were identified to the species level. Twenty different species were identified, with Staphylococcus chromogenes being the most common species identified (48% of isolates), followed by Staphylococcus simulans (19%) and Staphylococcus xylosus (10%). Of the 20 species identified, only 9 species were found in persistently infected quarters. Milk SCC was significantly higher in the CNS-infected mammary quarters than in the uninfected control quarters for 8 of the 20 species studied. Also, mean SCC differed significantly between mammary quarters infected with different CNS species. Within a given species, a high degree of variability was noted in milk SCC. These data corroborate recent data from Europe with regard to the predominance of certain species of CNS (e.g., Staph. chromogenes). In addition, some species of CNS appear to have a greater effect on milk SCC. Finally, some CNS species are associated with persistent IMI suggesting that some species (e.g., Staph. chromogenes and Staph. simulans) are better host-adapted, whereas others may have an environmental reservoir.

Quarter- and cow-level risk factors for intramammary infection with coagulase-negative staphylococci species in Swiss dairy cows

“…Grouping of CNS species was suggested for less prevalent species and performed based on other authors' observations on the effect of these species on udder health Fry et al, 2014). A very recent study investigated risk factors for IMI in fresh cows at the species level, grouping species according to their relevance and ecology (De Visscher et al, 2016).…”

Species Identification and Strain Typing of Staphylococcus agnetis and Staphylococcus hyicus Isolates from Bovine Milk by Use of a Novel Multiplex PCR Assay and Pulsed-Field Gel Electrophoresis

“…Historically, S. hyicus was found to be one of the most common organisms isolated from mammary gland secretions and teat canal keratin samples from primigravid heifers (8). When identified as a coagulase-negative staphylococcal (CNS) species, the reported prevalence of S. hyicus on dairy farms has been highly varied, with some researchers finding it to be one of the most prevalent species identified (7), while being rarely identified by others (3,9). Coagulase-positive S. hyicus has been described as a low-prevalence mastitis pathogen and has been found to be a greater problem in herds with a low prevalence of S. aureus IMI (6).…”

Characterization of Staphylococcus spp. strains in milk from buffaloes with mastitis in Brazil: the need to identify to species level to avoid misidentification

“…These results show the importance of identifying the CNS strains to the species level in order to avoid misidentification. Since the rrs gene has been questioned as a suitable discriminatory target gene to identify Staphylococcus species (Ghebremedhin et al, 2008), we decided to apply a PCR-RFLP protocol used by our group to identify Staphylococcus spp. The S. aureus and S. hyicus strains presented a restriction profile compatible with these species.…”

“…The identification of the species-specific restriction fragment profiles was based on the results published by Barros et al (2007) and Santos et al (2008). Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE) was applied to analyze extracts of whole-cell proteins corresponding to 10 7 CFU from overnight cultures of the strains were evaluated by SDS-PAGE as previously described (Laport et al, 2001). …”

“…The disease is classified as moderate or severe, and might be caused by different bacterial species, but mainly Staphyococcus strains (Pyörälä and Taponen, 2009 Coagulase-negative staphylococci (CNS) have been considered pathogens of lesser importance, while Staphylococcus aureus has been considered a more important pathogen due its ability to form biofilm (Lee et al, 2014). However, more recent studies have shown that CNS are emerging pathogens associated with the occurrence of mastitis and persistence of intramammary infection in dairy cattle (Fry et al, 2014).…”