Teat apex colonization with coagulase-negative Staphylococcus species before parturition: Distribution and species-specific risk factors.

Coagulase-negative staphylococci (CNS) are the main cause of bovine intramammary infections and are also abundantly present in extramammary habitats such as teat apices. Teat apex colonization (TAC) with CNS has already been explored in lactating dairy cows at the species level, whereas this is not true for dry cows and end-term heifers. Therefore, the aim of this observational study was to describe CNS TAC in nonlactating dairy cows and end-term heifers in Flemish dairy herds and to identify associated risk factors at the herd, cow, and quarter level. All CNS were molecularly identified to the species level using transfer RNA intergenic spacer PCR (tDNA-PCR) and sequencing of the 16S rRNA gene, allowing for species-specific statistical analyses using multivariable, multilevel logistic regression. Staphylococcus devriesei, Staphylococcus chromogenes, Staphylococcus haemolyticus, and Staphylococcus equorum were the most frequently isolated species. Staphylococcus chromogenes was the sole species colonizing teat apices of cows and heifers in all herds, whereas large between-herd differences were observed for the other species. Teat apices of red and white Holstein Friesians, of quarters dried off without an internal teat sealer, and swabbed in months with lower precipitation and higher ambient temperature were significantly more likely to be colonized by S. devriesei. Slightly dirty teat apices and teat apices swabbed in months with lower precipitation had higher odds of being colonized by S. chromogenes, whereas teat apices sampled in months with lower precipitation and higher ambient temperature were more likely to be colonized by S. haemolyticus. Dirty teat apices and teat apices swabbed in months with lower ambient temperature in combination with low precipitation had higher odds of being colonized by S. equorum. Diverse factors explaining CNS TAC, yet mostly related to humidity, ambient temperature, and hygiene, substantiate differences in epidemiological behavior and ecology between species.

De Visscher A ，Piepers S ，Haesebrouck F ，De Vliegher S ... -  《-》

Intramammary infection with coagulase-negative staphylococci at parturition: Species-specific prevalence, risk factors, and effect on udder health.

Coagulase-negative staphylococci (CNS) are the main cause of bovine intramammary infections (IMI) in many countries. Despite a high prevalence of CNS IMI at parturition, species-specific risk factor studies, relying on accurate identification methods, are lacking. Therefore, this observational study aimed at determining the prevalence and distribution of different CNS species causing IMI in fresh heifers and dairy cows in Flemish dairy herds and identifying associated species- and subgroup-specific risk factors at the herd, cow, and quarter level. The effect on udder health was investigated as well. Staphylococcus chromogenes, S. sciuri, and S. cohnii were the most frequently isolated species. The only CNS species causing IMI in fresh heifers and dairy cows in all herds was Staphylococcus chromogenes, whereas large between-herd differences in distribution were observed for the other species. Quarters from heifers and quarters with an inverted teat end had higher odds of being infected with S. chromogenes, S. simulans, or S. xylosus as well as with S. chromogenes solely. Prepartum teat apex colonization with S. chromogenes increased the likelihood of S. chromogenes IMI in the corresponding quarters at parturition. Quarters with dirty teat apices before calving were more likely to be infected with S. cohnii, S. equorum, S. saprophyticus, or S. sciuri, supporting the environmental nature of these CNS species. Three species (S. chromogenes, S. simulans, and S. xylosus) were associated with a higher quarter somatic cell count at parturition as compared with uninfected quarters.

De Visscher A ，Piepers S ，Haesebrouck F ，De Vliegher S ... -  《-》

Short communication: Species group-specific predictors at the cow and quarter level for intramammary infection with coagulase-negative staphylococci in dairy cattle throughout lactation.

Coagulase-negative staphylococci (CNS) are frequently isolated from quarters with subclinical mastitis, teat apices, and the cows' environment. Virulence, ecology, epidemiological behavior, and effect on udder health vary between different CNS species. Staphylococcus chromogenes, Staph. simulans, and Staph. xylosus are frequently present in milk and have a more substantial effect on quarter milk somatic cell count than other species. Therefore, these species are considered the "more relevant" CNS. As species-specific factors associated with CNS intramammary infection (IMI) have not yet been identified and susceptibility for IMI differs between cows and quarters, this study aimed to identify predictors for CNS IMI at the cow and quarter level (some of them changing over time) with a specific focus on the aforementioned more relevant CNS. Precise data were available from a longitudinal study (3,052 observations from 344 quarters from 86 dairy cows belonging to 3 commercial dairy herds). All CNS were molecularly identified to the species level, and multivariable, multilevel logistic regression models taking into account the longitudinal nature of the data, were fit to study the likelihood of infection. Staphylococcus chromogenes, Staph. xylosus, and Staph. cohnii were the most frequently isolated species from CNS IMI in older cows, whereas Staph. chromogenes, Staph. xylosus, and Staph. simulans were the main species found in IMI in heifers. Quarters from heifers (as opposed to multiparous cows), from heifers and multiparous cows in third or fourth month in lactation (as opposed to early lactation, <60 d in milk), and with an increasing quarter milk SCC were more likely to be infected with the more relevant CNS species. Quarter milk SCC was identified as the sole statistically significant predictor for IMI with other CNS species, although the size of the effect was lower [odds ratio of 1.6 (1.4-1.9) vs. 2.1 (1.8-2.5)] than the effect for IMI with the more relevant CNS. As a strong herd effect was present, studying herd-level predictors is warranted.

De Visscher A ，Piepers S ，Supré K ，Haesebrouck F ，De Vliegher S ... -  《-》

Prepartum teat apex colonization with Staphylococcus chromogenes in dairy heifers is associated with low somatic cell count in early lactation.

De Vliegher S ，Laevens H ，Devriese LA ，Opsomer G ，Leroy JL ，Barkema HW ，de Kruif A ... -  《-》

Further evidence for the existence of environmental and host-associated species of coagulase-negative staphylococci in dairy cattle.

Coagulase-negative staphylococci (CNS) are abundantly present in the dairy farm environment and on bovine skin and mucosae. They are also the most prevalent bacteria causing bovine intramammary infections (IMI). Reservoirs and transmission routes of CNS are not yet fully unraveled. The objectives of this study were to explore the distribution of CNS in parlor-related extramammary niches and to compare it to the distributions of CNS causing IMI in those herds. Niches that were targeted in this study were cows' teat apices, milking machine unit liners, and milker's skin or gloves. Each of the three herds had its own CNS microbiota in those niches. The most prevalent species in the parlor-related extramammary niches were Staphylococcus cohnii, S. fleurettii, and S. equorum in the first, second, and third herd, respectively, whereas S. haemolyticus and S. sciuri were found in all herds. S. cohnii and S. fleurettii, as well as S. haemolyticus, which was present in each herd, were also frequently found in milk samples. By contrast, S. chromogenes, S. simulans, and S. xylosus favored the mammary gland, whereas S. equorum was more common in the parlor-associated niches. Within each herd, species distribution was similar between teat apices and milking machine unit liners. In conclusion, some of the extramammary niches related to the milking process might act as infection sources for IMI-causing CNS. This study provides further evidence that the group of CNS species is comprised of environmental, opportunistic and host-adapted species which differ in ecology.

De Visscher A ，Supré K ，Haesebrouck F ，Zadoks RN ，Piessens V ，Van Coillie E ，Piepers S ，De Vliegher S ... -  《-》