Abstract
In this species differentiation study of Corynebacterium spp. (C. spp.), quarter foremilk samples from 48 farms were included. These were obtained from both clinically healthy cows and those with clinical mastitis. First, all samples were examined cyto-microbiologically and all catalase-positive rods were differentiated using the direct transfer method in MALDI-TOF MS. C. bovis, C. amycolatum, C. xerosis, and five other species were identified with proportions of 90.1%, 7.7%, and 0.8% for the named species, respectively, and 1.4% for the remaining unnamed species. In addition, somatic cell count (SCC) was determined by flow cytometry. Based on this, the isolates were classified into four udder health groups: “latent infection”, “subclinical mastitis”, “clinical mastitis” and “others”. Approximately 90% of isolates of C. bovis and C. amycolatum were from latently and subclinically infected quarters. Of the C. bovis isolates, 5.8% were obtained from milk samples from clinical mastitis, whereas C. amycolatum was not present in clinical mastitis. The distribution of groups in these two species differed significantly. The geometric mean SCC of all species combined was 76,000 SCC/mL, almost the same as the SCC of C. bovis. With 50,000 SCC/mL, the SCC of C. amycolatum was slightly below the SCC of C. bovis. Through the species-level detection and consideration of SCC performed here, it is apparent that individual species differ in terms of their pathogenicity. Overall, their classification as minor pathogens with an SCC increase is confirmed.
Highlights
Udder health in the dairy industry is one of the main concerns for the production of high quality food from healthy cows
C. bovis accounted for the majority of isolates (90.1%)
The second most common one was C. amycolatum (7.7%), whereas C. xerosis accounted for only 0.8% of the isolates
Summary
Udder health in the dairy industry is one of the main concerns for the production of high quality food from healthy cows. Economic losses in the dairy industry are mainly caused by subclinical and clinical mastitis due to intramammary infections and are substantially compounded by milk losses [1]. In one region in Germany, a study detected coryneforms in 90% of the farms [2] They are found frequently, they may still be underdiagnosed, possibly due to their slow growth [3]. There are studies that even suggest they may have a protective effect against major pathogens, stimulating the immune defense by increasing the somatic cell count (SCC) [5] In other studies, they were detected in subclinical and clinical cases of mastitis and are associated with increased somatic cell count [1,6]. They are categorized as minor pathogens, similar to non-aureus staphylococci
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