Changes in the bovine udder quarters naturally infected by Corynebacterium bovis

Short communication: Identification of Corynebacterium bovis by MALDI-mass spectrometry

Corynebacterium bovis is a mastitis-causing microorganism responsible for economic losses related to decrease in milk production. The aim of the study was identify Corynebacterium spp. strains recovered from milk samples of subclinical mastitis by using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Samples were collected during a 10-mo mastitis-monitoring program in a high-production dairy farm. In this study, 80 strains were analyzed; from these 54 (67.5%) were identified at species level as Corynebacterium bovis, 24 (31.2%) isolates were identified at the genus level as Corynebacterium spp., and only 1 (1.35%) isolated had unreliable identification. Results demonstrated that MALDI-MS could be an important technique for the identification of Corynebacterium spp. in milk.

Effects of bovine subclinical mastitis caused by Corynebacterium spp. on somatic cell count, milk yield and composition by comparing contralateral quarters

Subclinical mastitis caused by Corynebacterium spp. (as a group and at the species level) was investigated by evaluating contralateral (healthy and infected) mammary quarters for somatic cell count (SCC), milk yield and composition. Selection of cows with subclinical mastitis caused by Corynebacterium spp. was performed by microbiological culture of composite samples collected from 1242 dairy cows from 21 dairy herds. For each of the selected cows, milk yield was measured and milk samples were collected at the mammary quarter level (i.e., 1140 mammary samples collected from 285 cows) for analysis of milk composition and SCC. The identification of Corynebacterium spp. isolates was performed by 16S rRNA gene sequencing. One hundred and eighty Corynebacterium spp. isolates were identified, of which 167 (92.77%) were C.bovis and eight (4.44%) non-C.bovis; for five of the Corynebacterium spp. isolates (2.77%), sequencing of 16S rRNA genes did not allow identification at the species level. Mammary quarters infected with Corynebacterium spp. as a group had a higher geometric mean SCC (197,900 cells/mL) than healthy contralateral mammary quarters (85,800 cells/mL). Species of Corynebacterium non-C.bovis were infrequently isolated and did not change SCC, milk yield or milk solid contents when evaluated at the contralateral quarter level. Although C.bovis infection showed no effect on milk yield, fat, protein, casein or total solids in milk, it increased SCC and decreased lactose and milk solids non-fat content.

Udder health and risk factors for subclinical mastitis in organic dairy farms in Switzerland

1+ were submitted for somatic cell counting (SCC), bacteriological examination and to test for antibiotic susceptibility. The SCC and germ-cell counts of monthly bulk-tank milk samples were available through Dairy Inspection and Advisory Services and milk production data of 567 herd-book cows were available from breeding associations. Possible individual and environmental predictors of subclinical mastitis were identified using logistic models adjusted for clustering of the data at herd and cow levels. Data were analyzed separately for cows from 7 to 100 and from 101 to 305 days post partum. Prevalences of subclinical mastitis at the quarter level were 21.2% for lactation period 7-100 days and 34.5% for 101-305 days post partum. The geometric mean SCC in bulk-tank milk samples was 85.6x10(3)cells/ml. Samples at 7-100 and 101-305 days post partum were positive for Staphylococcus aureus in 16.0 and 7.4%, for coagulase-negative Staphylococci in 51.5 and 50.6%, for Streptococcus agalactiae in 0.0 and 0.8%, for other Streptococci in 19.4 and 15.6%, for E. coli in 1.0 and 0.4%, and for Corynebacterium bovis in 25.7 and 45.1%, respectively. Risks of subclinical mastitis increased significantly with increasing days post partum and advancing age of cow. Cows that were sampled when staying in alpine dairies had considerably higher risks of subclinical mastitis than cows staying in home barns. Significantly lower risks of subclinical mastitis were observed in farms where CMT was performed regularly as a control measure. Bacteria in milk from cows with mastitis exhibited antibiotic resistance at a comparable frequency as found previously in conventional farms.

Mastitis in Camelus dromedarius and the somatic cell content of camels' milk

Seven hundred and sixty-three camels from 400 herds of local Sudanese camel breeds were investigated for the prevalence of mastitis, identification of its bacterial causes and determination of the leucocyte contents of camel's milk. One hundred and forty-nine (19.5 per cent) of the 763 camels examined were diagnosed as mastitis cases based on clinical signs. One hundred and fifty-nine (47.3 per cent) of the 336 randomly selected milk samples were reactive in a rapid mastitis test and 16 of the 153 tested samples contained Brucella abortus agglutinating antibodies. Streptococcus, Staphylococcus, Micrococcus and Aerobacter species and Escherichia coli were found to be the main causes of mastitis (in descending order). The leucocyte contents of the 757 milk samples ranged from < 5 x 10(5) to > 7.5 x 10(6) leucocyte ml-1 and 42.8 per cent of the samples contained < 5 x 10(5) cells ml-1. Neither significant correlation between the leucocyte content of milk and isolated bacterial species nor significant variation in leucocyte contents during different stages of lactation were detected.