Antimicrobial susceptibilities of Mycoplasma isolated from bovine mastitis in Japan.

Mycoplasma spp. are highly contagious pathogens and intramammary Mycoplasma infection is a serious issue for the dairy industry. As there is no effective vaccine for Mycoplasma infection, control depends on good husbandry and chemo-antibiotic therapy. In this study, antimicrobial susceptibility of Mycoplasma strains recently isolated from cases of bovine mastitis in Japan was evaluated by minimum inhibitory concentration (MIC). All Mycoplasma bovis strains were sensitive to pirlimycin, danofloxacin and enrofloxacin, but not kanamycin, oxytetracycline, tilmicosin or tylosin. M. californicum and M. bovigenitalium strains were sensitive to pirlimycin, danofloxacin, enrofloxacin, oxytetracycline, tilmicosin and tylosin, but not to kanamycin. This is the first report to describe the MIC of major antimicrobial agents for Mycoplasma species isolated from bovine mastitis in Japan.

Reliability in somatic cell count measurement of clinical mastitis milk using DeLaval cell counter.

Somatic cell counts (SCC) measurements are typically performed using quantitative methods, such as the Breed method (Breed) and the Fossomatic method (FSCC). The DeLaval cell counter (DCC) developed recently is a quantitative somatic cell counter with a low initial cost and superior portability. However, since the DCC was specifically developed for measuring SCC of ≤ 4 × 10(6) cells/mL milk from bulk tanks or individual cows, its reliability for estimating SCC that exceed this concentration has not yet been clarified. This study therefore examined whether it is possible to accurately measure SCC by diluting milk samples with initial SCC of 4 × 10(6) cells/mL, as seen in clinical mastitis milk. We collected milk samples from 99 quarters of 99 Holstein cows with clinical mastitis. These milk samples were diluted 10-fold with saline and thoroughly mixed before performing SCC measurement with the DCC. The correlation coefficients of SCC measured by the FSCC, Breed and DCC methods indicated strong correlations between each pair of methods. The findings showed that DCC can be used to identify bovine clinical mastitis milk and is useful as a quantitative SCC measurement device on farm sites.

Relationship between concentration of lingual antimicrobial peptide and somatic cell count in milk of dairy cows.

Lingual antimicrobial peptide (LAP) belongs to the ß-defensin family in cattle and is found in milk. LAP concentrations increase in milk from mastitic udders; however, the relationship between LAP concentrations and the somatic cell count (SCC) in milk remains to be elucidated in detail. Therefore, the present study was undertaken to investigate the relationship between LAP concentrations and the SCC in bovine milk to assess whether LAP may be used as an indicator of SCC. Milk was collected from 66 udders showing various SCCs. The SCC and LAP concentrations were measured in the milk. A significantly higher LAP concentration was observed in milk having 500-5000 × 10(3)cells/ml and >5000 × 10(3)cells/ml SCC groups than in lower SCC groups (<50 × 10(3)cells/ml and 50-500 × 10(3)cells/ml). A significantly positive correlation between LAP concentrations and SCCs in milk was observed (r=0.68). In milk samples with >26 nM of LAP, 92.0% of milk samples had high SCCs (>200 × 10(3)cells/ml). The concentration of LAP in milk infected with Staphylococcus aureus, Streptococcus bovis, Streptococcus dysgalactiae, and Escherichia coli was significantly higher than that in uninfected milk. These results suggest that the concentration of LAP can be a useful indicator of the SCC in dairy cows.

Molecular-based identification of yeasts isolated from bovine clinical mastitis in Japan.

This study analyzed molecular-based identification of yeasts that associated with bovine clinical mastitis in Japan. Over 3,200 quarter milk samples from Holstein dairy cows collected in 2011 on Hokkaido and Honshu islands were examined. Yeast isolates were characterized by polymerase chain reaction amplification and sequencing of the D1/D2 region of the 26S rDNA. Molecular characterization confirmed that Candida spp. and Pichia spp. were most frequently isolated species. Our molecular analysis of mastitic milk samples demonstrated the prevalence of Pichia kudriavzevii(22/58) and Candida tropicalis(14/58). In addition, we demonstrated that molecular analysis of the D1/D2 region of the 26S rDNA is a rapid and reliable method for identifying clinically significant yeasts in dairy hygiene, including potentially new or emerging pathogenic species.