Prevalence of Contagious Mastitis Pathogens in Bulk Tank Milk from Dairy Farms in Lower Saxony, Germany

The aim of this study was to determine the prevalence of <i>Streptococcus</i> (<i>Sc.</i>) <i>agalactiae</i>, <i>Prototheca</i> spp., <i>Staphylococcus</i> (<i>S</i>.) <i>aureus</i>, and especially methicillin-resistant <i>S. aureus</i> as well as <i>Myco-plasmopsis</i> (<i>M</i>.) spp. and <i>M. bovis</i> in bulk tank milk (BTM) on dairy farms in Lower Saxony, Germany. BTM samples were collected in January 2023 from 208 selected dairy farms. The samples were quantitatively culturally analyzed for <i>S. aureus</i> and <i>Prototheca</i> spp. Presumptive <i>S. aureus</i> colonies were further confirmed by MALDI-TOF. Presumptive <i>Prototheca</i> spp. colonies were confirmed by light microscopy. <i>Sc. agalactiae</i> and <i>Mycoplasmopsis</i> spp. were detected by real-time polymerase chain reaction (rtPCR). <i>Sc. agalactiae</i> was detected in two herds (1% (Confidence Interval 95% (CI) 0.3–3.4)). <i>S. aureus</i> was confirmed by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) in 38 herds (18.3% (CI 13.6–24.1)), assuming a threshold of >10 cfu/mL milk. A total of 154 isolates identified as <i>S. aureus</i> by MALDI-TOF were transferred to agar with added oxacillin for resistance testing, of which 19 isolates (12.3% (CI 8–18.5)) showed growth. The 19 isolates came from eight different farms (3.8% (2–7.4)). <i>Prototheca</i> spp. were identified in 13 herds (6.3% (CI 3.7–10.4)). <i>Mycoplasmopsis</i> spp. were detected by PCR in 18 herds (8.7% (CI 5.5–13.3)). Of these, <i>M. bovis</i> was present in three herds (1.4% (0.5–4.2)). The herd prevalence of <i>Sc. agalactiae</i> in BTM appears to be at low levels in the sampled area. The prevalence of <i>Mycoplasmopsis</i> spp. in the herds was higher than expected compared to previous studies. It is interesting to note that the percentage of <i>M. bovis</i> in the total <i>Mycoplasmopsis</i> spp. was only 16.7%.