Short communication: Comparative performance of 3 on-farm culture systems for detection of mastitis pathogens interpreted by trained and untrained observers

On-farm culture (OFC) systems facilitate pathogen-based mastitis management and can antimicrobial stewardship on dairy farms. Interpretation of the results, however, may present a challenge for those with limited microbiology experience. Here, we compared results 3 OFC interpreted by trained untrained observers against standard laboratory reference method (aerobic mass spectrometry). Milk samples (280 quarter 60 composite) were selected from submissions routine diagnostic testing to Quality Production Services (Cornell University, Ithaca, NY) between August 2017 January 2018. Samples cultured simultaneously using commercially available that varied in detail pathogen identification (provided parentheses) as follows: (1) Minnesota Easy Culture System II Bi-plate (University Laboratory Udder Health, St. Paul; gram-positive, gram-negative), (2) Tri-plate (gram-positive, gram-negative, some genus level), (3) FERA Diagnostics Biologicals AccuMast plate (Ithaca, NY; level, species level). After 18 24 h incubation, plates 1 observer (>10 yr experience milk microbiology) 6 no previous training, only manufacturers' instructions guidance. Strength agreement (?) groups was determined outcomes each system. Interpreted observer, moderate identifying gram-positive organisms (Bi-plate, ? = 0.56) substantial Streptococcus spp. (Tri-plate, 0.64, 0.61). resulted fair (? 0.29–0.37) these organisms. Moderate 0.43–0.59) found across all gram-negative (Bi-plate), non-aureus staphylococci (Tri-plate AccuMast), Lactococcus spp., Enterococcus (AccuMast) when 0.31–0.53) among observers. Across OFC, almost perfect 0.80–0.89) Staphylococcus aureus 0.56–0.61) We concluded appeared suitable support operated Training beyond instruction manual is prerequisite make useful management.