Evaluation of an On-Farm Culture System (Accumast) for Fast Identification of Milk Pathogens Associated with Clinical Mastitis in Dairy Cows

Abstract

The present study aimed evaluate an on-farm culture system for identification of milk pathogens associated with clinical mastitis in dairy cows using two different gold standard approaches: standard laboratory culture in study 1 and 16S rRNA sequencing in study 2. In study 1, milk from mastitic quarters (i.e. presence of flakes, clots, or serous milk; n = 538) was cultured on-farm using a single plate containing three selective chromogenic media (Accumast—FERA Animal Health LCC, Ithaca, NY) and in a reference laboratory using standard culture methods, which was considered the gold standard. In study 2, mastitic milk was cultured on-farm and analyzed through 16S rRNA sequencing (n = 214). In both studies, plates were cultured aerobically at 37°C for 24 h and read by a single technician masked to gold standard results. Accuracy, sensitivity, specificity, positive (PPV) and negative predictive value (NPV) were calculated based on standard laboratory culture in study 1, and PPV was calculated based on sequencing results in study 2. Overall accuracy of Accumast was 84.9%. Likewise, accuracy for identification of Gram-negative bacteria, Staphylococcus sp., and Streptococcus sp. was 96.4%, 93.8%, and 91.5%, respectively. Sensitivity, specificity, PPV, and NPV were 75.0%, 97.9%, 79.6%, and 97.3% for identification of E. coli, 100.0%, 99.8%, 87.5%, and 100.0% for S. aureus, 70.0%, 95.0%, 45.7%, and 98.1% for other Staphylococcus sp., and 90.0%, 92.9%, 91.8%, and 91.2% for Streptococcus sp. In study 2, Accumast PPV was 96.7% for E. coli, 100.0% for Enterococcus sp., 100.0% for Other Gram-negatives, 88.2% for Staphylococcus sp., and 95.0% for Streptococcus sp., respectively. In conclusion, Accumast is a unique approach for on-farm identification pathogens associated with mastitis, presenting overall sensitivity and specificity of 82.3% and 89.9% respectively.

Test Agreement among Biochemical Methods, Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry, and 16S rRNA Sequencing for Identification of Microorganisms Isolated from Bovine Milk

“…This was a study of test agreement rather than of test accuracy (sensitivity and specificity). This is because there is no agreed-upon gold standard for "true" bacterial or yeast identification (4,5). No culture-negative samples were included.…”

An update on environmental mastitis: Challenging perceptions

“…In that time, information on the causative pathogen can be generated. In North America, this is largely done through on‐farm culture (Ganda et al., ; Lago et al., ). Elsewhere, this system that has not been adopted widely yet although methods for on‐farm culture have been in evaluated in Europe (Mansion‐de Vries et al., ; Viora et al., ) and Africa (Gitau et al., ).…”

Comparative analysis of four commercial on-farm culture methods to identify bacteria associated with clinical mastitis in dairy cattle

“…The development of a precise cow-side system for the diagnosis of mastitis pathogens is essential for quick therapeutic intervention. In the last decade, several multiple-media culture systems became available for on-farm identification of general levels of mastitis-related pathogens [ 8 , 19 , 20 ]. Besides the conventional differentiation among Gram-positive or Gram-negative pathogens, some on-farm plate systems also proposed a more specific diagnosis.…”