Detailed characterization of mastitis-causing pathogens previously identified as "other Streptococcal species" over time

Abstract

The epidemiology and etiology of mastitis-causing environmental streptococci, especially "other streptococci" and streptococci-like bacteria is not well known. The objectives of this research project will be: (a) to determine at species level the frequency of mastitis-causing pathogens identified phenotypically as "other Streptococcal species" using the technique of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS); and, (b) to characterize over time the mastitis-causing pathogens phenotypically identified as "other Streptococcal species" based on: stage of lactation, parity, effect on milk production, repeat cases of mastitis, SCC, length of time in the herd, cure rate (bacteriological cure and SCC resolution), and cow survival. Milk samples submitted to Quality Milk Production Services (QMPS) laboratory over a six month period identified in the lab as "streptococci species" will be forward to the main Animal Health Diagnostic Laboratory of Cornell University (Ithaca, NY, USA) for speciation using PCR and MALDI-TOF MS. Isolates of "streptococci species" collected from clinical mastitis in Brazilian dairy herds will be shipped to QMPS and submitted to the same identification procedure for comparison with isolates from US dairy herds. Cows from US dairy herds identified by mass spectrometry with mastitis caused by organisms within the genus Lactococcus, Streptococcus, Enterococcus and Aerococcus will be sampled each month from the original clinical quarter(s) for microbiological identification and SCC analysis. In addition, the individual cow's data will be tracked each month to evaluate the effect on SCC (composite) and milk production, which will be evaluated by linear multivariable regression analysis. Data at cow level as stage of lactation, parity, repeated cases of mastitis, treatment information and reasons of eventual death and culling will be recorded and evaluated. Cows identified as subclinically infected on DHIA test will be sampled each month to screen for subclinical mastitis caused by this group of organisms. Any cows identified with pathogens that fall into the "other Streptococcus" will be tracked and evaluated as well. The results of this study will promote scientific advances in the etiology and epidemiology of intramammary infections caused by this group of emergent and misidentified pathogens.