Comparison of the Overnighter with conventional culture
Results are detailed in the tables in the documents at the bottom of this page.
Project Design
One hundred random milk samples with no mastitis history were examined at both an outsourced laboratory and with the Overnighter in a controlled laboratory. The Overnighter tests were pipetted into the tubes and incubated in a standard laboratory incubator.
In the outsourced lab the samples were identified as negative, Staphylococcus aureus, coagulase negative staphylococcus (CNS), Streptococcus uberis or Streptococcus dysgalactiae. In the Overnighter testing, samples were identified as being negative, Staphylococcus, Staphylococcus aureus, Streptococcus, Streptococcus uberis or Streptococcus dysgalactiae.
All samples which gave discordant results between the Overnighter and the outsourced lab for Streptococcus uberis were further sub-cultured to confirm whether they were Streptococcus uberis.
Results
Of the 100 samples there was full microbiological agreement on 83 samples. Of these samples, 58 were negative by both tests, 12 cultured Streptococcus uberis, 7 cultured Staphylococcus aureus and 6 agreed at genus level but not at species level (Table 3). Agreement at the genus level should not alter the prescribing decision for treatment.
There were 17 results that were discordant. The Overnighter gave positive cultures for 8 samples in which the outsourced laboratory found no growth (see Table 2 for detail). The Overnighter gave negative results for two samples in which the outsourced laboratory identified Streptococcus dysgalactiae,
Of the remaining 7 discordant results (Table 3), three were such that while one pathogen was identified by both tests (one case each of Streptococcus uberis and Staphylococcus aureus) additional organisms were also identified. The major discordance was in four samples in which the Overnighter was positive for Streptococcus uberis (confirmed by sub-culture) while the outsourced laboratory identified CNS.
