Evaluation of the API® 20 Strep system for identification of Lactococcus lactis subspecies lactis isolated from bovine milk samples

Abstract

Environmental streptococci and streptococci-like bacteria, including Lactococcus lactis ssp lactis, account for approximately 40% of clinical mastitis cases in cows. Recently, Lactococcus lactis ssp lactis was associated with intramammary infections on several New York farms. Although Lactococcus lactis ssp lactis has been isolated from the bovine udder, its importance as a mastitis pathogen is unclear because of misidentification by use of traditional bacterial identification techniques. Molecular identification has improved correct identification of bacterial pathogens, but it is expensive for the clinical practitioner. In this study, the sensitivity (Se), specificity (Sp), positive predictive value (PPV), negative predictive value (NPV), and kappa (k) of the API 20 Strep system for identification of Lactococcus lactis ssp lactis were assessed by the use of molecular identification results as the standard.