Assessment of VITEK2 Compact automatic microbial analysis system for Staphylococcus in raw milk

Abstract:

[Objective] In order to evaluate the VITEK2 Compact automatic microbial analysis system in identifying Staphylococcus in raw milk. [Methods] We isolated 52 strains of Staphylococcus from milk samples from Xining, Baiyin and Xi’an, and these strains were identified by VITEK2 Compact. Then, we compared the results obtained from VITEK2 Compact to the results from Gram's staining, catalase test, plasma coagulase test and 16S rRNA gene sequence analysis. Furthermore, the stability of this system was tested by identifying the coagulase negative and positive Staphylococcus at different concentrations. [Results] With 16S rRNA gene sequence analysis as the reference standard, the coincidence rate of this system reached 96.15% for Staphylococcus at “Genus” level. With plasma coagulase test as the reference standard, the coincidence rate of this system was 92.86% for the coagulase negative Staphylococcus while 50% for the coagulase positive Staphylococcus. When it came to “Species” level, the coincidence rate of this system was only 44.23%. In stability test, coincidence rate was 100% and the reliability of appraisal result did not change by bacteria liquid concentration. [Conclusion] In conclusion, VITEK2 Compact automatic microbial analysis system could be used to identify Staphylococcus in milk at “Genus” level.

Key words:VITEK2 Compact automatic microbial analysis system, Staphylococcus, 16S rRNA gene sequence analysis, Accuracy, Stability