An Evaluation of a Kit Applied Bioluminescence Method for the Detection of Staphylococcus aureus

Abstract

A kit to detect Staphylococcus aureus, which often causes food poisoning and some other diseases, has been developed and commercially available. In the present study, the S. aureus rapid detection kit named “ Check Lite BH ” (Kikkoman Corporation) was evaluated andcompared with the conventional method. This kit was designed based on the enzyme-linked immunosorbent assay (ELISA), in which the bioluminescence method is applied. If protein A of S. aureus is detected, it can be judged that the existence of S. aureus was verified. This method began to be sold as a kit product, so we evaluated the application of this kit in a food microbiological test.
(1) One hundred forty strains were examined. Ninety-five strains, which were identified to be S. aureus by traditional biochemical tests, were positive for bioluminescence activity by the kit. Thirty-five strains of Staphylococcus spp. except for S. aureus and 10 strains belonging to other genera of bacteria, which were identified by traditional tests, were all negative by this method, and cross reactions were not observed.
(2) By “ direct method” (not enrichment), about 10⁴ cfu/ml of S. aureus FRI196E were detectable from cross-contamination samples with other bacteria in about 2 hours. Marked influences due to the contamination of other bacteria were not observed. Moreover there was a significant correlation between relative light units (RLU) and colony forming units (CFU) in the range of 10⁴ to 10⁶ cfu/ml of S. aureus.
(3) By the “ enrichment method” (culture for 7 hours), 10¹ cfu/ml of S. aureus FRI196E that was not detected on Egg-Yolk Mannitol Salt agar plate was detectable from the samples highly contaminated with 10⁵ cfu/ml of other mixed bacteria within a total of 9 hours.