Rapid detection and differentiation of Staphylococcus colonies using an optical scattering technology
Staphylococcus species are a major pathogen responsible for nosocomial infections and foodborne illnesses. We applied a laser-based BARDOT (bacterial rapid detection using optical scattering technology) for rapid colony screening and detection of Staphylococcus on an agar plate and differentiate these from non-Staphylococcus spp. Among the six growth media tested, phenol red mannitol agar (PRMA) was found most suitable for building the Staphylococcus species scatter image libraries. Scatter image library for Staphylococcus species gave a high positive predictive value (PPV 87.5–100%) when tested against known laboratory strains of Staphylococcus spp., while the PPV against non-Staphylococcus spp. was 0–38%. A total of nine naturally contaminated bovine raw milk and ready-to-eat chicken salad samples were tested, and BARDOT detected Staphylococcus including Staphylococcus aureus with 80–100% PPV. Forty-five BARDOT-identified bacterial isolates from naturally contaminated foods were further confirmed by tuf and nuc gene-specific PCR and 16S rRNA gene sequence. This label-free, non-invasive on-plate colony screening technology can be adopted by the food industries, biotechnology companies, and public health laboratories for Staphylococcus species detection including S. aureus from various samples for food safety and public health management.
KeywordsOptical sensor BARDOT Staphylococcus Food sample 16S RNA gene
T.S.A acknowledges King Saud University, the Kingdom of Saudi Arabia, for a graduate student fellowship. X.Z., a visiting scholar at Purdue University from College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing, China, acknowledges the scholarship support from China Scholarship Council, Beijing, China. We also acknowledge the help of Bruce M. Applegate and Marcela M. Chavez in procuring raw milk samples.
This research was supported through a cooperative agreement with the Agricultural Research Service of the US Department of Agriculture project number 8072-42000-077, USDA National Institute of Food and Agriculture (Hatch) project, and the Center for Food Safety Engineering at Purdue University.
Compliance with ethical standards
The authors declare that there were no ethical implications or research involving human or animals.
Conflict of interest
The authors declare that they have no conflict of interest.
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