Location: Quality and Safety Assessment Research UnitTitle: Detection of Salmonella from chicken rinsate with hyperspectral microscope imaging compared against RT-PCR
|GAYATRI, SETIA - US Department Of Agriculture (USDA)|
Submitted to: Talanta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/22/2018
Publication Date: 11/28/2018
Citation: Eady, M.B., Gayatri, S., Park, B. 2018. Detection of Salmonella from chicken rinsate with hyperspectral microscope imaging compared against RT-PCR. Talanta. 195:313-319. https://doi.org/10.1016/j.talanta.2018.11.071.
Interpretive Summary: Salmonella is a bacterium of significance to the poultry industry. For years traditional plating methods and DNA based methods such as real-time polymerase chain reaction (RT-PCR) have been the industry standard for detecting Salmonella in a chicken rinse. These methods are reliable but offer disadvantages in terms of time or reoccurring cost. Hyperspectral microscope images (HMI) offer a reduction in time and cost from traditional detection methods. Here, HMI is performed on colonies of Salmonella and non-Salmonella isolated from chicken rinses, to compare the accuracy of HMI to plating and RT-PCR results. Chickens were sampled, and the rinse was plated on Salmonella specific agar, followed by RT-PCR to determine if colonies grown on the plates were Salmonella positive or negative. The same colonies were sampled with HMI. The HMI represents a series of images collected in the visible light spectrum. These images are stacked, allowing for a unique spectral fingerprint of each bacterial cell in the image to be extracted. Following statistical analysis of these fingerprints HMI accuracy was 81.8%. A spectral preprocessing step was added to minimize the influence of shape on the spectra increasing the HMI accuracy to 98.5%. The results suggest that HMI is a potential detection tool for Salmonella in chicken rinses.
Technical Abstract: Salmonella is an organism of importance to the poultry industry with increasingly stringent government regulatory standards. Real-time polymerase chain reaction (RT-PCR) and plating procedures on nutrient enriched growth media have been the standard detection methods of Salmonella from broiler chicken carcasses for years. These methods are proven but offer disadvantages in the amount of time or reoccurring sample cost. Here, we propose the use of a hyperspectral microscope imaging (HMI) method for comparison to standard detection methods. Broiler chicken carcasses were rinsed and plated on Salmonella selective agar. Colonies from plates were picked and RT-PCR was used as a confirmation test to verify plating results, while HMI was collected from the same colonies. Spectral signatures of cells were extracted between 450 – 800 nm from HMI collected with 100x objective. A quadratic discriminant analysis (QDA) was used to classify cells as either Salmonella positive or negative (n = 341). Spectra preprocessing minimized the influence of cellular shape on the spectra, increasing the initial classification accuracy of 81.8% to 98.5%, yielding a sensitivity of 1.0, and a specificity of 0.963. Results showed the potential as an initial investigation of HMI as a microbial confirmation tool, compared to RT-PCR.