Defense Date
2023
Document Type
Directed Research Project
First Advisor
Dr. Baneshwar Singh
Second Advisor
Dr. Sarah Seashols-Williams
Third Advisor
J. Paul Brooks
Fourth Advisor
Dr. Denise Wohlfahrt
Abstract
Body fluid identification (BFID) is important in forensic investigations. Body fluid can be identified by catalytic, immunological, microscopic, microbiological, and molecular methods. Recent studies have shown that a bacterial signature-based BFID method can identify seven body fluids in a single test with an overall accuracy of more than 88%. The bacterial signature-based BFID method requires several validation studies before it can be implemented in a crime lab setting. Mouthwashes are commonly used to prevent oral disease and maintain oral health. The use of mouthwash can impact oral microbiome composition and hence can have an impact on the accuracy of saliva identification using bacterial signature-based methods. The main aim of this study is to determine the impact of mouthwash (Listerine® mouthwash) on oral microbiome, and its impact on the accuracy of human saliva identification using a bacterial signature-based method. Saliva samples were self-collected with cotton swabs immediately before Listerine® use (reference), immediately after (0 hour), 2 hours after, 8 hours after, and 24 hours after from ten subjects (n=50). Bacterial DNA was extracted using the QIAgen DNA Investigator kit and was quantified using a quantitative PCR (qPCR) based method. Variable region four (V4) of the 16S rDNA was amplified via a polymerase chain reaction (PCR) method, purified with the AMPure XP Kit, and sequenced with a dual-index high throughput sequencing strategy on the MiSeq FGx sequencing platform using the MiSeq reagent kit v2. No significant difference in bacterial DNA yield, bacterial diversity, and bacterial structure was observed between various treatments, i.e., the mouthwash treatment didn't alter oral bacterial signature significantly. Overall, Streptococcus, Gemella, Haemophilus, Veillonella, and Rothia were the top five bacterial genera associated with human saliva samples. The bacterial signature-based method for BFID accurately identified saliva in the samples with an overall accuracy of more than 90%. This study shows that oral samples collected even after the use of mouthwash have no significant impact on the bacterial signature associated with oral samples and the use of mouthwash did little to impact the accuracy of the bacterial signature-based method for BFID.
Rights
© The Author(s)
Is Part Of
VCU Master of Science in Forensic Science Directed Research Projects
Date of Submission
8-2-2023