RRC ID 57546
Author Ohta J, Sakurada K.
Title Oral gram-positive bacterial DNA-based identification of saliva from highly degraded samples.
Journal Forensic Sci Int Genet
Abstract Analyzing degraded evidence is an important challenge in forensic casework. Saliva remaining at a crime scene may deteriorate, due to various factors, making it difficult to identify. This study aims to clarify the efficacy of oral gram-positive and -negative bacterial DNA-based identification of saliva for analyzing highly degraded samples. Saliva samples were subjected to three different degradation treatments (heat denaturation: 40-80 °C in wet conditions; microbial decomposition: 1-5 days in humid soil; and ultraviolet (UV) irradiation: 0.01-1 J/cm2). We compared saliva markers' detectability from the degraded samples-oral gram-positive bacterial DNA (Streptococcus salivarius and Streptococcus oralis), oral gram-negative bacterial DNA (Veillonella atypica and Prevotella maculosa) and salivary α-amylase. Oral bacterial DNA was detected using a melting curve analysis following real-time PCR. The efficacy of short tandem repeats (STR) and mitochondrial DNA (mtDNA) analyses were also compared. All oral bacterial DNA were detected with specific melting peaks from the heat-denatured samples, while neither catalytic nor immunochromatographic tests detected salivary α-amylase from the heat (80 °C) samples. The gram-positive bacterial DNA (S. salivarius and S. oralis) was detected from the microbial degradation (1-5 days) samples. In contrast, the gram-negative bacterial DNA (V. atypica and P. maculosa) and salivary α-amylase were not detected from samples treated for more than two days. UV exposure made bacterial DNA-based saliva identification difficult in a dose-dependent manner; however, UV irradiation did not influence protein-based saliva tests using salivary α-amylase as an indicator. As a result of STR and mtDNA typing, partial or null STR profiles were generated from the severely degraded (microbial (2-5 days) and UV (0.1-1 J/cm2) degradation) samples, but full mtDNA profiles were obtained from all degraded samples. The forensic applicability of bacterial DNA test evaluated, using mock case samples, indicates that the oral gram-positive bacterial DNA was more resistant to degradation than the other markers. We conclude that the oral gram-positive bacterial DNA-based examination could be useful for identifying saliva from severely environmentally-exposed forensic samples as well as mtDNA typing.
Volume 42
Pages 103-112
Published 2019-9-1
DOI 10.1016/j.fsigen.2019.06.016
PII S1872-4973(19)30179-6
PMID 31302459
MeSH Adult Biomarkers / metabolism DNA Fingerprinting DNA, Bacterial / genetics* DNA, Mitochondrial / genetics Environmental Exposure / adverse effects Female Gram-Negative Bacteria / genetics* Gram-Positive Bacteria / genetics* Hot Temperature / adverse effects Humans Male Microsatellite Repeats Middle Aged RNA, Ribosomal, 16S / genetics Real-Time Polymerase Chain Reaction Saliva / metabolism Saliva / microbiology* Ultraviolet Rays / adverse effects Young Adult alpha-Amylases / metabolism
IF 4.884
Times Cited 0
DNA material Genomic DNA Streptococcus salivarius JCM 5707T (JGD08330) Streptococcus oralis subsp. oralis JCM 12997T (JGD07470) Prevotella maculosaJCM 15638T (JGD12444) Streptococcus sobrinus JCM 5176 (JGD08352) Staphylococcus epidermidis JCM 20345 (JGD07702) Actinomyces israelii JCM 12964T (JGD12771) Neisseria mucosa JCM 12992T (JGD07426)