PCR Applications in Identification of Saliva Samples Exposed to Different Conditions (Streptococci Detection based)

Abstract

Oral streptococci represent about 20% of the total oral bacteria, so if it is possible to detect the presence of oral specific bacteria from a forensic specimen by Polymerase chain reaction, this could be used to verify the presence of saliva. Aim of this study is detection of Streptococcus salivarius which is one of the most common streptococci in oral bacteria and Streptococcus mutans which is common in cases of dental caries in various body fluids and skin swabs and assessment of which one of both organisms is more reliable in saliva identification, cross sectional study on Egypt population. Negative control samples (15 samples) were taken from various body fluids (urine, semen) and skin swabs. Mock forensic samples (85 samples) included fresh saliva, saliva, cotton fabrics contaminated with saliva, cigarette butts, bitten apple and semen mixed with saliva samples). DNA extraction was done using DNeasy blood and tissue kit (Qiagen, Tokyo, Japan). Polymerase chain reaction was done for DNA amplification using Polymerase chain reaction master mix then gel electrophoresis was done for samples qualification. Control bacteria were S. salivarius and Streptococcus mutans. Streptococcus salivarius was detected in 83.5% of all saliva contained samples and S. mutans was detected in 67% of saliva contained samples. Both bacteria were not detected in other body fluids and skin swabs, so S. salivarius is more reliable in saliva identification as well as differentiating it from other body fluids. Polymerase chain reaction is valuable in detection of saliva by detecting S. salivarius.