Lactobacillus DNA usage in differentiation of normal vaginal fluids in premenopausal and postmenopausal females

The presence of vaginal fluid as a bio-stain in the crime scene of sexual assaults provides pivotal evidence. The vaginal secretions are known to be rich in Lactobacillus; hence the current work aims to identify vaginal secretions via detection and quantification of Lactobacillus DNA in pre and postmenopausal females and to test its stability over storage time using Critical Threshold method applied by Polymerase chain reaction approach. Comparative study is done by Critical Threshold and Relative Expression methods aiming to evaluate the two methods. Results showed that (ΔCT) <9 powerfully indicates the presence of vaginal fluids. Values of ΔCT in all vaginal samples are stable and not affected by storage. Two novel cutoff values are obtained in order to differentiate between premenopausal and postmenopausal vaginal fluid samples which are (8.42) using the Critical Threshold method and (0.24) using the Relative Expression method. One novel cutoff value is obtained to differentiate between fresh and stored vaginal samples by the Relative Expression method which is (0.39). It is concluded that Lactobacillus DNA quantification via PCR is a good positive identifier for vaginal secretions which is remarkably stable over storage time.