Study On Regional Specificity And Spatiotemporal Stability Of MLST Of Staphylococcus Epidermidis

In recent years,criminals have more and more diverse means of committing crimes,and their awareness of anti-investigation is also increasing.It is more and more difficult to find enough valuable DNA for forensic identification in the crime scene.Therefore,many researchers hope to find highly specific individual identification tags that can replace DNA,and the microorganisms on human skin surface are one of the research hot-spots.In this study,Staphylococcus epidermidis(S.epidermidis)was isolated and screened from the finger microorganisms of individuals.The method of bacterial typing in this study is Multilocus Sequence Typing(MLST)which is a high-resolution technique for bacterial typing.After identifying the Sequence Types(STs)of S.epidermidis carried by individuals,the regional specificity and spatiotemporal stability of these experimental results should be analyzed.The ultimate goal of the study is to determine whether MLST of S.epidermidis is of value in forensic identification.During the experiment,90 isolates of S.epidermidis were successfully isolated from individual microorganisms.They were divided into 54 STs,including 7 new alleles and 25 new STs.5 Clonal Complexes were constructed by cluster analysis of all strains with e BURST software.Among them,CC59 contained the largest number of isolates and the origin of STs in this CC is ST-59.A total of 8 strains of S.epidermidis were found in the experiment,and ST-59 was the most frequent type in the experimental samples.It was found that ST-59 accounted for the highest proportion in Asia in the MLST database of S.epidermidis.Therefore,the experimental results were consistent with the distribution pattern of the sequence types in the MLST database of S.epidermidis.In the regional specificity study of MLST of S.epidermidis,43 strains of S.epidermidis isolated from 43 individuals were divided into 29 STs.The STs ofS.epidermidis isolated from different individuals are quite different,which indicates that the MLST of S.epidermidis has high genetic diversity and individual specificity.In the spatiotemporal stability study of MLST of S.epidermidis,38 strains of S.epidermidis isolates were successfully isolated from these individuals by re-sampling.These strains were divided into 28 STs by MLST.Through comparative analysis,it was found that the STs of 13 individuals remained stable,and at least 3 alleles of the ST in 29 individuals remained unchanged,indicating that the MLST of S.epidermidis has good stability in a certain period of time.Phylogenetic analysis of strains sequences isolated from two different periods of time in the same dormitory showed that there was no significant change in the relationship between the two experimental strains,which means that the STs of S.epidermidis did not affect each other in the dormitory during the experimental period.