Evaluating Bioinformatic Pipeline Performance for Forensic Microbiome Analysis*,†,‡

Microbial communities have potential evidential utility for forensic applications. However, bioinformatic analysis of high-throughput sequencing data varies widely among laboratories. These differences can potentially affect microbial community composition and downstream analyses. To illustrate the importance of standardizing methodology, we compared analyses of postmortem microbiome samples using several bioinformatic pipelines, varying minimum library size or minimum number of sequences per sample, and sample size. Using the same input sequence data, we found that three open-source bioinformatic pipelines, MG-RAST, mothur, and QIIME2, had significant differences in relative abundance, alpha-diversity, and beta-diversity, despite the same input data. Increasing minimum library size and sample size increased the number of low-abundant and infrequent taxa detected. Our results show that bioinformatic pipeline and parameter choice affect results in important ways. Given the growing potential application of forensic microbiology to the criminal justice system, continued research on standardizing computational methodology will be important for downstream applications.     

Peer violence perpetration among urban adolescents: dispelling the myth of the violent immigrant

Researchers have found an inverse relationship between immigrant status and violence perpetration. Most studies have examined Mexican immigrants, and few have assessed immigration factors other than nativity. Additionally, the majority have focused on the most serious forms of violence despite the fact that moderate violence is more common. Using data from the 2008 Boston Youth Survey, we generated prevalence estimates of peer violence perpetration across immigration related factors, examined whether risk factors for peer violence differed by these variables, and explored the contribution of risk factors to peer violence perpetration. Recent immigrants had a significantly lower prevalence of peer violence compared to each other generations/time in U.S. group. Known risk factors for violence perpetration varied by generation/time in U.S.: compared to other groups, recent immigrants were less likely to have used substances, and were more likely earn A's and B's in school. Recent immigrants had a significantly lower risk of violence perpetration relative to U.S.-born (RR = 0.35, 95% CI: 0.19, 0.62). Adjusting for known risk factors did not attenuate differences in risk. While immigrant youth had a lower risk of peer violence, the protective effect was diminished among immigrants who had resided in the U.S. for >4 years. This pattern demonstrates that negative assimilation occurs within the first generation, not just across generations. Results suggest that perpetration of violence worsens with increased time in the U.S. Research is needed to identify factors that contribute to the acquisition of behaviors such as violence among recently arrived immigrant youth.