A Metagenomic Approach to Characterization of the Vaginal Microbiome Signature in Pregnancy

While current major national research efforts (i.e., the NIH Human Microbiome Project) will enable comprehensive metagenomic characterization of the adult human microbiota, how and when these diverse microbial communities take up residence in the host and during reproductive life are unexplored at a population level. Because microbial abundance and diversity might differ in pregnancy, we sought to generate comparative metagenomic signatures across gestational age strata. DNA was isolated from the vagina (introitus, posterior fornix, midvagina) and the V5V3 region of bacterial 16S rRNA genes were sequenced (454FLX Titanium platform). Sixty-eight samples from 24 healthy gravidae (18 to 40 confirmed weeks) were compared with 301 non-pregnant controls (60 subjects). Generated sequence data were quality filtered, taxonomically binned, normalized, and organized by phylogeny and into operational taxonomic units (OTU); principal coordinates analysis (PCoA) of the resultant beta diversity measures were used for visualization and analysis in association with sample clinical metadata. Altogether, 1.4 gigabytes of data containing >2.5 million reads (averaging 6,837 sequences/sample of 493 nt in length) were generated for computational analyses. Although gravidae were not excluded by virtue of a posterior fornix pH >4.5 at the time of screening, unique vaginal microbiome signature encompassing several specific OTUs and higher-level clades was nevertheless observed and confirmed using a combination of phylogenetic, non-phylogenetic, supervised, and unsupervised approaches. Both overall diversity and richness were reduced in pregnancy, with dominance of Lactobacillus species (L. iners crispatus, jensenii and johnsonii, and the orders Lactobacillales (and Lactobacillaceae family), Clostridiales, Bacteroidales, and Actinomycetales. This intergroup comparison using rigorous standardized sampling protocols and analytical methodologies provides robust initial evidence that the vaginal microbial 16S rRNA gene catalogue uniquely differs in pregnancy, with variance of taxa across vaginal subsite and gestational age

Author's response to letter to the editor [Refers to: Tomoyuki Kawada, Hiroko Suzuki, Takako Shimizu, Masao Katsumata Polygraphic sleep latency and subjective sleepiness by visual analog scale (VAS): The limitation of VAS Applied Ergonomics, Volume 43, Issue 1, January 2012, Pages 266]

Kawada et al. (2011) report a significant but moderately low correlation (r= -0.44) between subjective and objective sleepiness, measured by responses on a visual analogue scale (VAS) and sleep onset latency (SOL), respectively. Their correlation was calculated using single measures of VAS and SOL associated with a (daytime?) nap collected with 50 participants. The low correlation in this study was used to emphasize the point that VAS determined subjective sleepiness cannot be used as a substitute for objective sleepiness measured by SOL. Indeed, acceptable correlations for good measures of validity would normally have to be >0.70. Therefore, it could be dangerous to predict objective sleepiness at some specific time in a given individual from a single measure of subjective sleepiness