Cervicovaginal Microbiota Composition in Chlamydia trachomatis Infection: A Systematic Review and Meta-Analysis

In healthy women, the cervicovaginal microbiota is characterized by the predominance of Lactobacillus spp., whereas the overgrowth of anaerobic bacteria leads to dysbiosis, known to increase the risk of acquiring genital infections like Chlamydia trachomatis. In the last decade, a growing body of research has investigated the composition of the cervicovaginal microbiota associated with chlamydial infection via 16s rDNA sequencing, with contrasting results. A systematic review and a meta-analysis, performed on the alpha-diversity indices, were conducted to summarize the scientific evidence on the cervicovaginal microbiota composition in C. trachomatis infection. Databases PubMed, Scopus and Web of Science were searched with the following strategy: "Chlamydia trachomatis" AND "micro*". The diversity indices considered for the meta-analysis were Operational Taxonomic Unit (OTU) number, Chao1, phylogenetic diversity whole tree, Shannon's, Pielou's and Simpson's diversity indexes. The search yielded 425 abstracts for initial review, of which 16 met the inclusion criteria. The results suggested that the cervicovaginal microbiota in C. trachomatis-positive women was characterized by Lactobacillus iners dominance, or by a diverse mix of facultative or strict anaerobes. The meta-analysis, instead, did not show any difference in the microbial biodiversity between Chlamydia-positive and healthy women. Additional research is clearly required to deepen our knowledge on the interplay between the resident microflora and C. trachomatis in the genital microenvironment.