Genetic characterization of Trichomonas vaginalis isolates by use of multilocus sequence typing

Abstract

In this study, we introduce a multilocus sequence typing (MLST) scheme, comprised of seven single-copy housekeeping genes, to genetically characterize Trichomonas vaginalis. Sixty-eight historical and recent isolates of T. vaginalis were sampled from the American Type Culture Collection and female patients at area health care facilities, respectively, to assess the usefulness of this typing method. Forty-three polymorphic nucleotide sites, 51 different alleles, and 60 sequence types were distinguished among the 68 isolates, revealing a diverse T. vaginalis population. Moreover, this discriminatory MLST scheme retains the ability to identify epidemiologically linked isolates such as those collected from sexual partners. Population genetic and phylogenetic analyses determined that T. vaginalis population structure is strongly influenced by recombination and is composed of two separate populations that may be nonclonal. MLST is useful for investigating the epidemiology, genetic diversity, and population structure of T. vaginalis.

Figures

Fig 1

goeBURST analysis of 68 isolates representing 60 STs. goeBURST analysis revealed eight clonal complexes and 26 singleton STs within the sample population. Green ST nodes clustered to clade A in the neighbor-joining phylogram (NJ); red ST nodes clustered to clade B in the NJ phylogram. Large, bold numbers identify CCs, small numbers indicate ST nodes. Symbols: #, group founder; *, subgroup founder. Colored links: black, link drawn without recourse to tiebreak rules; blue, link drawn using tiebreak rule 1; and green, link drawn using tiebreak rule 2 (24).

Fig 2

Two-cluster population structure of T. vaginalis. Assignment of STs into two populations by STRUCTURE (A) and BAPS (B) was performed. The order of STs is the same in both graphs, and they are sorted by the percent ancestry into clade B (red) based on STRUCTURE analysis. The green cluster (n = 26 STs) and red cluster (n = 34 STs) are identical to the clades identified in the neighbor-joining tree. Asterisks indicate STs unassigned to populations (in panel A) and STs with significant admixture (in panel B).