Use your browser's BACK button to return to your page of origin.
Population-based genetic and evolutionary analysis of Chlamydia
trachomatis urogenital strain variation in the United States.
Journal of Bacteriology 2004;186(8):2457-2465.
Millman K, Black CM, Johnson RE, Stamm WE, Jones RB, Hook EW, Martin
DH, Bolan G, Tavare S, Dean D.
Abstract
Chlamydia trachomatis is a major cause of ocular and sexually transmitted diseases
worldwide. While much of our knowledge about its genetic diversity comes
from serotyping or ompA genotyping, no quantitative assessment of genetic
diversity within serotypes has been performed. To accomplish this, 507 urogenital
samples from a multicenter U.S. study were analyzed by phylogenetic and statistical
modeling. No B, Da, or I serotypes were represented. Based on our analyses,
all but one previous urogenital B serotype was identified as Ba. This, coupled
with the lack of B serotypes in our population, suggests that B has specific
tropism for ocular mucosa. We identified a Ba/D recombinant (putative crossover
nucleotide 477; P < 0.0001) similar to a B/D mosaic we described previously
from an African trachoma patient. Computational analyses of the Ba/D recombinant
indicated that upstream changes were less important for tissue tropism than
downstream incorporation of the D sequence. Since most serotypes had nonsynonymous/synonymous
ratios of <1.0, the major outer membrane protein, encoded by ompA, has
many functional constraints and is under purifying selection. Surprisingly,
all serotype groups except for J had a unimodal population structure indicating
rapid clonal expansion. Of the groups with a unimodal structure, E and Ia
and, to a lesser extent, G and K were prevalent, had infrequent incorporation
of mutations, and, compared to other groups, had a relatively greater degree
of diversifying selection, consistent with a selective sweep of mutations
within these groups. Collectively, these data suggest a diverse evolutionary
strategy for different serogroups of the organism.