Quantification of Chlamydia trachomatis Elementary Bodies in Urine by Ligase Chain Reaction

Modification of the standard Chlamydia trachomatis ligase chain reaction (LCR) detection assay resulted in a quantitative test. Sample rates from C. trachomatis standards ranging from 32 to 1,048,576 elementary bodies (EB)/ml of urine exhibited a linear correlation with concentration. Quantitative LCR (qLCR) was used to measure the number of EB per milliliter in 158 urine samples from women in Madagascar that tested positive for C. trachomatis by the standard LCR detection assay. C. trachomatis concentrations displayed an apparent bimodal distribution, with approximately one-third of samples (37%) in a peak ranging from 32 to 1,015 EB/ml (median = 297 EB/ml) and the remainder (63%) in a grouping with relatively higher concentrations, ranging from 1,086 to 218,670 EB/ml (median = 7,389 EB/ml). qLCR will be useful for studies of chlamydial infection aimed at understanding the associations of organism burden with clinical manifestations and transmission.