Failure of multiple passages to increase chlamydial recovery.

Because of a previous publication indicating that increasing the number of blind passages to five resulted in a marked increase in Chlamydia trachomatis isolation rates, we evaluated a multiple-blind-passage system in vials. Cervical specimens from 119 pregnant women and 82 specimens from other sources were tested for chlamydial infection. The recovery rate for C. trachomatis was not markedly increased after the first blind passage. Thus, we conclude that multiple blind passages are not necessary to maximize the C. trachomatis isolation rate in a vial system.