[Effect of the type of swab on the isolation of Chlamydia trachomatis]

The success in the isolation of C. trachomatis is dependent on several factors. One of them is the type of swab used for collection the specimens. As some types of swabs, such as calcium alginate and aluminum, cotton and wood have recently been shown to decrease the isolation rate, different types of swabs were prepared and tested in our laboratory. Commercial aluminum, type 5056 aluminum and stainless steel were used with the same type of cotton. Commercial swabs of cotton and wood were tested too. The swabs were incubated with 1 ml of transport medium and a known number of UFI for 24 h at 4 degrees C, then were processed for isolation. The isolation rate with commercial aluminum was 95%, with aluminum 5056 was 91% and with stainless steel was 98%. The swabs made of cotton and wood were toxic to McCoy cells, destroyed the monolayer and did not allow the recovery of C. trachomatis. The poor recovery of Chlamydia from some types of swab, indicates that the available swabs used in each laboratory should be periodically evaluated to avoid false negative results.