A Comparison of Treponema pallidum Subspecies pallidum Molecular Typing Systems: Multilocus Sequence Typing vs. Enhanced Centers for Disease Control and Prevention Typing

BACKGROUND At least 3 syphilis typing systems are proposed. Recent work suggests that multilocus sequence typing (MLST) may be superior to enhanced Centers for Disease Control and Prevention typing (ECDCT) by yielding a higher discriminatory power. The goal of this study was to compare the 2 systems and identify associations between neurosyphilis and strain types. METHODS Multilocus sequence typing for tp0136, tp0548, and tp0705 was determined for DNA from 78 Treponema pallidum subspecies pallidum isolates propagated in rabbits, 10 oral and 10 genital or non-genital lesion swabs, and 10 blood samples from patients with syphilis. These samples were chosen because they were completely typeable by ECDCT. Using both systems, association between strain types and neurosyphilis, defined as a reactive cerebrospinal fluid Venereal Disease Research Laboratory test, was determined. Partial and complete ECDCT types were also determined for samples from different anatomical sites in 35 patients, and from blood and blood isolates (rabbit propagated) from 13 patients. RESULTS The MLST type could be fully determined for 100 (92.6%) of 108 samples. Although MLST subdivided 3 common ECDCT types, it failed to distinguish among others. Neurosyphilis was more common in individuals infected with type 1.1.2 and tp0705 type 2 using MLST, and tp0548 type f using ECDCT. Enhanced Centers for Disease Control and Prevention typing was stable among anatomical sites and between patient-derived and rabbit propagated organisms. CONCLUSIONS Compared with ECDCT, MLST was not uniformly more discriminating. Both typing systems demonstrate that specific types may be more neurotropic than others.