Enhanced Molecular Typing ofTreponema pallidum: Geographical Distribution of Strain Types and Association with Neurosyphilis

Abstract

Background Strain typing is a tool for determining diversity and epidemiology of infections. Methods T. pallidum DNA was isolated from 158 syphilis patients from the US, China, Ireland, and Madagascar and from 15 T. pallidum isolates. Six typing targets were assessed: 1) number of 60 bp repeats in acidic repeat protein gene; 2) restriction fragment length polymorphism (RFLP) analysis of T. pallidum repeat (tpr) subfamily II genes; 3) RFLP analysis of tprC gene; 4) determination of tprD allele in tprD gene locus; 5) presence of 51 bp insertion between tp0126/tp0127; 6) sequence analysis of 84 bp region of tp0548. The combination of #1 and #2 comprises the CDC T. pallidum subtyping method. Results Adding sequence analysis of tp0548 to the CDC method yielded the most discriminating typing system. Twenty-four strain types were identified and designated as CDC subtype/tp0548 sequence. Type 14d/f was seen in 5 of 6 locations. In Seattle, strain types changed from 1999– 2008 (p<0.001). Twenty-two (50%) of 44 patients infected with type 14d/f had neurosyphilis compared to 9 (23%) of 39 infected with the other types combined (p=0.01). Conclusion We describe an enhanced T. pallidum strain typing system that shows biological and clinical relevance.

Syphilis: using modern approaches to understand an old disease

“…This method for subtype designation has been applied to patient samples taken from chancres, condyloma lata, mouth scrapings, ear lobe scrapings, blood, CSF, and laboratory-passaged T. pallidum isolates from diverse geographic areas (126)(127)(128)(129)(130)(131)(132)(133)(134). Epidemiological studies of strain types in San Francisco and Seattle in the last decade showed that most are subtype 14d (123,135), which may suggest a linked sexual network, while other studies indicate variation in the distribution of predominant strain types by location in the United States and worldwide (refs. 127-131, 133, 134, and Figure 3).…”

“…127-131, 133, 134, and Figure 3). Addition of a third gene to the typing scheme increased discriminatory power (123,135). Subtyping using the tp0548 gene demonstrated that the predominant 14d/f strain was replaced by the 14d/g strain in Seattle during the period from 1999 to 2008 (135).…”

Whole Genome Analyses of Treponemes: New Targets for Strain- and Subspecies-Specific Molecular Diagnostics

“…The differences among tested strains were also found in a number of 24 bp tandem repeats of TP0470, a gene encoding a hypothetical protein, and in indels present in the hypothetical TP0967 gene (Mikalová et al, 2010). As with the tprK-like insertion between the TP0126 and TP0127 genes, the number of 24 bp repetitions in TP0470 was reported to vary within individual bacterial isolates (Marra et al, 2010). …”

“…The greatest numbers of genotypes were found for the locus TP0548 (5) and for genetic variants detected by amplification of the arp gene (5). The use of the TP0548 locus in molecular typing of syphilis was first described by Flasarová et al (2006) and this locus was recently incorporated to the enhanced molecular typing system of Treponema pallidum (Marra et al, 2010). Analysis of TP0136 revealed 3 genotypes.…”

“…In contrast, screening of 23S rDNA for A2058G in syphilitic samples taken from patients in Madagascar revealed no such mutation in 141 samples (Van Damme et al, 2009). The recently improved CDC typing system (Marra et al, 2010) relies on detection of the number of repetitions in the arp gene, on amplification and restriction digest analysis of tprEGJ genes and on sequencing of a part of the TP0548 gene.…”