Use of Chlamydia trachomatis high-resolution typing: an extended case study to distinguish recurrent or persistent infection from new infection.
OBJECTIVE
Repeated infections of Chlamydia trachomatis may be new infections or persistent infections due to treatment failure or due to unresolved infections in sexual partners. We aimed to establish the value of using high-resolution multilocus sequence typing (CT-MLST) to discriminate repeated C trachomatis infections.


METHODS
Paired C trachomatis positive samples (baseline (T0) and after 6 months (T1)) were selected from two Dutch screening implementation studies among young heterosexual people. Typing with six CT-MLST loci included the ompA gene. The uniqueness of strains was assessed using 256 reference CT-MLST profiles.


RESULTS
In 27 out of 34 paired cases, full sequence types were obtained. A multilocus (13 cases) or single locus variant (4 cases) was seen, indicating 17 new C trachomatis infections at T1. The ompA genovar was identical for 5 of 17 discordant cases. The 10 cases with concordant typing results were categorised as treatment failure (5 cases) versus persistent or recurrent infections (5 cases). Surprisingly, these concordant cases had C trachomatis strains that were either unique or found in small clusters. The median time between T0 and T1 did not differ between the concordant and discordant cases.


CONCLUSIONS
High-resolution typing was superior in discriminating new infections compared with only using ompA genovar typing. Many cases (37%) showed exactly the same C trachomatis strain after 6 months. CT-MLST is not conclusive in distinguishing recurrent infections from treatment failure.
Division of Infectious Disease Control, Rotterdam-Rijnmond Public Health Service, , Rotterdam, The Netherlands.
Hannelore M
HM
Götz
Reinier J M
RJ
Bom
Mireille E G
ME
Wolfers
Johan
J
Fennema
Ingrid V F
IV
van den Broek
Arjen G C L
AG
Speksnijder
Sylvia M
SM
Bruisten
D000328:Adult; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics*; D016022:Case-Control Studies; D002690:Chlamydia Infections / Q000175:diagnosis* / Q000382:microbiology; D002692:Chlamydia trachomatis / Q000302:isolation & purification*; D016000:Cluster Analysis; D005260:Female; D005838:Genotype; D020010:Heterosexuality; D006801:Humans; D008297:Male; D058885:Multilocus Sequence Typing; D009426:Netherlands / Q000453:epidemiology; D012680:Sensitivity and Specificity
D001425:Bacterial Outer Membrane Proteins
Chlamydia Trachomatis; Epidemiology (Molecular); Molecular Typing