Evaluation of azithromycin resistance in Treponema pallidum specimens from Madagascar

A large screen identifies beta-lactam antibiotics which can be repurposed to target the syphilis agent

Syphilis, caused by the spirochete Treponema pallidum subsp. pallidum (hereafter called T. pallidum), is re-emerging as a worldwide sexually transmitted infection. A single intramuscular dose of benzathine penicillin G is the preferred syphilis treatment option. Both supply shortage concerns and the potential for acquired antibiotic resistance further the need to broaden the repertoire of syphilis therapeutics. We reasoned that other β-lactams may be equally or more effective at targeting the disease-causing agent, Treponema pallidum, but have yet to be discovered due to a previous lack of a continuous in vitro culture system. Recent technical advances with respect to in vitro T. pallidum propagation allowed us to conduct a high-throughput screen of almost 100 β-lactams. Using several molecular and cellular approaches that we developed or adapted, we identified and confirmed the efficacy of several β-lactams that were similar to or outperformed the current standard, benzathine penicillin G. These options are either currently used to treat bacterial infections or are synthetic derivatives of naturally occurring compounds. Our studies not only identified additional potential therapeutics in the resolution of syphilis, but provide techniques to study the complex biology of T. pallidum-a spirochete that has plagued human health for centuries.

Syphilis as Re-Emerging Disease, Antibiotic Resistance, and Vulnerable Population: Global Systematic Review and Meta-Analysis

Syphilis is a sexually transmitted disease that has become a public health problem, especially in vulnerable populations. A systematic review and time-free meta-analysis of the publications on the molecular detection of syphilis and mutations associated with antibiotic resistance, CORE group, and syphilis genotypes in PubMed databases, Scielo, and Cochrane was performed, and the last search was conducted in June 2022. Proportions were calculated, and standard errors and confidence intervals were reported for all results of interest. We included 41 articles for quantitative extraction and data synthesis. An increase was observed in the proportion of subjects diagnosed with syphilis and the presence of the A2058G mutation during the 2018−2021 period compared to 2006 (70% 95%CI 50−87 vs. 58% 95%CI 12−78), and we observed that the greater the proportion of the population participating in men who have sex with men (MSM) (<50% and >50%) syphilis increased (78% 95%CI 65−90 vs. 33% 95%CI 19−49). In conclusion, we suggest that there are a set of characteristics that are contributing to the resurgence of syphilis and the selective pressure of bacteria. The MSM population could be a vulnerable factor for this scenario and the global presence of A2058G and A2059G mutations that confer resistance to macrolides.

High-throughput nanopore sequencing of Treponema pallidum tandem repeat genes arp and tp0470 reveals clade-specific patterns and recapitulates global whole genome phylogeny

Sequencing of most Treponema pallidum genomes excludes repeat regions in tp0470 and the tp0433 gene, encoding the acidic repeat protein (arp). As a first step to understanding the evolution and function of these genes and the proteins they encode, we developed a protocol to nanopore sequence tp0470 and arp genes from 212 clinical samples collected from ten countries on six continents. Both tp0470 and arp repeat structures recapitulate the whole genome phylogeny, with subclade-specific patterns emerging. The number of tp0470 repeats is on average appears to be higher in Nichols-like clade strains than in SS14-like clade strains. Consistent with previous studies, we found that 14-repeat arp sequences predominate across both major clades, but the combination and order of repeat type varies among subclades, with many arp sequence variants limited to a single subclade. Although strains that were closely related by whole genome sequencing frequently had the same arp repeat length, this was not always the case. Structural modeling of TP0470 suggested that the eight residue repeats form an extended α-helix, predicted to be periplasmic. Modeling of the ARP revealed a C-terminal sporulation-related repeat (SPOR) domain, predicted to bind denuded peptidoglycan, with repeat regions possibly incorporated into a highly charged β-sheet. Outside of the repeats, all TP0470 and ARP amino acid sequences were identical. Together, our data, along with functional considerations, suggests that both TP0470 and ARP proteins may be involved in T. pallidum cell envelope remodeling and homeostasis, with their highly plastic repeat regions playing as-yet-undetermined roles.

Treponema pallidum genome sequencing from six continents reveals variability in vaccine candidate genes and dominance of Nichols clade strains in Madagascar

In spite of its immutable susceptibility to penicillin, Treponema pallidum (T. pallidum) subsp. pallidum continues to cause millions of cases of syphilis each year worldwide, resulting in significant morbidity and mortality and underscoring the urgency of developing an effective vaccine to curtail the spread of the infection. Several technical challenges, including absence of an in vitro culture system until very recently, have hampered efforts to catalog the diversity of strains collected worldwide. Here, we provide near-complete genomes from 196 T. pallidum strains-including 191 T. pallidum subsp. pallidum-sequenced directly from patient samples collected from 8 countries and 6 continents. Maximum likelihood phylogeny revealed that samples from most sites were predominantly SS14 clade. However, 99% (84/85) of the samples from Madagascar formed two of the five distinct Nichols subclades. Although recombination was uncommon in the evolution of modern circulating strains, we found multiple putative recombination events between T. pallidum subsp. pallidum and subsp. endemicum, shaping the genomes of several subclades. Temporal analysis dated the most recent common ancestor of Nichols and SS14 clades to 1717 (95% HPD: 1543-1869), in agreement with other recent studies. Rates of SNP accumulation varied significantly among subclades, particularly among different Nichols subclades, and was associated in the Nichols A subclade with a C394F substitution in TP0380, a ERCC3-like DNA repair helicase. Our data highlight the role played by variation in genes encoding putative surface-exposed outer membrane proteins in defining separate lineages, and provide a critical resource for the design of broadly protective syphilis vaccines targeting surface antigens.

Azithromycin resistance in Treponema pallidum in Reunion Island: A cross-sectional study

OBJECTIVE

Since the beginning of the 21st century, Reunion Island has experienced a syphilis epidemic. Infected patients are mostly heterosexual, with a high proportion of women, suggesting that congenital syphilis is present on the island. To determine whether azithromycin can be used for mass treatment of syphilis on Reunion Island, we assessed the prevalence of macrolide resistance in Treponema pallidum (TP).

METHODS

This monocentric cross-sectional study was conducted at the Reunion Island University Hospital. Samples were collected from lesions suggestive of primary or secondary syphilis. Samples positive for TP by multiplex polymerase chain reaction (PCR) were sent to the French National Reference Centre (NRC) for further analysis. Nested PCR-tpp47 was performed on these samples for detection of TP-DNA; 23s rRNA was amplified by PCR in confirmed positive samples. The Restriction Fragment Length Polymorphism (RFLP) technique was performed on samples with amplified 23s rRNA for detection of the A2058G mutation.

RESULTS

A total of 129 samples were collected from 119 patients. Of these, 18 tested positive for TP using multiplex PCR and were sent to the NRC. Fifteen (83.3%) of the 18 samples were confirmed positive by nested PCR-tpp47, and 23s rRNA was amplified in only 7 (38.9%) samples. Azithromycin resistance was detected in all TP strains with amplified 23s rRNA.

CONCLUSION

Amplification of 23s rRNA was successful in only 7 TP strains, all of which displayed resistance to macrolides. Keeping in mind the small sample size of our study, this suggests that azithromycin should not be used for mass treatment of syphilis in Reunion Island.

An Update on the Global Epidemiology of Syphilis

PURPOSE OF REVIEW

Syphilis continues to cause morbidity and mortality worldwide. While syphilis infection is easily identifiable and treatable, rates of syphilis infection continue to increase among select populations in high-income countries and remain at endemic levels in low- and middle-income counties.

RECENT FINDINGS

World Health Organization recommended strategies have led to the dual elimination of mother-to-child transmission of syphilis and HIV in several countries, however outbreaks among select populations need to be adequately addressed.

SUMMARY

Continued vigilance and investment is needed to address syphilis worldwide. The epidemiology of syphilis differs in high-income and low- and middle-income counties.

Treponema pallidum pallidum Genotypes and Macrolide Resistance Status in Syphilitic Lesions among Patients at 2 Sexually Transmitted Infection Clinics in Lima, Peru

We report the circulating genotypes and the frequency of macrolide-resistance patterns among Treponema pallidum pallidum DNA isolated from syphilitic lesions from patients who attended 2 sexual health clinics in Lima, Peru. We implemented and used a molecular typing scheme to describe local T. pallidum pallidum strains. Among 14 specimens, subtype 14d/f was the most prevalent strain in 7 fully typed T. pallidum DNA specimens obtained from men who have sex with men and transgender women presenting with chancre-like lesions. No macrolide-resistance mutations were found in T. pallidum DNA from 10 lesions.

First Report of the 23S rRNA Gene A2058G Point Mutation Associated With Macrolide Resistance in Treponema pallidum From Syphilis Patients in Cuba

This study aimed to assess the presence of macrolide-resistant Treponema pallidum subtypes in Havana, Cuba. Samples from 41 syphilis patients were tested for T. pallidum 23S rRNA gene mutations. Twenty-five patients (61%) harbored T. pallidum with the A2058G mutation, which was present in all 8 subtypes that were identified. The A2059G mutation was not detected.

Molecular typing of Treponema pallidum isolates from Buenos Aires, Argentina: Frequent Nichols-like isolates and low levels of macrolide resistance

A total of 54 clinical samples, including genital lesion swabs, whole blood and cerebrospinal fluid from patients diagnosed with syphilis were collected in 2006 and in 2013 in Buenos Aires, Argentina. Treponemal DNA was detected in 43 of the analyzed samples (79.6%) and further analyzed using Sequencing-based molecular typing (SBMT) and Enhanced CDC-typing (ECDCT). By SBMT, 10 different Treponema pallidum subsp. pallidum (TPA) genotypes were found, of which six were related to the TPA SS14 strain, and four to the TPA Nichols strain. The 23S rRNA gene was amplified in samples isolated from 42 patients, and in six of them (14.3%), either the A2058G (four patients, 9.5%) or the A2059G (two patients, 4.8%) mutations were found. In addition to Taiwan, Madagascar and Peru, Argentina is another country where the prevalence of Nichols-like isolates (26.8%) is greater than 10%.

Efficacy of Doxycycline in the Treatment of Syphilis

Doxycycline is an alternative antibiotic drug for the treatment of syphilis, but data on its efficacy, especially data on its efficacy against late latent syphilis, are limited. A retrospective study was conducted to evaluate the effectiveness of doxycycline for the treatment of patients with different stages of syphilis. Patients who received doxycycline treatment between June 2011 and June 2014 were involved. The serological response to doxycycline was defined as either a negative toluidine red unheated serum test (TRUST) result or a ≥4-fold decrease in titer at 12 months following the treatment. Univariate and multivariate logistic regression analyses were performed to identify factors associated with the serological response. During the study period, a total of 163 syphilis patients were treated with doxycycline, and 118 patients completed doxycycline treatment and the 12-month follow-up. Among the 118 patients, the serological response rate at 12 months was 100.0% (7/7) in patients with primary syphilis, 96.9% (62/64) in patients with secondary syphilis, 91.3% (21/23) in patients with early latent syphilis, and 79.2% (19/24) in patients with late latent syphilis. The total serological response rates were 92.4% (109/118) for preprotocol (PP) patients and 66.9% (109/163) for all intention-to-treat (ITT) patients. In multivariate analysis, patients who serologically responded at 12 months following treatment were positively associated with a higher baseline TRUST titer and an earlier syphilis stage than nonresponders. Our study showed excellent treatment outcomes in patients with different stages of syphilis. Our data, along with those from other reports, support the usage of doxycycline as a good alternative therapeutic option in the treatment of syphilis.

Macrolide Resistance in Treponema pallidum Correlates With 23S rDNA Mutations in Recently Isolated Clinical Strains

BACKGROUND

High rates of 23S rDNA mutations implicated in macrolide resistance have been identified in Treponema pallidum samples from syphilis patients in many countries. Nonetheless, some clinicians have been reluctant to abandon azithromycin as a treatment for syphilis, citing the lack of a causal association between these mutations and clinical evidence of drug resistance. Although azithromycin resistance has been demonstrated in vivo for the historical Street 14 strain, no recent T. pallidum isolates have been tested. We used the well-established rabbit model of syphilis to determine the in vivo efficacy of azithromycin against 23S rDNA mutant strains collected in 2004 to 2005 from patients with syphilis in Seattle, Wash.

METHODS

Groups of 9 rabbits were each infected with a strain containing 23S rDNA mutation A2058G (strains UW074B, UW189B, UW391B) or A2059G (strains UW228B, UW254B, and UW330B), or with 1 wild type strain (Chicago, Bal 3, and Mexico A). After documentation of infection, 3 animals per strain were treated with azithromycin, 3 were treated with benzathine penicillin G, and 3 served as untreated control groups. Treatment efficacy was documented by darkfield microscopic evidence of T. pallidum, serological response, and rabbit infectivity test.

RESULTS

Azithromycin uniformly failed to cure rabbits infected with strains harboring either 23S rDNA mutation, although benzathine penicillin G was effective. Infections caused by wild type strains were successfully treated by either azithromycin or benzathine penicillin G.

CONCLUSIONS

A macrolide resistant phenotype was demonstrated for all strains harboring a 23S rDNA mutation, demonstrating that either A2058G or A2059G mutation confers in vivo drug resistance.

Macrolide Resistance in the Syphilis Spirochete, Treponema pallidum ssp. pallidum: Can We Also Expect Macrolide-Resistant Yaws Strains?

Treponema pallidum ssp. pallidum (TPA) causes over 10 million new cases of syphilis worldwide whereas T. pallidum ssp. pertenue (TPE), the causative agent of yaws, affects about 2.5 million people. Although penicillin remains the drug of choice in the treatment of syphilis, in penicillin-allergic patients, macrolides have been used in this indication since the 1950s. Failures of macrolides in syphilis treatment have been well documented in the literature and since 2000, there has been a dramatic increase in a number of clinical samples with macrolide-resistant TPA. Scarce data regarding the genetics of macrolide-resistant mutations in TPA suggest that although macrolide-resistance mutations have emerged independently several times, the increase in the proportion of TPA strains resistant to macrolides is mainly due to the spread of resistant strains, especially in developed countries. The emergence of macrolide resistance in TPA appears to require a two-step process including either A2058G or A2059G mutation in one copy of the 23S rRNA gene and a subsequent gene conversion unification of both rRNA genes. Given the enormous genetic similarity that was recently revealed between TPA and TPE strains, there is a low but reasonable risk of emergence and spread of macrolide-resistant yaws strains following azithromycin treatment.

Syphilis testing, typing, and treatment follow-up: a new era for an old disease

PURPOSE OF REVIEW

The past 15 years have seen a dramatic increase in syphilis diagnoses in several regions including China, North America, Western Europe and Australia. Worldwide, the disease remains prevalent, contributing to substantial adult morbidity and neonatal mortality. Testing and treatment strategies are largely informed by data from the early antibiotic era, but increasing use of molecular diagnostics and new screening strategies could improve the management of syphilis substantially.

RECENT FINDINGS

The review explores new testing strategies for syphilis, including the importance of screening test selection and advances in point-of-care diagnostics. It then examines molecular studies of Treponema pallidum, covering typing; macrolide resistance; association between genotype and phenotype and the use of PCR in testing and monitoring strategies.

SUMMARY

Clinicians should be aware of testing strategies employed by their laboratories to ensure optimal sensitivity and specificity. Locally available T. pallidum PCR assays may improve the diagnosis of early disease and inform antibiotic choice. Robust serologic follow-up is still required, but predictors of potential treatment failure, including PCR-measured bacterial load, have been identified. Re-treatment should be considered for patients in the serofast state. The publication of T. pallidum genomes would allow further and more detailed study of strains and disease pathogenesis.

Failure of PCR to Detect Treponema pallidum ssp. pertenue DNA in Blood in Latent Yaws

Yaws, caused by Treponema pallidum ssp. pertenue, is a neglected tropical disease closely related to venereal syphilis and is targeted for eradication by 2020. Latent yaws represents a diagnostic challenge, and current tools cannot adequately distinguish between individuals with true latent infection and individuals who are serofast following successful treatment. PCR on blood has previously been shown to detect T. pallidum DNA in patients with syphilis, suggesting that this approach may be of value in yaws. We performed real-time PCR for Treponema pallidum ssp. pertenue on blood samples from 140 children with positive T. pallidum Particle Agglutination (TPPA) and Rapid Plasma Reagin (RPR) tests and 7 controls (negative serology), all collected as part of a prospective study of yaws in the Solomon Islands. All samples were also tested by a nested PCR for T. pallidum. 12 patients had clinical evidence of active yaws whilst 128 were considered to have latent yaws. 43 children had high titre rapid plasma reagins (RPRs) of ≥1:32. PCR testing with both assays gave negative results in all cases. It is possible that the failure to detect T. pallidum ssp. pertenue in blood reflects lower loads of organism in latent yaws compared to those in latent infection with T. pallidum ssp. pertenue, and/or a lower propensity for haematogenous dissemination in yaws than in syphilis. As the goal of the yaws control programme is eradication, a tool that can differentiate true latent infection from individuals who are serofast would be of value; however, PCR of blood is not that tool.

Yaws is a bacterial infection closely related to syphilis. The WHO has launched a worldwide campaign to eradicate yaws by 2020. For each clinically apparent case, many close contacts are infected but do not show clinical signs, which is called latent yaws. Currently, diagnosis for these patients relies on the detection of antibodies using syphilis serology. Reliance on detection of antibodies for diagnosis of latent yaws is problematic as the test may remain positive with a low titre despite successful treatment. This makes the interpretation of surveillance data in a post-mass treatment setting difficult for programme managers. In syphilis, PCR can detect T. pallidum ssp. pallidum in the blood of patients with latent disease. We used similar techniques to try and detect the yaws bacterium in the blood of patients seen as part of a study of yaws in the Solomon Islands. Although many people had positive antibodies for yaws consistent with latent yaws, we were unable to detect the bacterium in the blood. This may reflect the lower virulence of the yaws bacterium compared to syphilis. Currently available molecular techniques are therefore not able to aid programme managers in conducting post-mass drug administration surveillance for latent yaws. The development of alternative diagnostic tests should be considered.

Treatment of syphilis: a systematic review

IMPORTANCE

The incidence of syphilis in the United States is increasing; it is estimated that more than 55,000 new infections will occur in 2014. Treatment regimens are controversial, especially in specific populations, and assessing treatment response based on serology remains a challenge.

OBJECTIVE

To review evidence regarding penicillin and nonpenicillin regimens, implications of the "serofast state," and treatment of specific populations including those with neurosyphilis or human immunodeficiency virus (HIV) infection and pregnant women.

EVIDENCE REVIEW

We searched MEDLINE for English-language human treatment studies dating from January 1965 until July 2014. The American Heart Association classification system was used to rate quality of evidence.

FINDINGS

We included 102 articles in our review, consisting of randomized trials, meta-analyses, and cohort studies. Case reports and small series were excluded unless they were the only studies providing evidence for a specific treatment strategy. We included 11 randomized trials. Evidence regarding penicillin and nonpenicillin regimens was reviewed from studies involving 11,102 patients. Data on the treatment of early syphilis support the use of a single intramuscular injection of 2.4 million U of benzathine penicillin G, with studies reporting 90% to 100% treatment success rates. The value of multiple-dose treatment of early syphilis is uncertain, especially in HIV-infected individuals. Less evidence is available regarding therapy for late and late latent syphilis. Following treatment, nontreponemal serologic titers should decline in a stable pattern, but a significant proportion of patients may remain seropositive (the "serofast state"). Serologic response to treatment should be evident by 6 months in early syphilis but is generally slower (12-24 months) for latent syphilis. Evidence defining treatment for HIV-infected persons and for pregnant women is limited, but available data support penicillin as first-line therapy.

CONCLUSIONS AND RELEVANCE

The mainstay of syphilis treatment is parenteral penicillin G despite the relatively modest clinical trial data that support its use.

Syphilis: antibiotic treatment and resistance

Syphilis is a chronic, multi-stage infectious disease that is usually transmitted sexually by contact with an active lesion of a partner or congenitally from an infected pregnant woman to her fetus. Although syphilis is still endemic in many developing countries, it has re-emerged in several developed countries. The resurgence of syphilis is a major concern to global public health, particularly since the lesions of early syphilis increase the risk of acquisition and transmission of infection with human immunodeficiency virus (HIV). Because there is no vaccine to prevent syphilis, control is mainly dependent on the identification and treatment of infected individuals and their contacts with penicillin G, the first-line drug for all stages of syphilis. The emergence of clinically significant azithromycin resistance in Treponema pallidum subsp. pallidum, the syphilis agent, has resulted in treatment failures, thus precluding the routine use of this second-line drug. Information is presented here on the diagnosis and recommended antibiotic treatment of syphilis and the challenge of macrolide-resistant T. pallidum.

Molecular typing of Treponema pallidum in the Czech Republic during 2011 to 2013: increased prevalence of identified genotypes and of isolates with macrolide resistance

From January 2011 to December 2013, a total of 262 samples, from 188 patients suspected of having syphilis were tested for the presence of treponemal DNA by PCR amplification of five chromosomal loci, including the polA (TP0105), tmpC (TP0319), TP0136, TP0548, and 23S rRNA genes. Altogether, 146 samples from 103 patients were PCR positive for treponemal DNA. A set of 81 samples from 62 PCR-positive patients were typeable, and among them, nine different genotypes were identified. Compared to a previous study in the Czech Republic during 2004 to 2010, the number of genotypes detected among syphilis patients in a particular year increased to six in both 2012 and 2013, although they were not the same six. The proportion of macrolide-resistant clinical isolates in this 3-year study was 66.7%.

Azithromycin-resistant syphilis-causing strains in Sydney, Australia: prevalence and risk factors

Azithromycin has shown high efficacy in randomized trials when used for treating infectious syphilis in Africa. However, its use in clinical practice has been limited by the development of antimicrobial drug resistance. Resistance has not previously been reported from Australasia. The aim of this study was to determine the prevalence of and risk factors for azithromycin-resistant syphilis-causing strains in Sydney, Australia. We evaluated 409 samples that were PCR positive for Treponema pallidum DNA collected between 2004 and 2011 for the presence of the A2058G mutation, which confers resistance to macrolide antibiotics such as azithromycin. Overall, 84% of samples harbored the mutation. The prevalence of the mutation increased during the study period (P trend, 0.003). We also collected clinical and demographic data on 220 patients from whom these samples had been collected to determine factors associated with the A2058G mutation; 97% were from men who have sex with men. Reporting sex in countries other than Australia was associated with less macrolide resistance (adjusted odds ratio, 0.25; 95% confidence interval, 0.09 to 0.66; P = 0.005), with other study factors showing no association (age, HIV status, recent macrolide use, stage of syphilis, or history of prior syphilis). Azithromycin cannot be recommended as an alternative treatment for syphilis in Sydney.

The endemic treponematoses

The agents of human treponematoses include four closely related members of the genus Treponema: three subspecies of Treponema pallidum plus Treponema carateum. T. pallidum subsp. pallidum causes venereal syphilis, while T. pallidum subsp. pertenue, T. pallidum subsp. endemicum, and T. carateum are the agents of the endemic treponematoses yaws, bejel (or endemic syphilis), and pinta, respectively. All human treponematoses share remarkable similarities in pathogenesis and clinical manifestations, consistent with the high genetic and antigenic relatedness of their etiological agents. Distinctive features have been identified in terms of age of acquisition, most common mode of transmission, and capacity for invasion of the central nervous system and fetus, although the accuracy of these purported differences is debated among investigators and no biological basis for these differences has been identified to date. In 2012, the World Health Organization (WHO) officially set a goal for yaws eradication by 2020. This challenging but potentially feasible endeavor is favored by the adoption of oral azithromycin for mass treatment and the currently focused distribution of yaws and endemic treponematoses and has revived global interest in these fascinating diseases and their causative agents.

On the pathway to better birth outcomes? A systematic review of azithromycin and curable sexually transmitted infections

The WHO recommends the administration of sulfadoxine-pyrimethamine (SP) to all pregnant women living in areas of moderate (stable) to high malaria transmission during scheduled antenatal visits, beginning in the second trimester and continuing to delivery. Malaria parasites have lost sensitivity to SP in many endemic areas, prompting the investigation of alternatives that include azithromycin-based combination (ABC) therapies. Use of ABC therapies may also confer protection against curable sexually transmitted infections and reproductive tract infections (STIs/RTIs). The magnitude of protection at the population level would depend on the efficacy of the azithromycin-based regimen used and the underlying prevalence of curable STIs/RTIs among pregnant women who receive preventive treatment. This systematic review summarizes the efficacy data of azithromycin against curable STIs/RTIs.

[Syphilis. Part 2: Laboratory diagnostics, therapy and prevention]

Sexually transmitted infections and sexually transmitted diseases such as syphilis are a great problem for public health systems worldwide. Syphilis can be curatively treated with penicillin after early diagnosis, competent therapy and consistent monitoring. The fundamentals of syphilis diagnostics are direct and serological methods for pathogen detection. Prevention of syphilis includes exposition prophylaxis and in particular the routine use of condoms and the consistent education of affected persons and their sexual contacts.

Developments in therapy and diagnosis of yaws and future prospects

Yaws, a chronic and debilitating infectious disease caused by Treponema pallidum subsp. pertenue, and closely related to syphilis, although transmitted by skin-to-skin contact, remains an important public health challenge, causing a significant burden of morbidity in children in certain areas of the Pacific and Africa. Recent advances in its diagnosis and treatment have led to an enthusiastic upsurge of activities related to its control, and exciting perspectives of global eradication. Although possibly considered among the most neglected of all neglected diseases during decades, there seems to be now agreement that massive drug administration of the antibiotic azithromycin, coupled with adequate surveillance of foci of transmission could result in its eradication. In this review, we summarize current knowledge regarding the therapeutics of yaws and its diagnosis.

Yaws

Yaws is an infectious disease caused by Treponema pallidum pertenue-a bacterium that closely resembles the causative agent of syphilis-and is spread by skin-to-skin contact in humid tropical regions. Yaws causes disfiguring, and sometimes painful lesions of the skin and bones. As with syphilis, clinical manifestations can be divided into three stages; however, unlike syphilis, mother-to-child transmission does not occur. A major campaign to eradicate yaws in the 1950s and 1960s, by mass treatment of affected communities with longacting, injectable penicillin, reduced the number of cases by 95% worldwide, but yaws has reappeared in recent years in Africa, Asia, and the western Pacific. In 2012, one oral dose of azithromycin was shown to be as effective as intramuscular penicillin in the treatment of the disease, and WHO launched a new initiative to eradicate yaws by 2020.

Phylogenetic analysis of pbp genes in treponemes

Background

β-Lactamases are the main cause of bacterial resistance to penicillin, cephalosporins, and related β-lactam compounds. The presence of the novel penicillin-binding protein (pbp) Tp47 in Treponema pallidum has been reported to be a well-known mechanism for turnover of b-lactam antibiotics. Although, T. pallidum remains sensitive to penicillin, clinically significant resistance to macrolides has emerged in many developing countries. The genome sequence of T. pallidum has shown the presence of genes encoding pbp, but there are no current reports of the presence of mobile plasmids.

Methods

The phylogenetic analysis is used to study the diversity of chromosomal pbp genes and its relatedness to Tp47 in Treponema species.

Results

In our study, genes encoding penicillin-binding proteins that showed significant similarity to each other appeared in separate clusters.

Conclusion

Tp47 showed no substantial similarity to other β-lactamases in treponemes. The relatedness of Treponema denticola to other treponemes, including T. pallidum, and the reported presence of natural mobile antibiotic determinants highlight the importance of investigating the diversity of pbp genes in Treponema species. This will lead to a greater understanding of its potential to develop additional antibiotic resistance via horizontal gene transfer that could seriously compromise the treatment and control of syphilis.

Detection of the A2058G and A2059G 23S rRNA gene point mutations associated with azithromycin resistance in Treponema pallidum by use of a TaqMan real-time multiplex PCR assay

Macrolide treatment failure in syphilis patients is associated with a single point mutation (either A2058G or A2059G) in both copies of the 23S rRNA gene in Treponema pallidum strains. The conventional method for the detection of both point mutations uses nested PCR combined with restriction enzyme digestions, which is laborious and time-consuming. We initially developed a TaqMan-based real-time duplex PCR assay for detection of the A2058G mutation, and upon discovery of the A2059G mutation, we modified the assay into a triplex format to simultaneously detect both mutations. The point mutations detected by the real-time triplex PCR were confirmed by pyrosequencing. A total of 129 specimens PCR positive for T. pallidum that were obtained from an azithromycin resistance surveillance study conducted in the United States were analyzed. Sixty-six (51.2%) of the 129 samples with the A2058G mutation were identified by both real-time PCR assays. Of the remaining 63 samples that were identified as having a macrolide-susceptible genotype by the duplex PCR assay, 17 (27%) were found to contain the A2059G mutation by the triplex PCR. The proportions of macrolide-susceptible versus -resistant genotypes harboring either the A2058G or the A2059G mutation among the T. pallidum strains were 35.6, 51.2, and 13.2%, respectively. None of the T. pallidum strains examined had both point mutations. The TaqMan-based real-time triplex PCR assay offers an alternative to conventional nested PCR and restriction fragment length polymorphism analyses for the rapid detection of both point mutations associated with macrolide resistance in T. pallidum.

Two mutations associated with macrolide resistance in Treponema pallidum: increasing prevalence and correlation with molecular strain type in Seattle, Washington

BACKGROUND

Although azithromycin promised to be a safe and effective single-dose oral treatment of early syphilis, azithromycin treatment failure has been documented and is associated with mutations in the 23S rDNA of corresponding Treponema pallidum strains. The prevalence of strains harboring these mutations varies throughout the United States and the world. We examined T. pallidum strains circulating in Seattle, Washington, from 2001 to 2010 to determine the prevalence of 2 mutations associated with macrolide resistance and to determine whether these mutations were associated with certain T. pallidum strain types.

METHODS

Subjects were enrolled in a separate ongoing study of cerebrospinal fluid abnormalities in patients with syphilis. T. pallidum DNA purified from blood and T. pallidum strains isolated from blood or cerebrospinal fluid were analyzed for two 23S rDNA mutations and for the molecular targets used in an enhanced molecular stain typing system.

RESULTS

Nine molecular strain types of T. pallidum were identified in Seattle from 2001 to 2010. Both macrolide resistance mutations were identified in Seattle strains, and the prevalence of resistant T. pallidum exceeded 80% in 2005 and increased through 2010. Resistance mutations were associated with discrete molecular strain types of T. pallidum.

CONCLUSIONS

Macrolide-resistant T. pallidum strains are highly prevalent in Seattle, and each mutation is associated with discrete strain types. Macrolides should not be considered for treatment of syphilis in regions where prevalence of the mutations is high. Combining the resistance mutations with molecular strain typing permits a finer analysis of the epidemiology of syphilis in a community.

Evaluation of macrolide resistance and enhanced molecular typing of Treponema pallidum in patients with syphilis in Taiwan: a prospective multicenter study

Studies of macrolide resistance mutations and molecular typing using the newly proposed enhanced typing system for Treponema pallidum isolates obtained from HIV-infected patients in the Asia-Pacific region are scarce. Between September 2009 and December 2011, we conducted a survey to detect T. pallidum using a PCR assay using clinical specimens from patients with syphilis at six major designated hospitals for HIV care in Taiwan. The T. pallidum strains were genotyped by following the enhanced molecular typing methodology, which analyzed the number of 60-bp repeats in the acidic repeat protein (arp) gene, T. pallidum repeat (tpr) polymorphism, and the sequence of base pairs 131 to 215 in the tp0548 open reading frame of T. pallidum. Detection of A2058G and A2059G point mutations in the T. pallidum 23S rRNA was performed with the use of restriction fragment length polymorphism (RFLP). During the 2-year study period, 211 clinical specimens were obtained from 136 patients with syphilis. T. pallidum DNA was isolated from 105 (49.8%) of the specimens, with swab specimens obtained from chancres having the highest yield rate (63.2%), followed by plasma (49.4%), serum (35.7%), and cerebrospinal fluid or vitreous fluid (18.2%) specimens. Among the 40 fully typed specimens, 11 subtypes of T. pallidum were identified. Subtype 14f/f (18 isolates) was the most common isolates, followed by 14f/c (3), 14b/c (3), and 14k/f (3). Among the isolates examined for macrolide resistance, none had the A2058G or A2059G mutation. In conclusion, we found that type 14 f/f was the most common T. pallidum strain in this multicenter study on syphilis in Taiwan and that none of the isolates exhibited 23S rRNA mutations causing resistance to macrolides.

Genetic diversity in Treponema pallidum: implications for pathogenesis, evolution and molecular diagnostics of syphilis and yaws

Pathogenic uncultivable treponemes, similar to syphilis-causing Treponema pallidum subspecies pallidum, include T. pallidum ssp. pertenue, T. pallidum ssp. endemicum and Treponema carateum, which cause yaws, bejel and pinta, respectively. Genetic analyses of these pathogens revealed striking similarity among these bacteria and also a high degree of similarity to the rabbit pathogen, Treponema paraluiscuniculi, a treponeme not infectious to humans. Genome comparisons between pallidum and non-pallidum treponemes revealed genes with potential involvement in human infectivity, whereas comparisons between pallidum and pertenue treponemes identified genes possibly involved in the high invasivity of syphilis treponemes. Genetic variability within syphilis strains is considered as the basis of syphilis molecular epidemiology with potential to detect more virulent strains, whereas genetic variability within a single strain is related to its ability to elude the immune system of the host. Genome analyses also shed light on treponemal evolution and on chromosomal targets for molecular diagnostics of treponemal infections.

Single-dose azithromycin versus benzathine benzylpenicillin for treatment of yaws in children in Papua New Guinea: an open-label, non-inferiority, randomised trial

BACKGROUND

Yaws--an endemic treponematosis and, as such, a neglected tropical disease--is re-emerging in children in rural, tropical areas. Oral azithromycin is effective for syphilis. We assessed the efficacy of azithromycin compared with intramuscular long-acting penicillin to treat patients with yaws.

METHODS

We did an open-label, non-inferiority, randomised trial at Lihir Medical Centre, Papua New Guinea, between Sept 1, 2010, and Feb 1, 2011. Children aged 6 months to 15 years with a serologically confirmed diagnosis of yaws were randomly allocated, by a computer-generated randomisation sequence, to receive either one 30 mg/kg oral dose of azithromycin or an intramuscular injection of 50,000 units per kg benzathine benzylpenicillin. Investigators were masked to group assignment. The primary endpoint was treatment efficacy, with cure rate defined serologically as a decrease in rapid plasma reagin titre of at least two dilutions by 6 months after treatment, and, in participants with primary ulcers, also by epithelialisation of lesions within 2 weeks. Non-inferiority was shown if the upper limit of the two-sided 95% CI for the difference in rates was lower than 10%. The primary analysis was per protocol. This trial is registered with ClinicalTrials.gov, number NCT01382004.

FINDINGS

We allocated 124 patients to the azithromycin group and 126 to the benzathine benzylpenicillin group. In the per-protocol analysis, after 6 months of follow-up, 106 (96%) of 110 patients in the azithromycin group were cured, compared with 105 (93%) of 113 in the benzathine benzylpenicillin group (treatment difference -3·4%; 95% CI -9·3 to 2·4), thus meeting prespecified criteria for non-inferiority. The number of drug-related adverse events (all mild or moderate) was similar in both treatment groups (ten [8%] in the azithromycin group vs eight [7%] in the benzathine benzylpenicillin group).

INTERPRETATION

A single oral dose of azithromycin is non-inferior to benzathine benzylpenicillin and avoids the need for injection equipment and medically trained personnel. A change to the simpler azithromycin treatment regimen could enable yaws elimination through mass drug administration programmes.

FUNDING

International SOS and Newcrest Mining.

Molecular typing of Treponema pallidum: a systematic review and meta-analysis

BACKGROUND

Syphilis is resurgent in many regions of the world. Molecular typing is a robust tool for investigating strain diversity and epidemiology. This study aimed to review original research on molecular typing of Treponema pallidum (T. pallidum) with three objectives: (1) to determine specimen types most suitable for molecular typing; (2) to determine T. pallidum subtype distribution across geographic areas; and (3) to summarize available information on subtypes associated with neurosyphilis and macrolide resistance.

METHODOLOGY/PRINCIPAL FINDINGS

Two researchers independently searched five databases from 1998 through 2010, assessed for eligibility and study quality, and extracted data. Search terms included "Treponema pallidum," or "syphilis," combined with the subject headings "molecular," "subtyping," "typing," "genotype," and "epidemiology." Sixteen eligible studies were included. Publication bias was not statistically significant by the Begg rank correlation test. Medians, inter-quartile ranges, and 95% confidence intervals were determined for DNA extraction and full typing efficiency. A random-effects model was used to perform subgroup analyses to reduce obvious between-study heterogeneity. Primary and secondary lesions and ear lobe blood specimens had an average higher yield of T. pallidum DNA (83.0% vs. 28.2%, χ(2) = 247.6, p<0.001) and an average higher efficiency of full molecular typing (80.9% vs. 43.1%, χ(2) = 102.3, p<0.001) compared to plasma, whole blood, and cerebrospinal fluid. A pooled analysis of subtype distribution based on country location showed that 14d was the most common subtype, and subtype distribution varied across geographic areas. Subtype data associated with macrolide resistance and neurosyphilis were limited.

CONCLUSIONS/SIGNIFICANCE

Primary lesion was a better specimen for obtaining T. pallidum DNA than blood. There was wide geographic variation in T. pallidum subtypes. More research is needed on the relationship between clinical presentation and subtype, and further validation of ear lobe blood for obtaining T. pallidum DNA would be useful for future molecular studies of syphilis.

Predictors of serological cure and Serofast State after treatment in HIV-negative persons with early syphilis

BACKGROUND

Syphilis management requires serological monitoring after therapy. We compared factors associated with serological response after treatment of early (ie, primary, secondary, or early latent) syphilis.

METHODS

We performed secondary analyses of data from a prospective, randomized syphilis trial conducted in the United States and Madagascar. Human immunodeficiency virus (HIV)-negative participants aged ≥ 18 years with early syphilis were enrolled from 2000-2009. Serological testing was performed at baseline and at 3 and 6 months after treatment. At 6 months, serological cure was defined as a negative rapid plasma reagin (RPR) test or a ≥4-fold decreased titer, and serofast status was defined as a ≤ 2-fold decreased titer or persistent titers that did not meet criteria for treatment failure.

RESULTS

Data were available from 465 participants, of whom 369 (79%) achieved serological cure and 96 (21%) were serofast. In bivariate analysis, serological cure was associated with younger age, fewer sex partners, higher baseline RPR titers, and earlier syphilis stage (P ≤ .008). There was a less significant association with Jarisch-Herxheimer reaction after treatment (P = .08). Multivariate analysis revealed interactions between log-transformed baseline titer with syphilis stage, in which the likelihood of cure was associated with increased titers among participants with primary syphilis (adjusted odds ratio [AOR] for 1 unit change in log(2) titer, 1.83; 95% confidence interval [CI], 1.25-2.70), secondary syphilis (AOR, 3.15; 95% CI, 2.14-4.65), and early latent syphilis (AOR, 1.86; 95% CI, 1.44-2.40).

CONCLUSIONS

Serological cure at 6 months after early syphilis treatment is associated with age, number of sex partners, Jarisch-Herxheimer reaction, and an interaction between syphilis stage and baseline RPR titer.

Enhanced molecular typing of treponema pallidum: geographical distribution of strain types and association with neurosyphilis

BACKGROUND

Strain typing is a tool for determining the diversity and epidemiology of infections.

METHODS

Treponema pallidum DNA was isolated from 158 patients with syphilis from the United States, China, Ireland, and Madagascar and from 15 T. pallidum isolates. Six typing targets were assessed: (1) the number of 60‐bp repeats in the acidic repeat protein gene, (2) restriction fragment length polymorphism (RFLP) analysis of T. pallidum repeat (tpr) subfamily II genes, (3) RFLP analysis of the tprC gene, (4) determination of tprD allele in the tprD gene locus, (5) the presence of a 51‐bp insertion between tp0126 and tp0127, and (6) sequence analysis of an 84‐bp region of tp0548. The combination of targets 1 and 2 comprises the Centers for Disease Control and Prevention (CDC) T. pallidum subtyping method.

RESULTS

Adding sequence analysis of tp0548 to the CDC method yielded the most discriminating typing system. Twenty‐five strain types were identified and designated as "CDC subtype/tp0548 sequence type." Type 14d/f was found in samples from 5 of 6 locations. In Seattle, Washington, strain types changed from 1999 through 2008 (P < .001). Twenty‐one (50%) of 42 patients infected with type 14d/f had neurosyphilis compared with 10 (24%) of 41 patients infected with any of the other types combined (P = .02).

CONCLUSION

We describe an enhanced T. pallidum strain typing system that shows biological and clinical relevance.