Old foes, new challenges: syphilis, cholera and TB

Comparison of transcriptional profiles of Treponema pallidum during experimental infection of rabbits and in vitro culture: Highly similar, yet different

Treponema pallidum ssp. pallidum, the causative agent of syphilis, can now be cultured continuously in vitro utilizing a tissue culture system, and the multiplication rates are similar to those obtained in experimental infection of rabbits. In this study, the RNA transcript profiles of the T. pallidum Nichols during in vitro culture and rabbit infection were compared to examine whether gene expression patterns differed in these two environments. To this end, RNA preparations were converted to cDNA and subjected to RNA-seq using high throughput Illumina sequencing; reverse transcriptase quantitative PCR was also performed on selected genes for validation of results. The transcript profiles in the in vivo and in vitro environments were remarkably similar, exhibiting a high degree of concordance overall. However, transcript levels of 94 genes (9%) out of the 1,063 predicted genes in the T. pallidum genome were significantly different during rabbit infection versus in vitro culture, varying by up to 8-fold in the two environments. Genes that exhibited significantly higher transcript levels during rabbit infection included those encoding multiple ribosomal proteins, several prominent membrane proteins, glycolysis-associated enzymes, replication initiator DnaA, rubredoxin, thioredoxin, two putative regulatory proteins, and proteins associated with solute transport. In vitro cultured T. pallidum had higher transcript levels of DNA repair proteins, cofactor synthesis enzymes, and several hypothetical proteins. The overall concordance of the transcript profiles may indicate that these environments are highly similar in terms of their effects on T. pallidum physiology and growth, and may also reflect a relatively low level of transcriptional regulation in this reduced genome organism.

Epidemiological behavior and current forecast of syphilis in Mexico: increase in male population

OBJECTIVES

Even when new cases of syphilis are notifiable since 1944, the Mexican National Epidemiological Surveillance System lacks information on the changes of the rate of case reports considering the geographic and demographic variables. Therefore, it is necessary to have evidence, with particular attention to the study of the epidemiological behavior by the identification of risk factors and groups. The objective of this study was to analyze the epidemiology, geographical distribution, and forecast of syphilis in Mexico.

STUDY DESIGN

The design of the study was a secondary research of epidemiological databases.

METHODS

A retrospective analysis of the national surveillance data (2007-2017) of acquired and congenital syphilis (CS) issued by the General Directorate of Epidemiology was performed.

RESULTS

Of all cases, 34,998 and 1030 cases were reported for acquired syphilis (AS) and CS , respectively, reflecting an increasing trend in the whole country for both diseases. Cases and incidence of AS per year showed that, male gender presented an increase in reproductive age. Distribution of the rate of case reports is mostly commanded by the states in the extreme north (Gulf of California and northern Gulf of Mexico) and south (Gulf of southern Mexico and the Caribbean Sea). Likewise, the Seasonal Autoregressive Integrated Moving Average model was selected as the best-fit model for the forecast analysis. This model was used to forecast AS cases during 2018-2019. AS may have a slight fluctuation (on the rise) during the following 24 months.

CONCLUSIONS

These findings underscore the importance of intensifying, as well as expanding screening and treatment in adult population, including men, who are not routinely benefiting from maternal and reproductive service-based syphilis screening and treatment.

Complex contagion leads to complex dynamics in models coupling behaviour and disease

Models coupling behaviour and disease as two unique but interacting contagions have existed since the mid 2000s. In these coupled contagion models, behaviour is typically treated as a 'simple contagion'. However, the means of behaviour spread may in fact be more complex. We develop a family of disease-behaviour coupled contagion compartmental models in order to examine the effect of behavioural contagion type on disease-behaviour dynamics. Coupled contagion models treating behaviour as a simple contagion and a complex contagion are investigated, showing that behavioural contagion type can have a significant impact on dynamics. We find that a simple contagion behaviour leads to simple dynamics, while a complex contagion behaviour supports complex dynamics with the possibility of bistability and periodic orbits.

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.

Tracing the origin of Treponema pallidum in China using next-generation sequencing

Syphilis is a systemic sexually transmitted disease caused by Treponema pallidum ssp. pallidum (TPA). The origin and genetic background of Chinese TPA strains remain unclear. We identified a total of 329 single-nucleotide variants (SNVs) in eight Chinese TPA strains using next-generation sequencing. All of the TPA strains were clustered into three lineages, and Chinese TPA strains were grouped in Lineage 2 based on phylogenetic analysis. The phylogeographical data showed that TPA strains originated earlier than did T. pallidum ssp. pertenue (TPE) and T. pallidum ssp. endemicum (TPN) strains and that Chinese TPA strains might be derived from recombination between Lineage 1 and Lineage 3. Moreover, we found through a homology modeling analysis that a nonsynonymous substitution (I415F) in the PBP3 protein might affect the structural flexibility of PBP3 and the binding constant for substrates based on its possible association with penicillin resistance in T. pallidum. Our findings provide new insight into the molecular foundation of the evolutionary origin of TPA and support the development of novel diagnostic/therapeutic technology for syphilis.

The continuing threat of syphilis in pregnancy

PURPOSE OF REVIEW

Syphilis in pregnancy continues to be a worldwide threat to mothers and their fetuses, and in recent years has been increasing in prevalence. The purpose of this short review is to address current issues in the diagnosis and management of syphilis complicating pregnancies.

RECENT FINDINGS

Maternal syphilis infections and congenital syphilis appear to be increasing in both high and low resource settings. Treponema pallidum ssp. pallidum, the causative spirochete of syphilis, remains one of the few human infectious pathogens that has not been successfully cultured, making identification difficult and research in targeted antimicrobial therapies challenging. Fortunately, syphilis remains sensitive to penicillin, which remains the foundational therapy for this infection. Patients with syphilis and significant penicillin allergies remain a specific challenge in treatment. Of concern is the emergence of T. pallidum resistant to macrolides such as azithromycin. This will limit options in patients with penicillin allergies, and potentially contribute to suboptimal treatment. During pregnancy, penicillin is the only known effective treatment for congenital syphilis, and pregnant patients with penicillin allergy should be desensitized and treated with penicillin. Research focusing on protein expression of the genome of T. pallidum may lead to more accurate screening and diagnosis and development of novel antibiotic therapies.

SUMMARY

Obstetric and pediatric providers, public health organizations, and governments should recognize the re-emergence of syphilis globally and in their local healthcare environments. Screening of all pregnant patients with robust treatment and follow-up represents the most effective method to reduce congenital syphilis currently available.

Syphilis: Re-emergence of an old foe

Syphilis is caused by infection with Treponema pallidum subsp. pallidum, a not-yet-cultivable spiral-shaped bacterium that is usually transmitted by sexual contact with an infected partner or by an infected pregnant woman to her fetus. There is no vaccine to prevent syphilis. Diagnosis and treatment of infected individuals and their contacts is key to syphilis control programs that also include sex education and promotion of condom use to prevent infection. Untreated syphilis can progress through four stages: primary (chancre, regional lymphadenopathy), secondary (disseminated skin eruptions, generalized lymphadenopathy), latent (decreased re-occurrence of secondary stage manifestations, absence of symptoms), and tertiary (gummas, cardiovascular syphilis and late neurological symptoms). The primary and secondary stages are the most infectious. WHO estimates that each year 11 million new cases of syphilis occur globally among adults aged 15-49 years. Syphilis has re-emerged in several regions including North America, Western Europe, China and Australia. Host-associated factors that drive the re-emergence and spread of syphilis include high-risk sexual activity, migration and travel, and economic and social changes that limit access to health care. Early, uncomplicated syphilis is curable with a single intramuscular injection of benzathine penicillin G (BPG), the first line drug for all stages of syphilis. Emergence of macrolide-resistant T. pallidum has essentially precluded the empirical use of azithromycin as a second-line drug for treatment of syphilis. Virulence attributes of T. pallidum are poorly understood. Genomic and proteomic studies have provided some new information concerning how this spirochete may evade host defense mechanisms to persist for long periods in the host.

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.

Evaluation of syphilis serostatus on the safety of IVF treatment

An increasing number of infertile syphilis-infected individuals have turned to assisted reproductive technology; however, the safety of syphilis carrier serostatus on IVF and embryo transfer outcomes has not been evaluated. Data from 482 patients who delivered singletons were analysed. In the retrospective study, the rate of IVF and intracytoplasmic sperm injection fertilization was 79.50% ± 17.57%/78.72% ± 16.66% in the Treponema pallidum particle agglutination assay negative (TPPA-negative) and rapid plasma reagin negative (RPR-negative) group, 76.12% ± 22.99%/74.05% ± 20.31% in the TPPA-positive and RPR-negative group, and 75.66% ± 21.72%/70.90% ± 16.11% in the TPPA-positive and RPR-positive group. The clinical pregnancy rate was 39.79% in the TPPA-negative and RPR-negative group, 46.30% in the TPPA-positive and RPR-negative group, and 36.59% in the TPPA-positive and RPR-positive group. No significant differences were found between the groups. The neonatal gestational age and mean birth weight were not significantly different between the TPPA-negative and TPPA-positive groups. Multiple linear regression analysis also showed no association between TPPA serostatus and newborn birth weight and gestational age. The present retrospective study showed that TPPA and RPR serostatus did not affect the outcomes of IVF and embryo transfer. Syphilis-infected individuals can undergo IVF and embryo transfer cycles after penicillin treatment.

Point of care diagnostics for sexually transmitted infections: perspectives and advances

Accurate and inexpensive point-of-care (POC) tests are urgently needed to control sexually transmitted infection epidemics, so that patients can receive immediate diagnoses and treatment. Current POC assays for Chlamydia trachomatis and Neisseria gonorrhoeae perform inadequately and require better assays. Diagnostics for Trichomonas vaginalis rely on wet preparation, with some notable advances. Serological POC assays for syphilis can impact resource-poor settings, with many assays available, but only one available in the U.S. HIV POC diagnostics demonstrate the best performance, with excellent assays available. There is a rapid assay for HSV lesion detection; but no POC serological assays are available. Despite the inadequacy of POC assays for treatable bacterial infections, application of technological advances offers the promise of advancing POC diagnostics for all sexually transmitted infections.