Syphilis is a sexually transmitted disease caused by Treponema pallidum (T.p.) subsp. pallidum. Its global prevalence has crept upward since 2000, to circa 36 million cases at present, and over 11 million new infections annually. Over 90% of new syphilis cases occur in developing countries, but it is also a health concern in developed nations. The higher risk population are young people, men who have sex with men, and sex workers.

Current therapeutic options for syphilis are restricted to injected penicillin. Despite its high efficacy, penicillin is suboptimal for different reasons, notably its incapacity to penetrate the central nervous system (CNS) where T.p. pallidum can survive after administration of the antibiotic, the growing shortage in global production and supply, and the high prevalence (~10%) of self-reported penicillin allergy in the population.

These worrisome trends clearly suggest that current syphilis control measures are not sufficient to stem the spread of this infection.

Yaws is a poverty-related infectious disease caused by Treponema pallidum (T.p.) subsp. pertenue. It affects the skin and bones of children 1-15 years of age that can cause irreversible malformations resulting in a major physical and psychological burden. There are 100,000 new infections reported annually and more than 89 million people living at risk, in endemic regions of 15 countries in Africa and Asia-Pacific.

The WHO has already begun implementing a programme designed to eradicate the disease worldwide based on azithromycin, a safe, affordable, and easy-to-administer treatment. However, this eradication program is based on the Mass Drug Administration (MDA) of the drug, hence it is threatened by the risk of azithromycin resistance.

Our work to find new antibiotic combinations is timely to address this matter before it becomes an insurmountable obstacle.