New Antibiotic for 'Superbug' Gonorrhea

Theresa Bebbington

August 07, 2017

Some types of the sexually transmitted infection known as gonorrhea have become resistant to several antibiotics – but laboratory research on a new drug is showing promise against this 'superbug'.

Without treatment, gonorrhea infection can lead to pelvic inflammatory disease and infertility in adults, and vision damage in babies when passed from the mother during childbirth.

The organism that causes gonorrhea, Neisseria gonorrheae, can adapt and build up resistance to treatment. The first antibiotic it managed to beat was penicillin, which had been curing gonorrhea infections for the first 70 years from when the medicine was first introduced.

Cases of gonorrhea resistant to the antibiotic azithromycin have occurred in England, with Public Health England (PHE) reporting 34 cases between November 2014 and April 2016. The cases have been confirmed in both heterosexual men and women, as well as in men who have sex with men. Although the strain of gonorrhea in that outbreak was treatable by a second antibiotic, ceftriaxone, resistance could build up to that drug, too.

The World Health Organisation (WHO) currently recommends a combination of both ceftriaxone, which is given by injection, and azithromycin, which is taken by mouth.

Antimicrobial resistance occurs when a strain of bacteria evolves to resist each consecutive treatment until no treatments are left, leaving these so-called 'superbugs' incurable. Some strains of N. gonorrheae are now currently untreatable due to the lack of alternative treatments. The first case of antibiotic-resistant gonorrhea was reported in Japan in 2011, and similar cases have since been found worldwide.

Potential of a New Antibiotic

Closthioamide, a new class of natural antibiotics discovered in 2010, might eventually offer an alternative for current drugs that are becoming less effective against gonorrhea. For the first time, researchers from Imperial College London and the London School of Hygiene and Tropical Medicine have tested closthioamide on gonorrhea samples in the laboratory.

The researchers used 149 samples of N. gonorrheae taken from hospital patients with infections in the throat, urethra, cervix and rectum. They found that very low amounts (equal to or less than 0.125mg/L) of closthioamide was effective against 146 of the 149 samples – and against all of the samples provided to them by WHO that were known to be resistant to other antibiotics. The results of the study are published in the journal Antimicrobial Agents and Chemotherapy.

This laboratory-based study is in an early stage of research. The drug has not yet been tested on animals and humans, but the researchers say the antibiotic shows tremendous promise and could be an exciting new step in the fight against gonorrhea. However, further research is necessary to assess the drug's safety and effectiveness, and it will be a number of years before closthioamide can be used in real-life human cases.

In reaction to the study, Dr Michael Brady, medical director at Terrence Higgins Trust, says: "We still have much to do to address the nation's poor sexual health and the rates of STIs [sexually transmitted infections] in those most at risk. This research is an important contribution to our efforts, as it raises the hope that this new antibiotic, closthioamide, may be a novel and effective treatment for gonorrhea.

"It is early days and further research is needed to demonstrate the same effect in people that is seen in the laboratory, but this signals an important new step in fighting the infection."

Prevention Is Key

Meanwhile, it remains important to try to prevent the spread of gonorrhea. According to statistics from the sexual health charity FPA ( Family Planning Association), there were 41,193 new cases of gonorrhea diagnosed in 2015, with men who have sex with men accounting for more than 55% of all gonorrhea diagnoses in 2015.

In his reaction, Dr Brady points out that between 2008 and 2015 gonorrhea rates in the UK rose by 175%. He says: "It is vital that we continue to educate people on how to protect themselves from STIs, including drug resistant gonorrhea, and encourage people to test regularly."

PHE recommends that people help protect themselves by using condoms. They should use them correctly and consistently with new or casual partners until all partners have a sexual health screen. People should avoid overlapping relationships and get screened regularly if they belong in a higher risk group, such as men who have sex with men.

Although symptoms in men usually develop within two weeks, some men and women don't have any symptoms.

In men, symptoms of gonorrhea noticeable in the penis include:

  • A yellowish, white or green discharge

  • A burning feeling, especially when urinating

  • Swelling of the foreskin

In women, gonorrhea in the vagina can cause:

  • A change in discharge

  • A burning feeling when urinating

  • Bleeding between periods

"In vitro susceptibility to closthioamide among clinical and reference strains of Neisseria gonorrheae", published in Antimicrobial Agents and Chemotherapy
Imperial College London news release
Terrence Higgins Trust emailed statement
FPA (Family Planning Association)