Oral antibiotic eye infection tablet may be effective medicine for a treatment-resistant sex bug

Reviewed by Emily Henderson, B.Sc.Jan 31 2023

An oral antibiotic tablet used to treat common eye infections may prove an effective medicine for a sexually transmitted bug that has become resistant to usual recommended treatment, suggest doctors in the journal Sexually Transmitted Infections.

They successfully treated a young man with Mycoplasma genitalium (non-gonococcal) urethritis with chloramphenicol.

Data from the UK Health Security Agency suggest rising antimicrobial resistance to first and second choice drugs used to treat this infection, while there's currently no strong evidence for third choice options, say the authors.

They describe a case of a young man with recurrent non-gonococcal urethritis symptoms, a common sexually transmitted infection caused by Mycoplasma genitalium that has become increasingly difficult to treat with currently recommended antibiotics.

The young man initially turned up at the clinic with 2-day old symptoms, a fortnight after having unprotected sex with a casual partner.

He was initially treated with a week's course of doxycycline, pending test results to identify the exact bacterial cause of his infection.

The results showed that he was infected with M genitalium and he was then prescribed another antibiotic, azithromycin. Once the lab analysis revealed that it was a treatment resistant strain, he was then given a third antibiotic, moxifloxacin.

But 5 days after completing all the courses of antibiotics, he still had symptoms. After considering other options, which were dismissed due to cost, availability, or licensing issues, the authors decided to try chloramphenicol: 1g tablet taken four times a day for 14 days.

Their decision was prompted by test tube evidence showing that chloramphenicol stopped M genitalium in its tracks and the ready availability of the drug.

After 14 days of treatment, the young man's symptoms had cleared up and lab tests confirmed that he no longer had urethritis.

This is just one case, and the findings should be taken in that context. But point out the authors: "When considering what to choose after first- and second-line treatment failure, there is a lack of novel agents readily available in the UK, and a paucity of data to underpin recommendations."

Chloramphenicol is generally well tolerated, with the serious side effects rare (1 in 30,000), they highlight. And in the absence of viable effective alternatives, it merits further investigation, they suggest.

"Options for third-line therapies in treatment-resistant M genitalium are urgently required. Chloramphenicol may have an application in this scenario, and should be considered as a possible drug for investigation," they conclude.