Mycoplasma genitalium, and the organisms we do not screen for

Mycoplasma genitalium, Mgen for short, was only identified in the 1980s, which makes it a newcomer in a field of ancient afflictions. It has spent the decades since quietly becoming common and, more worryingly, learning to resist the antibiotics we throw at it faster than almost anything else in sexual health. It has been called the next chlamydia, and the comparison is fair in more ways than one.

Why Mgen earns its place

Mgen is a genuine pathogen, not a passenger. It causes urethritis, the burning, stinging, discharge that makes men wince, and in women it can ascend and contribute to pelvic inflammatory disease, with the same painful, tube-scarring consequences as chlamydia. Like chlamydia it is often silent. What makes it modern, and genuinely worrying, is the resistance. This is not an infection you can rely on clearing with a quick course. A large share of Mgen is now resistant to the first-choice antibiotic, some cases need two different drugs in sequence, some need a test to guide which will even work, and a stubborn minority defeat several attempts and need specialist input. Treating it casually also helps breed the strains that beat the next drug. It is one of the harder infections in this whole field to be sure you have cured, which is exactly why it should be tested for and treated properly when there is a reason, not chased blindly.

The bugs that sell panels but rarely matter

Here is where the story turns to irony. Testing technology now lets a lab hunt for a long list of organisms from a single sample, and some commercial panels proudly test for everything they can find. Two names in particular, Ureaplasma and Mycoplasma hominis, turn up constantly, and a positive result reliably produces alarm, an urgent phone call, and a course of antibiotics. The inconvenient truth is that these two live harmlessly in the genital tract of a large proportion of perfectly healthy people. Finding them usually means nothing except that you looked. So the more organisms a panel triumphantly detects, the more anxiety and needless antibiotics it can generate for no benefit. This is the rare corner of medicine where testing for more is doing less.

We do not routinely screen for Ureaplasma or Mycoplasma hominis. Where there is a specific clinical reason we test and explain why; otherwise leaving them be is the careful choice, not the lazy one. A doctor deciding what is worth looking for is the whole value here.

The honest summary

Mycoplasma genitalium is a real and increasingly stubborn infection worth finding when there is a reason. Ureaplasma and Mycoplasma hominis are mostly harmless lodgers that panic people for a living. More tests is not more health; the right tests is.