'Stealth' gonorrhoea on the rise

"Stealth" strains of gonorrhoea that fail to show up in tests are on the rise across the world, researchers have discovered, because the tests used by doctors to identify the bacteria look for an enzyme no longer present in those strains.

The rising prevalence of these strains was found in Australia, New Zealand, England, Scotland and Denmark. The findings should prompt clinics to change practice and use at least two tests that work in different ways to detect the infection, the scientists say.

The prolyliminopeptidase (PIP) enzyme was previously thought to be present in all strains of gonorrhoea and was therefore used in many diagnostic tests. However, mutations or deletions in the PIP gene that prevent the production of this enzyme had been identified in some strains. Gonorrhoea is known for its ability to mutate throughout its entire growth phase.

Magnus Unemo, a microbiologist at Orebro University Hospital, Sweden and colleagues examined a total of 41 samples lacking the PIP enzyme from patients in Australia, New Zealand and Scotland. The samples were obtained between 2001 and 2004.

To see how widespread this stealth strain is across the globe, they then compared these with samples from other studies in England and Denmark.

Widespread dissemination
All the samples from New Zealand and Scotland, and 83% of Australian samples, were indistinguishable or very similar to the English and Danish samples and had evolved from a single original strain. The data show "widespread dissemination" of the strain, the researchers say.

The strain was previously known to be circulating among homosexual men, but the new work suggests it has become a growing concern within the heterosexual population as well.

The strain did not appear resistant to the antibiotics typically used to treat gonorrhoea and all patients were given treatment.

Untreated gonorrhoea infections can cause severe and permanent health problems and can even be fatal. It can also cause infertility by harming the testicles or fallopian tubes. These risks mean it is "crucial that a rapid, highly sensitive and specific confirmation of N. gonorrhoeae is provided," the authors say.

LINK