Molecular typing can reveal how gonorrhoea infections are spread.

Sexually transmitted infections (STIs) have shown an alarming resurgence in recent years. Control measures could be targeted more effectively if it were better understood how STIs are being spread. Recent research from a group at Imperial College London suggests that molecular typing of different strains of bacteria can identify groups of individuals within sexual networks (i.e. those infected with the same strain due to shared sexual partners). This could reveal important patterns in the spread of infection.

The group characterised more than 2000 isolates of Neisseria gonorrhoeae from patients at 13 STI clinics in London during a six-month period. They identified 21 major strains, each infecting between 20 and 124 individuals. Seven of these strains were predominantly seen in male homosexuals; the remaining 14 were predominantly from heterosexuals.

Interestingly, while there did not appear to be any behavioural or demographic factors linked to any of the strains seen in homosexual men, clear associations did turn up in the heterosexual population (e.g. some strains were seen mainly in people from particular age groups).

The high-throughput analysis of different strains used here can thus identify local networks of infection, and should allow new outbreaks to be identified and controlled. The results also suggest that particular strains tend to spread within either homosexual or heterosexual populations, but not usually between the two.

External links

• Choudhury B et al. Identification of individuals with gonorrhoea within sexual networks: a population-based study. Lancet 2006;368(9530):139–46.

Image: Neisseria gonorrhoeae bacteria, courtesy of M I Walker, Medical Photographic Library