Identification of individuals with gonorrhoea within sexual networks: a population-based study.
BACKGROUND
Molecular typing of Neisseria gonorrhoeae and contact tracing provide a combined approach for analysis of sexual networks in metropolitan areas, although there are some difficulties in application. Our aim was to examine the application of high-throughput molecular approaches that can identify individuals in linked sexual networks.


METHODS
We characterised 2045 isolates of N gonorrhoeae from patients presenting at 13 major sexually transmitted infection clinics in London, UK, between June 1 and Nov 30, 2004. All isolates were assigned a sequence type (strain) on the basis of the sequences of internal fragments of two highly polymorphic loci, por and tbpB. These types were matched to demographic and behavioural data obtained at the clinic for each patient. We assessed the congruence in the demographic and behavioural characteristics of individuals infected with the same strain.


RESULTS
We identified 21 prevalent strains in this diverse gonococcal population, each infecting between 20 and 124 individuals. Seven of these strains were predominantly from men who have sex with men; the remaining 14 were predominantly from heterosexual people. No differences were recorded between the strains associated with men who have sex with men in the demographic or behavioural characteristics of infected individuals. By contrast, significant differences in age (p<0.0001), ethnicity (p=0.001), proportion of women (p=0.01), and HIV status (p=0.03) were noted between the 14 prevalent heterosexual-associated strains. Heterosexuals with strains not shared by others in the sample were significantly older (p=0.0005) and more likely to have had sex outside the UK (p<0.0001) than those sharing a strain with at least one other.


CONCLUSIONS
The discriminatory high throughput strain characterisation method applied here identified localised transmission networks and suggests little bridging between networks of men who have sex with men and heterosexual networks.
Choudhury
Bhudipa
B
Department of Infectious Disease Epidemiology, Imperial College London, London, UK.
Risley
Claire L
CL
Ghani
Azra C
AC
Bishop
Cynthia J
CJ
Ward
Helen
H
Fenton
Kevin A
KA
Ison
Catherine A
CA
Spratt
Brian G
BG
D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006069:Gonorrhea / Q000453:epidemiology* / Q000235:genetics / Q000635:transmission; D018451:Homosexuality, Male; D006801:Humans; D008131:London / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D017720:Molecular Epidemiology / Q000379:methods*; D009344:Neisseria gonorrhoeae / Q000145:classification / Q000302:isolation & purification*; D011159:Population Surveillance / Q000379:methods*; D015995:Prevalence; D012725:Sexual Behavior