The diversity of the opa gene in gonococcal isolates from men who have sex with men.
OBJECTIVE
To use a molecular typing method (opa-typing) to characterise gonococcal isolates obtained from men who have sex with men (MSM) attending a genitourinary medicine (GUM) clinic in Edinburgh during 2001. To compare the results of opa-typing with A/S (auxotype/serovar) phenotyping, and with epidemiological information obtained by contact tracing.


METHODS
Isolates were opa-typed by a PCR-RFLP method where the restriction fragments resulting from digestion with three separate restriction enzymes were resolved by polyacrylamide gel electrophoresis. Isolates were considered to have the same opa-type if the band patterns were identical or if they differed by one band between the three digestions.


RESULTS
40 opa-types were detected from a collection of 73 gonococcal isolates from 61 patients. 26 opa-types were unique, being found in one individual each, 14 different opa-types were found in more than one patient. Opa-typing was found to have a discrimination index (DI) of 0.96, compared to a DI of 0.87 for A/S phenotyping, indicating that opa-typing is better at discriminating between unrelated isolates. Opa-typing confirmed three epidemiological links established by contact tracing, and uncovered a further 13 clusters of isolates.


CONCLUSIONS
Opa-typing is a more discriminative method than A/S phenotyping when determining relatedness in gonococcal isolates. The ability of opa-typing to identify sexual networks not disclosed by contact tracing and conventional phenotyping make it a useful method for studying the spread of gonorrhoea with the potential to contribute to the control of this infection.
Howie
F
F
Scottish Neisseria gonorrhoeae Reference Laboratory, Department of Laboratory Medicine, Edinburgh Royal Infirmary, 51 Little France Crescent, Edinburgh EH16 4SA, Scotland, UK.
Young
H
H
McMillan
A
A
D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000302:isolation & purification; D015373:Bacterial Typing Techniques; D006069:Gonorrhea / Q000382:microbiology*; D018451:Homosexuality, Male; D006801:Humans; D008297:Male; D009344:Neisseria gonorrhoeae / Q000235:genetics*; D010641:Phenotype; D016133:Polymerase Chain Reaction / Q000379:methods; D012150:Polymorphism, Restriction Fragment Length
D001425:Bacterial Outer Membrane Proteins; C090348:Opa protein, Neisseria