OPA-TYPING - A HIGH-RESOLUTION TOOL FOR STUDYING THE EPIDEMIOLOGY OF GONORRHEA

A single gonococcus possesses a family of 11 distinct and highly varia ble opa genes, The extensive variation and rapid evolution of the opa gene repertoire has been exploited to provide a high-resolution typing method for studies of the short-term transmission of gonorrhoea. The 11 opa genes are amplified with a single pair of primers by the polyme rase chain reaction, digested with frequently-cutting restriction enzy mes, and the fragments are fractionated on polyacrylamide to provide a n opa-type. The method appeared to be highly discriminatory as the opa -types of gonococci, isolated world-wide over the last 30 years, were all different. Opa-typing discriminated between isolates of the same a uxotype/serovar class. Similarly, there were 41 opa-types among 43 con secutive isolates from a sexually transmitted disease (STD) clinic. Th e two pairs of isolates from this clinic that gave the same opa-types were identical by other criteria and may have been from unsuspected se xual contacts, With one minor exception, identical opa-types were obta ined from gonococci recovered from known sexual contacts, These result s suggest that variation in the family of 11 opa genes evolves so rapi dly that the opa-types of gonococci are distinguishable, unless the is olates are from sexual contacts or a short chain of disease transmissi on. The identification of gonococci with identical opa-types is theref ore believed to be a good indicator that the individuals from which th ey were recovered were sexual partners, or part of a short chain of di sease transmission.