Continuing evolution of the pattern of quinolone resistance in Neisseria gonorrhoeae isolated in Sydney, Australia.

Multiple phenotypes of quinolone-resistant Neisseria gonorrhoeae isolated in Sydney since 1984 originated in Asia and increased in number and level of resistance in 1995. To study the origins, characteristics, and infection pattern of quinolone-resistant Neisseria gonorrhoeae in Sydney from 1995 to 1997 and to compare these results with prior findings. Quinolone minimal inhibitory concentrations, phenotype, and geographic source of quinolone-resistant Neisseria gonorrhoeae isolated in Sydney from 1995 to 1997 were analyzed. Two hundred nineteen episodes of infection with quinolone-resistant Neisseria gonorrhoeae from 2,236 gonococcal isolates occurred during 1995 through 1997. The rate of isolation of quinolone-resistant Neisseria gonorrhoeae increased significantly at the end of 1996 and was maintained through 1997. The increase resulted from sustained domestic transmission of a limited number of phenotypes in heterosexual patients. The pattern of isolation of quinolone-resistant Neisseria gonorrhoeae in Sydney changed from the sporadic isolation of multiple phenotypes of imported quinolone-resistant Neisseria gonorrhoeae to a higher rate of endemic disease caused by a few subtypes. Alterations in antibiotic treatment regimens in the affected patient group were required.