Abstract
Female sex workers (FSWs) aged ≥18 years without known HIV infection living in Tijuana and Ciudad Juarez, Mexico who had recent unprotected sex with clients underwent interviews and testing for chlamydia and gonorrhoea using nucleic acid amplification. Correlates of each infection were identified with logistic regression. Among 798 FSWs, prevalence of chlamydia and gonorrhoea was 13.0% and 6.4%, respectively. Factors independently associated with chlamydia were younger age, working in Tijuana versus Ciudad Juarez and recent methamphetamine injection. Factors independently associated with gonorrhoea were working in Tijuana versus Ciudad Juarez, using illegal drugs before or during sex, and having a recent male partner who injects drugs. Chlamydia and gonorrhoea infection were more closely associated with FSWs' drug use behaviours and that of their sexual partners than with sexual behaviours. Prevention should focus on subgroups of FSWs and their partners who use methamphetamine and who inject drugs.