Asymptomatic gay and bisexual men who use pre-exposure prophylaxis (PrEP) are twice as likely to have Mycoplasma (M.) genitalium infection than non-users, Sydney researchers say.

They also warn that high rates of macrolide-resistant mutations among men who have sex with men (MSM) could indicate that azithromycin is no longer an effective treatment option.

The cross-sectional study included 742 asymptomatic MSM (median age 31) who were tested for M. genitalium at the Sydney Sexual Health ­Centre in early 2017.

The bacterium was detected in 52 men (7%) and resistance was present in 75% of cases.