Macrolide Resistance in Mycoplasma genitalium in Singapore

BACKGROUND: Mycoplasma genitalium was first reported as a cause of non-gonococcal urethritis in 1980. It has progressed from being an ‘emerging’ sexually transmitted infection (STI) to an accepted STI. Prevalence of infection has been reported as the Netherlands 4.5%, Sweden 6.3%, UK 1.2% and France 4%. M. genitalium has the smallest known bacterial genome and was the second bacterial genome fully sequenced. It has minimal requirements and is said to approach the minimum possible for a living cell. It is extremely fastidious; only a few strains have been cultured worldwide. Diagnosis relies on direct detection. It does not have a cell wall so it is not susceptible to antibiotics such as penicillins and cephalosporins. Therapy depends on fluoroquinolones and macrolides but resistance to macrolides has been widely reported: 13% France, 18% Sweden, 40% UK, Australia and Denmark, 100% Greenland, 30% Japan. METHODS: Ethics approval was granted. DNA extracts left over after routine clinical diagnostics at the Department of STI Control (DSC) Clinic, Kelantan Lane, Singapore were harvested. DNA had been extracted on a Cobas 4800 instrument (Roche) from urine and urethral swabs collected for testing for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG). A 2-plex real-time PCR assay targeting the pdhD and mgpB genes was used to screen for M. genitalium. Samples were deemed positive if both targets were detected. If only one target was detected, the sample was retested; if reactive in either target upon retest, the sample was considered positive for M. genitalium. Positive DNA preps were then screened for macrolide resistance mutations after Sanger sequencing of the 23S rRNA gene. RESULTS: 368 anonymised DNA elutes from 254 urines and 114 urethral swabs were collected between May and July 2016. One hundred eighty-four were CT/NG positive and 184 were CT/NG negative. Sixteen (4.3%) were positive for M. genitalium. Four (25%) of these 16 samples contained macrolide resistance associated mutations; A2058T (x2), A2058G (x1), and A2059G (x1). CONCLUSION: M. genitalium was detected in 4.3% of samples. Macrolide resistance mutations were detected in 25%, similar to international rates. Some guidelines recommend testing for resistance to guide therapy and to perform a test of cure. DISCLOSURES: All authors: No reported disclosures.