MCR-2 confers resistance to colistin, a `last-line' antibiotic against extensively resistant Gram-negative pathogens. It is a plasmid-encoded phosphoethanolamine transferase that is closely related to MCR-1. To understand the diversity in the MCR family, the 1.12 Å resolution crystal structure of the catalytic domain of MCR-2 was determined. Variable amino acids are located distant from both the di-zinc active site and the membrane-proximal face. The exceptionally high resolution will provide an accurate starting model for further mechanistic studies.

Introduction Sexuality is a complex topic in sociology and healthcare. It is multifactorial; combining gender, sex, sexual orientation and erotic desires. Three sexuality descriptors are commonly used: heterosexual, bisexual and homosexual. Women who have sex with women (WSW) and men who have sex with men (MSM) are classified as homosexual. These three descrip-tors are sometimes used in sexual health clinics in the UK as part of the coding to understand the demographics of service users. Aims We wished to review if these descriptors matched patients' described behaviours in an integrated sexual health clinic. Methods We reviewed 300 patients presenting to a UK sexual health clinic between April 2013 and September 2013. 100 patients were randomly chosen based on their sexuality descrip-tor, which had been self-selected when booking in. Electronic patient records were used to access patient histories. Stated sex-uality and sexual behaviour were compared. Results Out of the 300 patients selected, 88 were excluded, leaving 212 for analysis. 18.1% of patients described behaviour outside of the stated sexuality descriptor. 50.1% of the bisexual cohort, 1.8% of the heterosexual cohort and 3.5% of the homosexual cohort described behaviour different from the descriptor. Conclusion Our findings suggest that the current classifications of sexuality are inadequate to fully capture behaviours, although due to full sexual history taking clinical care is not compromised by this. Personal identity and choice of sexuality descriptors may bias epidemiological understanding of sexual behaviours if relying on these three traditional descriptors.

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