A rare case of female-to-female sexual transmission of HIV is reported in the online edition of the journal Clinical Infectious Diseases, due to be published on Feb. 1, 2003, according to a report on Aidsmap.com.

Doctors suggest that the 20-year-old woman from Philadelphia, US, may have been infected by her bisexual female HIV-positive partner through sharing sex toys after drug resistance tests found striking similarities between the genotypes of both women.

The 20-year-old woman, who had a negative HIV test result six months earlier, had been in a monogamous lesbian relationship for the past two years, and denied having had any other sexual partners of either sex. She has no tattoos or body piercing.

The woman had never received blood products or injected drugs. A medical examination also found that she was in good health with no evidence of injecting drug use, or nasal damage from cocaine snorting. The woman also had good oral health, which physicians took to mean that oral transmission could be ruled out.

The report stated that the couple's sexual practices included the sharing of sex toys, and oral sex and had occasionally used sex toys vigorously enough to draw blood except during menstruation.

The investigators note that this is the "first reported case of female-to-female sexual transmission of HIV supported by identification of similar HIV genotypes in the source patient and the recipient."

They conclude that whilst reports of woman-to-woman sexual transmission of HIV are scarce, lesbians in HIV-discordant relationships should be advised regarding safer sexual practices.

The 20 year old woman was infected with multi-drug resistant HIV, which carried the following mutations: T215Y (associated with resistance to AZT, d4T and abacavir), D30N (associated with resistance to nelfinavir), K103N (associated with resistance to NNRTIs), L63P (a polymorphism), V77I (also a polymorphism), and M41L (associated with resistance to AZT and d4T, and with resistance to other NRTIs in the presence of T215Y). Her partner's genotype carried mutations at each of these points, plus M184V (associated with resistance to 3TC).