STIs and HIV drug resistance

Nearer the present, a study from 2007 found that infection with acute STIs may increase the likelihood of drug-resistant HIV being transmitted.¹ The mechanism behind this may be that, because drug-resistant strains of HIV are less fit, they require especially favourable conditions – such as recent HSV-2 infection or genital ulceration – to cross from one person to another.

UK researchers looked at 185 cases of primary HIV infection (acquired during the preceding six months), culled from 604 new HIV diagnoses made between 2000 and 2005. These cases were nearly all in white gay and bisexual men.

Genotypic resistance testing was performed on blood samples from all individuals, and 28 (15%) were found to have resistance mutations. A variety of resistance patterns were identified, predominantly nucleoside reverse transcriptase inhibitor (NRTI) or non-nucleoside reverse transcriptase inhibitor (NNRTI) resistance (61% and 43% respectively); protease inhibitors (PI) and multi-class resistance were found in two cases (7%) each.

Two-thirds of the participants had been screened for STIs at HIV diagnosis or within the preceding three months, and one or more STIs were identified in 45% of those screened.

However, STIs were more than twice as prevalent in the group that had transmitted HIV drug resistance than in the group with wild-type HIV (68% versus 31%, p=.03). The most frequent STIs identified were non-specific urethritis (22%), gonorrhoea (17%), and chlamydia (10%). Syphilis, genital herpes and trichomoniasis were found in 2% or less and multiple STIs were diagnosed in 5%.

The investigators say: “[In] this cohort of predominantly MSM we have demonstrated that TDR is significantly associated with the presence of an acute STI. The high prevalence of STIs in those with recent HIV infection and their effect in increasing viral shedding strongly supports the need for routine STI screening in those newly diagnosed with HIV and the need for close cooperation between HIV and STI services.”