Human immunodeficiency virus infection and syphilis among homeless people in a large city of Central-Western Brazil: prevalence, risk factors, human immunodeficiency virus-1 genetic diversity, and drug resistance mutations.

Homeless people are at high risk for sexually transmitted infections (STIs), such as human immunodeficiency virus (HIV) infection and syphilis. We investigated the epidemiology of HIV-1 infection and syphilis among homeless individuals in a large city in Central-Western Brazil. In this cross-sectional study, we interviewed and tested 355 individuals from September 2014 to August 2015. Rapid test samples positive for syphilis were retested using the Venereal Disease Research Laboratory (VDRL) test. Blood samples from HIV-infected participants were collected for POL sequencing using HIV-1 RNA extracted from plasma, reverse transcription, and nested polymerase chain reaction. Anti-HIV-1-positive samples were subtyped by sequencing the nucleotides of HIV-1 protease and part of the HIV-1 reverse transcriptase genes. Transmitted and acquired drug resistance mutations and susceptibility to antiretroviral drugs were also analyzed. Anti-HIV was positive in 14 patients (3.9%; 95% confidence interval [CI]: 2.3-6.4). HIV-1 RNA was detected in 8 of the 14 samples. Two of the eight (25%) isolates showed HIV-1 drug resistance mutations. Furthermore, 78 (22%; 95% CI: 17.9-26.5) and 29 (8.2%; 95% CI: 5.6-11.4) homeless individuals tested positive for syphilis using the rapid test and VDRL test, respectively. Two individuals were anti-HIV-1 and VDRL test positive. Daily alcohol use (adjusted odds ratio [AOR]: 3.2, 95% CI: 1.0-10.4), sex with people living with HIV (PLWH) infection (AOR: 6.8, 95% CI: 1.9-25.0), and sex with people of the same sex (AOR: 5.4, 95% CI: 1.7-17.5) were predictors of HIV infection. Age ≤35 years (AOR: 3.8, 95% CI: 1.4-10.8), previous syphilis testing (AOR: 3.5, 95% CI: 1.4-8.4), history of genital lesions (AOR: 4.9, 95% CI: 1.3-19.1), and crack use in the last six months (AOR: 3.1, 95% CI: 1.3-7.6) were predictors of syphilis. Our findings highlight the importance of STI prevention and control strategies among the homeless.