Nosocomial HIV-transmission in an outpatient clinic detected by epidemiological and phylogenetic analyses

variable immunodeficiency, and with no known risk factors for HIV-infection, could be due to horizontal nosocomial transmission. Methods: For determination of time of transmission stored serum-samples from GP were analysed for HIV RNA content. Patient records were used to identify patients, who had received intravenous therapy on the same day as GP. Samples from GP and these possible source patients were identified and phylogenetic analyses of the env, gag and RT-encoding region of pol were performed. Furthermore, routines in conjunction with intravenous therapy were examined. Results: We identified a patient (FDL) harbouring virus almost indistinguishable from the virus isolated from GP. The pairwise nucleotide distance between the C2-V3-C3 region of the env and gag sequences from the two patients were 1.9 and 0.9% respectively. In addition, GP harboured HIV RNA with a foscarnet resistance mutation further lending support to virus from the foscarnet-treated FDL being the source of the infection. Interestingly, CP experienced increases in immunoglobulin production after contracting the HIV-infection, and decreases after antiretroviral-induced viral suppression. a clinical procedure which, under stressful conditions, could lead to breaches in infection control measures was identified. The source of the infection was most likely a contaminated multidose vial. Conclusion: Through epidemiological and phylogenetic analyses a case of horizontal nosocomial HIV-transmission was disclosed. Identification of multidose vials as possible vehicles for horizontal nosocomial transmission recently led to the recommendation of restriction of the use of multidose vials, a recommendation supported by the present study. The study underlies the importance of a constant survey of infection control precautions. (C) 1999 Lippincott Williams & Wilkins.