Molecular tracking of infections by Leishmania infantum

Leishmania infantum is a major opportunistic parasite in patients with acqu ired immune deficiency syndrome and is very variable in these subjects. Iso enzyme characterization is not able to explain this variability, since half of the stocks isolated from patients co-infected with human immunodeficien cy virus and Leishmania belong to zymodeme MON-1. Amplification of L. infan tum minicircles by the polymerase chain reaction (PCR) and digestion of the amplified product to reveal, restriction fragment length polymorphisms (RF LP) has proved very useful in distinguishing between relapses and reinfecti ons in coinfected, treated patients. We have confirmed the existence of a l eishmaniasis outbreak among intravenous drug users in north-east Spain, pre viously detected by isoenzymatic analysis. We have documented persistence o f the same strain of Leishmania in 2 treated co-infected patients throughou t several years, regardless of the theoretical rapid evolution ascribed to kinetoplast deoxyribonucleic acid minicircle sequences. We suggest using th is PCR-RFLP technique to detect reinfections in treated co-infected subject s.