Culture microtitration: a sensitive method for quantifying Leishmania infantum in tissues of infected mice

We developed a microtitration method to determine the parasite burdens in homogenized organs of mice infected with Leishmania infantum. This method proved more sensitive than direct enumeration of amastigotes in stained organs, was appropriate for describing the kinetics of infection, and can be considered for physio-pathological or pharmaceutical experimental studies. Rodent models of visceral leishmaniasis have been used for experimental purposes for at least 6 decades (3). Assessment of parasite burdens is usually based on microscopic enumera-tion of amastigotes against host cell nuclei on tissue imprints (4). However, when parasites are confined to a few infected macrophages, optical quantification is not considered reliable (2). Thus, we adapted the sensitive microtitration method of Titus et al. (5) to develop a culture-based micromethod for quantification of parasite burdens in tissues of mice infected with Leishmania infantum, the species responsible for most Leishmania infections in AIDS patients (1)