Cultures on NNN medium for the diagnosis of leishmaniasis

Cutaneous and visceral leishmaniasis (VL, CL) represent the most frequent vector-borne diseases in Tunisia. Their biological confirmation is necessary before the administration of restricting, expensive and toxic specific treatments. Retrospective evaluation of the contribution of Leishmania cultures on NNN medium in leishmaniasis diagnosis have been done using the data of 375 cultures concerning 214 CL cases and 125 VL cases consecutively recruited in Pasteur Institute of Tunisia between 1995 and 2007. The global sensitivity of the culture in the course of CL was of 68.2%. It was significantly higher during zoonotic CL (78.8%) compared to that during sporadic CL (54.9%); p<0.001. This difference is explained by the easier thrust in NNN medium of Leishmania (L.) major, the agent of zoonotic CL than that of L. infantum, particularly its zymodeme MON-24, agent of sporadic CL. In the course of VL, and in spite of the better sensitivity of bone marrow aspirates (BMA) culture (70.8%), the blood buffy-coat, which permit to avoid the trauma induced by BM aspiration gave promising results (58.2%), the difference being not significant. Besides, in the course of both CL and VL, the direct examination of smears is revealed more sensitive, respectively 89.7% and 93.4% (p<0.01 and p<0.01). Although, systematic cultures practise, in parallel with direct examination, is recommended. In fact, in addition of straightening out some diagnosis, 22 cases in our series, the culture provide the isolation and the isoenzymatic identification of the causative species and strains allowing a better comprehend of parasite life cycles and a disposing of important epidemiological data for suitable control measures. As known with all cultures, those of Leishmania are also exposed to the contamination problem, which reached 5.9% in our study. In conformity with previsions, the contamination concerned much more cutaneous samples (8.4%) than blood or BM ones (2.5%; p=0.015).