Stained smears as a source of DNA

Abstract

The molecular biological analysis of infectious agents requires the availability of a reliable source of microorganisms to be used to recover DNA. Clinical samples can be obtained directly from in-fected patients or can be propagated using in vitro or in vivo systems. However, not infrequently, the repeated sampling from patients is not possible because, among other reasons, the procedure is invasive or fastidious, the treatment has been initi-ated, the patients do not accept the repetition of the procedure or it is not possible to locate them again. Moreover, the in vitro culture of some mi-croorganisms is not possible (e.g. Plasmodium vivax) or requires weeks to months (e.g. Mycobac-terium tuberculosis). Neither do all laboratory set-tings have access to animal models for in vivo sys-tems. Several procedures for DNA extraction from stained specimens and paraffin-embedded tissues have recently been reported. These procedures have yielded DNA from microbial agents in blood stained smears containing P. vivax (RS Witzig, RH