I - GENETIC-HETEROGENEITY IN PNEUMOCYSTIS-CARINII - AN INTRODUCTION

Molecular techniques have played an important role in demonstrating a high level of heterogeneity among the different types of organisms whi ch are collectively known as Pneumocystis carinii. Genetic heterogenei ty has been observed in Pneumocystis organisms isolated from different host species, suggesting that Pneumocystis infection is host-species specific. On the basis of this generic divergence a provisional trinom ial nomenclature has been adopted, in which different types of Pneumoc ystis organisms are designated a 'special form'. Multiple special form s of Pneumocystis have been detected in some host species, for example in infected rat and ferret lungs, but not in human lungs. Lower level s of genetic heterogeneity have been observed within each Pneumocystis special form, and in particular in human-derived Pneumocystis. Analys is of the genetic heterogeneity of populations of Pneumocystis is cont ributing to the understanding of the epidemiology and pathophysiology of this infection. (C) 1998 Federation of European Microbiological Soc ieties. Published by Elsevier Science B.V. All rights reserved.