Implications of mycoplasma contamination in Plasmodium falciparum cultures and methods for its detection and eradication

Mycoplasma contamination of eukaryotic cell cultures is a common and widely recognised problem, estimated to affect 15–80% of all long term cell lines [1]. Infection with mycoplasmas can lead to a variety of effects such as impaired growth [2], chromosome abnormalities [3], enzyme inhibition [4], proteolytic degradation [5], B-lymphocyte proliferation [6], cytokine induction [7] and superantigen activity [8]. Mycoplasmas are small free-living prokaryotes lacking a cell wall, and they cannot be seen by routine staining procedures such as Giemsa-stained thin films. We have recently discovered that mycoplasmas can infect and survive in long term in vitro cultures of P. falciparum. Similar findings have recently been reported elsewhere [9]. Mycoplasma contamination was detected using a commercially available polymerase chain reaction (PCR) method (ATCC, Rockville, MD). Culture supernatants from overnight cultures of the P. falciparum clones R29, A4, C18I (derived in Oxford [10]) and 3D7 (gift of Professor David Walliker, University of Edinburgh, UK) were tested as described by the manufacturer. The R29 clone gave two PCR products (236 and 290 bp; Fig. 1(A)) indicating the presence of two species of mycoplasma. A4 and C18I gave a 290 bp product Abbre6iations: PCR, polymerase chain reaction; MRA, mycoplasma removal agent; TNF, tumour necrosis factor. * Corresponding author. Tel: +44 1865 222302; fax: +44 1865 222444; e-mail: arowe@worf.molbiol.ox.ac.uk