Misdiagnosis of Piscirickettsia salmonis antigens in mycoplasma infected cell lines

Salmonid Rickettsial Septicaemia (SRS), caused by Piscirickettsia salmonis, is a serious and emerging bacterial pathogen of salmonids. It is therefore important to accurately and rapidly diagnose this disease in order to enac t prophylactic or eradicative strategies. Recently, P. salmonis infected fi sh cell lines were reported to display typical, Gram negative, lipopolysacc harides (S.R. Jones et al., 1998. Dis. Aquat. Organ. 33: 25-31). Here we de monstrate that such diagnostic patterns are erroneously derived from mycopl asma infected fish cell lines, typically producing lipoglycans and nor lipo polysaccharides. These results also emphasize that important precautionary measures be taken to ensure that mycoplasma-free cell lines are used for vi ruses or intracellular pathogens destined for vaccines.