OCCURRENCE OF PLASMIDS IN PATHOGENIC STRAINS OF NOCARDIA

The purpose of the present study was to determine the relative distrib ution of plasmids in 87 clinical isolates of Nocardia, belonging to th e five major pathogenic species, A correlation between plasmid content and the site of infection within the host, resistance to antibiotics and enzymic profiles was procedure of Kado and Liu was used, Electroph oretic analysis plasmid bands, ranging in size from <8 to >50 kb, in 2 7 strains (31%), Based on the number of isolates tested, the incidence of plasmid-bearing strains was significantly higher among N. farcinic a than N. asteroides strains, Within N. farcinica, the incidence of pl asmids was higher among strains isolated in the Paris area than in str ains isolated elsewhere, such as in the French provinces or outside Fr ance, A statistically significant correlation was demonstrated between the cutaneous localisation of infections and the incidence of plasmid -bearing strains, The presence of plasmids in nocardiae could not be a ssociated with specific phenotypic traits such as resistance to antibi otics or enzymic activity. The fact that the majority of Nocardia clin ical isolates (60 of 87) did not contain plasmids suggests that plasmi ds are not involved directly in virulence and that there is no selecti ve pressure for plasmid acquisition.