GENETIC-CHARACTERIZATION OF PLASMID-ENCODED MULTIPLE ANTIBIOTIC-RESISTANCE IN A STRAIN OF LISTERIA-MONOCYTOGENES CAUSING ENDOCARDITIS

One susceptible and two multiply resistant isolates of Listeria monocy togenes from a patient suffering from prosthetic valve endocarditis ar e described. They could not be distinguished by several typing methods . Two isolates were resistant to chloramphenicol, macrolide/lincosamid e/streptogramin antibiotics and tetracycline. The resistance determina nts were located on a 39 kb plasmid pWDB100 that was transferable by f ilter mating to several gram-positive bacteria. Evidence was obtained to support the hypothesis that the resistant variant had primarily inf ected the patient's blood and prosthetic valve, and later lost the res istance plasmid. The three resistance determinants showed homology to other known markers, cat221/cat223, ermB and tetM, which are frequentl y found in different gram-positive genera. Plasmid pWDB100 showed exte nsive homology to the Streptococcus agalactiae broad-host-range plasmi d pIP501. It was also very similar to two listerial plasmids found in France. Thus, plasmid pWDB100 and the homologous plasmids from France, although isolated in geographically distant regions, may illustrate s pread of a plasmid and its relatives.