DETECTION OF CYTOTOXIC ACTIVITY ON VERO CELLS IN CLINICAL ISOLATES OFSERRATIA-MARCESCENS

Cytotoxin production was studied in 60 Serratia marcescens strains iso lated from hospitalized patients. Association of cytotoxic activity wi th serotype, source of isolation and presence of plasmids was also eva luated. Thirteen of the 60 S. marcescens strains produced a cytotoxic effect on Vero cells. These strains were isolated from distinct clinic al sources and classified into seven different serotypes (01:H7; 04:NM ; 010:NT; 019:NM; 06,14:H4; 06,14:NM and 06,14:H1). No relationship wa s observed between cytotoxic activity and clinical source or serotypes of the strains. Plasmids from five cytotoxin-producing S. marcescens strains were transferred to E. coli K12/711. The transconjugants did n ot exhibit cytotoxicity, indicating that the cytotoxic effect is not p lasmid-mediated among these strains. Although a cytotoxic activity was demonstrated in filtrates of some S. marcescens strains, further stud ies should be performed to assess the role of this toxin in pathogenes is.