TYPING OF NOSOCOMIAL STRAINS OF SERRATIA-MARCESCENS - COMPARISON OF RESTRICTION ENZYME CLEAVED GENOMIC DNA FRAGMENT (PFGE) ANALYSIS WITH BACTERIOCIN TYPING, BIOCHEMICAL PROFILES AND SEROTYPING

Eighty-eight selected clincial isolates of Serratia marcescens, repres enting 27 putative outbreaks of nosocomial cross-infection encountered during 1980-1995, were tested comparatively by bacteriocin typing, ca rbon source assimilation tests, serotyping (O and H antigens), and res triction pattern (RFLP) analysis of restriction cleaved (SpeI, XbaI) g enomic DNA fragments after pulsed-field gel electrophoresis (PFGE). Se rotyping served as the ''gold standard'' of the phenotypic methods. On e pseudo-outbreak (bacteriocin typing incriminated type 26) was uncove red through serotyping as well as the biochemical profile and confirme d by PFGE analysis of genomic DNA. Bacteriocin typing and determinatio n of biochemical profiles disclosed several instances of phenotypic va riation; serotyping revealed two episodes of shifts from motility (H12 ) to nonmotility. Resolution of restricted genomic DNA fragments with the PFGE procedure permitted detection of 27 PFGE patterns (A-M, N-1-N -3, O-1, O-2, P-1-P-3, Q-1-Q-3, R-1-R-3, S-1, and T). Based on the ana lysis of PFGE patterns against the background of epidemiological data, the number of nosocomically significant strains of S. marcescens coul d be reduced to 16 (PFGE patterns A-M, N-2, O-1, P-2, and T). It was c oncluded that PFGE analysis of restricted genomic DNA of S. marcescens was superior to the three phenotypic methods.