Repeated epidemics caused by extended-spectrum beta-lactamase-producing Serratia marcescens strains

Eur J Clin Microbiol Infect Dis. 1998 Sep;17(9):629-36. doi: 10.1007/BF01708345.


An outbreak of Serratia marcescens involving 42 patients admitted to the general intensive care unit of the Hospital of Varese, Italy, occurred from March 1994 to August 1995. The causative strains were resistant to oxyimino-cephalosporins and monobactams due to their production of an extended-spectrum beta-lactamase. Another outbreak caused by Serratia marcescens strains had occurred in the same unit a few months earlier, from February to October 1993, with the strains involved producing a novel TEM-derived extended-spectrum beta-lactamase. In order to verify whether there were any relationships between isolates from the two epidemics, the strains and their enzymes were characterized. Biochemical data and gene amplification experiments showed that the isolates of the second outbreak harbored a non-conjugative plasmid of approximately 48 kb, codifying for the production of an SHV-derived extended-spectrum beta-lactamase with pI 8.2. Restriction fragment length polymorphism analysis of total genomic DNA by pulsed-field gel electrophoresis of Serratia marcescens isolates unambiguously identified two different bacterial clones responsible for the two epidemics. Epidemiological and microbiological investigations demonstrated the long persistence of Serratia marcescens strains and their circulation in other hospital wards, thus suggesting their possible role as a long-term reservoir for further epidemic spread.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cross Infection / epidemiology*
  • Cross Infection / microbiology
  • Disease Outbreaks*
  • Drug Resistance, Microbial
  • Humans
  • Intensive Care Units
  • Isoelectric Point
  • Italy / epidemiology
  • Microbial Sensitivity Tests
  • Plasmids
  • Polymerase Chain Reaction
  • Polymorphism, Restriction Fragment Length
  • Serratia Infections / epidemiology*
  • Serratia Infections / microbiology
  • Serratia marcescens / drug effects
  • Serratia marcescens / enzymology*
  • Serratia marcescens / genetics
  • Serratia marcescens / isolation & purification
  • beta-Lactamases / biosynthesis*
  • beta-Lactamases / chemistry
  • beta-Lactamases / genetics
  • beta-Lactamases / metabolism


  • beta-Lactamases