Decreased biocide susceptibility of adherent Legionella pneumophila

J Appl Bacteriol. 1991 Dec;71(6):531-8. doi: 10.1111/j.1365-2672.1991.tb03828.x.


In a study of the in vitro effectiveness of biocides against Legionella pneumophila, some aspects of the cooling tower environment were replicated in the laboratory, paying particular attention to water hardness and pH. Pieces of Douglas fir and polyvinyl chloride were colonized in a recirculating system and the comparative efficacy of two biocides (Bronopol and Kathon) against the sessile and planktonic populations was examined. While the biocides were relatively effective against the planktonic L. pneumophila population over a short period of time (minimum 9-12 h), substantially longer periods of time (maximum greater than 48 h) were required to reduce the number of cultivable bacteria to below detectable levels in the adherent population. The results indicate that failure to monitor the sessile population of L. pneumophila in laboratory studies of biocides may result in the use of incorrect dosages and/or contact times in field trials with apparently reduced in situ efficacy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Bacterial Adhesion
  • Disinfectants / pharmacology
  • Environmental Microbiology
  • Legionella pneumophila / drug effects*
  • Legionella pneumophila / ultrastructure
  • Microscopy, Electron, Scanning
  • Polyvinyl Chloride
  • Propylene Glycols / pharmacology*
  • Thiazoles / pharmacology*
  • Wood


  • Anti-Bacterial Agents
  • Disinfectants
  • Propylene Glycols
  • Thiazoles
  • 2-methyl-4-isothiazolin-3-one
  • bronopol
  • Polyvinyl Chloride
  • 5-chloro-2-methyl-4-isothiazolin-3-one