Biofilms: when are bacteria really dead?

Last month, CSJ examined the problem of contaminated hospital water systems and described how control of biofilms harbouring pathogenic micro-organisms lies at the heart of the latest guidelines on prevention of waterborne hospitalacquired infections.1,2,3 This risk management approach to microbiological safety of water is based on identification of potential microbiological hazards and includes very specific schedules for microbiological testing. But what if the very basis of this microbiological testing, along with some of the control methods outlined in the guidelines, is called into question?

Compelling evidence from ongoing research in Germany now indicates that the tried and tested method used to assess water quality does not necessarily reflect the true picture of bacterial contamination of water. What could that mean for the control of these organisms?

Speaking at a recent one-day conference on the prevention of waterborne infections, Professor Hans- Curt Flemming, director of the Biofilm Centre at the University of Duisburg- Essen, illustrated how bacteria can survive in a dormant state that cannot be detected by the ‘gold standard’ method, which relies on culturing ‘growing’ bacteria. He also outlined how some of the standard control strategies such as copper piping, commonly considered to be ‘antibacterial’, may induce this ‘sleep’ from which the cells can be revived. He concluded: “The presence of pathogens is being underestimated.”