Evaluating Biofilm Eradication Strategies

A systematic approach to assess biofilm eradication treatment strategies might include the following suggestions.

  • Develop an in vitro model that reasonably simulates the indwelling catheter biofilm with respect to substratum, properties of the growth medium, biofilm age and cell density, and presence of serum proteins, and that uses bloodstream isolates of clinically relevant organisms. Murga et al. (2001) and Curtin and Donlan (2006) can be consulted for examples of in vitro model systems for growing and testing biofilms on indwelling medical devices. The Drip Flow Reactor (Curtin and Donlan 2006) can be modified and used for growing and testing biofilms on the lumens of central venous catheters (Figs. 3, 4). Other screening approaches incorporating the MBEC Device (Ceri et al. 1999) or the CDC Biofilm Reactor (Donlan et al. 2004) can provide higher throughput testing but under less relevant conditions.
  • Validate results obtained in the in vitro model under more rigorous conditions by using either explanted biofilms (as done by Kite et al. 2004) and/or an animal model. Treatments that appear effective in in vitro models often do not show the same level of effectiveness in animal models, due to such complicating factors as the response of the host immune system and presence of serum proteins.
  • Ascertain that the treatment can be tolerated by the patient and is compatible with the normal-use regimen of the device.

Fig. 3 Modified Drip Flow Reactor

  1. 4 In vitro model system for growing and testing biofilms on central venous catheters. 1, Mixing plate; 2, bacterial inoculum; 3, sterile medium reservoir; 4, peristaltic pump; 5, Modified Drip Flow Reactor containing catheter sections; 6, waste reservoir. Bacterial inoculum is pumped through catheter sections for approximately 2 h to provide initial bacterial attachment, followed by continuous irrigation with sterile medium to allow biofilm growth
  2. 4 In vitro model system for growing and testing biofilms on central venous catheters. 1, Mixing plate; 2, bacterial inoculum; 3, sterile medium reservoir; 4, peristaltic pump; 5, Modified Drip Flow Reactor containing catheter sections; 6, waste reservoir. Bacterial inoculum is pumped through catheter sections for approximately 2 h to provide initial bacterial attachment, followed by continuous irrigation with sterile medium to allow biofilm growth

• Assure that catheter biofilms are recovered and quantified when conducting clinical studies to evaluate the treatment. Resolution of patient symptoms may not predict eradication of the biofilm from the catheter. Biofilm recovery and detection methods should also be validated (Donlan et al. 2001).

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