Chapter 36, Problem 4CHI

Legionella pneumophila is a bacterium that is often found in water systems (e.g., shower heads, air-cooling towers). The dispersal of these bacteria can lead to the development of Legionnaires’ disease, a particularly virulent pneumonia in the elderly and immunocompromised. Water systems are routinely monitored for L. pneumophila contamination using GVPC medium, which contains glycine and the antibiotics vancomycin, polymyxin B, and cyclohexamide. However, this method is known to underestimate the number of L. pneumophila cells in the environment. Flow cytometry (FC) is one approach to count cells. How would you go about determining if FC is a good way to monitor L. pneumophila in the environment? Specifically, how would you collect your samples and compare your results to those obtained by the currently accepted approach (i.e., plating on GVPC medium)? What controls would you need to perform? Based on this information, how do you think the results from FC would compare to those of GVPC cultures obtained from the same samples?

Read the original paper: Allegra, S. 2008. Use of flow cytometry to monitor Legionella viability. Appl. Environ. Microbiol. 74:7813.