Award Date

May 2019

Degree Type


Degree Name

Master of Public Health (MPH)


Environmental and Occupational Health

First Committee Member

Patricia Cruz

Second Committee Member

Mark Buttner

Third Committee Member

Brian Labus

Fourth Committee Member

Eric Wert

Fifth Committee Member

Robert A. Schill

Number of Pages



Legionella pneumophila can cause pneumonic and non-pneumonic disease in humans. Infections occur from aerosolized contaminated water. This bacterium is an opportunistic intracellular pathogen able to infect both protozoans, such as Acanthamoeba polyphaga, and human macrophages. Both L. pneumophila and A. polyphaga resist commonly used water treatments, such as chlorination, but L. pneumophila has displayed greater resistance in the presence of A. polyphaga. Therefore, there is concern that L. pneumophila could become established in plumbing systems after water treatment, leading to infections. The objective of this study was to show the effect of chlorine and chlorine dioxide exposures on the survival of A. polyphaga internalized L. pneumophila. Gentamicin was used to kill extracellular L. pneumophila and samples were exposed to the oxidants, then the reactions were quenched and incubated at 30°C. The concentration of L. pneumophila was determined by culture analysis following lysis of Acanthamoeba on days 0, 7, and 14. Chlorine achieved ~1 log reduction at a concentration of 56.7 mg.min/L and ~2 log reduction at 376.3 mg.min/L. Chlorine dioxide achieved ~1 log reduction at a concentration of 74.21 mg.min/L and ~2 log reduction at 249.4 mg.min/L. All but one ClO2 concentration tested showed increasing log reduction throughout the 14-day monitoring period. This project addresses a concern of water treatment facilities and public health officials regarding the survival of intracellular Legionella. The results of this study show the need for greater understanding of other microorganisms’ impact on Legionella control and will be useful to water treatment in determining oxidant levels needed for ensuring that potable water does not pose a delayed threat to the public.



File Format


Degree Grantor

University of Nevada, Las Vegas




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Microbiology Commons