2009
Margaret Williams, PhD; Claressa Lucas, PhD;Tatiana Travis, BS

Under a moderately-high magnification of 5000X, this colorized scanning electron micrograph (SEM) depicted a large grouping of Gram-negative <i>Legionella pneumophila</i> bacteria. Please see PHIL 11092 through 11154 for additional SEMs of these organisms, specifically PHIL 11147 for a black and white version of this image. Of particular importance, is the presence of polar flagella, and pili, or long streamers, which due to their fragile nature, in some of these views seem to be dissociated from any of the bacteria.
 
You’ll note that a number of these bacteria seem to display an elongated-rod morphology. <i>L. pneumophila</i> are known to most frequently exhibit this configuration when grown in broth, however, they can also elongate when plate-grown cells age, as it was in this case, especially when they’ve been refrigerated. The usual <i>L. pneumophila</i> morphology consists of stout, “fat” bacilli, which is the case for the vast majority of the organisms depicted here. These bacteria originated on a 1 week-old culture plate (+/- 1 day), which had incubated a single colony, at 37<sup>?</sup>C upon a buffered charcoal yeast extract (BCYE) medium with no antibiotics.

Legionnaire’s disease is a type of pneumonia, caused by inhaling mist droplets containing legionella bacteria. Risks of illness increase in persons over the age of 50, in smokers, and individuals with weakened immune systems and can be severe enough to cause death in about 1 in 10 people.

Legionella bacteria exists naturally in water and moist soil but can become an issue in buildings through water main breaks, water temperature fluctuations, and inadequate levels of disinfectant. These conditions can promote the growth of Legionella bacteria and spread to devices such as hot water tanks, showerheads, and hot tubs. Outbreaks are often identified in connection with hospitals, care homes, and hotels, where potable hot water temperatures are moderated to avoid burns.

Because there are no vaccines that can prevent Legionnaires’ disease, maintenance of the building water supply in key in preventing Legionella growth and spread. Building owners and managers can reduce the risk of Legionella in their buildings by developing and implementing a water management program.

For further information on Legionella, visit the CDC at https://www.cdc.gov/legionella/index.html or sign up for our course “Legionella & Legionnaires Disease – Fundamentals for Facility Operations”.

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