Month: April 2019

So, like I said in the first post, the mystery and history behind this microorganism is the reason why I chose to research and blog about it. Here is what I found out! Legionella pneumophila was first discovered in 1976 after a mystery outbreak among 221 individuals attending a convention in Philadelphia—all staying at the Bellevue-Stratford Hotel (Denenea, J., 2018). The major symptom consistent in each individual who fell victim to the outbreak was pneumonia; an infection of the lungs. Symptoms of pneumonia include high fever, chest pain, difficulty breathing, and coughing (Denenea, J., 2018). Symptoms began to appear as soon as one day after the outbreak occurred, but by the time it was no longer spreading, there were 34 casualties (Denenea, J., 2018).

 

So, after making sure everyone was safe and healthy, it was imperative for scientists to figure out the root of the problem. During this time, people thought it was a hoax, poisoning, extra-terrestrial attack, and plenty of other reasons, but scientists ruled out all of the rumors including swine flu. It took them six entire months, but the CDC eventually found Legionellato be the cause of the epidemic after investigation and experimentation. It was found that the Legionellawas being spread through the hotels air conditioning system; it is not spread via person-to-person contact. With this newly discovered bacterium, scientists could now look back and figure out the reason for many similar, unexplained outbreaks in previous years; unfortunately, it had to be at the cost of one of the most lethal outbreaks of the 20^thcentury (Denenea, J., 2018). Legionella outbreaks were then found to be the source of outbreaks from, 1965, 1968, 1973, 1974, 1975, and 1976 from places all around the world (Denenea, J., 2018). This epidemic was then named by the CDC as Legionnaires’ disease in 1977. Since then, there have still been cases of Legionnaires’ disease, but not nearly as often or as lethal. Today, antibiotics are available to treat infection, and places like hospitals, hotels, cooling towers, etc. have been informed on which measures to take to avoid the outbreaks from occurring. Mystery solved!

If you have time, and are interested, here is an entire documentary telling the story of how this little microorganism caused one of the greatest epidemics in American history!

References:

Denenea, J. (2018, August 13). The History of Legionnaires Disease Cases and Outbreaks. Retrieved from https://thelegionnaireslawyer.com/history-legionnaires-disease/

And we’re back! This time with more information and more pictures, this time pertaining to the growth of this bacteria which we know as Legionella pneumophila. As stated in the last post, this is a rod shaped, gram-negative bacteria. It does not form spores, and it is oxygenated. We also discussed how it can grow up to 20 micrometers in length. But in what conditions do these bacteria grow? Optimally, they grow at 36 degrees Celsius, and under these temperatures they can generate/grow within 99 minutes (Botzenhart, K., et al, 1996). Also, they optimally grow in fresh water and soil alongside other bacteria (Botzenhart, K., et al, 1996). To grow, they also require iron salts and L-cysteine (Botzenhart, K., et al, 1996). Legionella pneumophila is characterized as a heterotrophic bacterium, meaning that it obtains its nutrients from other organic forms of matter. Legionella reproduce both intracellularly and extracellularly through the process of binary fission. If you are not familiar, binary fission is a process in which a body of a bacterium divides into two; this is a form of asexual reproduction. Surprisingly, this bacterium has no insanely different forms of reproduction, this is as textbook as it gets! Here is a diagram of how it works below:

References:

Botzenhart, K., Bartram, J., Butler, J., Havelaar, A., Lee, J., Mariee, T., . . . Yu, V. (1996). Legionella. Water Sanitation Health.

So, last week, we did not dive into much detail about this microbe – Legionella pneumophila. It’s never any fun to read or learn about something when you have no clue what it looks like, so let’s discuss. Below, is a picture of the microbe, to start off.

Legionella pneumophila is a rod-shaped, Gram-negative bacteria that is relatively thin/small in size; only ranging from 2-20 micrometers (Winn WC Jr., 1996). Legionella posses both membranes, typical of Gram-negative bacteria. The inner membranes contain antigens such as peptidoglycan, proteins and lipopolysaccharides. The outer membrane (the envelope) contains majority enzymes (Shevchuk, Jäger, Steinert, 2011). This bacteria uses its envelope to provide structure, signaling, and interact with its surrounding environment (Shevchuk, Jäger, Steinert, 2011). Proteins, carbohydrates, and lipids serve structural roles in the bacterial envelope (Shevchuk, Jäger, Steinert, 2011). For purposes of locomotion, this bacteria has both pili and flagellum (Winn WC Jr., 1996). In the Legionella genus, there are 39 known species. 

Structurally, Legionella pneumophila is not very complex and also isn’t very different from other bacteria. Next time, we will dive a little deeper into how this bacteria works, but until then enjoy this short video giving another visual of Legionella pneumophila.

 

References:

Shevchuk, O., Jäger, J., & Steinert, M. (2011). Virulence properties of the legionella pneumophila cell envelope. Frontiers in microbiology, 2, 74. doi:10.3389/fmicb.2011.00074

Winn WC Jr. Legionella. In: Baron S, editor. Medical Microbiology. 4th edition. Galveston (TX): University of Texas Medical Branch at Galveston; 1996. Chapter 40. Available from: https://www.ncbi.nlm.nih.gov/books/NBK7619/

Over my [very uneventful] spring break, I had the pleasure of visiting the CDC museum here in Atlanta, GA. After going through the super intense security, I finally made it inside and began exploring the many exhibits that the museum had to offer. There were so many exhibits that I had no idea where to begin; I ended up spending almost two hours there because each exhibit really intrigued me. One of the last exhibits I came across, however, was the exhibit based on a “mystery illness” which was later discovered to be caused by Legionella pneumophilia. Anyone who knows me knows I love a good mystery, so I decided to choose this one so I could later read more into the situation which we will get deeper into in future posts. Until then, below are some pictures taken during my visit to the museum (which I plan on returning to ASAP)!