Listeria monocytogenes - A Bacterium With an Attitude
Jennifer McCann

I am Listeria monocytogenes.  First, I will provide you with my physical description, then you will learn where I live and how I affect you
I am a rod shaped bacterium, with flagella which allow me to move around in my environment.  Scientists have also described me as a Gram positive, facultative aerobe.  The characteristic I am most proud of is my resistance to freezing, drying, and heating, despite the fact that I don't form spores (boy does this amaze scientists!).  I grow best at 4 degrees Celsius, or 39.2 degrees Fahrenheit, which means I can grow and multiply very well in a refrigerator.  I am found living in soil and water, and I may even be an inhabitant of your intestines.

I only live in 1 to 10% of the population, so your chances of having me are slim.  For those of you in that group, don't worry, you will never know I am there.  You tend to be healthy people, and your body just goes about it's business while I go about mine.

Scientists have labeled me a pathogen, but that is such a harsh term.  They call me this because I may cause a disease, Listeriosis, once I become an inhabitant of certain people.  I like to go for the easy targets: pregnant women and their fetuses, cancer patients, the elderly, and persons who are immunocompromised.  These people don't put up much of a fight when I am trying to move in, so I always go for them.  Once inside, I mover through their body, infecting various areas.  I have also been lucky enough to be the cause of some epidemics, where many people were infected with me by eating a certain food product.

How do I get to you?  As I have told you, I live in the water and soil.  From there, I can easily become associated with vegetables, other plants, and animals.  Then, all you have to do is eat one of these products.  Through digestion, you also ingest me.  Once inside, I like to get into your macrophages.  Before I can get into those cells, I must induce a series of elevations of intracellular calcium level in your cytoplasm, using listeriolysin O and two phospholipases.  Once inside, I multiply and have easy access to other parts of your body via your bloodstream.  After I am in my new home, your body reacts and shows signs such as fever, muscle aches, and sometimes gastrointestinal symptoms like nausea and diarrhea.  Should I make it to your nervous system, I may cause headaches, stiff neck, confusion, loss of balance, convulsions, or menigitis.  Scientist have not yet figured out how many of me it takes to cause these problems in people; let's just say that this information is on a need to know basis and they don't need to know.  However, they have figured out ways to kill me after people realize that I am the source of their ailments.  It seems that your average antibiotic helps fight against me, because some of my relatives were killed in a war against penicillin.

So, now I guess you want to know how to avoid me.  Well, it's really not that hard.  Simply make sure you wash raw foods well and cook food as instructed.  As I told you before, I grow well in your refrigerator, so be sure to watch expiration dates, keep items sealed tightly, keep uncooked meats and raw food separate from cooked and ready to eat foods, and wash all utensils and trays after each use.  Also, the government and food industries have taken measures to keep me from contaminating foods before they get to your house.  (I can't believe I just told you all of that!)

Now that you know what I look like, where I live, and how I can affect you, it is up to you to protect yourself.

Works Cited

Bad Bug Book.  March 11, 1999.

Preventing Foodborne Illness: Listeriosis. March 1, 1999.

What is Listeria monocytogenes?   March 1, 1999.

Goldfine, Dr. Howard.  Research Summary. March 11, 1999.

*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.


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