Examples of Germs

Henry G. Spratt, Jr., Ph.D.

Department of Biological and Environmental Sciences

University of Tennessee at Chattanooga

Henry-spratt@utc.edu

Introduction:

            Germs are all around us.  Humans are constantly encountering many different types of bacteria, viruses, and fungi that could be called germs.  Of the microbes we come across, some of them might be disease-causing pathogens, but many of them are harmless.  Whether or not you contract a disease as a result of one of these encounters depends on many factors.  Some people are naturally resistant to all but the worst pathogens.  Others might develop symptoms of disease by simply touching, breathing, drinking, or eating something contaminated with the germ.  With such variation in susceptibility to disease, avoidance of pathogens becomes the best option to remain healthy for most people.  The best way to avoid pathogens is to know something about the worst ones and to modify lifestyle choices that might lead to more encounters. 

            To help you learn to make life choices that will avoid contamination with some of the worst pathogens you will find a description of a selection of diseases that are commonly talked about.  In fact these diseases have the distinction of making the Centers for Disease Control and Prevention (CDC) web page “Top Requested Diseases & Conditions”, a statement of their significance.  Each of these diseases is known to cause humans much distress.  Please read about these diseases and be sure you learn how to avoid contact with the microbes.  These actions just might save you or a loved one’s life!

Name of Germ:  “Staph”

What is it and why is it special?

 “Staph” is a short term that refers to a genus of bacteria called Staphylococcus.  Within this genus are numerous species.  Probably the best known of these species is Staphylococcus aureus.  This species is known as the pathogenic species of Staphylococcus and is most often associated with the short-term name “Staph” when referring to a certain type of infection.

Where do we find it?

            We find Staphylococcus species in many different places.  Most commonly, these species are associated with the skin of an animal or human.  There are “good” (non-pathogenic) species of Staphylococcus found all over the human body.  These are most often associated with hair follicles and sweat glands.  Many humans can carry the potentially pathogenic Staphylococcus aureus species in their nostrils.

What does it do?

            If it’s the non-pathogenic species of Staphylococcus it basically does no harm.  If it’s Staphylococcus aureus and it has made its way into a cut or scratch on the skin, it can cause disease.  The intensity of this disease can vary based on the actual strain of Staphylococcus aureus involved.  Usually, the infection will be nothing more than a large pimple. In some cases the bacteria can make their way into the person’s circulatory system.  These “Staph” infections can be life or limb threatening unless drastic medical intervention occurs.  This intervention can include IV antibiotics or even surgery.  

Are they dangerous?

            In years past, before the advent of antibiotics, “Staph” infections that got into the circulatory system often lead to the death of the patient.  In fact, in many wars soldiers who were mildly wounded (often just scratched) frequently died of “Staph” infections.  Military applications of antibiotics during World War II and other modern wars changed the way we fight wars.  Interestingly, today, a new threat exists.  That is the existence of antibiotic resistant strains of Staphylococcus aureus (and many other species of bacteria).  A commonly know problem we face in many hospitals today is the MRSA “Staph” infection.  MRSA stands for Methicillin Resistant Staphylococcus aureus.  Methicillin is an antibiotic in the penicillin class that was the first class of antibiotics to effectively stop “Staph” infections.  MRSA is common to many hospitals, and frighteningly, now common to gyms, locker rooms, and other similar facilities.  There are currently only a few antibiotics that will kill the MRSA bacteria, and the bacteria are developing resistance to some of those antibiotics.  Hopefully, new antibiotics will be discovered that will help reduce the risk of infections by MRSA.  For now, a change of behavior through avoidance measures may prove to be our best defense.

How do you avoid Staph?

            One of the best ways to avoid infection by Staphylococcus aureus is to follow good personal hygiene.  Frequent hand washing or disinfection is a critical first step.  Since some of the most pathogenic strains of Staph have been found either in health care facilities or in gyms or locker rooms (e.g., MRSA), be especially careful around those areas.  If you are using a gym, follow the rules to clean the equipment and mats with disinfectant before and after using it.  If disinfectant is not provided, be sure to talk with the gym’s management to ask that it be made available, and ask them to explain their procedures to reduce potential infections.  After exercising be sure to thoroughly clean any parts of your body that touched exercise equipment or mats. Also attempt to avoid self-contamination by any contact between your nostrils, where pathogenic Staphylococcus aureus may be found, and your skin, or someone else’s skin.  Lastly, should you develop a pimple that seems to be larger than usual, and is possibly sore, watch it carefully.  Should you ever see swelling around the pimple and begin feeling ill (possibly running a fever) you should seek medical help and advice as soon as possible.  If caught early in the infection, antibiotics can control Staph.  However, in some cases, surgery may be required to limit potentially life-threatening outcomes.

Name of Germ:   E. coli

What is it and why is it special?

            The name E. coli is actually a shortened form of the actual name of a bacterium ordinarily found in the intestines of mammals.  The full name of this bacterium (its genus and species) is Escherichia coli.  In most cases the presence of E. coli in our intestines causes no harm.  In fact, having normal levels of this bacterium in our intestines actually help with digestion of some foods and provides us with some key vitamins.  Additionally, these harmless bacteria by outcompeting the pathogens help limit the ability of these pathogens to gain a foothold in our intestines.  Since this bacterium is found in the fecal matter of mammals, it is often used as an indicator of fecal contamination of water or food.  The presence of E. coli in water or food would indicate the possible presence of other pathogens that might also be present in feces (e.g., Salmonella).   A great deal of attention to E. coli in recent years has been due to a strain (E. coli 0157:H7) of the bacterium that may be found in the intestines of cattle and some other mammals, but is not usually found in humans.  It is estimated that some 2% to 3% of cattle in the U.S. carry pathogenic E. coli. Human infection by E. coli 0157:H7 may lead to symptoms of disease.  Another name for this pathogenic E. coli is the “Shiga toxin” producing strain, in reference to a toxin they produce that enhances their pathogenicity. This strain of E. coli in humans causes a disease because it has the ability to attach to the walls of human’s intestines, and also through the release of the Shiga toxin.  The usual, healthy strain of E. coli found in human intestines does not attach to the intestinal walls.  In some cases the impact of the Shiga toxin on the kidneys may lead to kidney failure.

 Where do we find it?

            Generally, outbreaks of pathogenic E. coli that make the news are associated with eating undercooked ground beef.  Some people have contracted this pathogen by drinking unpasteurized beverages or even eating some fresh vegetables.  The first widely publicized outbreak of this pathogen in the U.S. occurred in 1993 and was associated with people who ate hamburgers from a west coast fast food company.  There have also been outbreaks of pathogenic E. coli at water parks.  Generally, even though the number of cattle in the U.S. that carry pathogenic E. coli is relatively low, slaughterhouse contamination helps to spread the pathogen widely.  Additionally, areas where large numbers of livestock are kept in confined areas often have problems dealing with animal manure.  Should bacteria associated with the manure, including the pathogenic E. coli, make their way into water draining the livestock area, then this pathogen may become a waterborne problem.  Most often this water associated pathogenic E. coli has caused problems when that water is used to irrigate vegetables, especially those used directly (without being washed thoroughly) for salads. 

What does it do?

            Infection with the pathogenic strain of E. coli can cause bloody diarrhea, and in worst cases can cause a disease called hemolytic uremic syndrome that leads to kidney failure.  Although E. coli can infect anyone, those most susceptible are children under the age of five and the elderly.  In a normally healthy adult, symptoms of infection with pathogenic E. coli generally last from one to three days. If symptoms last longer than this, or if conditions worsen, the infected person might be susceptible to the

Are they dangerous?

            As noted above, many healthy adults may encounter pathogenic E. coli.  Most often these people will suffer a bout of diarrhea lasting from one to three days, and then completely recover.  Others, estimated at about 6% of those contracting this pathogen, may develop a bloody diarrhea.  These people usually recover with no lasting impact.  Those most susceptible to the worst infections tend to be young children or the elderly.  It is estimated that 5% to 10% of small children infected may progress to the condition where their kidneys are harmed by the Shiga toxin.  Of those children developing the worst symptoms, the mortality rate is approximately 5%.  Some of the survivors of the worst infections may require kidney dialysis or even kidney transplants.  Effective treatment of the disease is available, including the use of antibiotics and aggressive rehydration.  Worst-case infections will require hospitalization.

How would you avoid E. coil?

            Sadly, according to the U.S. Department of Agriculture, pathogenic E. coli has been found in nearly 90% of U.S. produced ground meats.  So, it is important that people know to thoroughly cook ground beef.  Basically, ground beef should be cooked until the internal temperature of a patty reaches 155 ^oF.  At this temperature the meat will no longer have a pink color, and any juices coming out of it will be clear.  If you are at a restaurant and receive a hamburger that is pink in the middle, do not eat it.  Let the restaurant managers know about this problem. You should also be very careful to thoroughly clean any kitchen surfaces that may have been contaminated by raw meat.  This includes washing your hands and any utensils used to prepare the meal (use hot, soapy water).  Also be sure to avoid placing properly cooked meat back onto platters or trays that may have been contaminated by the raw meat.  Lastly, it is important to be informed as to any local recalls of ground beef or announcements of vegetables that may have been contaminated by pathogenic E. coli.  As with most diseases, knowledge of the problem may allow you to take necessary avoidance measures to help keep you and your family healthy.