Escherichia Coli: A Dangerous Bacterium or a Test Model?
With the recent reports of serious foodborne illnesses that are occurring throughout the country, and in a myriad of recent situations, the question of where exactly our food comes from, and how it can become contaminated by various agents, has had widespread coverage by the media. By taking the prevalence of food related diseases into consideration and combining this with the fact that a good friend of mine had been hospitalized from such a food related illness just last week, I couldn’t help but take a closer look into what exactly I have been eating and where my food was coming from. The main cause of the majority of the recently publicized sicknesses is a bacterium called Escherichia coli; or E. coli as it is commonly known. It is this bacterium that is responsible for the outbreak related to fresh spinach grown in fields in Salinas Valley, California, which sickened 199 people and killed 3 (2). In addition, it had also been linked to the current outbreak of illness associated with those who have eaten at Taco Bell restaurants, like my unfortunate friend. As the latest epidemic-like outbreak of E. coli has been garnering even more media attention, public fear has been rising about this potentially dangerous bacterium and information concerning it is pertinent.
Escherichia coli was first discovered by a German bacteriologist and pediatrician by the name of Theodor Escherich, in the year 1919 (2). Not only was the disease named after him, he also isolated and determined the majority of its properties. He found that E. coli is a bacterium that, more times then naught, resides in the intestines of most mammals (2). Of the hundreds of different types of E. coli that exist, there is only one that is able to sicken humans. Most strands are harmless to humans; in fact, there are between 100 billion and 10 trillion individual E. coli bacteria that are excreted through human feces everyday. However, the E. coli strain O157:H7, the strain that does negatively affect humans, produces a powerful poison or toxin. It is these toxins that are released into the body cavity, where the bacteria is not usually found, that triggers the illness in humans (5).
Although E. coli is present in most things, there are certain and specific ways in which humans may first become infected. The most common way is through food that has been contaminated with the bacteria. Most cases of the illness are associated with an individual eating undercooked ground beef or similar meat products (4). The bacteria can contaminate the meat during the slaughter process and is often accidentally mixed into the meat while it is being ground up. However, there are other ways in which a person can become infected. The bacterium can also be carried in water that has been contaminated. Thus, it can be found in raw vegetables that have been treated or washed in water where the bacteria is present and in lakes or rivers that have sewage in them (4). Because of this fact, swallowing water that has not been cleaned well should be avoided. Another source where it can be found is on cows utters, which is why drinking milk that has not been pasteurized is dangerous. In addition, it can also be spread by those who are already contaminated and who have not washed their hands thoroughly after going to the bathroom (4). Although a person has countless ways in which to become infected, there are a limited number of symptoms that one can experience. In addition, the E. coli bacteria invade all individual’s systems in the same matter.
When a person is contaminated with the bacteria, they do not immediately show symptoms of the illness. This is because there is an incubation period from anywhere between 3 and 9 days, during which is it possible to spread the bacteria. When a person is infected, the bacterium travels through their stomach and into their small intestines. Afterwards, it travels to the large intestine and attaches itself to the inside surface of the large intestine. Here, the toxins that are released by the bacteria cause the walls of the large intestine to become irritated and inflamed (2). Once the bacterium manifests itself within large intestines of a person, they then begin to experience the illness. The first of many symptom people usually experience is hemorrhagic colitis, which is sudden arrival of abdominal pain and cramping (1). These cramps are quite often very painful and abrupt. This primary symptom is then followed by diarrhea, usually within 24 hours of the onset of the abdominal pain. As time goes on, the diarrhea will become watery and bloody. Also, vomiting is another possible symptom, but there is rarely a fever associated with this illness. Unfortunately for the affected person, these symptoms will continue for the duration of the sickness, which is about a week, and there are no medicines or antibiotics that are available for their symptoms.
Those who have been infected will with E. coli usually fully recover within a week with no additional health problems related to the illness. However, 5%-10% of those who have been contaminated will experience more serious health problems that frequently continue for the rest of their lives. Children under the age of 5 and the elderly are at a particularly higher risk to this happening to them (5). One potential long-term health problem that E. coli infection can lead to is known as Hemolytic Uremic Syndrome (HUS). This complication was first recognized in 1955 and is now the most common cause of childhood kidney failure, over 90% of cases are attributed to this (5). This is a very complex, rare, and confusing side effect and there are still components that cannot be explained. Still, this disease can be characterized by three separate, distinct, and telltale features. They are the destruction of red blood cells, destruction of platelets, and acute renal failure (1). This leads to kidney failure of the patient and leads to serious, lifelong complications.
In order to prevent such problematic health issues which are associated with E. coli, one must take the necessary measures to prevent contamination. There are a number of different precautions that can and should be taken during an E. coli breakout. First and most importantly, all ground beef and hamburgers should be cooked thoroughly. It must be noted that while cooking ground meat, the beef can turn brown before all of the “disease-causing bacteria” are killed, so a digital thermometer is recommended (4). In addition, it is important to keep raw meat away from foods, especially those that are ready to be eaten. This way, cross contamination due to the mixing of foods may be prevented. Avoiding unpasteurized liquids and drinking water from only safe sources are also recommended (4).
Although the bacteria and its ensuing illness in humans is serious issue, especially concerning a person’s food and its contamination, there is another important issue that must be addressed. It concerns E. coli, its role in microbiology, the problems associated with it, and how they can be applied to other bacterium. While studying the different aspects of the E. coli bacterium, the property of bacterial conjugation was first discovered (2). This ability, which concerns bacteria in general, is the transference of genetic material, otherwise known as DNA, between different bacteria through cell-to-cell contact. This is also known as horizontal gene transfer (3). This ability to spread the particular genetic code and the bacteria could and does make the bacteria harder to deal with. This is because the particular strain of E. coli can mutate and, through bacterial conjugation, allow the new mutation to transfer through an entire population (3). Not only could this lead to more strains of the bacteria that could sicken humans, it also spreads traits of the bacteria that may not be beneficial to the person who is infected. Thus, if a particular strain is antibiotic resistant, this trait could spread through the population, making it more difficult for a person to be treated for and recover from the illness. Although this is not directly relevant to the E. coli bacterium, because it cannot be treated with antibiotics, the study of the E. coli bacterium does allow for a unique insight into bacterial conjugation. It would be feasible to experiment with the E. coli bacteria, which is easier and less dangerous to handle in lab situations then other bacterium, and apply and explore the discoveries with similar bacteria.
From the time of its discovery in 1919, Escherichia Coli has been an ever-changing and fascinating bacterium that has brought about almost as much knowledge about microbiology as it has illnesses. Regardless of the potential positive aspects that the testing of E. coli may have on the scientific community, the incessant dangers of it must not be overshadowed. The toxins and the associated illness caused by the E. coli bacteria produce a week of painful and dangerous symptoms that incessantly plague the patient. In addition, there are potentially serious, although rare, complications related to the illness caused by E. coli, all of which can last a lifetime. Proper knowledge of the methods of possible contamination and the ways in which contamination can be prevented are the main concern with regards to the E. coli bacterium.
1) "About E Coli: Your Source for E Coli Information." Marler Clark. <http://www.about-ecoli.com/page3.htm>.
2) "Bacterial Conjugation." Wikipedia: The Free Encyclopedia. <http://en.wikipedia.org/wiki/Bacterial_conjugation>.
3) "Escherichia Coli." Wikipedia, the Free Encyclopedia. <http://en.wikipedia.org/wiki/E_coli>.
4) “Frequently Asked Questions." Center for Disease Control. <http://www.cdc.gov/ncidod/diseaseinfo/escherichiacoli_g.htm>.
5) "Questions & Answered: Sickness Caused by E. Coli." Center for Disease Control. <http://www.cdc.gov/ecoli/qa_ecoli_sickness.htm>.