Term Paper on "Bacteria Virus Eukaryote"

Term Paper 14 pages (3590 words) Sources: 1+

[EXCERPT] . . . .

Statistics and Part Maintenance

L. Jones

Infectious Bacteria, Viruses, Eukaryotes:

When one considers the possibilities of human disease, be it originating from a virus, bacteria, or even eukarote, it is important to first consider possible ports of entry. Most disease causing organisms prefer specific entry points to gain access to their hosts. These entry points are known as "ports of entry" that are particularly vulnerable to the offending organism. This means that whereas a particular virus, bacteria or parasite may be relatively harmless if it comes in contact with the skin, for example, may be extremely infectious should it gain entry into the mouth.

Indeed, the specialized preferences of many organisms with regard to ports of entry are so consistent that it is often taken as a hallmark of a particular organism in the diagnosis phase. This is especially important when one notes that the symptoms of characteristic of a specific infection usually give clear clues as to the point of entry. Although it is important to consider the point of entry when diagnosing the cause of illness in a patient, it can also be important for many aspects of disease prevention, especially when a high risk for a particular organism is present in one's environment. For example, if one knows that he or she is working in an environment where there is a high incidence of an airborne pathogen, steps can be taken (the wearing of masks the use of patient isolation procedures for example) to minimize possible exposures to that pathogen.

Typical portals of entry include the mouth, ears, eyes, urethra, nose and skin. Non-typical portals might include wounds, broken skin, insect bites, or even animal bites or stings. For example, the herpes virus can be acquired through the eyes and mucus membranes, parasitic amoebas can be introduced through the nose, and rabies can be acquired through the bite of an infected animal. Additionally, even the way in which an organism can gain entry into a particular portal can vary. For example, the mouth can act as an entry point for a pathogen that survives on surfaces or food and water, as a skin entry point should the mouth tissues be injured, or even as an entry point for organisms that survive in the air or in aerosol form.

Although in today's bioterrorism age, much emphasis is placed on the perils of airborne pathogens (anthrax, for example), one of the most likely sources of illness are contact-based. This is especially true of some of the most interesting (and potentially damaging) diseases are acquired through the mouth, and, by extension, passed on to the gastrointestinal system. Three of these include Escherichia coli or "E. Coli" (a bacteria), Hepatitis a (a virus), and Guardia lamblia (a eukaryote).

The Mouth and Gastrointestinal Tract:

Defense Mechanisms

Although many infectious organisms can enter trough the mouth, there are actually several "defense mechanisms" designed to prevent disease. First among these are the various microbes that normally "set up house" in the mouth. These are usually "symbiotic" in that their existence in the mouth both benefits the microbe, as well as the host (the human) in that their presence there prevents other organisms (many potential pathogens), from moving in (Hulbert, 1999). Further, the presence of saliva serves to continually flush microbes into the stomach (which can either help or harm matters).

The stomach itself also has very effective defense mechanisms, foremost among them the presence of stomach acid which kills many infectious microbes. Beneath the stomach, the small intestine also contains substances (digestive enzymes and bile) which serve to destroy many microbes as well. Additionally, the anaerobic atmosphere of the small intestine also functions to "kill off" oxygen dependent microbes quickly (Hulbert).

Even the last leg on the gastrointestinal tract, the large intestine acts to prevent infection through its protective mucus layer, which protects the cells lining the walls of the large intestinal tract. This is particularly remarkable when one considers that the end product arising out the large intestine (feces) weighs in at about %40% bacteria (Hulbert). Additionally, it is also in this area that one of the most obvious defense mechanisms against infection occurs, namely diarrhea. However, like the defense mechanism of the upper GI tract (vomiting), it must also be noted that without proper fluid and electrolyte maintenance, these defenses can actually do more harm than good to the patient. In severe cases, they can even lead to due to dehydration or heart problems.

The E. coli Bacteria

Escherichia coli are a dangerous cause of illness in humans. Although E. Coli resides within the intestines, and as such is normally not harmful to the human, some strains of the bacteria, particularly E. Coli O-157 can cause significant disease -- with an acute onset of acute bloody diarrhea and cramping that can resolve within one week, to a more severe reaction (typically in patients under five or elderly), including Hemolytic uremic syndrome -- a condition characterized by "acute renal failure, microangiopathic hemolytic anemia, fever, and thrombocytopenia with Diarrhea and upper respiratory infection are the most common precipitating factors" (eMedicine, 2004). Further, this more severe reaction to the bacteria can either result in the need for dialysis or transfusions, neurological impairment, loss of portions of the bowel, or even death.

E. Coli Taxonomy and Virulence:

The E. coli bacteria discussed here is Escherichia coli serotype O157:H7. It is a Gram negative, rod-shaped bacterium producing Shiga toxin (CDC, 2004). The specific action of this toxin works on the lining of the blood vessels, known as the vascular endothelium. More specifically:

The B. subunits of the toxin bind to a component of the cell membrane known as Gb3 and the complex enters the cell. When the protein is inside the cell, the a subunit interacts with the ribosomes to inactivate them. Like ricin a subunit, the a subunit of Shiga toxin is an N-glycosidase that modifies the RNA component of the ribosome to inactivate it and so bring a halt to protein synthesis leading to the death of the cell. The vascular endothelium has to continually renew itself, so this killing of cells leads to a breakdown of the lining and to hemorrhage. The first response is commonly a bloody diarrhea. (CBW, 2004)

Additionally, it is important to note that although the toxin is effective against the blood vessels in the digestive tract, kidney, and in some cases, the lungs, it does not effect the large blood vessels (arteries or major veins). Instead, the toxin seems to particularly target the "vascular endothelium of the glomerulus," which is "the filtering structure that is a key to the function of the kidney. Destroying these structures leads to kidney failure and the development hemolytic uremic syndrome" (CBW).

Treatment and Prevention:

Because there is no known antidote to toxin produced by the E. coli bacteria 0-157, the best course of action in care of the patient affected by its effects is supportive. This means that effort should be applied to the maintenance of fluid and electrolyte levels, and the support and monitoring of kidney function. However, if serious kidney involvement or bowel perforation occurs, many patients will require blood transfusions to replace lost red blood cells, treatment for severe anemia, as well as kidney dialysis or transplant. Of course, the best course of action is always preventing the infection to begin with. In the case of E. coli, the bacteria can be destroyed by steam treatment, bleach and reactive sterilants (including glutaraldehyde) (CBW).

The reservoir of the bacteria is widely agreed to be found in Cattle. Additionally, many assert that humans also may function as a reservoir for person to person transmission. Further, there seems to be evidence that deer in North America may also serve as a reservoir as well (DOH, 2002). Further, the bacterium is normally transmitted via the ingestion of contaminated food which is either undercooked, or that has come into contact with contaminated meat products or cattle feces. Although it is more rare, it is possible for the bacteria to be transmitted person to person (as a result of bad hand washing practices), and it can be transmitted via water (DOH).

Hepatitis a Hepatitis a is one of the most common forms of viral Hepatitis in the world. Of particular prevalence in Asia, South America, and parts of Africa, Hepatitis a is growing in incidence within the United States due to travel and immigration. Further, many consider the reason that the virus is becoming more common is due to the fact that immunization is voluntary, and that food handlers often neglect to wash their hands before preparing food. Additionally, although many consider the virus to be low on the danger scale, many die each year as a result of liver complications resulting from the effects of the virus -- particularly the very young, or the very old.

Taxonomy

Unlike illness resulting from E. coli bacteria, the illness arising from Hepatitis a infection results from a virus. Specifically, Hepatitis a is known as an enteric virus. It… READ MORE

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