A Look At How Meningitis Works Biology Essay


Bacteria are ubiquitous organisms meaning they can be found anywhere. They are incredibly resilient organisms capable of handing the most mundane to the most extreme environments. Examples of this can be seen in the abyssal waters of the ocean where "bacteria are thriving in waters whose temperatures are so high that other organisms would instantaneously melt from the temperature." (Madigan et al, 2006). This ubiquitous trait that all bacteria have enables them to be extremely pathogenic and hazardous to human health. The purpose of this research paper is to accurately describe the bacterial form of meningitis and its effects in humans. This will be done by describing the function and composition of the meninges as well as identifying the cause of Meningococcal meningitis and how the infection is spread. In addition, this paper will determine which areas in the human brain are most affected by Meningococcal meningitis and what effects or symptoms are seen as a direct result of the brain damage. Finally, it will cover treatment options and will also show how the infection could possibly spread out of the meninges and what the implications of the spreading would infer.

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The human brain is wrapped in tissue called the meninges; its purpose is to protect the brain and spinal cord from the outside world. The meninges has three layers, the Dura mater, which helps keep the brain from moving around, the Arachnoid which contains blood vessels that clean and filter liquid around the brain and finally the Pia mater, which fits snugly around the whole brain only being penetrated by blood vessels which deliver the much needed glucose and oxygen to the brain.

Infection and the resulting inflammation of the meninges is commonly known as meningitis. A number of variables cause meningitis, ranging from a skull fracture, which may create an opening between the nasal sinuses and the subarachnoid space, allowing different organisms to infect the area, to viruses which are surprisingly less harmful infections. However, the most lethal result from any initial cause is a bacterial infection. The most fatal form of bacterial meningitis is called Meningococcal meningitis, "which is caused by the Neisseria meningitidis (N. meningitidis) bacterium" (CDC). Meningococcal meningitis spreads from person to person via saliva, sneezing, coughing, handshakes, and general close contact.

Interestingly, N. meningitidis "can only survive in humans, as its iron requirements are too high for any other animal to sustain them" (WHO). N. meningitidis normally inhabits the nose and upper respiratory system of some people without causing any problems. On some occasion, N. meningitidis infects the brain without a clear and identifiable reason; in other cases, infection develops because the immune system is weakened by either a previous illness or by a drug that may suppresses it.

The most common route to brain damage from Meningococcal meningitis occurs when, the blood brain barrier (BBB), which is the separation of blood that's circulating throughout the body and the cerebral spinal fluid which occupies the space in and around areas of the brain, comes under attack from N. meningitidis. Because of this, the entire brain can be directly affected by Meningococcal meningitis as a direct result of its characteristic swelling of the meninges. This swelling may cause lobes of the brain to shift, and if those lobes are shifted to a point where they can be "pressed through one of the small natural openings in the tissues that separate the brain into compartments, a life-threatening disorder called brain-herniation results" (Merck & Co).

The exact mechanism of brain damage comes from the response of the immune system to a potential pathogen. When the immune system identifies a threat, it will "stimulate the release of cytokines to recruit more immune cells and stimulate other tissues to participate in the immune response" (Kalat, 2007). As a direct result of this action, the BBB starts becoming more permeable leading to a cerebral edema, a building up of fluids in and around brain cells, forming and coupled with the white blood cells entering the cerebral spinal fluid via the circulatory system, the meninges start to become infected and therefore inflamed.

The first signs of meningococcal meningitis manifest themselves as high fever and sensitivity to light, coupled with neck stiffness and headaches. "Purple rashes or bruises will appear on the skin as the capillaries start to leak blood" (CDC). As the infection works its way deeper into the brain, these symptoms will soon be followed by projectile vomiting, indicating some inflammation or damage to the medulla, general disorientation and confusion, showing signs of damage to the "Orbitofrontal cortex (OFC) which is located in the frontal lobes in the brain" (Kalat, 2007).

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Bacterial meningitis can be treated with a number of antibiotics, including intravenous penicillin for a continuous 7 - 10 days. It is extremely important that treatment be started early in the course of the disease. "Appropriate antibiotic treatment of most common types of bacterial meningitis should reduce the risk of dying from meningitis to below 15%, although the risk is higher among the elderly" (CDC).

If you are lucky enough to survive the bacterial infection, after effects could still present themselves. Memory loss or lack of concentration is very common and would result from the intracranial pressure on the hippocampus, whose primary function is "long-term memory storage and spatial awareness" (Kalat, 2007). Additional common after effects are: deafness, hearing problems, loss of balance and tinnitus. All of which can be attributed to damage to the temporal lobe, again as a result from the increased intracranial pressure. In rare occasions, loss of vision has been known to occur, which indicative of occipital lobe damage, from yet again damage is caused by the swelling of the meninges.

Unfortunately, most people diagnosed with meningococcal meningitis are living in the "belt of sub-Saharan Africa, stretching from Senegal in the west to Ethiopia in the east" (WHO). Because of their location, the availability of treatment centers is highly limited; survival is rarely an option as the infection spreads through what was once the protective covering of the brain, eating away at the blood brain barrier that keeps toxins out of the brain. While the localized infection is serious and highly damaging in the brain itself, "when meningococcal meningitis enters the bloodstream, the infection puts all of the body's organs at risk, this disorder is called Meningococcemia" (WHO).

As a result of meningococcemia, spatially random blood clots will start forming thereby increasing blood pressure in the veins, arteries, and capillaries, inevitably causing them to rupture which leads to; tissues deterioration and rapid bleeding occurring under the skin and in the digestive tract. In addition to these mounting serious maladies, "bleeding can occur within the adrenal glands" (CDC), whose primary functions include releasing hormones in an attempt to control stress and inflammation. The loss of blood to the adrenal glands causes them to shutdown. The continued surmounting breakdown of the body leads to damaged blood cells seeping back into the brain thereby clogging the blood vessels. The resulting brain damage will cause shock, a life-threatening situation in which the blood pressure is too low to sustain life, as the brain no longer has control over the blood flow in the body. When the brain finally shuts down from this continuous massive assault, so will the patient, death will occur soon after.