The fever could have developed in two ways. First, the influenza virus could have produced exogenous pyrogens that are readily absorbable by the brain blood barrier. Second, Peters immune system produced various molecules like cytokines and interferons in response to the viral infection. Cytokines and interferons are endogenous pyrogens because they are produced by systems present inside the body. Both the exogenous and endogenous pyrogens reach the hypothalamus. The hypothalamus is the temperature center of the brain, and it responds to these pyrogens by activating several peripheral thermo-responsive organs. For example, the smooth muscles of the endothelium contract resulting in vasoconstriction. Vasoconstriction reduces blood flow to the skin thus reducing heat loss through the skin. In addition, the hypothalamus activates skeletal muscle contraction thereby generating heat through shivering. Fever plays a key role in recovery from an infection. The first role of fever is deactivation of pathogens. Some pathogens are only active at the physiological temperature. When the bodys temperature increases, the replication and toxin release of pathogens decreases greatly. The second role of fever is enhancement of immune cellular movement. This enables quick and efficient response of immune cells to pathogenic infection.
Given that influenza is caused by a virus, why was Peter prescribed an antibiotic? The doctor prescribed phenoxymethylpenicillin. Discuss the mode of action of phenoxymethylpenicillin. Explain why antibiotics are not effective against viruses.
Influenza is caused by Influenza A or B virus from the myxoviridae family. This virus infects the upper respiratory tract. Viral changes in the upper respiratory tract predispose one to bacterial infections of the lower and upper respiratory tract. The most common bacteria that infect the respiratory tract are Streptococcus pneumoniae, Haemophilus influenza and Staphylococcus aureus. However, other bacteria that cause atypical pneumonia like Legionella and Listeria can opportunistically infect a person suffering from an influenza infection. In other words, there is a high likelihood of bacterial co-infection or secondary infection as a result of influenza. The doctor was therefore right to administer an antibiotic to Peter to cater for any bacterial infection. Additionally, the yellow-white exudate covering his throat is normally a sign of bacterial infection as neutrophils respond in number after a bacterial infection.
Phenoxymethylpenicillin is a penicillin derivative. Penicillin was the first antibiotic to be discovered in 1928. Penicillin is a beta lactam, meaning that its chemical structure is a four sided molecule with an amide group and oxygen attached to the ring by a double bond. All beta lactam antibiotics have this basic structure. Phenoxymethylpencilin, also called penicillin V, has the basic penicillin ring plus phenoxy and methyl groups added to its basic structure. Penicillin V is effective against most gram positive bacteria and can be given orally. Gram positive bacteria have a cell wall that is made of a peptidoglycan. This peptidoglycan is formed through polymerization of sugar molecules and amino acids. Penicillin V inhibits this polymerization, thus rendering the bacteria unable to replicate and colonize a particular body organ
Antibiotics have various modes of action that are targeted to counter the replicative actions of the bacteria. Some antibiotics like macrolides, beta lactams and anti-metabolites target different organelles of a bacterial cell. The structure of the virus is different from that of the bacteria, viruses being simpler in structure than bacteria. Essentially, the infection and subsequent replication of viruses are totally different from those of bacteria. Bacteria are extracellular while viruses are intracellular. Therefore, its impossible to target a virus using a drug that is designed for extracellular micro-organisms.
Describe two (2) possible ways that Peter could have contracted the influenza virus (modes of transmission). Identify two (2) ways by which the modes of transmission could be broken.
There are two modes by which influenza may be transmitted. The first method involves direct transmission from one person to another. This may happen when an infected person coughs, sneezes or talks, releasing droplets of saliva that contain the influenza virus. The influenza virus gets into the upper respiratory tract of another individual through inhalation or passively from the effect of sneezing. The virus lodges at the epithelial cells lining the respiratory tract to initiate an infection. The other method of transmission is indirect. A person may acquire influenza virus through fomites or other objects that have come into contact with an infected person. For example, an infected person may cough or sneeze on his hands. Then, they use the hands to hold an object like a door knob or a supermarket trolley handle. When an uninfected person holds the contaminated surfaces and eats without taking any hygienic measure like washing the hands, the second person may get infected. The direct transmission may be broken by covering ones nose when sneezing or coughing. The indirect mode can be broken by hand washing with soap and clean water for both the infected and uninfected person.
Describe the physiological basis of the three (3) signs and symptoms of Peters throat. Relate your response to this case study.
Coughing is an important physiological mechanism used by the body to clear infection of any foreign substances lodged in the respiratory tract. The coughing reflex during a viral infection of the upper respiratory tract is accentuated as compared to the one under non-infectious conditions. Active release of mucus, cytokines and other neurotransmitters during an infection activates the cough receptors in the trachea and pharynx. The afferent nerves transmit this impulse through the vagus nerve to the cough centers in the brainstem. The cough center then coordinates a series of muscles in the abdomen and chest cavity to affect a cough through the efferent nerves of the vagal bundle and laryngeal nerves. The diaphragm is the most important muscle in the cough reflex. The diaphragm contracts and creates a negative pressure in the chest cavity. Air rushes in from the lungs to occupy this partial vacuum. The larynx intermittently closes, and the abdominal, intercostal and diaphragm muscles relax to create a high air pressure in the lungs. The larynx opens up and releases this high pressure air to the outside.
Influenza is an infection of the upper respiratory tract. Comparatively, the upper respiratory tract is not as fatal when infected as the lower respiratory tract. An infection that spreads to the lungs is likely to be fatal, and the body must respond in every way to prevent such spread. During infection, the goblet cells lining the upper respiratory tract produce excessive mucus to prevent the spread of the virus to the lung to prevent further infection. This massive production of the mucus presents as a runny nose.
Lymphadenopathy is the enlargement of lymph nodes around the neck. The lymph nodes are anatomically modified to screen for any pathogens present in the lymph. Lymph is an ultra-filtrate of the blood and is likely to contain pathogens that have found their way into the blood stream. The lymph node contains many immunological cells including the macrophages and B cells. The influenza virus during Peters infection found their way into the lymph nodes and prompted an increase in macrophages and B-cell in an attempt to deactivate the virus.
Compare and contrast the processes by which viruses and bacteria replicate
Replication in bacteria is through binary fusion. Two bacterial daughter cells emerge from a single bacterial cell through the process of mitosis. Replication starts at the nuclear material and later to the other cell organelles. On the other hand, replication of the virus involves only the nuclear material since the virus has no organelles. Replication in bacteria uses the bacterias own enzymes while replication in viruses may uses the virus own enzymes or use the replication enzymes of the host. The DNA of bacteria is circular and therefore replication involves two replication forks while DNA viruses have only one replication fork. There is reverse transcription in viral replication in case of RNA viruses, while this feature is not there in bacterial replication. Despite these differences in replication, both viruses and bacteria result in more copies of the organism than before. Additionally, replication in both microorganisms uses enzymes to catalyze the replication process.
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