1. Identify the causative fungus of either a fungal eye infection or Pneumocysti
ID: 79638 • Letter: 1
Question
1. Identify the causative fungus of either a fungal eye infection or Pneumocystis pneumonia. Then: (a) Describe how the causative fungus infects the body. (b) Describe how the disease manifests as an illness (i.e., symptoms) and whether it can be lethal or not. If not lethal, describe how it harms the body. (c) Explain how the disease is typically treated and any drug(s) used. (d) Briefly describe how the drug(s) affect the fungal disease agent.
2. List five benefits that lichens provide to Earth ecosystems. Then explain how they do so by providing an example of each.
Explanation / Answer
1) The causative organism in Pneumocystis pneumonia (PCP) is Pneumocystis jirovecii.
a) P. jirovecii is an opportunistic pathogen. It is not found in normal immunocompetent individuals. It is generally found in individuals with weakened immune system such as those taking steroids, organ transplant individuals taking immunosupressent medications, people taking anticancer drugs and those affected by HIV/AIDS.
b) PCP manifests as fever, non-productive cough, shortness of breath on exertion, weight loss, and night sweats. The disease itself is not lethal. The disease attacks the interstitial tissue of the lungs, with marked thickening of the alveolar septa leading to significant hypoxia. Oxygen is not able to diffuse into the blood, leading to hypoxia. Hypoxia, along with high arterial carbon dioxide levels, stimulates hyper-ventilatory effort, causing dyspnea.
c) Co-trimoxazole is the most commonly used drug in the treatment of PCP. Other drugs like pentamidine and atovaquone are also used sometimes. Steroids are used as an adjunct therapy.
d) Co-trimoxazole contains sulphamethoxazole and trimethoprim. Both inhibit successive steps in the folate synthesis pathway. Sulphamethoxazole competes with p-aminobenzoic acid (PABA) for the enzyme dihydropteroate synthase and trimethoprim blocks the enzyme dihydrofolate reductase.
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