Microbiology

Microbiology Study Guide

Chapter 5: Biology of Infectious Diseases

Objectives 1. Describe the causes, symptoms, and treatment of diseases, including the those that effect the respiratory tract, gastrointestinal tract, and urogenital tract. 2. Differentiate between disease features of skin and wound diseases, blood diseases, nosocomial diseases, and Acquired Immunodeficiency Syndrome (AIDS). 5.1 Respiratory Tract Diseases Microorganisms cause a number of diseases in the respiratory system of humans. Organs that are affected by microorganisms are the nose, sinuses, pharynx, and middle part of the ear. However, there are some organs that resist the formation of infections and diseases, like ciliated hairs and mucous membranes; still, infections are likely to occur, as these organs are highly exposed to the external environment. Other internal organs of the respiratory system that are likely to be affected include respiratory tubes and the alveoli of the lungs. These organs are not exposed to the external environment but organisms are likely to affect them since these organs constitute excessive moisture and nutrients. Bacterial Diseases Tuberculosis The acid-fast bacterium rod mycobacterium tuberculosis is responsible for causing the disease tuberculosis. The bacteria retain the stains of carbolfuchsin that cause the infection and affect the lung tissues. The disease is transmitted by respiratory droplets. The disease leads to the formation of tubercle on the lung tissues, which has a soft center surrounded by macrophages and T-lymphocytes layers. When the lesion of the disease begins to heal, the stage is known as Ghon’s complex. However, in extreme cases, healing does not happen as the tubercle continues to produce and microorganisms migrate to other body organs through the bloodstream. This stage is known as military tuberculosis. Treatment of tuberculosis is long-term with proper medications and drug therapy, including isoniazid, rifampin, ethambutol, streptomycin, and pyrazinamide. The disease can be diagnosed using various laboratory tests and prevention is possible through Bacille calmette guerin vaccination. Diphtheria The club shape gram-positive bacterium rod Carynebacterium contributes to the disease diphtheria. Symptoms of the disease include soreness in the throat, swelling in the neck, and blockage of the respiratory passageway. Bacteria generate an exotoxin that causes a membrane-like accumulation, which leads to the destruction of the cells along the epithelial lining. The treatment of diphtheria is possible by injecting antitoxins along with a DPT vaccine.

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