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Microbiology - Diseases of the Respiratory System

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    Study Guide Microbiology – Diseases of the Respiratory System 1. Fungal and Protozoal Diseases of the Respiratory System Some microorganisms — especially fungi and protozoa — can infect the lungs and cause serious respiratory diseases. These infections are often spread through the air by inhaling dust or spores and are more dangerous in people with weakened immune systems. Below are several important respiratory diseases expla ined in an easy - to - understand way. 1.1 Histoplasmosis Histoplasmosis is a fungal disease caused by the yeast Histoplasma capsulatum . Once inside the body, the infection mainly affects the lungs and can closely resemble tuberculosis , especially in individuals with weakened immune systems. In severe cases, the disease may spread beyond the lungs to other organs and become progressive. Most infections occur after exposure to bird or bat droppings , which release fungal spores into the air. When these spores are inhaled, they can enter the lungs. The antifungal drug amphotericin B is commonly used to treat histoplasmosis, especially in serious cases. 1.2 Blastomycosis Blastomycosis is caused by Blastomyces dermatitidis , a yeast - like fungus . This disease is found mainly in areas around the Mississippi Valley and is spread through dust . After inhalation, the fungus infects the lungs and produces lesions that look similar to those seen in tuberculosis. In some cases, the infection may spread from the lungs to other organs of the body. Treatment typically involves the antifungal drug amphotericin B .

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    Study Guide 1.3 Coccidioidomycosis (Valley Fever) Coccidioidomycosis is caused by the fungus Coccidioides immitis , which lives in the soil of the southwestern United States . The disease is especially common in the San Joaquin Valley of California , which is why it is often called valley fever . Infection occurs when fungal spores are stirred up in dust and inhaled. Common symptoms include: • Fever • Coughing • General tiredness and discomfort Some cases progress into more serious disease. Farm workers and others exposed to soil dust are at higher risk. Severe infections are treated with amphotericin B . 1.4 Aspergillosis Aspergillosis is caused by the fungus Aspergillus fumigatus . In this disease, the fungus grows directly in lung tissue and forms a dense ball of fungal filaments , called a mycelial mass. This mass can block airways and interfere with breathing. Because medication alone is often not enough, surgical removal of the fungal mass is frequently required. 1.5 Pneumocystis Pneumonia Pneumocystis pneumonia is caused by Pneumocystis carinii . Although it is traditionally classified as a protozoan , biochemical evidence suggests it may actually be a fungus. This disease is most commonly seen in AIDS patients and others with weakened immune systems. In healthy individuals, the organism is often present in the lungs but does not cause disease. When immunity is compromised: • The organisms multiply in the lungs • Severe lung consolidation occurs • Breathing becomes difficult and life - threatening

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    Study Guide Without treatment, Pneumocystis pneumonia can be fatal. The drug pentamidine isethionate is commonly used for therapy. Approximately half of AIDS - related deaths are linked to Pneumocystis pneumonia. Pneumocystis carinii has a complex life cycle that includes mature cysts and highly resistant forms , allowing it to persist in the body until immune defenses weaken. Key Takeaway Fungal and protozoal respiratory diseases are often acquired by inhaling spores from the environment. While many infections remain mild, they can become severe or life - threatening in immunocompromised individuals. Early diagnosis and appropriate antifungal treatment are critical for successful outcomes. 2. Bacterial Diseases of the Respiratory System Bacterial diseases of the respiratory system can affect either the upper or lower respiratory tract. • The upper respiratory system includes the nose, pharynx, middle ear, and sinuses. Even though this area has strong defenses — such as mucus and ciliated hairs — infections are common because it is constantly exposed to the outside environment. • The lower respiratory system includes the trachea, bronchi, and alveoli of the lungs. Bacteria grow easily here because the lungs provide warmth, moisture, and nutrients . 2.1 Strep Throat Strep throat is caused by a group A beta - hemolytic streptococcus called Streptococcus pyogenes . This Gram - positive, encapsulated bacterium produces an enzyme called streptokinase , which dissolves fibrin clots and allows the bacteria to spread to nearby tissues. Common signs include: • Sore throat • Swollen lymph nodes • Inflamed throat tissues • Pus on the tonsils

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