The Lower Respiratory Tract

Common Clinical Conditions

Bacterial diseases of the LRT are outlined below. Other Bacterial Diseases Bacterial Infections Common Clinical Conditions Pertussis (whooping cough): Caused by Bordetella Bacterial Pneumonias pertussis, this highly contagious childhood disease pro- Pneumococcal pneumonia: Streptococcus pneumo- duces mucus in the respiratory system, which triggers niae is responsible for about 80% of all pneumonia coughing. Straining for air causes the “whooping” cases. It usually starts after an URT viral infection dam- sound. [FOM pp. 279–280] ages the airways. Without appropriate antibiotic treat- Tuberculosis: An infection by Mycobacterium tuber- ment, mortality is high, especially in the elderly. [FOM he lower respiratory tract (LRT) consists of the (Streptococcus, Mycoplasma, Chlamydia), producing culosis, the major causative agent of tuberculosis (TB), pp. 289–290] Tlarynx (voice box), trachea (windpipe), bronchial a thick mucus that narrows the airways. starts by inhaling bacilli from an infected person. In the Primary atypical (walking) pneumonia: Caused by tubes, and the alveoli. Due to the mucous membrane Bronchiolitis: Usually restricted to young chil- alveoli, the bacilli reproduce, leading to calcified aggre- and filtering mechanisms of the bronchial tubes, the Mycoplasma pneumoniae, the infection is common in gations of activated macrophages and lymphocytes dren, a viral infection of the bronchiole lining children and teenagers. The disease is rarely fatal. LRT normally contains few microbes. Therefore, if (tubercles) surrounding the bacteria. [FOM pp. causes a swelling and narrowing of the airways, [FOM pp. 290–292] 284–288] pathogens enter the LRT, serious respiratory disease making expiration difficult (a wheezing sound Legionellosis (Legionnaires’ disease): Legionella may result. Inhalation anthrax: Without treatment, this deadly heard). pneumophila is inhaled as aerosols from air-condition- disease begins with typical cold symptoms, but quickly ing devices or water supplies contaminated with the Several microbial diseases are associated with the LRT. Pneumonia: An acute and complex syndrome leads to breathing difficulties and shock from toxins Two of the bacterial diseases are pneumonia and bacteria. After several days of incubation, symptoms produced by the cells from the germinated Bacillus resulting from an infection of the lung tissue and appear with pneumonia being the most likely out- anthracis spores. [FOM pp. 344–346] tuberculosis, historically the two greatest infectious alveoli. Impaired gas exchange causes rapid and come. [FOM pp. 293–296] killers of humans. Infections of the LRT also exhibit labored breathing, and cough. Q fever: This pneumonia-like infection, caused by themselves in several ways (see opposite page): Coxiella burnetii, is transmitted by inhaling aerosol Treatment Bronchitis: An inflammation of the bronchial droplets or consuming contaminated meat or unpas- lining (wall) by viruses or bacteria teurized milk from infected animals. The mortality rate is low. [FOM pp. 296–297] Penicillin is the drug of choice for pneumococcal pneu- monia. Primary atypical and chlamydial pneumonia are Ornithosis (psittacosis): A rare pneumonia caused treated with erythromycin or tetracycline. Legionellosis by the bacterium Chlamydia psittaci. The obligate also can be treated with erythromycin. Q fever can be intracellular bacteria are inhaled in dried droppings treated with doxycycline, while ornithosis is best treat- Signs and Symptoms from infected birds (parrots, parakeets, pigeons, ed with tetracycline. Pneumococcal pneumo- turkeys). Most cases are mild. [FOM pp. 298–299] nia: High fever, chest pain, Inhalation anthrax: Fever, Chlamydial pneumonia: Chlamydia pneumoniae TB treatment involves extended use of isoniazid and chills, cough, chest pain, persistent cough, rust-colored rifampin for 6 to 9 months. Pertussis can be treated sputum; increased pulse, and also causes a form of pneumonia with symptoms and headache, malaise; severe outcomes similar to primary atypical pneumonia. [FOM with erythromycin and, if caught very early, inhalation breathing and shock result. difficulty breathing. pp. 300–-301] anthrax is treatable with ciprofloxacin.

Tuberculosis: Fever, fatigue, weight loss, cough; shortness of breath and chest pain; Q fever: Dry cough, high Trachea tubercle development. fever, chest pain, and severe headache.

Primary atypical and Bronchitis chlamydial pneumonia: Gradual and mild symptoms with fever, fatigue, and dry, hacking cough. Legionellosis: Pneumonia symptoms with fever, dry cough, diarrhea, and vomiting.

Pertussis: Catarrhal stage: Bronchiolitis malaise, dry cough, fever; Paroxysmal stage: violent (whooping) cough; Pneumonia Convalescent stage: sporadic Ornithosis: Fever, headache, cough that slowly subsides. and dry cough. Alveoli False-colored chest X ray showing tuberculosis. The lungs contain lesions (pink) of infected tissue. (© Du Cane Medical Imaging, Other Pneumonias Ltd./Photo Researchers, Inc.) Klebsiella pneumoniae and Serratia marcescens may produce pneumonias through a hospital-acquired infection. [FOM pp. 292–293] 10 Syndromes associated with the LRT. 11