The Mucociliary Escalator

1. Ciliated cells line much of the respiratory tract and remove microorganisms by constantly propelling mucus out of the respiratory system. (Figure 23.1a)

23.2 Normal Flora (Table 23.1)

1. Secretions of the nasal entrance are often colonized by diphtheroids and Staphylococcus aureus, a coagulase-positive staphylococcus.

2. Viruses and microorganisms are normally absent from the lower respiratory system.

Summary 595

Infections of the Upper

Respiratory System

23.3 Bacterial Infections of the Upper Respiratory System

Strep Throat (Streptococcal Pharyngitis) (Tables 23.2,23.3)

1. Streptococcus pyogenes causes strep throat, a significant bacterial infection that may lead to scarlet fever, rheumatic fever, toxic shock, or glomerulonephritis. (Figures 23.2, 23.3,23.4)

Diphtheria (Table 23.4)

1. Diphtheria, caused by Corynebacterium diphtheriae, is a toxin-mediated disease that can be prevented by immunization. (Figures 23.5, 23.6)

Pinkeye, Earache, and Sinus Infections

1. Conjunctivitis (pinkeye) is usually caused by Haemophilus influenzae or Streptococcus pneumoniae, the pneumococcus. Viral causes, including adenoviruses and rhinoviruses, usually result in a milder illness.

2. Otitis media and sinusitis develop when infection extends from the nasopharynx. (Figure 23.7)

23.4 Viral Infections of the Upper Respiratory System

The Common Cold (Table 23.5)

1. The common cold can be caused by many different viruses, rhinoviruses being the most common. (Figure 23.8)

Adenoviral Pharyngitis (Table 23.6)

1. Adenoviruses cause illnesses varying from mild to severe, which can resemble a common cold or strep throat.

Infections of the Lower

Respiratory System

23.5 Bacterial Infections of the Lower Respiratory System

Pneumococcal Pneumonia (Table 23.7, Figures 23.9,23.10)

1. Streptococcus pneumoniae, one of the most common causes of pneumonia, is virulent because of its capsule.

Klebsiella Pneumonia (Table 23.7)

1. Klebsiella pneumonia, a Gram-negative bacterial pneumonia, is representative of many nosocomial pneumonias that cause permanent damage to the lung. (Figure 23.11)

2. Serious complications such as lung abscesses and bloodstream infection are more common than with many other bacterial pneumonias.

3. Treatment is more difficult, partly because klebsiellas often contain R factor plasmids.

Mycoplasmal Pneumonia (Table 23.7, Figure 23.12)

1. Mycoplasmal pneumonia is often called walking pneumonia; serious complications are rare.

2. Penicillins and cephalosporins are not useful in treatment because the cause, M. pneumoniae, lacks a cell wall.

Whooping Cough (Pertussis) (Table 23.8, Figures 23.13,23.14)

1. Whooping cough is characterized by violent spasms of coughing and gasping.

2. Childhood immunization against the Gram-negative rod, Bordetella pertussis, prevents the disease. (Figure 23.15)

Tuberculosis (Table 23.9, Figures 23.16, 23.17, 23.18, 23.19)

1. Tuberculosis, caused by the acid-fast rod Mycobacterium tuberculosis, is generally slowly progressive or heals and remains latent, presenting the risk of later reactivation.

Legionnaires' Disease (Table 23.10, Figure 23.20)

1. Legionnaires' disease occurs when there is a high infecting dose of the causative microorganisms or an underlying lung disease. The cause, Legionella pneumophila, is a rod-shaped bacterium common in the environment.

23.6 Viral Infections of the Lower Respiratory System

Influenza (Table 23.11, Figure 23.21)

1. Widespread epidemics are characteristic of influenza A viruses. Antigenic shifts and drifts are responsible. (Figure 23.22)

2. Deaths are usually but not always caused by secondary infection.

3. Reye's syndrome may rarely occur during recovery from influenza and other viral infections but is probably not caused by the virus itself.

Respiratory Syncytial Virus Infections (Table 23.12)

1. RSV is the leading cause of serious respiratory disease in infants and young children.

Hantavirus Pulmonary Syndrome (Table 23.13, Figure 23.23)

1. Hantavirus pulmonary syndrome is contracted from inhalation of dust contaminated by mice infected with the hantavirus and is often fatal.

23.7 Fungal Infections of the Lung

Valley Fever (Coccidioidomycosis) (Table 23.14, Figure 23.25)

1. Coccidioidomycosis occurs in hot, dry areas of the Western Hemisphere and is initiated by airborne spores of the dimorphic soil fungus Coccidioides immitis.

(Figure 23.24)

Spelunker's Disease (Histoplasmosis) (Table 23.15)

1. Histoplamosis is similar to coccidioidomycosis but occurs in tropical and temperate zones around the world. (Figure 23.27)

2. The causative fungus, Histoplasma capsulatum, is dimorphic and found in soils contaminated by bat or bird droppings.

(Figure 23.26)

596 Chapter 23 Respiratory System Infections

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