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CHAPTER

Microbial Diseases of

the Respiratory System

Chapter Outline

Structures of the Respiratory System (pp. 672–674)

Structures of the Upper Respiratory System, Sinuses, and Ears

Structures of the Lower Respiratory System

Microbiome of the Respiratory System

Bacterial Diseases of the Upper Respiratory System, Sinuses, and Ears

(pp. 674–678)

Streptococcal Respiratory Diseases

Diphtheria

Viral Diseases of the Upper Respiratory System (pp. 679–680)

Common Cold

Bacterial Diseases of the Lower Respiratory System (pp. 680–690)

Bacterial Pneumonias

Legionnaires’ Disease

Tuberculosis

Pertussis (Whooping Cough)

Inhalational Anthrax

Viral Diseases of the Lower Respiratory System (pp. 690–697)

Influenza

Coronavirus Respiratory Syndromes

Mycoses of the Lower Respiratory System (pp. 698–703)

Coccidioidomycosis

Chapter 22 Microbial Diseases of the Respiratory System

Chapter Summary

Structures of the Respiratory System (pp. 672–674)

The respiratory system functions to exchange gases between the atmosphere and the blood.

Anatomists commonly divide its structures into upper and lower systems.

Structures of the Upper Respiratory System, Sinuses, and Ears

The upper respiratory system includes the nose, the nasal cavity, and the pharynx. These struc-

tures are lined with tiny hairs and a ciliated mucous membrane that filter inspired air. The uvula

partially closes the opening between the nasal cavity and pharynx during swallowing. Sinuses

Structures of the Lower Respiratory System

The lower respiratory system begins at the larynx (voice box), trachea (windpipe), bronchi, and

bronchioles leading to the alveoli (air sacs), which make up the lungs. The lungs are surrounded

by the pleurae (protective membranes). Below the lungs is the diaphragm, the major muscle of

Microbiome of the Respiratory System

The lower respiratory system normally lacks microorganisms; however, the upper division is in-

Bacterial Diseases of the Upper Respiratory System, Sinuses,

and Ears (pp. 674–678)

Bacteria can infect the upper respiratory system and spread into the sinuses and auditory tubes.

Streptococcal Respiratory Diseases

Physicians recognize a variety of diseases of the upper respiratory system caused by species of

Instructor’s Manual for Microbiology with Diseases by Body System, 5e

coughing). Streptococcal pharyngitis can also progress to scarlet fever (scarlatina) when the

microbe releases pyrogenic and erythrogenic toxins that trigger fever and a rash, followed by

skin sloughing. Untreated streptococcal pharyngitis can be complicated by acute glomerulone-

Diphtheria

Diphtheria, a potentially fatal respiratory disease, is endemic in countries that lack adequate

immunization. Symptoms include sore throat, localized pain, pharyngitis, fever, and the for-

mation of a pseudomembrane that adheres to the tonsils, uvula, roof of the mouth, pharynx, and

larynx and can cause suffocation. Virulent strains of Corynebacterium diphtheriae, a Gram-

Rhinosinusitis and Otitis Media

Rhinosinusitis (inflammation of the sinuses, formerly called sinusitis) and otitis media (in-

flammation of the middle ear) are usually caused by bacteria resident in the pharynx that spread

to the nose, sinuses, or ears. These include Streptococcus pneumoniae, Staphylococcus aureus

(1–2% of cases), Haemophilus influenzae (20–30% of cases), Moraxella catarrhalis (10–15% of

cases), and Streptococcus pyogenes.

Viral Diseases of the Upper Respiratory System (pp. 679–680)

Viral diseases of the upper respiratory system are among the most common human diseases.

Chapter 22 Microbial Diseases of the Respiratory System

Common Cold

Symptoms of the common cold are sneezing, rhinorrhea (runny nose), congestion, sore throat,

malaise, and cough. Of the over 200 different serotypes of viruses that cause the common cold,

the major culprits are in the genus Enterovirus (family Picornaviridae, also called Rhinovirus).

Coronaviruses, adenoviruses, and some reoviruses and paramyxoviruses also commonly cause

Bacterial Diseases of the Lower Respiratory System

(pp. 680–690)

The lower respiratory organs are axenic, that is, they are normally devoid of microorganisms.

Successful bacterial colonization can cause life-threatening disease.

Bacterial Pneumonias

The term pneumonia describes an inflammation of the lungs in which the alveoli and bronchi-

oles become filled with fluid. When pus is present the disease is known as empyema. Pleurisy

refers to the painful inflammation called pleurae. Pneumonias are classified according to the af-

fected region and the causative organism. The most common types of bacterial pneumonia in-

clude the following:

 Pneumococcal pneumonia is the most common (~85%) type of bacterial pneumonia cases,

accounting for most cases of community acquired pneumonia (CAP) and about 30% of HAI

pneumonia cases. It is caused by Streptococcus pneumoniae (commonly known as pneumo-

 Primary atypical (mycoplasmal) pneumonia (also called walking pneumonia) is caused by

Mycoplasma pneumoniae. It is the leading type of pneumonia in children and young adults.

Early symptoms include fever, headache, sore throat, and excessive sweating. These are fol-

Instructor’s Manual for Microbiology with Diseases by Body System, 5e

 Klebsiella pneumonia is caused by infection with the opportunistic Gram-negative Klebsiella

pneumoniae, a major cause of HAI (nosocomial) pneumonia cases and death. Klebsiella

pneumonia is characterized by thick, bloody sputum, resulting from destruction of alveoli,

and recurrent chills. Bacterial cell death releases endotoxin that can trigger shock and dissem-

inated intravascular coagulation. Physicians diagnose Klebsiella pneumonia from its signs

and symptoms and by culturing Klebsiella from sputum specimens. Cephalosporin can be

used against Klebsiella, but the release of endotoxin can cause irreversible damage to the

lungs. No vaccine is available.

Legionnaires’ Disease

Legionnaires’ disease is named for an outbreak of the disease at an American Legion conven-

tion in 1976 during which 29 people died. Infection initially manifests as fever, chills, cough,

headache, and pleurisy—pleurae inflammation—may also develop. If left untreated, rapid and

severe inflammation of the lungs follows, resulting in death of up to 50% of patients. Of the 19

Tuberculosis

Tuberculosis (TB) is the leading disease killer in the world. It is an infection of the lungs

caused by the intracellular pathogen Mycobacterium tuberculosis. The symptoms are initially

mild fever and cough, but progression of the disease leads to labored breathing, fatigue, malaise,

weight loss, chest pain, wheezing, and coughing up blood. The cell walls of M. tuberculosis

contain mycolic acid, a waxy lipid that protects the pathogen from lysis, drying out, and many

antimicrobial drugs, and cord factor, which inhibits migration of neutrophils and kills host

presence of tubercles. The BCG vaccine is administered in countries with high rates of TB, but

cannot be used for immunocompromised persons.

Pertussis (Whooping Cough)

Infection with the Gram-negative coccobacillus Bordetella pertussis causes pertussis (whoop-

ing cough), a disease of children characterized by coughing so severe that it can cause vomiting,

diarrhea, ruptured blood vessels in the eyes, choking, suffocation (cyanosis), and even death.

The bacterium produces a number of virulence factors: filamentous hemagluttinin, an adhe-

sin; pertussis toxin, an adhesin, which also causes excess mucus production; adenylate cyclase

toxin also increases mucus production and inhibits leukocyte movement, phagocytosis, and kill-

ing; dermonecrotic toxin causes cell death and tissue destruction by interrupting blood flow; and

tracheal cytotoxin inhibits ciliary motion on respiratory cells.

Inhalational Anthrax

Bacillus anthracis causes the most lethal form of anthrax, inhalational anthrax, which pro-

gresses from symptoms of a common cold to more severe coughing, nausea, vomiting, fainting,

confusion, lethargy, shock, and death within days unless aggressively treated. B. anthracis pro-

Viral Diseases of the Lower Respiratory System (pp. 695–697)

Of the viral diseases of the lower respiratory system, the most prevalent is influenza.

Influenza

The signs and symptoms of influenza (or flu) usually include sudden fever, pharyngitis, conges-

tion, dry cough, malaise, headache, and myalgia. Most people recover within two weeks. The

Instructor’s Manual for Microbiology with Diseases by Body System, 5e

causative organisms are two species of viruses, designated types A and B. The viruses have

segmented genomes of eight RNA molecules surrounded by lipid envelopes with glycoprotein

spikes composed of hemagglutinin (HA) or neuraminidase (NA) that help the viruses attach to

the cells of the lungs. Mutations in the genes coding for these glycoprotein spikes are responsi-

Coronavirus Respiratory Syndromes

Recent emerging respiratory syndromes, severe acute respiratory syndrome (SARS) and

Middle East respiratory syndrome (MERS), are caused by coronaviruses that destroy lung cells

and may spread via the bloodstream to the heart and kidneys. Coronavirus respiratory syn-

Respiratory Syncytial Virus (RSV) Infection

Respiratory syncytial virus (RSV) infection is the leading respiratory disease of infants

worldwide. In infants and the immunocompromised infants, RSV triggers fever, rhinorrhea, cy–

anosis, coughing, and wheezing, as well as bronchiolitis (inflammation of the bronchioles) and

Hantavirus Pulmonary Syndrome (HPS)

Infection with Hantavirus causes Hantavirus pulmonary syndrome, a disease initially charac-

terized by fever, fatigue, and muscle aches in the trunk and legs. These symptoms rapidly pro-

gress to coughing, difficulty breathing, and shock, as inflammation causes the lungs to fill with

fluid and the blood pressure to drop precipitously. Fifty percent of diagnosed patients die,

drowning in their own fluids, despite intensive medical care. Hantavirus is a genus of enveloped

−ssRNA viruses that infect species of mice. Transmission is via inhalation of dried mouse urine,

Chapter 22 Microbial Diseases of the Respiratory System

Other Viral Respiratory Diseases

Several viruses cause respiratory disease in children, the elderly, and the immunocompromised.

They include Cytomegalovirus (see Chapter 21), Metapneumovirus, and parainfluenzaviruses.

Mycoses of the Lower Respiratory System (pp. 698–703)

Systemic mycoses are fungal infections that spread throughout the body.

Coccidioidomycosis

Initial symptoms of coccidioidomycosis, also known as valley fever, resemble those of pneu-

monia or TB, but can range from mild and self-limiting to severe. In the immunocompromised,

Blastomycosis

Infection with Blastomyces dermatitidis spores causes blastomycosis, a fungal disease that be-

gins with flulike symptoms. Spread of the fungus may cause lesions on the skin or purulent le-

sions, necrosis, and cavity formation in bones and other tissues. Inhalation of dust carrying

Histoplasmosis

The most common fungal systemic disease affecting humans is histoplasmosis. It is asympto-

matic in 95% of patients, but about 5% of patients develop clinical disease, which can take four

Instructor’s Manual for Microbiology with Diseases by Body System, 5e

Pneumocystis Pneumonia (PCP)

Infection with Pneumocystis jiroveci causes Pneumocystis pneumonia (PCP) in malnourished,

premature infants; weakened elderly patients; and people with AIDS. P. jiroveci (formerly

known as P. carinii) is part of the respiratory microbiota in some individuals. Asymptomatic in