Chapter 22 Diseases of the Respiratory System
Structure of the Respiratory System
• Function of the respiratory system
• Exchange of gases between the atmosphere and the blood
• Respiratory system divided into two main parts
• Upper respiratory system
• Lower respiratory system
Upper Respiratory System
• Function of the upper respiratory system
• Collects air, filters contaminants from the air, and delivers it to the
lower respiratory organs
• Components of the upper respiratory system
• Nose-external portion of the respiratory system
• Nasal cavity-lined with hairs and a ciliated mucous membrane that
help filter and trap particles and microbes
• Pharynx-lined with a ciliated mucous membrane that pushes
contaminants into the digestive system
• Tonsils-aggregations of lymphoid tissue
Lower Respiratory System
• Components of the lower respiratory system
• Larynx-contains the vocal cords
• Trachea, bronchi, bronchioles-series of tubes that allow movement
of air through to the lungs
• Alveoli-small air sacs of the lungs where oxygen from air enters the
blood while carbon dioxide diffuses from the blood into the alveoli
to be exhaled
• Diaphragm-muscle involved in breathing
• Protective components of the lower respiratory system include a ciliated
mucous membrane, alveolar macrophages, and secretory antibodies
Normal Microbiota of the Respiratory System
• Lower Respiratory System
• Typically microorganisms are not present
• Upper Respiratory System
• The normal microbiota remove nutrients and produce substances
that limit growth of pathogenic organisms
• Some normal microbiota are opportunistic pathogens
• Examples of normal microbiota
• Hemophilus influenzae can colonize the nose
• Staphylococcus aureus is present as normal microbiota in
some individuals without causing disease
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Diphtheroids can colonize the nose and nasal cavity
Bacterial Diseases of the Upper Respiratory System
• Bacteria can infect the upper respiratory system and cause such
conditions as sore throat
• Examples of bacterial upper respiratory infections
• Streptococcal respiratory diseases
• Diphtheria
Streptococcal Respiratory Diseases
• Cause: Group A streptococci (S. pyogenes)
• Virulence factors: M proteins, hyaluronic acid capsule, streptokinases, C5a
peptidase, pyrogenic toxins, streptlysins
• Portal of entry: Upper respiratory tract via respiratory droplets
• Signs/Symptoms: Sore throat, difficulty swallowing; may progress to
scarlet or rheumatic fever
• Susceptibility: Children typically most susceptible
• Treatment: Penicillin is the standard treatment
• Prevention: Infectious individuals are infectious for two days after
treatment and should stay at home
Diphtheria
• Cause: Cornybacterium diphtheriae
• Virulence factor: Diphtheria toxin prevents polypeptide synthesis and
causes cell death
• Portal of entry: Spread person to person via respiratory droplets or skin
contact
• Signs/Symptoms: Sore throat, oozing fluid that hardens into a
pseudomembrane that can obstruct airways
• Susceptibility: Immunocompromised or nonimmune individuals develop
symptomatic infections
• Treatment: Administration of antitoxin and antibiotics
• Prevention: Immunization
Bacterial Diseases of the Sinuses and Ears
• Bacteria present in the pharynx can infect the sinuses or middle ear and
cause disease
• Examples of infections of the sinuses and ears
• Sinusitis
• Otitis media
Sinusitis
• Cause: Various bacteria such as Streptococcus pneuomoniae,
Staphylococcus aureus, Haemophilus influenzae, and Moraxella catarrhalis
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Portal of entry: Bacteria in the pharynx spread to the sinuses via their
connection with the throat
Signs/Symptoms: Pain and pressure of the affected sinus accompanied by
malaise
Susceptibility: Adults are most often affected
Diagnosis: Symptoms are often diagnostic
Prevention: No known ways to prevent sinusitis
Otitis Media
• Cause: Various bacteria such as Streptococcus pneuomoniae,
Staphylococcus aureus, Haemophilus influenzae, and Moraxella catarrhalis
• Portal of entry: Bacteria in the pharynx spread to the middle ear via the
auditory tubes
• Signs/Symptoms: Severe pain in the ears
• Susceptibility: Children are most often affected
• Diagnosis: Symptoms are often diagnostic
• Treatment: Antimicrobial drugs
• Prevention: Various measures may be taken to prevent otitis media such
as tonsil removal and placement of plastic tubes in the ear to allow
drainage
Viral Diseases of the Upper Respiratory System
• Viral respiratory diseases are some of the most common human diseases
• The common cold is the primary viral disease of the upper respiratory
system
Common Cold
• Cause: Rhinoviruses are the most common although numerous viruses
cause colds
• Portal of entry: Transmitted via coughing/sneezing, fomites, or person-toperson contact
• Signs/Symptoms: Sneezing, runny nose, congestion, sore throat, malaise,
and cough
• Susceptibility: Children acquire colds most often
• Diagnosis: Symptoms are usually diagnostic
• Treatment: Supportive care for symptoms
• Prevention: Antisepsis and disinfection of fomites
Bacterial Diseases of the Lower Respiratory System
• Lower respiratory organs are usually axenic
• When bacterial infection of the lower respiratory system occurs lifethreatening illness can result
• Examples of bacterial infections of the lower respiratory system
• Bacterial pneumonia
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Legionnaire’s disease
Pertussis (whooping cough)
Tuberculosis
Bacterial Pneumonias
• Pneumonia is inflammation of the lungs accompanied by fluid filled alveoli
and bronchioles
• Pneumonia can be categorized by the affected region or the organism
causing the disease
• Lobar pneumonia-involves entire lobes of the lungs
• Mycoplasmal pneumonia-caused by the bacterium Mycobacterium
• Nosocomial pneumonia-pneumonia acquired in a health care
setting
• Bacterial pneumonias are the most serious of the pneumonias and the
most frequent in adults
Pneumococcal Pneumonia
• Cause: Streptococcus pneumoniae
• Virulence factors: Adhesins, capsule, pneumolysin
• Portal of entry: Inhalation
• Signs/Symptoms: Fever, chills, congestion, cough, chest pain, and short,
rapid breathing
• Incubation period: One to three days
• Susceptibility: Immunocompromised individuals
• Treatment: Penicillin is the drug of choice
• Prevention: Vaccination
Primary Atypical (Mycoplasmal) Pneumonia
• Cause: Mycoplasma pneumoniae
• Virulence factors: Adhesion protein
• Portal of entry: Nasal secretions among individuals in close contact
• Signs/Symptoms: Atypical symptoms including fever, malaise, sore throat,
excessive sweating
• Incubation period: One to four weeks
• Susceptibility: High school and college students
• Treatment: Tetracycline and erythromycin
• Prevention: Difficult to prevent because individuals can be infective
despite lack of symptoms
Klebsiella pneumonia
• Cause: Klebsiella pneumoniae
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Virulence factors: Capsule
Portal of entry: Inhalation
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Signs/Symptoms: Typical pneumonia symptoms combined with a thick,
bloody sputum and recurrent chills
Incubation period: One to three days
Susceptibility: Hospitalized individuals
Treatment: Cephalosporins and supportive care
Prevention: Aseptic technique by health care workers
Other Bacterial Pneumonia
• Cause: Hemophilus influenzae, Staphylococcus aureus, Yersinia pestis,
and Chlamydia species
• Portal of entry: Inhalation, also via blood with Y. pestis
• Signs/Symptoms: Typical pneumonia symptoms along with frothy, bloody
sputum in the case of Y. pestis
• Incubation period: Variable depending on cause although Y. pestis can
produce symptoms in hours
• Susceptibility: Typically young children
• Treatment: Antibiotic treatment
• Prevention: Good hygiene; vaccine available for H. influenzae
Legionellosis (Legionnaire’s Disease)
• Cause: Legionella pneumophila
• Portal of entry: Inhalation of Legionella-filled vesicles
• Signs/Symptoms: Typical pneumonia symptoms and possible
complications of the gastrointestinal tract, CNS, liver, and kidneys
• Susceptibility: Includes the elderly, smokers, immunocompromised
individuals
• Diagnosis: Presence of Legionella or antibodies against the bacterium
• Treatment: Erythromycin is the drug of choice
• Prevention: Reduce bacterial presence in water
Tuberculosis
• Signs and Symptoms
• Initial symptoms include minor cough and mild fever
• Later symptoms include difficulty breathing, chest pain, wheezing,
and coughing up blood
• Pathogen and Virulence Factors
• Mycobacterium tuberculosis is the causative agent
• Presence of virulence factors aid in pathogenesis
• Mycolic acid present in the cell wall has various effects
• Cord factor is required for mycobacteria to cause disease
• Pathogenesis
• M. tuberculosis can remain viable for long periods in aerosol drops
due to protection of the mycolic acid in the cell wall
• Three types of tuberculosis
Primary tuberculosis-initial case of tuberculosis disease
Secondary tuberculosis-reestablished tuberculosis
Disseminated tuberculosis-tuberculosis involving multiple
systems
Epidemiology
• Immunocompromised individuals are most at risk
• Tuberculosis is the leading killer of HIV+ individuals
Diagnosis, Treatment, and Prevention
• Tuberculin skin test identifies previous exposure to M. tuberculosis
• Doesn’t distinguish between active disease, chronic carriers,
or those who have been vaccinated
• Treatment requires multi-drug regimen
• Prevention includes vaccination in some countries and surveillance
of patients to limit spread of disease
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Pertussis (Whooping Cough)
• Cause: Bordetella pertussis
• Virulence factors: Pertussis toxin, adenylate cyclase toxin, dermonecrotic
toxin, and tracheal cytotoxin
• Portal of entry: Inhalation of bacteria in airborne droplets
• Signs/Symptoms: Catarrhal stage: symptoms resemble a cold; Paroxysmal
stage: characteristic severe cough; Convalescent stage: cough slowly
subsides
• Susceptibility: Unimmunized children
• Treatment: Combination antibiotic therapy
• Prevention: DTaP vaccine
Inhalation Anthrax
• Cause: Bacillus anthracis
• Virulence factors: Capsule, anthrax toxin
• Portal of entry: Inhalation of endospores
• Signs/Symptoms: Initial symptoms resemble a cold or flu but progress to
severe coughing, shortness of breath, shock, and death
• Diagnosis: Identification of bacteria in sputum
• Treatment: Various antimicrobials
• Prevention: Anthrax vaccine available to military personnel, researchers,
health care workers dealing with anthrax patients
Influenza
• Signs and Symptoms
• Sudden fever, pharyngitis, congestion, cough, myalgia
• Pathogens and Virulence Factors
• Influenza virus types A and B are the causative agents
Strains named as follows: Type/Location /Month (as number)/Year
(HA and NA antigen types)
• Hemagglutinin and neuraminidase mutations produce the ever
changing array of strains
• Mutations occur via two main processes
• Antigenic drift
• Antigenic shift
Signs and Symptoms
• Sudden fever, pharyngitis, congestion, cough, myalgia
Pathogens and Virulence Factors
• Influenza virus types A and B are the causative agents
• Strains named as follows: Type/Location /Month (as number)/Year
(HA and NA antigen types)
• Hemagglutinin and neuraminidase mutations produce the ever
changing array of strains
• Mutations occur via two main processes
• Antigenic drift
• Antigenic shift
Pathogenesis
• Symptoms of influenza are produced by the immune response to
the virus
• Flu patients are susceptible to secondary bacterial infections due to
virally produced damage to the lung epithelium
Epidemiology
• Influenza is transmitted via inhalation of airborne viruses or by
self-inoculation
• Complications occur most often in the elderly, children, and those
with chronic diseases
Diagnosis
• Signs and symptoms during a community-wide outbreak are often
diagnostic
Treatment
• Four drugs are approved to treat influenza
• Amantadine, rimantadine, oseltamivir, zanamivir
• Treatment also involves supportive care to relieve symptoms
Prevention
• Immunization with a multivalent vaccine
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Severe Acute Respiratory Syndrome (SARS)
• Cause: SARS-associated coronovirus
• Portal of entry: Respiratory droplets enter through mucous membranes
via close person-to-person contact
• Signs/Symptoms: High fever, head and body aches, malaise, dry cough,
pneumonia develops
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Incubation period: Typically two to seven days
Susceptibility: Some individuals may be genetically susceptible
Treatment: Primarily supportive care
Prevention: Quarantine infected persons, good hygiene
Respiratory Syncytial Virus Infection
• Most common childhood respiratory disease
• Signs and Symptoms
• Fever, runny nose, coughing, in babies or immunocompromised
individuals
• Mild coldlike symptoms occur in older children and adults
• Pathogen
• Respiratory syncytial virus (RSV)
• Pathogenesis
• Formation of syncytia can help viruses evade the immune system
and also infect new cells
• Epidemiology
• Transmission occurs via close contact with infected persons
• Diagnosis, Treatment, and Prevention
• Diagnosis of RSV infection made by immunoassay combined with
signs of respiratory distress
• Supportive treatment for young children
• Prevention includes aseptic technique of health care workers and
day care employees
Hantavirus Pulmonary Syndrome (HPS)
• Cause: Hantavirus strains
• Portal of entry: Inhalation of infected rodent excrement or saliva
• Signs/Symptoms: High fever, head and body aches, malaise, dry cough,
pneumonia develops
• Incubation period: Fourteen to thirty days
• Susceptibility: Individuals exposed to rodents in endemic areas
• Treatment: Supportive care
• Prevention: Avoidance of rodent droppings
Other Viral Respiratory Diseases
• Other viruses cause respiratory disease in children, the elderly, or
immunocompromised individuals
• Cytomegalovirus
• Metapneumovirus
• Estimated to be the second most common cause of viral
respiratory disease behind rhinoviruses
• Parainfluenzaviruses
• Three strains cause croup and viral pneumonia
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Occurs primarily in young children
Fungal Infections of the Lower Respiratory System
• Certain systemic mycoses can involve the respiratory system
• Coccidioidomycosis
• Blastomycosis
• Histoplasmosis
• Pneumocystis pneumonia is a common fungal pneumonia of AIDS
patients
Coccidioidomycosis
• Commonly called valley fever
• Cause: Coccidioides immitis
• Portal of entry: Inhalation of arthroconidia in the soil
• Signs/Symptoms: Symptoms can resemble pneumonia or tuberculosis;
infection can become systemic in immunocompromised persons with
various symptoms
• Epidemiology: Endemic to southwestern U.S. and Mexico
• Diagnosis: Presence of spherules in clinical specimens
• Treatment: Amphotericin B
• Prevention: Protective masks can prevent exposure to arthroconidia for
those in occupations with high risk
Blastomycosis
• Cause: Coccidioides immitis
• Portal of entry: Inhalation of fungal spores in dust
• Signs/Symptoms: Flulike symptoms: systemic infections can produce
painless lesions on the face and upper body or purulent lesions on various
organs
• Epidemiology: Endemic to southeastern U.S. and Canada
• Diagnosis: B. dermatitidis in clinical samples
• Treatment: Amphotericin B
Histoplasmosis
• Most common fungal systemic disease of humans
• Cause: Histoplasmosis capsulatum
• Portal of entry: Inhalation
• Signs/Symptoms: Dry cough with blood tinged sputum and skin lesions
• Epidemiology: Endemic to eastern U.S. but also found in parts of Africa
and Central and South America
• Susceptibility: Children and those exposed to soil
• Diagnosis: Presence of budding yeast in macrophages
• Treatment: Amphotericin B
• Prevention: Minimize exposure to soil
Pneumocystis Pneumonia (PCP)
• Cause: Pneuocystis jiroveci (Previously P. carinii)
• Portal of entry: Inhalation of droplets containing the fungus
• Signs/Symptoms: Difficulty breathing, mild anemia, hypoxia, and fever
• Susceptibility: Immunocompromised patients particularly those with AIDS
• Treatment: Trimethoprim and sulfamethoxazole (TMP-SMX)
• Prevention: Cannot avoid the fungus but maintenance of a healthy
immune system limits disease