The Upper Respiratory System

      - Nose

      - Pharynx (throat)

      - Middle ear

      - Eustachian tubes

 

The Lower Respiratory System

      - Larynx

      - Trachea

      - Bronchial tubes

      - Alveoli

      - Pleura

 

Normal Microbiota of Respiratory System

      - Suppress pathogens by competitive inhibition in upper respiratory system

      - Lower respiratory system is sterile

 

Check Understanding

      - What is the function of hairs in the nasal passages? 24-1

      - Normally, the lower respiratory tract is nearly sterile. What is the primary mechanism responsible? 24-2

 

Upper Respiratory System Diseases

      - Pharyngitis

      - Laryngitis

      - Tonsillitis

      - Sinusitis

      - Epiglottitis: H. influenzae type b

 

Streptococcal Pharyngitis

      - Also called strep throat

      - Streptococcus pyogenes

      - Resistant to phagocytosis

      - Streptokinases lyse clots

      - Streptolysins are cytotoxic

      - Diagnosis by enzyme immunoassay (EIA) tests

 

Scarlet Fever

      - Streptococcus pyogenes

      - Pharyngitis

      - Erythrogenic toxin produced by lysogenized S. pyogenes

 

Diphtheria

      - Corynebacterium diphtheriae: Gram-positive rod

      - Diphtheria toxin produced by lysogenized C. diphtheriae

      - Diphtheria membrane: Fibrin, tissue, bacterial cells

      - Prevented by DTaP vaccine

      - Diphtheria toxoid

      - Cutaneous diphtheria

      - Infected skin wound leads to slow-healing ulcer

 

Otitis Media

      - S. pneumoniae (35%)

      - H. influenzae (20–30%)

      - M. catarrhalis (10–15%)

      - S. pyogenes (8–10%)

      - S. aureus (1–2%)

      - Incidence of S. pneumoniae reduced  by vaccine

 

The Common Cold

      - Rhinoviruses (50%)

      - Coronaviruses (15–20%)

 

Picornaviridae

      - Single-stranded RNA,  + strand, nonenveloped

      - Enterovirus

      - Poliovirus and coxsackievirus

      - Rhinovirus

      - Hepatitis A virus

 

Coronaviridae

      - Single-stranded RNA, + strand, enveloped

      - Upper respiratory infections

      - Coronavirus

      - SARS

 

Check Understanding

      - Which one of the following is most likely to be associated with a headache: pharyngitis,  laryngitis, sinusitis, or epiglottitis? 24-3

      - Among streptococcal pharyngitis, scarlet fever,     or diphtheria, which two diseases are usually caused by the same genus of bacteria? 24-4

      - Which viruses, rhinoviruses or coronaviruses, cause about half of cases of the common cold?  24-5

 

Lower Respiratory System Diseases

      - Bacteria, viruses, and fungi cause

      - Bronchitis

      - Bronchiolitis

      - Pneumonia

 

Pertussis (Whooping Cough)

      - Bordetella pertussis

      - Gram-negative coccobacillus

      - Capsule

      - Tracheal cytotoxin of cell wall damaged ciliated cells

      - Pertussis toxin

      - Prevented by DTaP vaccine (acellular Pertussis cell fragments)

      - Stage 1: Catarrhal stage, like common cold

      - Stage 2: Paroxysmal stage—violent coughing sieges

      - Stage 3: Convalescence stage

 

Tuberculosis

      - Mycobacterium tuberculosis

      - Acid-fast rod; transmitted from human to human

      - M. bovis: <1% U.S. cases; not transmitted from human to human

      - M. avium-intracellulare complex infects people with late-stage HIV infection

      - Treatment: Prolonged treatment with multiple antibiotics

      - Vaccines: BCG, live, avirulent M. bovis; not widely used in United States

      - Tuberculin skin test screening

      - Positive reaction means current or previous infection

      - Followed by X-ray or CT exam, acid-fast staining of sputum, culturing of bacteria

 

Pneumococcal Pneumonia

      - Streptococcus pneumoniae

      - Gram-positive encapsulated diplococci

      - Symptoms: Infected alveoli of lung fill with fluids; interferes with oxygen uptake

      - Diagnosis: Optochin-inhibition test or bile solubility test; serological typing of bacteria

      - Treatment: Penicillin, fluoroquinolones

      - Prevention: Pneumococcal vaccine

 

Haemophilus influenzae Pneumonia

      - Gram-negative coccobacillus

      - Predisposing factors: Alcoholism, poor nutrition, cancer, or diabetes

      - Symptoms: Resemble those of pneumococcal pneumonia

      - Diagnosis: Isolation; special media for nutritional requirements

      - Treatment: Cephalosporins

 

Mycoplasmal Pneumonia

      - Primary atypical pneumonia; walking pneumonia

      - Mycoplasma pneumoniae

      - Pleomorphic, wall-less bacteria

      - Common in children and young adults

      - Symptoms: Mild but persistent respiratory symptoms; low fever, cough, headache

      - Diagnosis: PCR and serological testing

      - Treatment: Tetracyclines

 

Legionellosis

      - Legionella pneumophila

      - Gram-negative rod

      - Found in water

      - Transmitted by inhaling aerosols; not transmitted from human to human

      - Symptoms: Potentially fatal pneumonia that tends to affect older men who drink or smoke heavily

      - Diagnosis: Culture on selective media, DNA probe

      - Treatment: Erythromycin

 

Psittacosis (Ornithosis)

      - Chlamydophila psittaci

      - Gram-negative intracellular bacterium

      - Transmitted to humans by elementary bodies from bird droppings

      - Reorganizes into reticulate body after being phagocytized

      - Symptoms: Symptoms, if any, are fever, headache, chills

      - Diagnosis: Growth of bacteria in eggs or cell culture

      - Treatment: Tetracyclines

 

Chlamydial Pneumonia

      - Chlamydophila pneumoniae

      - Transmitted from human to human

      - Symptoms: Mild respiratory illness common in young people; resembles mycoplasmal pneumonia

      - Diagnosis: Serological tests

      - Treatment: Tetracyclines

 

Q Fever

      - Causative agent: Coxiella burnetii

      - Reservoir: Large mammals

      - Tick vector

      - Can be transmitted via unpasteurized milk

      - Symptoms: Mild respiratory disease lasting 1–2 weeks; occasional complications such as endocarditis occur

      - Diagnosis: Growth in cell culture

      - Treatment: Doxycycline and chloroquine

 

Melioidosis

      - Causative agent: by Burkholderia pseudomallei

      - Reservoir: Soil

      - Mainly in southeast Asia and northern Australia

      - Symptoms: Pneumonia, or tissue abscesses and severe sepsis

      - Diagnosis: Bacterial culture

      - Treatment: Ceftazidime

 

Check Understanding

      - Another name for pertussis is whooping cough. This symptom is caused by the pathogens’ attack on which cells? 24-6

      - What group of bacterial pathogens causes what  is informally called “walking pneumonia”? 24-7

      - The bacterium causing melioidosis in humans also causes a disease of horses known as what? 24-8

 

Viral Pneumonia

      - Viral pneumonia occurs as a complication of influenza, measles, or chickenpox

      - Viral etiology suspected if no other cause is determined

 

Respiratory Syncytial Virus (RSV)

      - Common in infants; 4500 deaths annually

      - Causes cell fusion (syncytium) in cell culture

      - Symptoms: Pneumonia in infants

      - Diagnosis: Serological test for viruses and antibodies

      - Treatment: Ribavirin, palivizumab

 

Paramyxoviridae

      - Single-stranded RNA, – strand, one RNA strand

      - Paramyxovirus

      - Morbillivirus

      - Parainfluenza

      - Mumps

      - Newcastle disease (chickens)

 

Influenza (Flu)

      - Symptoms: Chills, fever, headache, and muscle aches

      - No intestinal symptoms

      - 1% mortality, very young and very old

      - Treatment: Zanamivir and oseltamivir inhibit neuraminidase

      - Prophylaxis: Multivalent vaccine

      - Hemagglutinin (HA) spikes used for attachment to host cells

      - Neuraminidase (NA) spikes used to release virus from cell

 

Orthomyxoviridae

      - Single-stranded RNA,       – strand, multiple RNA strands

      - Envelope spikes can agglutinate RBCs

      - Influenzavirus (influenza viruses A and B)

      - Influenza C virus

 

The Influenza Virus

      - Antigenic shift

      - Changes in HA and NA spikes

      - Probably due to genetic recombination between different strains infecting the same cell

      - Antigenic drift

      - Point mutations in genes encoding HA or NA spikes

      - May involve only 1 amino acid

      - Allows virus to avoid mucosal IgA antibodies

 

Check Understanding

      - Is reassortment of the RNA segments of the influenza virus the cause of antigenic shift or antigenic drift? 24-9

 

Histoplasmosis

      - Histoplasma capsulatum, dimorphic fungus

 

Coccidioidomycosis

      - Causative agent: Coccidioides immitis

      - Reservoir: Desert soils of Southwest U.S.

      - Symptoms: Fever, coughing, weight loss

      - Diagnosis: Serological tests

      - Treatment: Amphotericin B

 

Pneumocystis Pneumonia

      - Causative agent: Pneumocystis jirovecii

      - Reservoir: Unknown; possibly humans or soil

      - Symptoms: Pneumonia

      - Diagnosis: Microscopy

      - Treatment: Trimethoprim

 

Blastomycosis

      - Causative agent: Blastomyces dermatitidis

      - Reservoir: Soil in Mississippi valley area

      - Symptoms: Abscesses; extensive tissue damage

      - Diagnosis: Isolation of pathogen

      - Treatment: Amphotericin B

 

Other Fungi Involved in Respiratory Disease              

      - Systemic

      - Predisposing factors:

      - Immunocompromised state

      - Cancer

      - Diabetes

      - Aspergillus fumigatus

      - Mucor

      - Rhizopus

 

Check Understanding

      - The droppings of both blackbirds and bats support the growth of Histoplasma capsulatum; which of these two animal reservoirs is normally actually infected by the fungus? 24-10