Chapter 21
Microbial Diseases of the Respiratory System
Structure of the respiratory system
• Upper respiratory system
– Nose
– Pharynx (throat)
– Middle ear and auditory tubes
– Larynx (voice box)
• Lower respiratory system
– Trachea (windpipe)
– Bronchial tubes
- Lungs (alveoli –sac)
Respiratory System
• Function of the respiratory system:
• Upper respiratory system: Collects air, filters contaminants from the a
it to the lower respiratory organs
• Lower respiratory system: Exchange of gases
The Normal Microbiota
• Upper Respiratory System: The normal microbiota prevents the growth of p
organisms. Some normal microbiota are opportunistic pathogens.
– Haemophilus influenzae, Staphylococcus aureus, Neisseria meningitid
Diphtheroids (colonize the nose and nasal cavity)
• Lower Respiratory System: Typically microorganisms are not present
How the microbes are prevented of reaching the lungs?
• Particles (microbes) are removed from larynx, trachea and bronchial tubes b
escalator (first line of defense)
• Cilia propel particles upward
• Microbes reaching the lungs are removed by phagocytosis
VIRAL DISEASES OF THE UPPER RESPIRATORY SYSTEM
The Common Cold - Rhinitis
• Caused by 200 different viruses (Rhinoviruses, Coronaviruses)
• Immunity is accumulated during the lifetime
• Symptoms: sneezing, nasal secretion, congestion
• Primary infection is in the throat but can spread to the lower respiratory syste
middle ear
The Common Cold
• Virus is transmitted by air and hands to the nose mucous membrane
, • Result of rhinitis
• Viral infection causes inflammation of eustachian tubes – accumulation of flu
• Becomes the site of bacterial infection Streptococcus pneumoniae; Haemop
• Treatment: Broad-spectrum antibiotics
Streptococcal pharyngitis (Strep throat)
• Causative agent: S. pyogenes
• Symptoms: Inflammation of throat mucous membrane, lymph nodes (tonsillit
swallowing
• May progress to scarlet or rheumatic fever and endocarditis
• Transmitted by respiratory secretion
• Treatment: penicillin
Strep Throat Diagnosis
• Pharyngeal swab samples
• Blood Agar Streak
• Quick Strep: ELISA in a small tube….can be done in a physician’s office.
• Only about 30% people diagnosed with Strep Throat actually have a S. pyog
• Major Problem – people recovering from Strep throat are contagious – even
therapy
Virulence Factors of S. pyogenes
Includes:
• Polysaccharides- protection against lysozyme
• Lipoteichoic acid – adherence to epithelial cells in the pharynx
• M protein – a spiky surface projections – resistance against phagocytosis
• Hyaluronic acid capsule – adherence
• Toxins - streptolysins – cytotoxic to tissue cells
Rheumatic Fever
• May develop two to three weeks after a Group A streptococcal infection – str
• Antibodies developed against streptococcal M protein cross react with the he
joints
• Damage to heart valves
Diphtheria
• Used to be the leading cause of fatal infectious diseases of children
• Caused by Corynebacterium diphteriae
– Gr+ non-endospore irregular rods – pleomorphic morphology
• Symptoms: Sore throat, fever, grayish membrane in the throat (can block the
• Lysogenized bacteria produce powerful toxin
• Treatment: penicillin and erythromycin + antitoxin
• Vaccine available DTP
Virulence Factors of
Corynebacterium diphteriae
Microbial Diseases of the Respiratory System
Structure of the respiratory system
• Upper respiratory system
– Nose
– Pharynx (throat)
– Middle ear and auditory tubes
– Larynx (voice box)
• Lower respiratory system
– Trachea (windpipe)
– Bronchial tubes
- Lungs (alveoli –sac)
Respiratory System
• Function of the respiratory system:
• Upper respiratory system: Collects air, filters contaminants from the a
it to the lower respiratory organs
• Lower respiratory system: Exchange of gases
The Normal Microbiota
• Upper Respiratory System: The normal microbiota prevents the growth of p
organisms. Some normal microbiota are opportunistic pathogens.
– Haemophilus influenzae, Staphylococcus aureus, Neisseria meningitid
Diphtheroids (colonize the nose and nasal cavity)
• Lower Respiratory System: Typically microorganisms are not present
How the microbes are prevented of reaching the lungs?
• Particles (microbes) are removed from larynx, trachea and bronchial tubes b
escalator (first line of defense)
• Cilia propel particles upward
• Microbes reaching the lungs are removed by phagocytosis
VIRAL DISEASES OF THE UPPER RESPIRATORY SYSTEM
The Common Cold - Rhinitis
• Caused by 200 different viruses (Rhinoviruses, Coronaviruses)
• Immunity is accumulated during the lifetime
• Symptoms: sneezing, nasal secretion, congestion
• Primary infection is in the throat but can spread to the lower respiratory syste
middle ear
The Common Cold
• Virus is transmitted by air and hands to the nose mucous membrane
, • Result of rhinitis
• Viral infection causes inflammation of eustachian tubes – accumulation of flu
• Becomes the site of bacterial infection Streptococcus pneumoniae; Haemop
• Treatment: Broad-spectrum antibiotics
Streptococcal pharyngitis (Strep throat)
• Causative agent: S. pyogenes
• Symptoms: Inflammation of throat mucous membrane, lymph nodes (tonsillit
swallowing
• May progress to scarlet or rheumatic fever and endocarditis
• Transmitted by respiratory secretion
• Treatment: penicillin
Strep Throat Diagnosis
• Pharyngeal swab samples
• Blood Agar Streak
• Quick Strep: ELISA in a small tube….can be done in a physician’s office.
• Only about 30% people diagnosed with Strep Throat actually have a S. pyog
• Major Problem – people recovering from Strep throat are contagious – even
therapy
Virulence Factors of S. pyogenes
Includes:
• Polysaccharides- protection against lysozyme
• Lipoteichoic acid – adherence to epithelial cells in the pharynx
• M protein – a spiky surface projections – resistance against phagocytosis
• Hyaluronic acid capsule – adherence
• Toxins - streptolysins – cytotoxic to tissue cells
Rheumatic Fever
• May develop two to three weeks after a Group A streptococcal infection – str
• Antibodies developed against streptococcal M protein cross react with the he
joints
• Damage to heart valves
Diphtheria
• Used to be the leading cause of fatal infectious diseases of children
• Caused by Corynebacterium diphteriae
– Gr+ non-endospore irregular rods – pleomorphic morphology
• Symptoms: Sore throat, fever, grayish membrane in the throat (can block the
• Lysogenized bacteria produce powerful toxin
• Treatment: penicillin and erythromycin + antitoxin
• Vaccine available DTP
Virulence Factors of
Corynebacterium diphteriae
