These lecture notes will provide an outline of information from the lectures. They are not complete. They should be used to help follow the lecture and as a guideline for information I think is important. You will need to fill in the gaps.

These notes were updated April 17, 2001, and are ready for printing by Spring 2001 Med Micro. students.

Chapters 7, 12, 14, 15 (pp. 201-228; 369-378; 463-465)

Diseases of the Upper Respiratory Tract

Pharyngitis
Laryngitis
Tonsillitis
Sinusitis; mastoiditis (air-filled chambers of skull, sinuses, mastoid)
Rhinitis
Epiglottitis
Otitis Media
Conjunctivitis
The eyes and the nose are the two main "portals of entry" to the respiratory system
Environment is very different from adjacent skin: dark, hot, humid, lower in oxygen and higher in carbon dioxide

Common Causes

Viruses are most common causes
- Rhinovirus (common cold, croup)
- Adenovirus (common cold, pharyngitis)
- Parainfluenzae (croup)
- Viral infections may set the stage for secondary bacterial infections
Other causes:
- Streptococcus pyogenes
- Haemophilus influenzae
- Cornynebacterium diphtheriae
- Streptococcus pneumoniae

Streptococcal Diseases of URT

All caused by S. pyogenes (AKA Group A, beta hemolytic strep)
- Gram positive cocci, in chains, catalase negative, bacitracin positive
- Droplet transmission
- M protein in cell wall and pili encourages adherence to pharyngeal tissue and retards phagocytosis
Pharyngitis
Scarlet fever
- This is strep throat accompanied by a skin rash
- This strain of strep produces erythrogenic toxin
Complications
- Rheumatic fever
- Glomerular nephritis
- Transmission to skin abrasions (erysipelas)
- Invasion of fascia (necrotizing fasciitis)
- Infection of uterus during birth process (puerperal sepsis or childbed fever)

Corynebacterium diphtheriae

Gram positive rod, pleomorphic
Droplet transmission
Potent cytotoxin affecting epithelial cells lining respiratory tract
- Dead tissue accumulates with mucus, WBC, fibrous material to form a pseudomembrane
- Treatment requires both an antimicrobial and an antitoxin
  - Toxin will damage the heart, kidneys, and nerve endings
- Vaccine-preventable (toxoid)
- There is a cutaneous form

Otitis Media

Infection of middle ear
Most common causes
- S. pneumoniae (important cause of conjunctivitis also)
- H. influenzae (important cause of conjunctivitis also)
- Moraxella catarrhalis
- S. pyogenes
- S. aureus
- Some viruses, such as respiratory syncytial virus

Epiglottitis

Inflammation of epiglottis
H. influenzae b
- Gram negative, encapsulated rod
- Occurs in young children mostly
- Vaccine-preventable

Influenzae

Acute, contagious disease of the upper respiratory tract
Droplet transmission
Infects respiratory epithelium with destruction of tissue
Abrupt onset
- Sudden chills
- Fatigue
- Headache
- Pronounced pain in chest, back, legs
- Fever and cough
- Normally short-lived with favorable prognosis
Antigenic drift (mutations) requires new vaccine for every season
Largest morbidity due to secondary bacterial penumonias (S. aureus, H. influenzae, S. pyogenes )
Both Reyes syndrome and Guilanin-Barre syndrome are possible complications

Diseases of the Lower Respiratory Tract

Laryngitis
Bronchitis (both smoking and infection can cause this)
Bronchiolitis (viral)
Pneumonitis (inflammation of the alveoli that are the main bulk of lung tissue)
Pneumonia (when alveoli fill with pus and fluid)
- Bacterial (more common in adults)
- Viral (more common in children)
- Fungal
- Non-infectious (e.g., inhalation/aspiration)
Pleurisy (membranes adhering to lung and chest wal and diaphragm)
Whooping Cough
Tuberculosis
These are all much less common because pathogens are stopped by body defenses; however, when they occur, they are much more serious

Bordetella pertussis

Causes whooping cough
Aerobic, Gram negative coccobacillus
Encapsulated (virulent strains)
Exotoxins
Adheres to ciliated cells in trachea
- Impedes their action and kills them
- Ciliated escalator does not work
First stage resembles the common cold
Second stage, violent whooping coughing, occurs as result of damage to ciliary escalator
Convalescence stage lasts for months (secondary infections possible here)
Vaccine-preventable, but boosters required

Tuberculosis

Mycobacterium tuberculosis
Obligate aerobe, Gram positive rod
- Grows VERY slowly (20 hour generation time!)
- Acid fast (not decolorized with acid alcohol)
- Waxy cell wall
- Very resistant to antiseptics, disinfectants, and antimicrobials
- Bacillus can replicate inside macrophages to form tubercle
  - This is a walled-off area of large aggregates of macrophages and infected cells
  - Shows up on x-rays ("Ghon complex")
  - Tubercle may break, releasing virulent bacilli into airways and cardiovascular/lymphatic systems
  - If disseminated, called "miliary tuberculosis"
Airborne transmission
Long-term treatment includes isoniazid, rifampin, pyrazinamide, ethambutol, streptomycin
- Long-term treatment is important because organism hides in macrophages and because of prolonged generation time
- Early detection: tuberculin test, which is positive if patient has been exposed to tubercle bacilli (note that a positive test is NOT indicative of infection--it may mean patient is immunized or that there has been a past exposure to the bacillus!)

Bacterial Pneumonia

Streptococcus pneumoniae
- AKA known as "pneumococcal pneumonia"
- Gram positive, diplococcus, a hemolytic, catalase negative, optochin positive
- Virulent form is encapsulated
- Antimicrobials can start following a positive Gram stain
Other causes
- Mycoplasma pneumoniae ("primary atypical pneumonia"; no cell wall; airborne!)
- K. pneumoniae and H. influenzae (high mortality): occurs in patients with lowered resistance either as a primary or secondary (nosocomial) disease
- Serratia marcesens found in compromised patients, similarly to K. pneumoniae
- P. aeruginosa (primary cause of pneumonia in cystic fibrosis patients)
- Legionella pneumophila is the cause of Legionnaires' disease
- Chlamydia psittaci and Chlamydia pneumoniae
- Coxiella burnetti a rickettsiae transmitted by a vector arthropod: Q fever
- S. aureus, M. catarrhalis, S. pyogenes: lowered resistance and less common

Viral Pneumonia

Respiratory syncitial virus
- Most common cause of viral respiratory disease in infants
- Also causes a life-threatening pneumonia in elderly
- Almost all children infected by age 2
- Symptoms: coughing and wheezing
- Also implicated in some otitis media
Hanta virus: emerging disease

Fungal Pneumonia

Histoplasma capsulatum (histoplasmosis)
Coccidioides immitis (coccidioidomycosis)
Pneumocystis carinii (pneumocystis pneumonia)
- Found in healthy lungs, but causes disease among immunocompromised, especially AIDS patients
Blastomyces dermatitidis (blastomycosis)
Immunosuppressed infections:
- Aspergillus
- Rhizopus
- Mucor

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