Chapter 22: Microbial Diseases of the Respiratory System

Respiratory system

Exchanges gases between the atmosphere and the blood.

What are the components of the upper respiratory system?

• Nose

• Nasal cavity

• Pharynx

• Uvula

• Antimicrobial chemicals

What are the components of the lower respiratory system?

• Larynx

• Trachea

• Bronchi

• Alveoli

• Diaphragm

• Protective components

Lower respiratory system

Typically microorganisms are not present.

Upper respiratory system

Colonized by many microorganisms. Normal microbiome limits growth of pathogens. Also, normal microbiome may be opportunistic pathogens.

Streptococcus Pharyngitis

Causative agent: Group A. Streptococcus pyogenes

Classification: Low G+C Gram Pos.

Signs/Symptoms: pharyngitis, fever, headache, malaise, laryngitis, and bronchitis.

Pathogenesis: normal flora depleted, virulence factors, adaptive immunity impaired.

Epidemiology: spread via droplets, winter and spring

Diagnosis: white spots in the throat, throat swab

Treatment: Penicillin

Prevention: hand washing

Diphtheria

Causative agent: Corynebacterium diphtheria

Classification: High G+C Gram Pos.

Signs/Symptoms: sore throat, localized pain, fever, presence of pseudo membrane.

Pathogenesis: Diphtheria toxin prevents polypeptide, cell death, synthesis

Epidemiology: spread via droplets, skin to skin contact.

Diagnosis: presence of pseudo membrane.

Treatment: antitoxin and antibiotics

Prevention: immunizations

Rhino-sinusitis

Causative agent: respiratory microbiota

Classification: Low G+C Gram Pos. ?

Signs/Symptoms: malaise, headache, inflamed nasal passages

Pathogenesis: damage to upper respiratory system or auditory tubes.

Epidemiology: more common in adults

Diagnosis: symptoms

Treatment: flushing nasal passages and sinus cavities with saline solution.

Prevention: no way to prevent.

Otitis Media

Causative agent: respiratory microbiota

Classification: Low G+C

Signs/Symptoms: severe pain in ears.

Pathogenesis: damage to auditory tubes/upper respiratory system

Epidemiology: more common in young children

Diagnosis: symptoms

Treatment: flushing nasal passages and sinus cavities

Prevention: no way to prevent

Common cold

Causative agent: enteroviruses or rhinoviruses

Classification: viral infection of URI

Signs/Symptoms: sneezing, runny nose, congestion, sore throat, malaise, coughing

Pathogenesis: cold viruses replicate at low temps. and kill infected cells of the nasal cavity.

Epidemiology: rhinoviruses highly infective, spread by fomites, person to person contact.

Diagnosis: signs and symptoms

Treatment: pleconaril can reduce symptoms

Prevention: hand antisepsis

Pneumococcal Pneumonia

Causative agent: streptococcus pneuominae

Classification: Low G+C

Signs/Symptoms: fever, chills, congestion, cough, chest pain

Pathogenesis: bacterial replication, virulence factors, pneumococcal A destroy and secrete IgA

Epidemiology: occurs by inhaling bacteria

Diagnosis: identifying diplococci in sputum smears

Treatment: Penicillin, some are resistant

Prevention: Vaccinations

Tuberculosis

Causative agent: Mycobacterium tuberculosis

Classification: High G+C Gram Pos.

Signs/Symptoms: not always apparent. Minor cough and mild fever

Pathogenesis: mycolic acid is present.

Epidemiology: spreading via inhalation of droplets

Diagnosis: skin tests, chest X-rays

Treatment: drug resistant strain of M. Tuberculosis

Prevention: BCG vaccine

Whooping Cough

Causative agent: bacterium bordetella pertussis

Classification: Gram negative coccobacillus

Signs/Symptoms: cold like symptoms, cough develops

Pathogenesis: adhesion and toxins, virulence factors

Epidemiology: highly contagious, airborne droplets

Diagnosis: symptoms

Treatment: supportive

Prevention: Dtap vaccine

Influenza

Causative agent: influenza virus A & B

Classification: negative sense, RNA single strand

Signs/Symptoms: fever, pharyngitis, congestion, cough, myalgia

Pathogenesis: mutations in hemaggulation and neuraminidase

Epidemiology: transmitted via inhalation, self inoculation

Diagnosis: signs and symptoms

Treatment: oseltamavir, supportive care, zanamivir

Prevention: multivalent vaccine

Respiratory Syncytial Virus

Causative agent: human respiratory syncytial virus

Classification: negative sense, RNA virus, distantly related to measles and mumps viruses

Signs/Symptoms: fever, runny nose, coughing in babies and immunocomprised individuals, cold-like symptoms in older children and adults.

Pathogenesis: virus causes syncytia to form in the lungs. Immune response to RSV further damages the lungs.

Epidemiology: most common childhood respiratory disease, transmission via close contact with infected person.

Diagnosis: immunoassay

Treatment: supportive treatment for young children

Prevention: aseptic technique of health care and day care employees