The Respiratory System

Jul 21, 2024

Chapter 19: The Respiratory System

Overview

  • Most common portal of entry for microbes because we are constantly breathing.
  • Divided into two sections:
    • Upper Respiratory Tract: Mouth, nose, sinuses, throat (everything from the throat up).
    • Lower Respiratory Tract: Trachea, bronchi, bronchioles, and alveoli (everything from the neck down).

Defense Mechanisms

  • Nose hairs & cilia: Catch or push out microbes.
  • Mucus: Traps microbes; cilia push them either up towards the mouth and nose to cough/sneeze out or down towards the esophagus to be swallowed and killed by stomach acid.
  • Cilia Example: Bacteria trapped and moved along by cilia and mucus.
  • Smoking Impact: Stuns cilia for 20 minutes, allowing microbes to grow; smokers have different microbiota that may link to cancer or other diseases.

Normal Biota

  • Upper Respiratory Tract: Thousands of microbes, commensal or beneficial.
  • Lower Respiratory Tract: Recently found to have low levels of colonization.

Upper Respiratory System Infections

1. Pharyngitis (Strep Throat)

  • Causes: Bacteria (e.g., Streptococcus pyogenes) or viruses.
  • Transmission: Respiratory droplets or direct contact with mucus secretions.
  • Prevention: Good hygiene; no vaccine.
  • Treatment: Antibiotics (for bacterial infection), wait out viral infection.
  • Symptoms: Sore throat, painful swallowing, red swollen tonsils, white patches, sometimes red spots on the palate.

2. Common Cold

  • Causes: Hundreds of viruses (mainly rhinoviruses, some coronaviruses).
  • Transmission: Respiratory droplets, indirect contact (fomites).
  • Symptoms: Itchy/watery eyes, stuffy nose, sneezing, sore throat, possible fever.
  • Treatment: Antihistamines (e.g., Benadryl), zinc (effectiveness varies).

3. Sinusitis

  • Causes: Bacterial, viral, fungal; allergies.
  • Transmission: Direct/indirect contact.
  • Symptoms: Sinus inflammation/pressure/pain.
  • Prevention/Treatment: Hygiene; antibiotics/antifungals for bacterial/fungal; allergy medicine for allergies.

4. Otitis Media (Middle Ear Infection)

  • Causes: Bacteria (e.g., Streptococcus pneumoniae) or viruses.
  • Symptoms: Ear pain, difficulty hearing, possible eardrum rupture.
  • Transmission: Usually secondary infection from upper respiratory tract.
  • Prevention/Treatment: Vaccines (Streptococcus pneumoniae), antibiotics, ear tubes for frequent cases.

5. Diphtheria

  • Causes: Bacteria (Corynebacterium diphtheriae).
  • Transmission: Respiratory droplets.
  • Virulence: Diphtheria toxin causes issues.
  • Symptoms: Pseudo membrane in throat can lead to suffocation.
  • Prevention: DTaP and Td vaccines.
  • Treatment: Antibiotics with antitoxins.

Both Upper and Lower Respiratory Tract Infections

1. Influenza (Flu)

  • Causes: Influenza viruses (A, B, C).
  • Transmission: Inhalation of droplets, fomites.
  • Symptoms: Fever, chills, headache, body aches, sore throat, extreme fatigue. No intestinal effects.
  • Virulence Factors: H spikes (attachment), N spikes (release).
  • Prevention: Annual vaccination.
  • Treatment: Antivirals if taken early (e.g., Tamiflu).
  • Mutations: Antigenic drift (small changes), antigenic shift (major changes).

2. Pertussis (Whooping Cough)

  • Causes: Bacteria (Bordetella pertussis).
  • Transmission: Respiratory droplets.
  • Prevention: DTaP vaccine.
  • Symptoms: Severe coughing fits leading to exhaustion and possible rib fractures; divided into three stages (cataract, paroxysmal, convalescent).
  • Treatment: Antibiotics.

3. Respiratory Syncytial Virus (RSV)

  • Causes: Virus causing syncytia (multi-nucleated cells).
  • Transmission: Respiratory droplets, fomites.
  • Symptoms: Severe respiratory issues in babies; mild cold in older children/adults.
  • Prevention: No vaccine; passive antibodies for high-risk infants.
  • Treatment: For severe cases in infants.

Lower Respiratory System Infections

1. Tuberculosis (TB)

  • Causes: Bacteria (Mycobacterium tuberculosis).
  • Transmission: Respiratory droplets.
  • Stages: Primary (latent, non-symptomatic & non-contagious), Secondary/Reactivate (symptomatic & contagious).
  • Symptoms: Chronic cough, fever, weight loss, tissue damage.
  • Prevention/Treatment: BCG vaccine (not common in the US), prolonged multi-drug treatment, MDR and XDR-TB are concerns.

2. Pneumonia

  • Causes: Various organisms (bacteria, viruses, fungi).
  • Transmission: Droplet contact, vehicle transfer.
  • Symptoms: Chest pain, shortness of breath, coughing, blood-stained phlegm.
  • Prevention/Treatment: Varies by the cause; vaccines for Streptococcus pneumoniae, antibiotics for bacterial, antifungals for fungal.

3. Histoplasmosis

  • Causes: Fungus (Histoplasma capsulatum).
  • Transmission: Inhaling spores (from soil, bat/bird droppings).
  • Symptoms: Acute pneumonia, potentially fatal in immunocompromised.
  • Prevention/Treatment: Avoid contaminated areas, antifungals.

Important Notes:

  • Smoking and poor hygiene increase the risk of respiratory infections.
  • Vaccinations play a crucial role in prevention (e.g., DTaP for diphtheria, pertussis).
  • Emerging Research shows new findings about microbiota in respiratory tracts and the impact of smoking.
  • Antibiotic Resistance increasing concern for diseases like TB.