Respiratory System

Protection of Lower Respiratory Tract

Saliva, tears, mucous surfaces, nose hairs

Protection of Lower Respiratory Tract

• Ciliary escalator

• Alveolar macrophages

• Mucus

Normal Microbiota of Respiratory System

• Potentially pathogenic microbes are part of normal microbiota

• Lower respiratory is nearly sterile

Cause of Streptococcal pharyngitis ( Strep throat)

Group A Streptococci (GAS) ; Streptococcus pyogenes

• Resistant to phagocytosis

• Streptokinases lyse clots

• Streptysins are cytotoxic

Transmission of Streptococcal pharyngitis ( Strep throat)

Respiratory droplets (via coughing, sneezing, or talking) and direct contact with infected mucus or saliva

Signs/Symptoms of Streptococcal pharyngitis ( Strep throat)

Local inflammation, fever, tonsillitis, enlarged lymph nodes

Cause of Scarlet Fever

Streptococcus pyogenes (strain that cause strep) produces erythrogenic (reddening) toxin from being lysed

Scarlet Fever Transmission

Through respiratory droplets (coughs or sneezes) or direct contact with an infected individual

Scarlet Fever Signs/Symptoms

A distinctive red, sandpaper-like rash, a high fever, and a very sore throat

Diphtheria Cause

Corynebacterium diphtheriae ; Gram-positive rod; pleomorphic

Diphtheria Transmission

Through respiratory droplets, such as when an infected individual coughs or sneezes

Diphtheria Signs/Symptoms

• Start with sore throat and fever

• Progress to form tough greyish membrane in throat

  • Blocks passage to lungs

  • Fibrin and dead tissue

How does Diphtheria get into blood?

The exotoxin that gets produced when it gets lysed can enter bloodstream ; can damage heart and kidneys

Diphtheria Treatment/Preventative

• Treatment : antibiotics and antitoxin

• Preventative : DTaP vaccine

Otitis Media Cause

Streptococcus pneumoniae (most common), Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pyogenes, Respiratory syncytial viruses (RSV)

DTaP Vaccine

Diphtheria, tetanus (lockjaw), and pertussis (whooping cough) vaccine for children under 7

Otitis Media

Infection of middle ear ; formation of pus puts pressure on eardrum

Otitis Media Treatment

Broad-spectrum penicillins

Common population that gets infected with Otitis Media

Children because auditory tube connecting middle ear to throat is small and more horizontal ; easily blocked

Common Cold Cause

Over 200 different viruses ; most are Enterovirus rhinovirus (30-50%)

Common Cold Transmission

Through airborne droplets and direct contact with contaminated surfaces or people

Common Cold Signs/Symptoms

Sneezing, nasal secretions, congestion ; can lead to laryngitis and otitis media.

No fever

Common Cold Treatment

No cure, but you can get relief via cough suppressants and antihistamines

Pertussis (Whooping Cough) Cause

Bordetella pertussis ; Gram-negative coccobacillus

How does Bordetella pertussis affect body?

• Produces a capsule that allows attachment to ciliated cells in trachea and destroys it.

• Tracheal cytotoxin damages ciliated cells

• Pertussis toxin can enter bloodstream

  • Cause systemic symptoms

Catarrhal Stage of Pertussis

Resembles the common cold

Paroxysmal Stage of Pertussis

Violent coughing, gasping for air (last 1-6 weeks)

Convalescence Stage of Pertussis

Recovery phase where the intense coughing fits subside, making way for a gradual return to health ; can last months

Pertussis Prevention/Treatment

• Prevention : TDaP vaccine

• Treatment : eryhtromycin or other lacrolides

  • Not effective in paroxysmal stage, but can reduce transmission

Pertussis Transmission

Airborne/droplets

Tuberculosis Cause

Mycobacterium tuberculosis ; Acid-fast rod; obligate aerobe

Tuberculosis Transmission

Airborne

Tuberculosis Signs/Symptoms

Bad cough lasting three weeks or longer, chest pain, and coughing up blood or phlegm

Diagnosis of TB

• QuantiFERON Gold or skin test

• Followed by chest x-ray, CT, staining, and culture of sputum (if previous was positive)

TB Treatment

Minimum 6 months of drug therapy due to slow growth and dormancy of bacteria

TB First-Line Drugs (First Option)

isoniazid, rifampin, ethambutol, pyrazinamide

TB Second-line drugs

aminoglycosides, fluoroquinolones, streptomycin, para-aminosalicylic acid (PAS)

Pathogenesis of TB

• Microbe phagocytized by alveolar macrophage

• Mycolic acid in cell wall stimulate inflammatory response

• Microbe is isolated in walled off tubercles

  • Can be calcified (latent TB)

  • Reactivate (Active)

TB Prevention

BCG vaccine ; most widely used worldwide, but not in USA

• Can cause TB test to be positive

• Uneven effectiveness

• Can cause fatal infection in children with HIV

Bacterial Pneumonia

• Typically caused by Streptococcus pneumoniae (typical pneumonia)

  • Health-care is usually Staphylococus aureus

Atypical Pneumonia

Pneumonia caused by other microbes that’s not S.pneumoniae

Lobar Pneumonia

Pneumonia that affects lobes of lungs

Bronchopneumonia

Pneumonia that affects alveoli adjacent to bronchi

Pleurisy

Inflamed pleural membrane

Pneumococcal Pneumonia

• Caused by Streptococcus pneumoniae

  • Gram-positive, encapsulated diplococci

• Infects bronchi/alveoli, filling with fluids, RBCs, and neutrophils

• Symptoms: high fever, chest pain, difficulty breathing

Pneumococcal Pneumonia Diagnosis and Treatment/Prevention

• Diagnosis: culture of mucus/fluid of infected areas

• Treated with macrolides

• Prevented with conjugated pneumococcal vaccine (23 types)

Haemophilus Influenzae Pneumonia

• Gram-negative coccobacillus

• Symptoms resemble those of pneumococcal pneumonia

  • high fever, chest pain, difficulty breathing

Haemophilus Influenzae Pneumonia Diagonsis and Treatment/Prevention

• Diagnosis: isolation on special media for nutritional requirements (X and V factors)

• Hib vaccine

• Treated with third generation cephalosporins

Mycoplasmal Pneumonia

• atypical pneumonia or walking pneumonia

• Caused by Mycoplasma pneumoniae ; no cell wall

• Mild but persistent respiratory symptoms; low fever, cough,
  headache

Mycoplasmal Pneumonia Diagnosis and Treatment

• “Diagnosis: PCR test

• Treated with tetracyclines (antibiotic)

Legionellosis / Legionnaires’ disease

• Caused by Legionella pneumophila ; Aerobic, gram-negative rod

• Transmitted by inhaling aerosols; not transmitted person to person

• Symptoms: high fever and cough

Legionellosis / Legionnaires’ disease Treatment

Treated with azithromycin and macrolides

Viral Pneumonia

• Occurs as a complication of influenza, measles, chickenpox or COVID

• Non-contagious, but viruses that can cause it is ; ex. COVID and influenza

• Fever, dry cough, headache, and muscle pain

COVID-19

• Caused by coronavirus SARS-CoV-2

• Fever, shortness of breath, cough, runny nose, nasal congestion, sore throat, headache, muscle/joint pain, fatigue, abdominal pain, diarrhea, vomiting, loss of smell and taste

• Can cause pneumonia

Respiratory Syncytial Virus (RSV)

• Most common viral respiratory disease in infants

• Causes cell fusion (syncytium) in cell culture

• Coughing and wheezing for more than a week

Respiratory Syncytial Virus (RSV) Diagnosis and Treatment/Prevention

• Diagnosis: serological test for viruses and antibodies

• Treated with palivizumab

• Prevent with RSV vaccine