chapter 21 micro learning objectives

What causes strep throat?

Streptococcus pyogenes (Group A strep), Gram-positive, β-hemolytic

Key symptoms of strep throat?

Sore throat, fever, red throat with pus patches, difficulty swallowing

What causes diphtheria?

Corynebacterium diphtheriae (Gram-positive rod)

Key symptom that distinguishes diphtheria?

Thick pseudomembrane in throat + “bull neck” swelling

Major difference in pathogenesis? (Strep vs diphtheria)

• Strep: invasive bacterial infection of throat

• Diphtheria: toxin-mediated disease (kills cells by stopping protein synthesis)

Serious complications? (Strep vs diphtheria)

• Strep: rheumatic fever, glomerulonephritis

• Diphtheria: heart failure, paralysis

Most common cause of the common cold?

Rhinoviruses (~30–50%)

Key symptoms of common cold?

Runny nose, sore throat, cough, usually no fever

Hallmark of adenovirus infection?

Fever is common

Other adenovirus symptoms?

Sore throat, pus on tonsils, swollen lymph nodes, pink eye

Main difference? (Cold vs adenovirus)

• Cold: mild, afebrile

• Adenovirus: fever + more severe symptoms, may mimic strep/pneumonia

Pneumococcal pneumonia cause

Streptococcus pneumoniae (Gram+ diplococcus)

Distinctive feature of pneumococcal pneumonia

Rust-colored sputum

Klebsiella Pneumonia Cause?

Klebsiella pneumoniae (Gram− rod, large capsule)

Distinctive feature of Klebsiella Pneumonia

Bloody, jelly-like sputum

Typical patients of Klebsiella Pneumonia

Alcoholics, hospitalized, immunocompromised

Mycoplasma Pneumonia (“Walking Pneumonia”) Cause?

Mycoplasma pneumoniae (no cell wall)

Mycoplasma Pneumonia (“Walking Pneumonia”) Distinctive features?

• Mild symptoms

• Dry cough

• Gradual onset

• Common in young adults

Compare the 3 pneumonias

• Pneumococcal: acute, rust sputum

• Klebsiella: severe, jelly sputum

• Mycoplasma: mild, dry cough (walking pneumonia)

What is antigenic drift?

Small mutations in HA/NA genes → seasonal flu

What is antigenic shift?

Major reassortment of RNA segments → new strain

Epidemiological impact of drift?

Causes annual epidemics

Epidemiological impact of shift?

Causes pandemics (global outbreaks)

Why new flu vaccines yearly?

Due to antigenic drift

RSV (Respiratory Syncytial Virus) Who is most affected?

Infants & young children

RSV symptoms

Wheezing, bronchiolitis, difficulty breathing

Hantavirus Pulmonary Syndrome Transmission?

Inhalation of rodent droppings/urine dust

Hantavirus Pulmonary Syndrome Key features?

Rapid progression → severe lung fluid buildup, shock, high mortality

SARS (Coronavirus) Cause?

SARS-CoV (coronavirus)

SARS (Coronavirus) Unique feature vs other respiratory infections?

No early upper respiratory symptoms

SARS (Coronavirus) Symptoms

Fever, dry cough, pneumonia, respiratory distress

Compare RSV, Hantavirus, and SARS

• RSV: infants, bronchiolitis, wheezing

• Hantavirus: rodent exposure, severe lung failure

• SARS: coronavirus, severe pneumonia, systemic illness