Microbiology Chapter 24
What is the most common type of human infection?
Upper respiratory infections.
What prevents microorganisms from reaching the lungs?
The ciliary escalator.
What antibody is found in respiratory mucus?
IgA.
Why don’t normal throat microbiota cause disease?
Competition with predominant microbes.
Why is the lower respiratory system usually sterile?
Ciliary escalator action.
Streptococcal Pharyngitis
What organism causes strep throat?
Group A β‑hemolytic Streptococcus pyogenes.
What is the treatment for strep throat?
Penicillin.
What toxin causes scarlet fever?
Erythrogenic toxin (from lysogenized S. pyogenes).
What are hallmark signs of scarlet fever?
Red rash, high fever, strawberry tongue, peeling skin.
What produces diphtheria toxin?
Lysogenized Corynebacterium diphtheriae.
What dangerous structure forms in the throat?
A tough gray membrane that can block the airway.
What does diphtheria toxin inhibit?
Protein synthesis.
What vaccine prevents diphtheria?
DTaP (diphtheria toxoid).
What causes the pain in otitis media?
Pus pressure on the eardrum.
Major bacterial causes of otitis media?
What virus causes ~50% of colds?
Rhinovirus.
How are colds most often transmitted?
Indirect contact.
Why do rhinoviruses prefer the upper airway?
They grow best at slightly lower temperatures.
What blocks ciliary action in pertussis?
Dense masses of bacteria in trachea/bronchi.
What are the 3 stages of pertussis?
What vaccine prevents pertussis?
Acellular pertussis vaccine (part of DTaP).
What gives TB its acid‑fast property?
High lipid content in the cell wall.
What is a Ghon complex?
Calcified caseous lesion seen on X‑ray.
What is miliary TB?
Disseminated TB with millet seed‑like lesions.
What drugs treat TB?
INH, rifampin, streptomycin, ethambutol.
What vaccine is used outside the U.S.?
BCG (live attenuated M. bovis).
What organism causes pneumococcal pneumonia?
Streptococcus pneumoniae
What sputum color is classic for pneumococcal pneumonia?
Rust‑colored sputum.
Why is Mycoplasma pneumoniae atypical?
No cell wall → “walking pneumonia”.
Where does Legionella grow?
Water systems (AC cooling towers, plumbing).
What is the reservoir for psittacosis?
Birds (parrots, parakeets).
What is the most common cause of infant pneumonia?
RSV.
What viral structures define influenza strains?
H (hemagglutinin) and N (neuraminidase) spikes.
What causes pandemics?
Antigenic shift.
What causes seasonal outbreaks?
Antigenic drift.
What region is Coccidioides immitis found in?
Southwestern U.S. (dry soils).
What form is seen in tissue?
Spherules with endospores.
What patients are most at risk for Pneumocystis pneumonia?
AIDS / immunosuppressed.