PathologyLesson 1 of 1 in the course Respiratory System Infections

Bacterial Respiratory Infections: Pathogens, Mechanisms, and Clinical Features

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

This lesson focuses on group A streptococcal infections, especially strep throat, and the important complications that may follow an untreated infection. Understanding the organism, its symptoms, transmission, diagnosis, and sequelae helps explain why timely treatment matters.

Streptococcal pharyngitis, commonly called strep throat, is usually caused by Streptococcus pyogenes. It is a gram-positive coccus that typically forms chains. Lancefield classification groups streptococci according to cell-wall carbohydrate antigens. S. pyogenes is the main member of Lancefield group A, so it is also called group A strep, or GAS.

All flashcards

How do acute otitis media and otitis media with effusion differ?
Acute otitis media is an infection of the middle ear; otitis media with effusion is trapped fluid that can occur without active infection.
Which bacteria commonly cause bacterial rhinosinusitis?
Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis are common causes.
What is consolidation in pneumonia?
Accumulation of fluid and white blood cells in the alveoli, which impairs gas exchange.
What is a Ghon complex?
A calcified lesion associated with tuberculosis that may be visible on a chest radiograph.
What serious complication can chronic Q fever cause?
Chronic Q fever can cause endocarditis, which may be fatal.

Quiz questions

  1. How does streptokinase help Streptococcus pyogenes spread through tissue?Answer: It activates plasmin, which breaks down fibrin and dissolves clots.
  2. How does diphtheria toxin damage host cells?Answer: It inactivates elongation factor 2 and blocks protein synthesis.
  3. Why are beta-lactam antibiotics ineffective against Mycoplasma pneumoniae?Answer: It lacks the cell wall that beta-lactams target.
  4. During which stage of pertussis is a person most infectious?Answer: The catarrhal stage, when symptoms resemble a mild cold.
  5. How does Legionella pneumophila survive inside alveolar macrophages?Answer: It prevents lysosomal fusion with the phagosome.

Based on Microbiology by Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu, Philip Lister, Brian M. Forster (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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