Diseases of the Respiratory System: Microbiology Study Notes

Glimpse of History

Rebecca Lancefield and Streptococcal Classification

Rebecca Lancefield made significant contributions to the classification of streptococci, which are important bacterial pathogens in human disease.

• Lancefield Grouping: A system for classifying streptococci based on cell wall carbohydrates (surface antigens), rather than blood agar hemolysis.

• Strains from human infections often share the same cell wall carbohydrate ("A"), which differs from strains from other sources.

• This system is a better predictor of pathogenic potential than hemolysis patterns.

• Rebecca Lancefield was the first woman president of the American Association of Immunologists and was elected to the National Academy of Sciences.

Additional info: The Lancefield grouping is still used today to identify and differentiate clinically important streptococcal species, such as Streptococcus pyogenes (Group A Streptococcus).

Respiratory Infections

Overview and Classification

Respiratory infections are among the most common infectious diseases, ranging from mild to life-threatening. They are classified based on the part of the respiratory tract affected.

• Upper Respiratory Infections: Affect the head and neck (e.g., common cold). These are very common, generally mild, and usually resolve without treatment within about a week.

• Lower Respiratory Infections: Affect the chest (e.g., pneumonia, tuberculosis). These are less common but often more serious and potentially fatal.

Key Terms:

• Upper respiratory system: Includes the nose, nasal cavity, pharynx (throat), and epiglottis.

• Lower respiratory system: Includes the larynx (voice box), trachea (windpipe), bronchi, and lungs.

Example: The image provided shows a case of pharyngitis (sore throat), a common upper respiratory infection.

Anatomy, Physiology, and Ecology of the Respiratory System

Functions and Structure

The respiratory system is responsible for gas exchange, sound production, and olfaction. It is divided into upper and lower tracts, each with distinct anatomical and physiological features.

• Gas Exchange: Replenishes oxygen (O2) and removes carbon dioxide (CO2).

• Vocalization: Vocal cords produce sounds.

• Olfaction: The nose detects odors.

• Portals of Entry: Eyes and ears are not part of the respiratory system but serve as major portals of entry for pathogens.

Additional info: The mucociliary escalator and immune defenses (e.g., tonsils, macrophages) play crucial roles in protecting the respiratory tract from infection.