Bacterial Diseases and Pathogenesis Lecture Review

Flashcards covering bacterial diseases, pathogenic actions, key bacteria like Neisseria meningitidis and Haemophilus influenzae type B, their clinical manifestations, and virulence factors.

Bacterial Disease

Caused by damage produced by bacteria and the consequences of innate and adaptive immune responses. Signs and symptoms depend on the function and importance of the affected tissue.

Incubation Length (Bacterial Disease)

The time required for bacteria or the host's immune response to cause sufficient damage to initiate discomfort or interfere with essential functions.

Pathogenic Actions of Bacteria

Include tissue destruction by bacterial by-products

release of endotoxins

secretion of exotoxins.

Tissue Destruction (Bacterial)

Caused by bacterial by-products (e.g., products of fermentation) that are toxic to tissue.

Endotoxins

Part of the bacterial cell structure (e.g., Lipid A in LPS), released only when the bacterial cell dies, capable of causing damage.

Exotoxins

Proteins produced inside pathogenic bacteria that are secreted into the surrounding medium and can damage other cells.

Superantigens

A special type of toxin that broadly activates T cells by binding to MHC class II and TCR outside the antigen-binding site, leading to a massive cytokine release.

Meningococcal Disease

One of the main causes of meningitis, particularly in young adults, with peak incidence among college students.

Neisseria meningitidis

A Gram-negative

encapsulated

aerobic diplococcus bacterium,

categorized into serotypes, which is a common cause of meningococcal disease.

Diplococcus

A type of bacterium that is spherical in shape and typically appears in pairs.

Gram-negative bacteria

Bacteria that do not retain the crystal violet stain during the Gram staining procedure and appear red or pink after counterstaining.

Meningococcal Disease Transmission

Transmitted by aerosol droplets or direct contact, such as kissing. Carriage rates are higher among adolescents and young adults, and it becomes dangerous when the organism enters the bloodstream.

Meningitis Symptoms

Include abrupt onset of fever, headache, photophobia, malaise, stiff neck (nuchal rigidity), nausea, vomiting, confusion, and can sometimes lead to seizures or a rash.

Acute Meningitis

A common clinical manifestation of meningococcal disease characterized by rapid onset of symptoms like fever, headache, photophobia, and nuchal rigidity.

Meningococcemia

A severe form of sepsis caused by Neisseria meningitidis, leading to high white blood cell counts and potentially fatal outcomes or permanent sequelae.

Photophobia (Meningitis)

Increased sensitivity to light, a common symptom associated with meningitis.

Nuchal Rigidity

Stiff neck, a distinctive symptom of meningitis.

Pathogenesis of Meningococcal Disease

Involves attachment to pharyngeal mucosal cells via pili

replication to establish a carrier state

entry into the bloodstream

rapid bacterial doubling

endotoxins in outer membrane vesicles

endotoxin levels correlate with disease severity.

Manifestations of Meningococcal disease

Headache

Fever

Stiff Neck

Confusion

Increase sensitivity to light

Nausea

Vomiting

Hib bacteria (Haemophilus Influenzae type B)

A Gram-negative coccobacillus bacterium whose serotype b is the most important in human pathogenesis, primarily due to its polysaccharide capsule acting as a major virulence factor.

Coccobacillus

A bacterium shaped as a short rod, intermediate between a coccus (spherical) and a bacillus (rod-shaped).

Polysaccharide capsule (Hib)

A major virulence factor for Haemophilus influenzae type b, enhancing its survival, particularly in the bloodstream.

Hib infection

An infection caused by Haemophilus influenzae type b that can lead to serious conditions like meningitis and septicemia, spread by respiratory droplets or close contact.

Virulence factors of Hib

Include its polysaccharide capsule

endotoxins (toxic to epithelial cells)

pili for adherence to host cells.

Pathogenesis of Hib infection

Involves entering the respiratory tract, colonizing mucosa

potentially entering the bloodstream to cause disease at distal sites such as meningitis, cellulitis, pneumonia, or arthritis.

Sequelae

A condition that is a consequence of a previous disease or injury