Bacterial Pathogenesis Flashcards

Vocabulary-style flashcards covering the mechanisms of bacterial pathogenesis, virulence factors, toxins, and specific study of pathogens like S. pyogenes and M. tuberculosis.

Pathogenesis

Processes used by pathogens to produce disease.

Virulence factors

Pathogen products that enhance their ability to cause disease.

Fibronectin

Large plasma glycoprotein in plasma and extracellular matrix that serves as a common target for pathogen binding.

Fimbriae

Specialized pili with an adhesive tip that bind to specific receptors on a host cell to bypass negative charges.

Tir (Translocated intimin receptor)

A bacterial protein placed into host intestinal cells via a type III secretion system to interact with Intimin and form a pedestal for attachment.

Intimin

A protein on pathogenic Escherichia coli cells that interacts with Tir on intestinal cells to help form lesions that release nutrients.

Capsule

An extracellular loose matrix of polysaccharides that provides attachment, blocks opsonization, interferes with phagocytosis, and mimics "self" molecules.

Siderophores

Iron-binding molecules produced by bacteria that compete with host iron-binding proteins to obtain limiting nutrients.

Hemolysin

A type of cytolysin that lyses host cells, such as erythrocytes, to allow pathogens access to their iron stores.

Endotoxins

Toxins that are part of the bacterial cell wall structure and induce inflammatory responses, such as Lipopolysaccharide (LPS).

Lipopolysaccharide (LPS)

The most common endotoxin on Gram-negative cells, consisting of O-antigen, core polysaccharide, and Lipid A.

Lipid A

The specific portion of the Lipopolysaccharide (LPS) molecule that induces inflammatory responses.

Lipoteichoic acid (LTA)

An endotoxin found on Gram-positive cells that is recognized by TLRs and capable of inducing inflammation.

Exotoxins

Toxins released outside the producing cell, categorized into A-B toxins, cytolysins, and superantigens.

A-B toxins

Toxins where the B subunit binds to a host cell receptor and the A subunit exerts enzymatic activity inside the host cell.

Cytolysins

Exotoxins that work on plasma membranes by forming pores or degrading phospholipids.

Superantigens

Exotoxins that nonspecifically stimulate a large population of $CD4^+$ T cells to secrete massive amounts of cytokines.

Diphtheria toxin

An A-B toxin produced by Corynebacterium diphtheriae that adds an ADP-ribose unit to translation factor EF2, halting protein synthesis.

Pseudomembrane

A distinctive fibrous, walled-off lesion in the pharynx resulting from local cell death caused by diphtheria toxin.

Botulinum toxin

An A-B toxin that cleaves SNARE proteins in stimulatory nerve terminals, preventing the release of acetylcholine and blocking muscle contraction.

Tetanus toxin

An A-B toxin that cleaves the SNARE protein synaptobrevin in inhibitory nerve terminals, leading to continuous muscular contraction.

Listeriolysin

A cytolysin produced by Listeria monocytogenes that forms pores in the acidic environment of the phagosome, allowing the pathogen to escape into the cytoplasm.

Staphylococcus aureus \alpha-hemolysin

A pore-forming cytolysin that binds to host cells as monomers and oligomerizes to form small pores that allow calcium ion influx, inducing apoptosis.

Post-streptococcal sequelae

Conditions such as glomerulonephritis or rheumatic heart disease that occur as a consequence of a previous Streptococcus pyogenes infection.

M protein

A Streptococcus pyogenes virulence factor that binds antibodies in an inverted orientation and can cross-react with heart myosin.

Mycolic acids

Unusual cell wall components found in the genus Mycobacterium that resist common staining methods.

Lipoarabinomannan (LAM)

A complex cell wall component of Mycobacterium tuberculosis that downregulates the oxidative burst and neutralizes toxic oxygen species.

Granulomas

Walled-off areas of chronic inflammation in lung tissue created when macrophages cannot eliminate Mycobacterium tuberculosis.

Caseous necrosis

A condition in the lungs with a pale, cheese-like consistency resulting from the release of toxic macrophage compounds when granulomas crack open.

Pathogenicity Islands

Large stretches of DNA in pathogenic strains that code for virulence factors and often have unusually high or low $G+C$ content.

Horizontal Gene Transfer (HGT)

The rapid swapping of genetic information, such as antibiotic resistance genes, through conjugation, transposable elements, plasmids, or phages.