Chapter 15

Vocabulary flashcards covering key terms and concepts from Chapter 15 on microbial pathogenicity, including portals of entry, virulence factors, enzymes, and toxins.

Pathogenicity

Ability of a microbe to cause disease by overcoming host defenses.

Virulence

Degree or extent of pathogenicity that a microbe possesses.

Portal of Entry

Specific route by which a pathogen gains access to a host.

Mucous Membranes

Linings of respiratory, gastrointestinal, genitourinary tracts, and conjunctiva that can be penetrated by pathogens.

Respiratory Tract Entry

Inhalation of microbes; the easiest and most common portal of entry.

Gastrointestinal Tract Entry

Ingestion of pathogens via contaminated food, water, or fingers.

Genitourinary Tract Entry

Sexual transmission portal; includes HIV, gonorrhea, syphilis, etc.

Skin (Portal)

Entry through breaks such as hair follicles, sweat gland ducts, or wounds.

Parenteral Route

Direct deposition of microbes beneath skin or mucous membranes via punctures, bites, injections, surgery, etc.

Preferred Portal of Entry

Specific route a pathogen must use to cause disease successfully.

ID50

Infectious dose required to infect 50 % of a test population.

LD50

Lethal dose of a toxin that kills 50 % of a test population.

Adherence (Adhesion)

Attachment of a microbe to host tissue; essential for infection.

Adhesin (Ligand)

Surface molecule on a pathogen that binds to specific host-cell receptors.

Glycocalyx (Adhesion)

Sticky capsule used for attachment; e.g., Streptococcus mutans.

Fimbriae

Hair-like appendages that aid attachment; e.g., Escherichia coli.

Biofilm

Community of microbes attached to a surface and embedded in an extracellular matrix.

Capsule

Polysaccharide coat that prevents phagocytosis (e.g., S. pneumoniae).

M Protein

Cell-wall protein of Streptococcus pyogenes that resists phagocytosis.

Opa Protein

Outer-membrane protein of Neisseria gonorrhoeae that inhibits T helper cells.

Mycolic Acid

Waxy lipid in Mycobacterium tuberculosis cell wall that resists digestion.

Coagulase

Bacterial enzyme that coagulates fibrinogen to form blood clots.

Kinase

Enzyme that digests fibrin clots, allowing pathogen spread.

Hyaluronidase

Enzyme that hydrolyzes hyaluronic acid in connective tissue.

Collagenase

Enzyme that breaks down collagen, facilitating tissue invasion.

IgA Protease

Enzyme that destroys protective IgA antibodies on mucosal surfaces.

Antigenic Variation

Process by which pathogens alter surface antigens to evade immunity.

Invasin

Bacterial protein that rearranges host actin to enter cells (e.g., Salmonella).

Siderophore

Pathogen-secreted protein that binds host iron more tightly than host molecules.

Toxin

Substance produced by microbes that contributes to pathogenicity.

Toxigenicity

Ability of a pathogen to produce toxins.

Toxemia

Presence of toxins in the bloodstream.

Toxoid

Inactivated toxin used as a vaccine to induce immunity.

Antitoxin

Antibody that neutralizes a specific toxin.

Exotoxin

Protein toxin secreted by living bacteria; highly potent and specific.

A-B Toxin

Exotoxin with an Active (A) enzyme part and Binding (B) part; e.g., diphtheria toxin.

Membrane-Disrupting Toxin

Exotoxin that lyses host cells by damaging plasma membranes.

Superantigen

Exotoxin provoking massive cytokine release from T cells, causing severe inflammation.

Genotoxin

Exotoxin that damages host DNA, leading to mutations or cancer.

Leukocidin

Membrane-disrupting toxin that kills phagocytic leukocytes.

Hemolysin

Toxin that lyses erythrocytes by forming channels in membranes.

Streptolysin

Hemolysin produced by streptococci; damages blood cells and tissues.

Endotoxin

Lipid A portion of LPS in gram-negative bacteria released on cell lysis.

Lipid A

Toxic component of lipopolysaccharide responsible for endotoxin effects.

Endotoxic Shock

Life-threatening drop in blood pressure caused by high endotoxin levels.

Limulus Amebocyte Lysate (LAL) Assay

Laboratory test using horseshoe crab blood cells to detect endotoxins.

Portal of Exit

Route by which a pathogen leaves the host (e.g., respiratory droplets, feces, blood).