PRELIM 06 - Bacterial Mechanisms of Pathogenicity Flashcards
The ability to cause disease by overcoming host defenses
Pathogenicity
The degree of pathogenicity
Virulence
3 portals of entry
Mucous membranes, Skin, Parenteral
Epithelium lining the respiratory tract, GIT, GUT, and conjunctiva
Mucous membranes
Skin that is impenetrable by most microorganisms
Unbroken skin
Is a parasite that bores through intact skin
Hookworm
It grows on keratin in skin or infect the skin itself
Fungi
The number of pathogen cells or virions required to cause active infection in 50% of inoculated animals
ID50/Median infective dose
The number of pathogenic cells or virions required to kill 50% of infected animals
LD50/Median lethal dose
These bind surface receptors on the cells of certain host tissues
Adhesins/Ligands
Glycocalyx (Adherence factors)
Streptococcus mutans
Fimbriae (Adherence factors)
Actinomyces, Streptococcus pyogenes
Fimbriae, pili (Adherence factors)
Enteropathogenic Escherichia coli
Fimbriae, opacity associated proteins (Adherence factors)
Neisseriae gonorrhoeae
Tapered end as hook (Adherence factors)
Treponema pallidum
Produces adhesins that bind to laminin and fibronectin on skin cells (Adherence factors)
Staphylococcus aureus
Converts fibrinogen to fibrin that coagulates the blood to protect bacteria from phagocytosis and defenses (Enzymes)
Coagulase
Breaks down fibrin and digests clots (Enzymes)
Kinase
A kinase produced by Streptococcus pyogenes
Fibrinolysin/Streptokinase
Hydrolizes hyaluronic acid, which holds together cells in connective tissues (Enzymes)
Hyaluronidase
Breaks down collagen in connective tissues (Enzymes)
Collagenase
Destroys IgA (Enzymes)
IgA protease
Prevents phagocytic cells from adhering to the bacterium
Capsule
A heat-resistant and acid-resistant protein produced by Streptococcus pyogenes
M protein
Waxy lipid that makes up the cell wall of Mycobacterium tuberculosis
Mycolic acid
An aggregate of interactive bacteria attached to a solid surface or to each other and encased in an exopolysaccharide matrix
Biofilms
Process by which pathogens can alter surface antigens
Antigenic variation
2 examples of bacteria that undergo antigenic variation
Neisseria gonorrhoeae, Borrelia recurrentis
Enables M. tuberculosis, L. monocytogenes, Brucella species, and Legionella species to live and grow in the hostile environment within PMN, macrophages, or monocytes
Intracellular pathogenicity
These take the iron away from iron-transport proteins by binding the iron even more tightly
Siderophores
Can induce host epithelial cells to engulf them similarly to phagocytosis
Direct damage
Poisonous substances that are produced by certain microorganisms
Toxins
Capacity to produce toxins
Toxigenicity
Refers to the presence of toxins in the blood
Toxemia
Caused by the presence of a toxin; not by microbial growth
Intoxication
2 types of toxins
Endotoxins, Exotoxins
Are toxins that are part of bacterial cells, not a metabolic product; released during bacterial multiplication
Endotoxins
A sensitive test to identify the presence of endotoxin in drugs, medical devices, and body fluids
Bacterial endotoxin test
Other name for bacterial endotoxin test
Limulus amebocyte lysate (LAL) assay
The hemolymph of the horshoe crab, __________, contains white blood cells called amebocytes, which have large amounts of a protein that causes clotting
Limulus polyphemus
Are toxins produced inside a bacterium as part of growth and metabolism; secreted into the outside medium or released following lysis
Exotoxins
Diphtheria toxin is an example of __________
Exotoxin
Antibodies that provide immunity to exotoxins
Antitoxins
Exotoxins inactivated by heat or by formaldehyde, iodine, or other chemicals
Toxoids
3 types of exotoxins
A-B toxins, Membrane-disrupting toxins, Superantigens
Are toxins that include 2 polypeptides: A (enzyme component) and B (binding component)
A-B toxins
A component in A-B toxins
Enzyme component
B component in A-B toxins
Binding component
Botulinum toxin is an example of an __________ toxin
A-B toxin
Are toxins that cause lysis of host cells by disrupting their plasma membranes
Membrane-disrupting toxins
Kill phagocytes by forming protein channels
Leukocidins
Kill erythrocytes by forming protein channels
Hemolysins
Are produced by streptococci
Streptolysins
Are produced by Listeria monocytogenes
Membrane-attack complexes (MACs)
Are antigens that provoke a very intense immune response
Superantigens
Toxic shock syndrome toxin-1 (TSST-1) is an example of __________
Superantigen
Are factors related to resistance to antibiotics
R factors
Diseases that occur primarily in animals and can be transmitted to humans
Zoonoses
Antibiotic used for Staphylococcus aureus infection
Cefazolin
