Virulence Factors Definitions Flashcards
- Cell wall – useful for bacterial viability, homeostasis, protect the bacteria
from attack by host lysozyme
- protein A - bind Fc of IgG protects, blocks immune response, & opsonization
- binding or clamping factors – attachment to host proteins
- Capsule (slime layer) – useful for
adhesion
prevents chemotaxis and
inhibit phagocytosis by polymorphonuclear leukocytes
- Adhesion
- Hide/cover the surface of the bacterial cell by depositing host sialic
acid residues on their surfaces - Thus, capsule prevents bacterial recognition by phagocytes, prevents
complement assisted opsonization (inhibit phagocytic killing)
- hyaluronidase - breaks down connective tissue between adjacent cells
(digs deeper between cells)
- catalase – protects against host reactive oxygen species (ROS) e.g. H2O2
- coagulase - clots blood to hide in it
- staphylokinase - lyses clots (fibrin) to come out of it and disperse itself
- lipase - digest lipids, thus allows to colonize skin surface & sebaceous
glands
- protease - destroys tissue proteins
- beta-lactamases - inactivate beta-lactam drugs’ thus, survive treatment
- hemolysin (alpha, beta, or gamma) - destroys red blood cells,
neutrophils, macrophages, platelets
- cytolytic toxins (leukocidin)- destroy cell membranes of host cells
(leukocytes)
- exfoliative toxin – separate skin layers, resulting in impetigo & skin
layer peel off
- toxic shock syndrome (TSS) toxin – causes
a. shock &
b. superantigens (Mass T cell activation i.e. 20% of all body T cells)
- enterotoxins – 20 toxins in total. They cause
a. food poisoning by stimulating the gut motility (vomiting) &
b. superantigens
Lipoteichoic
acid
* Adhesion
* Cytotoxic for most host cells
Protein M
- Adhesion and inhibition of phagocytic ingestion.
- Protein M binds the Fc region of IgG & prevents opsonization
Protein G
* Compete with complement to bind with the constant Fc region of IgG
of diverse animal species.
* It binds and accumulates IgG on the bacterial surface through non-
immune binding, leading to prevention for opsonization
Nuclease
(Type A,B, C,
& D)
* Facilitate liquefaction of pus (converts pus to resources/substrates
to utilize it and grow)
* Have DNase activity (A & C) and RNase activity (B&D) to destroy
host cells and host defense
Streptokinases
* Catalyze conversion of plasminogen to plasmin, leading to digestion
of fibrin (lyse blood clots to escape and spread from the clots)
C5a
peptidases
* Destroy C’ chemotactic signals (C5a); thus blocks chemotaxis or
host defense cell recruitment to the infection site
Hemolysin
(, , and )
* destroys RBCs, neutro/mac/plat
Exotoxins
(streptolysin
O & S)
1. Hemolytic on blood agar
2. kills many cells including phagocytes
3. Inhibit phagocyte attraction (inhibit chemotaxis)
enterococcus
Aggregation substance = binds to host cells or bacteria-to-bacteria (conjugation)
Trafficker of AMR genes by transferring them horizontally to enterococci spp.
Acquired broad-spectrum antimicrobial resistance (AMR).
Cytolysin/hemolysin (also called bacteriocin or enterocin) =
1. kills by pore-forming on cell envelope of red and white blood cells
2. kills Gram-negative bacteria competitors = to defend its territory that contributes to niche control
Sex pheromone = stimulate expression of aggregation substances which results in conjugation;
thus, it is a means of acquiring and accumulating plasmids
Phospholipase
Pore-forming lysis on
endocytosis membrane of
the host to free itself from
lysosome (vacuoles) in the
cytoplasm of the host cell
Beta-hemolysin and Listeriolysin O
Pore-forming lysis on endocytosis
membrane of the host to free
itself from lysosome (vacuoles)
in the cytoplasm of the host cel
Actin-polymerizing protein (
actA)
instructs host cell for deposition of its actin-
filaments on the end of Listeria
Then Listeria uses the host actin filaments for
propelling to the nearby cells.
Such host actin-based zipper mechanism for
propelling and transmission from cell to cell are
used by:
Listeria, Rickettsia, and Yersinia pseudotuberculosis
Surface protective proteins (spA, B and C antigens) – for biofilm formation,
adhesion, and to elicit immune response.
These surface proteins can be used as a protective vaccine
Neuraminidase (sialidase) – for bacterial attachment, invasion, destroy blood
vessels leading to hemorrhage and thrombosis
This can lead to bacterial emboli and infarction in the heart valves (endocarditis), spleen, liver,
lung, kidney, and joints (polyarthritis)
Neutrophils is the target of the oedema factor.
Macrophages, dendritic cells neutrophils and some epithelial and endothelial cells are
the target of the lethal factor
Tetanus toxin (tetanospasmin)
* Zinc endopeptidase binds to the neurons, which release
gamma-aminobutyric acid (GABA) and glycine, the major
inhibitory neurotransmitters
* Hydrolyzes the docking proteins (VAMP aka synaptobrevin)
required by neurotransmitter-containing vesicles to fuse with the
pre-synaptic membrane
* Once the docking proteins are hydrolyzed, the synapse degenerates,
taking weeks-months to regenerate
- Botulinum neurotoxins (BoNT)
- Act in the neuromuscular junction
- Zinc endopeptidases with identical activity that binds to
cholinergic nerve cells - Decreases the release of acetylcholine
- Once hydrolyzed, the synapse degenerates, taking weeks to months
to regenerate - BoNT are secreted with accessory proteins
- Aid in the survival in the GI tract
Epsilon toxin
* Increases intestinal permeability, causes vascular damages, fluid losses,
edema
Clostridium difficile toxins
* Toxin A (Tox A or TcdA)
* ENTEROTOXIN
* Breakdown of cytoskeletal components of the affected
cell
* Disruption of the tight junctions between intestinal
epithelial cells
* RESULTS IN CELL DEATH
* Stimulates influx of polymorphonuclear cells
* Synthesis of prostaglandins
* RESULTS in secretion of chloride ions and water (Diarrhea)
