Virulence Factors Definitions

Question 1

1. Cell wall – useful for bacterial viability, homeostasis, protect the bacteria
   from attack by host lysozyme

Question 2

2. protein A - bind Fc of IgG protects, blocks immune response, & opsonization

Question 3

3. binding or clamping factors – attachment to host proteins

Question 4

4. Capsule (slime layer) – useful for
    adhesion
    prevents chemotaxis and
    inhibit phagocytosis by polymorphonuclear leukocytes

Answer 4

• 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)

Question 5

1. hyaluronidase - breaks down connective tissue between adjacent cells
   (digs deeper between cells)

Question 6

2. catalase – protects against host reactive oxygen species (ROS) e.g. H2O2

Question 7

3. coagulase - clots blood to hide in it

Question 8

4. staphylokinase - lyses clots (fibrin) to come out of it and disperse itself

Question 9

5. lipase - digest lipids, thus allows to colonize skin surface & sebaceous
   glands

Question 10

6. protease - destroys tissue proteins

Question 11

7. beta-lactamases - inactivate beta-lactam drugs’ thus, survive treatment

Question 12

1. hemolysin (alpha, beta, or gamma) - destroys red blood cells,
   neutrophils, macrophages, platelets

Question 13

2. cytolytic toxins (leukocidin)- destroy cell membranes of host cells
   (leukocytes)

Question 14

3. exfoliative toxin – separate skin layers, resulting in impetigo & skin
   layer peel off

Question 15

4. toxic shock syndrome (TSS) toxin – causes
   a. shock &
   b. superantigens (Mass T cell activation i.e. 20% of all body T cells)

Question 16

5. enterotoxins – 20 toxins in total. They cause
   a. food poisoning by stimulating the gut motility (vomiting) &
   b. superantigens

Question 17

Lipoteichoic
acid
* Adhesion
* Cytotoxic for most host cells

Question 18

Protein M

Answer 18

• Adhesion and inhibition of phagocytic ingestion.
• Protein M binds the Fc region of IgG & prevents opsonization

Question 19

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

Question 20

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

Question 21

Streptokinases
* Catalyze conversion of plasminogen to plasmin, leading to digestion
of fibrin (lyse blood clots to escape and spread from the clots)

Question 22

C5a
peptidases
* Destroy C’ chemotactic signals (C5a); thus blocks chemotaxis or
host defense cell recruitment to the infection site

Question 23

Hemolysin
(, , and )
* destroys RBCs, neutro/mac/plat

Question 24

Exotoxins
(streptolysin
O & S)
1. Hemolytic on blood agar
2. kills many cells including phagocytes
3. Inhibit phagocyte attraction (inhibit chemotaxis)

Question 25

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).

Question 26

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

Question 27

Sex pheromone = stimulate expression of aggregation substances which results in conjugation;
thus, it is a means of acquiring and accumulating plasmids

Question 28

Phospholipase
Pore-forming lysis on
endocytosis membrane of
the host to free itself from
lysosome (vacuoles) in the
cytoplasm of the host cell

Question 29

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

Question 30

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

Question 31

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

Question 32

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)

Question 33

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

Question 34

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

Question 35

• 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

Question 36

Epsilon toxin
* Increases intestinal permeability, causes vascular damages, fluid losses,
edema

Question 37

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)