VIRULENCE FACTORS

Question 1

Virulence factor found in the outer leaflet of the cell wall of gram-negative organisms

Answer 1

Lipopolysaccharide (LPS)

-composed of LIPID A, a CORE POLYSACCHARIDE, and O ANTIGEN, LPS leads to activation of macrophages with the release of IL-1, with the development of DIC and SEPTIC SHOCK

Question 2

Produces a trivalent exotoxin composed of protective antigen, edema factor, and lethal factor

Answer 2

Bacillus anthracis

-protective antigen mediates CELL BINDING, edema factor is a secreted ADENYLATE CYCLASE, and lethal factor causes CNS DEPRESSION

Question 3

Produces an exotoxin that blocks the release of Ach at the neuromuscular junction

Answer 3

Clostridium botulinum

-treatment includes the use of ANTITOXIN produced in HORSES, with the possibility of SERUM SICKNESS

Question 4

The toxin produced by this organism can be used in minute amounts to treat dystonias, strabismus, and wrinkles

Answer 4

Clostridium botulinum

-toxin causes a FLACCID PARALYSIS of the injected muscles

Question 5

The virulence factors associated with this organism include the ability to grow intracellularly and the production of cord factor

Answer 5

Mycobacterium tuberculosis

-cord factor is thought to contribute to the FORMATION OF GRANULOMAS

Question 6

One of the virulence factors of this organism is an anti-phagocytic capsule composed of D-glutamic acid

Answer 6

Bacillus anthracis

-although typically composed of polysaccharides, other organisms with unique capsular components include SIALIC ACID in Streptococcus agalactiae and HYALURONIC ACID in Pasterulla multocida

Question 7

Produces a heat stable toxin Sta, that stimulates the production of cGMP, with similar effects to those of increased cAMP

Answer 7

Enterotoxigenic Escherichia coli

-in addition, the organism produces a STb TOXIN that is cyclic nucleotide independent

Question 8

The 3 major pyogens for which a polysaccharide capsule is the major virulence factor

Answer 8

Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis

-the capsule PREVENTS OPSONIZATION by host cell immunoglobulins

Question 9

Produces an AB toxin that transfers ADP-ribose from NAD+ to the stimulatory G protein subunit (Gs)

Answer 9

Vibrio cholerae

-similar to the LABILE TOXIN [LT] OF ENTEROTOXIGENIC E. coli, this toxin results in the increase of cAMP with hypersecretion of Cl- and HCO3- with the OSMOTIC REFLUX of up to 30 L of water/day

Question 10

A virulence factor produced by these 2 organisms is a typical AB toxin that catalyzes the transfer of ADP-ribose from NAD+ to elongation factor-2

Answer 10

Corynebacterium diphtheria and Pseudomonas aeruginosa

-ADP ribosylation of EF-2 results in the INHIBITION OF PROTEIN SYNTHESIS and death of the cell

Question 11

Produces Toxic shock syndrome toxin

Answer 11

Staphylococcus aureus

-Toxic shock syndrome, associated with the use of SUPERABSORBENT TAMPONS, results from the production of this toxin, which causes POLYCLONAL ACTIVATION OF T CELLS through antigen-independent activation of the T-cell receptor

Question 12

Produces erythrogenic toxin, resulting in Scarlet fever

Answer 12

Streptococcus pyogenes (Group A)

-erythrogenic toxin is a PHAGE-ENCODED SUPERANTIGEN that causes the rash often accompanying pharyngitis

Question 13

M antigen is the most important virulence factor

Answer 13

Streptococcus pyogenes (Group A)

-prevents phagocytosis, and antibodies to this molecule underlie the long-term sequelae of infection, namely, CHRONIC RHEUMATIC HEART DISEASE

Question 14

Protein A is a major virulence factor

Answer 14

Staphylococcus aureus

-BINDS TO THE Fc REGION OF AN ANTIBODY, preventing complement fixation and phagocytosis

Question 15

Produces exfoliant toxin

Answer 15

Staphylococcus aureus

-the toxin causes an exfoliative dermatitis, SCALDED SKIN SYNDROME, that appears as a sunburn-like rash

Question 16

Produces a lecithinase and hyaluronidase that results in cellulitis and myonecrosis

Answer 16

Clostridium perfringens

-the lecithinase can be demonstrated by culturing on egg YOLK AGAR normally the organism produces a DOUBLE ZONE OF HEMOLYSIS on blood agar

Question 17

Produces an AB toxin that ADP-ribosylates the small GTP binding protein Rho

Answer 17

Clostridium difficile

-results in the depolymerization of the cytoskeleton with NECROSIS OF THE COLONIC EPITHELIUM

Question 18

Produces a typical AB toxin that catalyzes the transfer of ADP-ribose from NAD+ to the inhibitory G protein subunit (Gi)

Answer 18

Bordetella pertusis

-interference of G PROTEIN-COUPLED RECEPTORS such as those employed by chemokines results in significant LYMPHOCYTOSIS; other virulence factors include FILAMENTOUS HEMAGGLUTININ and TRACHEAL CYTOTOXIN

Question 19

Produces a toxin that irreversibly inactivates the 60s ribosomal subunit with the cessation of protein synthesis and cell death

Answer 19

Shigella dysenteriae

-toxins similar to SHIGA TOXIN are produced by EHEC and are known as VEROTOXINS

Question 20

The toxin elaborated by this organism inhibits the release of the inhibitory neurotransmitters, GABA, and glycine, resulting in a spastic paralysis

Answer 20

Clostridium tetani

-the DaPT vaccine includes the highly immunogenic TETANUS TOXOID; a booster is recommended every 10 years and also after a puncture wound