Bacterial Pathogenicity

Question 1

Pathogenicity ?

Answer 1

The ability to cause diseases

Question 2

Virulence?

Answer 2

the severity or harmfulness of a disease or poison

Question 3

Infecting dose ?

Answer 3

the number of microorganisms required to produce infection

Question 4

Phases of bacterial pathogenicity

Answer 4

1. Adhesion and colonization
   2.Invasion of host tissues and pathogen replication
2. Production of toxins
3. Immunopathogenesis

Question 5

Quorum sensing?

Answer 5

Quorum sensing is the regulation of gene expression in response to fluctuations
in cell-population density. Quorum sensing bacteria produce and release
chemical signal molecules called autoinducers that increase in concentration as a function of cell density.

Question 6

Invasins?

Answer 6

The chemicals that r used by enterobacteria that make the cell membrane of the host to take up the bacteria

Question 7

Hydrolytic enzymes ?

Answer 7

Bacterial extracellular enzymes can act on human tissues at the site of infection, playing a role in tissue injury and spread of pathogens( hyaluronidase, DNAse, collagenase, coagulase, neuraminidase)

Question 8

Exotoxin?

Answer 8

Is a toxin secreted by bacteria and possesses an enzymatic activity that induces damage in the host cell

Question 9

Endotoxin ?

Answer 9

Component of outer layer of bacteria
LPS in gram negative and teichoic acid in gram positive

Question 10

What do endotoxins bind to?

Answer 10

They bind Toll-like receptors

Question 11

Endotoxin and the pyrogen in response ?

Answer 11

The macrophage Engulfs the bacteria, bacteria release toxins which make the macrophage release IL-1 which go to the hypothalamus through blood and cause the fever

Question 12

Dissemination of LPS can trigger____?

Answer 12

Septic shock

Question 13

levels of virulence:

Answer 13

low, moderate, high, extremely high

Question 14

a pathogen must be able to:

Answer 14

1. enter a host
2. find a unique niche
3. avoid normal host def
4. replicate fast
5. cause an injury

Question 15

What are bacterial adhesins?

Answer 15

Bacterial adhesins are cell-surface components or appendages of bacteria that facilitate adhesion or adherence to other cells or to surfaces

Question 16

Hyaluronidase:

Answer 16

Produced by staphylococci, streptococci and clostridia,
depolymerizes the connective tissue by hydrolyzing hyaluronic acid

Question 17

DNAse:

Answer 17

Produced by Staphylococcus aureus, strains, degrades DNA.

Question 18

Collagenase:

Answer 18

Produced by clostridia, breaks down collagen

Question 19

Coagulase:

Answer 19

Produced by S. aureus, produces a typical enzyme whose
coagulase is able to convert fibrinogen to fibrin. So producing a fibrin clot
that can protect the bacteria cells from host defenses. Also the same
microorganism is able to produce enzyme capable of dissolving fibrin
clots

Question 20

Neuraminidase:

Answer 20

Cleaves sialic acid that is present in host mucin,
glycolipids, and glycoproteins

Question 21

Streptokinase and Staphylokinase:

Answer 21

Produced by Streptococci and
Staphylococci, they act on plasminogen by catalyzing its transformation
into plasmin. That is like this enzyme capable of dissolving the cell
building blocks

Question 22

Hemolysins, Phospholipases and Lecithinases:

Answer 22

Can act on cells near the
site of infection or far away. They’re also produced by Streptococci and
Staphylococci like Streptokinase and Staphylokinase (hemolysins and
phospholipases) also clostridia (lecithinases). Cytolitic exotosins are called
if act far away from the site of infection

Question 23

sigA Protease:

Answer 23

Cleaves human sigA1 antibodies(important defense mechanism for hosts) in the hinge region to release the Fc portion from the
Fab fragment

Question 24

The endotoxin is released by?

Answer 24

the lysis of the bacterial cell

Question 25

monomeric toxins(superantigens) are able to bind to antigen-presenting cells, act as polyclonal stimulators of T cells causing __________?

Answer 25

massive cytokine release ( IL-1, IL-2, TNF-α and Interferon γ ) with systematic effects such as shock

Question 26

Examples of superantigen exotoxins are

Answer 26

enterotoxin and toxic shock syndrome toxins of Staphylococcus aureus, streptococcal pyrogenic exotoxins (SPE) of Streptococcus pyogenes. Symptoms are similar to endotoxin ones(severe shock)

Question 27

The exotoxin is usually made by 2 subunits:

Answer 27

A (active) domain and B (binding) domain active one is responsible for the pathogenicity and binding is responsible for the binding to the receptor

Question 28

Cholera toxins act on _______?

Answer 28

intestinal epithelial cells

Question 29

Cholera toxin A-1 subunit, after dissociation from B subunit, bind to and ADP ribosylates the GS-alpha subunit of adenylate cyclase in the cell membrane, leading to an___________________

Answer 29

increase in intracellular concentration of cyclic AMP. The increased intracellular cyclic AMP concentrations in villus cells mainly inhibit the uptake of NaCI and water. So the result is dehydration

Question 30

examples of Exotoxins Altering Intracellular Cyclic AMP Concentration

Answer 30

Health-labile toxin of Escherichia coli (LT) Pertussis toxin: Has two toxins that act in increasing intracellular concentration of cyclic AMP with two diverse mechanisms. While toxins with intrinsic adenylate-cyclase activity independently synthesize cyclic AMP: cyclosis from Bordetella pertussis EF from Bacillus anthracis.

Question 31

Clostridium tetani and Clostridium botulinum neurotoxins exert their effect at ______________

Answer 31

neural sites, they cause diseases like tetanus and botulism. These are diseases whose clinical manifestations are due to only exotoxins

Question 32

What causes the infection in tetanus?

Answer 32

The spore of tetani

Question 33

Both ____________ toxin and ________ toxin act by blocking the release of neurotransmitters at the synaptic site. These neurotoxins cause paralysis.

Answer 33

botilinum and tetanus

Question 34

Bacterial ability to face host defenses:

Answer 34

a. Antiphagocytic factors: Polysaccharide capsules and surface proteins (interference with complement C3b deposition, oxinizing factor present in body fluids) b. Survival in professional phagocytes c. Escape by specific humoral immunity

Question 35

what is Opsonophagocytosis?

Answer 35

is the engulfment, by macrophages and other phagocytic cells like neutrophils, of bacteria opsonized (opsonines are macromolecules that cover the microorganism, increasing radically the efficiency of phagocytosis since they are recognized from receptors present on the membrane of phagocytes), with antibodies and/or complement proteins. Thus, microbial cells in the blood or within a specific tissue that become coated with IgG are soon recognized by patrolling macrophages and neutrophil

Question 36

Capsule polysaccharides and surface proteins interfere with complement C3b deposition by binding serum factor H so that ______________

Answer 36

accelerates the degradation of C3b, contrasting the opsogenic ability, so bacteria are protected from phagocytosis.

Question 37

which bacteria when englobed by the phagocytes enzymatically lyse the phagosome membrane and multiply in the nutrient-rich host cell cytoplasm?

Answer 37

Listeria, Shigella

Question 38

which bacteria remain in the phagosome and replicate even in professional phagocytes. Known mechanisms for avoidance of the killing action of phagolysosome include: prevention of phagosome, lysosome fusion, block of acidification to the optimum pH for digestive enzyme activity, production of enzymes (catalase, superoxide dismutase) that neutralize the phagocytes’ oxidative burst?

Answer 38

Salmonella serotype Typhi, Mycobacterium tuberculosis

Question 39

examples of Escape by specific humoral immunity:

Answer 39

Molecular mimicry: the epitopes on the bacteria are similar to the ones of the host cells bacterial antigenic variation: constantly changing antigens

Question 40

______________ are distinct genetic elements on the chromosomes of a large number of bacterial pathogens. PAIs encode various virulence factors and are normally absent from non-pathogenic strains of the same or closely related species

Answer 40

Pathogenicity islands (PAIs)

Question 41

what do Pathogenicity islands (PAIs) do?

Answer 41

encode virulence factors and other accessory proteins, but no essential proteins.

Question 42

Pathogenicity islands are transferred ________________ through plasmids or transposons

Answer 42

horizontally

Question 43

Most of the parasites are not __________ but __________

Answer 43

pathogens, commensals

Question 44

__________ is the main protozoan disease. It was the second infectious disease after tuberculosis, before COVID pandemic.

Answer 44

Malaria

Question 45

In sporozoan, asexual multiplication occurs by a process of multiple fission termed ___________

Answer 45

schizogony. The nucleus of a trophozoite divides into several parts, forming a multinucleated schizont. The cytoplasm then condenses around each nuclear portion to form new daughter cells, or merozoites, which burst from their intracellular location to invade new host cells