Chapter 15: Mechanisms of Pathogenicity

Question 1

Disease

Answer 1

Any condition in which the normal structure or function of the body is damaged or imparied

Question 2

Infection

Answer 2

A successful colonization of the hoast by a microorganism

Question 3

Infectious disease

Answer 3

Any disease directly caused by the effect of a pathogen

Question 4

Pathogen

Answer 4

May be a bactureium, virus, fungi or yeast, viroid, prion

single celled organisms (not parasites) or a cellular

Question 5

Fungal infections

Answer 5

not in temperate climates

require humid/ moist conditions

if aquaired can be very serious

systemic infeciton with antifungals can still be upwards of 40% mortality

Question 6

superfical infection

Answer 6

skin and mucus layers

Question 7

systemic infeciton

Answer 7

all throughout the body

Question 8

Viroid

Answer 8

tiny virus without a capsid

mainly attack plants and single celled organisms

dont really attack humans

Question 9

Communicalble disease

Answer 9

capable of being spread from person to person

Question 10

non-communicable disease

Answer 10

not capable of being spread from person to person

usually from the environment ot a host

(a bacterium like vibrio vulnificans entering a cut from the soil)

Question 11

Contagious disease

Answer 11

a disease easily spread from person to person

an infectious disease

Question 12

Zoonotic disease

Answer 12

A disease pread between a non-human host to a human host

animal to human

(not usually insects, those are usually refered to as vectors), but his can be the case?

Question 13

Perioids of disease

Answer 13

incubation

prodromal

illness

decline

convalescence

Question 14

incubation

Answer 14

after colonization but not enough pathogens to cause signs and symptoms

Question 15

prodromal

Answer 15

start of signs and symptoms, not definitive or diagnostic

Question 16

illness

Answer 16

signs and symptoms are most severe and obvious or diagnostic

Question 17

Decline

Answer 17

decrease in the number of pathogens in the body, decrease in severity of signs and symptoms

Question 18

Convalescence

Answer 18

return to normal function (health), may be long term or permanent damage

Question 19

Acute disease

Answer 19

fast progression through the periods, hours to days

Question 20

Chronic disease

Answer 20

slow progression through the periods, weeks to months

Question 21

Latent disease

Answer 21

pathogen becomes dormant, ro replication, usually no cultavatable pathogens in blood or other samples

may be life long

Question 22

Molecular kochs postulates

Answer 22

revision of kochs postualtes to demonstrate that a single gene is responsible for pathogenicity

virulence factors???

the pathogenic phenotype should be associated only with pathogenic strains

Inactive (mutate, delete) the gene suspected of encoding the virulence factor, this should reduce pathogenicity

replace the inactivated gene with a functional copy, this should restore pathogenicity

Question 23

Why are some strains for a species pathogenic while others are not

Answer 23

Molecular kochs postulates

In Gram-negative bacteria, this is often due to the presence of a gene in pathogenic staisn abstent in non-pathogenic strains

virulence factors???

Question 24

Pathogenicity

Answer 24

the ability of a microorganism to cause disease

should be a yes/ no definition

Question 25

Virulence

Answer 25

The degree to which a microorganism can cause disease variable from avirulent (not pathogenic) to hihghly virulent

Question 26

Infectious does (median) ID50

Answer 26

the number of pathogens required to cause infection in 50% of test subjects

Question 27

Lethal dose (median) LD50

Answer 27

the number of pathogens required to kill 50% of test subjects fig 15.5 x-axis (dose) is in a logarithmic scale

Question 28

Primary pathogen

Answer 28

a pathogen which can cause disease regardless of the state of the immune system of the host

Question 29

Opportunistic pathogen

Answer 29

can only infect a damaged or immuno-compromised host

Question 30

5 stages of pathogenesis

Answer 30

exposure adhesion invasion infeciton transmission

Question 31

Exposure

Answer 31

some type of physical contact with the pathogen, not necessarily the start on an infection not every exposure results in infection, but every infection comes from exposure

Question 32

Adhesion

Answer 32

some mechanism by which the pathogen sticks to cells of the body or to mucosal membranes portals of entry skin (damaged) mucosal membranes parenteral - through the skin or mucosus membbranes adhesins on pathogen stick to receptors on host cells

Question 33

Invasion

Answer 33

pathogen spreads throughout tissue locally or throughout the whole body, usually through the bloodstream can produce factors whcih aid in invasion (proteaases, lipases, toxins) => morphology = membrane ruffling to induce its self to be phagocytosed salmonella and lysteria some bacteral and all viral pathogens enter inside cells by endocytosis, some bacteria are ingested by host phagocytes and reproduce inside these cells

Question 34

Infection

Answer 34

pathogens reproduces in or on the host local infection is in a small part of the host pretty much the same thing for a fungal infection systemic infection is when the pathogen spreads throughout the body (blood stream) secondary infection is when a second different pathogen infects a host after disease caused by the first pathogen = example = influenza increases the risk of streptococcus pneumonia secondary infections which cause death

Question 35

Transmission

Answer 35

for a disease to reamin in a host population it must spread from the infected host to a new one may leave by the original portal on entry or a new route = fecal oral route or really the oral fecal route = most airborne diseases enter and leave through the respiratory tract

Question 36

Virulence factors of bacteria and viruses

Answer 36

virulence factors are individual properties or mechanisms which allow pathogenicity and increase virulence a product of a single or a couple of genes sometimes, cumulative effect of bacteria leads to virulence. best example is a toxin is produced that causes the symptoms of a disease

Question 37

adhesion

Answer 37

pathogens need a mechanism to stick to hosts A virulence factor often is specific to a host species or type of cell = trophism = species specificity, is also tissue specificity mediated by specific molecules both on the host and the pathogen

Question 38

Exozymes

Answer 38

Type of virulence factor are soluable, not toxins, are protiens are SECREATED enzymes which damage the host, increase the spread of the pathogen or increase it's survival proteses hydrolyse the protein which connect cells into tissue, destroy antibodies, kill cells killing cells allows an entry point, also releases nutrients (like the iron from haemolysis) (phospho)lipases damage membranes and kill cells nucleases breakdown DNA which can trap cells (puss) (NETosis)

Question 39

Toxins

Answer 39

type of virulence factors protiens or not often enzymes, sometimes not compounds which damage the host and usually kill host cells the production of toxins is called toxigenicity

Question 40

Portal of entry

Answer 40

how the pathogen gets into you nose, mouth, cuts or abbression skin is only a portal of entry unless it is damaged (except fungi) mucosal membranes are the major point on entry disease symtpoms and outcomes depend on the portal of entry

Question 41

Parenteral

Answer 41

going through the skin (or sometimes a mucus membrane) usually from injetions, Or insect bites skin damage

Question 42

Adhesions

Answer 42

used by the pathogen to stick to receptors on host cells sometimes just refered to as a receptor? but more specific?

Question 43

endotoxins

Answer 43

not enzymes ex= LPS, lipid A which is very toxin = induction of fever, and septic shock ex= fragmented peptidoglycan induces fever and inflammation (not as toxic as lipid a)

Question 44

Exotoxins

Answer 44

are protein toxins with enzymatic activity may cause all the symptoms of the disease such as tetanus toxin in tetanus (see table 15.10) AB toxins have two different proteins, A for binding to a host receptor and B which is the actual toxin (See enzymology notes)

Question 45

superantigen

Answer 45

are proteins which cause an excessive stimulaiton of immune system cells which can damage the host causes toxic shock syndrome = low blood pressure, shock, organ failure death lots of cytokines

Question 46

Virulence factors for immune evasion

Answer 46

in mammals the immune system detects and kills or removes pathogens many bacterial and viral pathogens have evolved mostly protiens (exozymes) whihc interfere or suppress the immune system capsules inhibit phagocytosis by mactophages (polysaccharides) = streptococcus pneumonia => these interfere or suppress the immune system produce catalase to break down hydrogen peroxide protein A and G bind antibodies (non-catalytic inactivaiton of antibodies) M protiens prevents complement activaiton (and thus the complement cascade, MAC attack) many viruses down regulate interferon production antigenic variation many many O antigens in salmonella and e. coli. Or phase variatiohn in lyseria