Pathogens and the host

Question 1

pathogenic bacteria

Answer 1

bacteria capable of causing disease.

Question 2

signs and symptoms of clinical infection

Answer 2

• inflammation
• pain
• pyrexia
• tachycardia
• rigors
• increased white cell count
• increased C reactive protein (CRP)

Question 3

pyrexia

Answer 3

high temp.

Question 4

tachycardia

Answer 4

heart rate that exceeds the normal resting rate.

Question 5

rigors

Answer 5

sudden feeling of cold, increased temperature, sweating and shivering

Question 6

pathogen

Answer 6

organism that can cause disease.

Question 7

commensal

Answer 7

organism which is part of the normal body flora.

Question 8

requirements for pathogenicity

Answer 8

infectivity

virulence

Question 9

infectivity

Answer 9

ability to become established

Question 10

virulence

Answer 10

ability to cause harmful effects once established

Question 11

methods to increase infectivity

Answer 11

• attachment

- acid resistance

Question 12

virulence factors

Answer 12

• invasiveness
• toxin production
• evasion of immune system

Question 13

invasiveness example: streptococcus pyogenes

Answer 13

• necrotising fasciitis
• cellulitis
• connective tissue breakdown
• fibrinolysis

Question 14

types of toxins produced by pathogens

Answer 14

exotoxins
enterotoxins
endotoxins

Question 15

exotoxins

Answer 15

released extracellularly by the micro-organism.

Question 16

enterotoxin

Answer 16

act on the GI tract

Question 17

endotoxin

Answer 17

structurally part of the gram negative cell wall

Question 18

tetanus

Answer 18

caused by clostridium tetani, exotoxin released acts on nerve synapse and causes the inhibition of inhibitory neurotransmitter release.

Question 19

tetanus treatment

Answer 19

debridement (removal of dead/infected tissue), antibiotics and antitoxin

Question 20

cholera

Answer 20

causes by vibrio cholerae, colonises small intestine produces an enterotoxin which causes increase in cAMP levels, increases ion conc in small intestine which causes dehydration.

Question 21

treatment of cholera

Answer 21

rehydration

Question 22

superantigens

Answer 22

certain exotoxins of strep pyogenes and Staph aureus stimulate the division of T-cells in the absence of specific antigen. overwhelming cytokine production causes toxic shock

Question 23

endotoxin action

Answer 23

caused by E. coli and other gram negative bacilli. induces uncontrolled host response, cytokine production, fevers, rigors hypotension, tachycardia, collapse

Question 24

colonisation

Answer 24

the establishment of the pathogen at the appropriate portal of entry

Question 25

latent infection

Answer 25

after the primary infection the virus lies dormant in host cells, viral DNA and RNA in host cells which is not expressed in large quantities.

Question 26

asymptomatic infection

Answer 26

infected host is a carrier for the disease but does not show any symptoms.

Question 27

infection

Answer 27

the invasion of an organism’s body tissues by disease-causing agents, their multiplication, and the reaction of host tissues to the infectious agents and the toxins they produce

Question 28

innate immunity

Answer 28

non-specific immunity formed of skin, gastric acid. muco-ciliary escalator and phagocytic cells

Question 29

phagocytic cells

Answer 29

• polymorphs eg. neutrophils, eosinophils, basophils (fight acute infection
• macrophages (fight chronic infection)

Question 30

aquired immunity

Answer 30

specific response to antigen concerned, an immunological memory is creates.
has a humoral (antibody) and cellular (t-cell) response

Question 31

IgM

Answer 31

involved in primary response

Question 32

IgG

Answer 32

involved in secondary response

Question 33

IgA

Answer 33

mucosal immunity

Question 34

IgE

Answer 34

allergy and helminth infection

Question 35

sites of viral entry

Answer 35

• conjunctiva (mucus membrane over eye)
• respiratory tract
• arthropod
• alimentary tract
• skin
• urinogenital tract

Question 36

acute viral infection

Answer 36

short time where host is infected with virus then nothing after. localised to specific site of body or can develop viraemia which causes widespread infection of tissues.

Question 37

examples of acute viral infections

Answer 37

influenza A virus

enterovirus

Question 38

influenza A

Answer 38

virus infects cells of the respiratory tract, destruction of respiratory epithelium, fever caused by altered cytokine expression.

Question 39

antigenic drift

Answer 39

minor changes in genes of a virus over time to generate antigenic variants.

Question 40

antigenic shift

Answer 40

abrupt major changes in virus antigenic structure.

Question 41

enterovirus infection

Answer 41

virus infects gut then can cause viraemia which allows it to spread to neural (causes paralysis) and non-neural tissue

Question 42

examples of enterovirus infections

Answer 42

Poliomyelitis (poliovirus)
Aseptic meningitis (many enteroviruses)
Myocarditis (coxsackie B viruses)
Pancreatitis (coxsackie B viruses)
Respiratory infections (many enteroviruses)

Question 43

virus induced tumours

Answer 43

virus infects cells and viral nucleic acid. this is incorporated into host genome causing change in cellular gene expression.
This can cause uncontrolled cell multiplication and tumour formation.

Question 44

production of antibodies

Answer 44

antibodies produced by B-lymphocytes when specific epitope is recognised, this is aided by t helper cells (CD4 T cells)

Question 45

antibody in infection

Answer 45

• Neutralises bacterial toxins
• Neutralises viruses in viraemic stage
• Prevents adherence of microorganisms
• Opsonises capsulate organisms
• Useful means of diagnosis (serology)

Question 46

cell mediated immunity

Answer 46

CD4 Th1 helper cells activate macrophages to ingest and kill or contain pathogen.

Question 47

humoral immunity

Answer 47

memory B-cells are retained after an infection so that they can rapidly divide when the infection reoccurs.

Question 48

superantigens

Answer 48

Certain exotoxins of Strep pyogenes and Staph aureus
are able to stimulate division of T cells in the absence of specific antigen. Causes overwhelming cytokine production, causing “toxic shock”.