infectious diseases (W9)

Question 1

exemplar bacterial pathogens?

Answer 1

staphylococcus aureus
streptococcus pneumoniae
uropathogenic escherichia coli
neisseria meningitidis

Question 2

what can infectious diseases be caused by

Answer 2

bacteria
viruses
fungi
parasites
prions

Question 3

definition of infection/infectious disease?

Answer 3

invasion, multiplication and establishment of one or more pathogens in the body
infections can spread through the body causing disease (localised or systemic)

Question 4

what is a pathogen

Answer 4

any organism which can inflict damage/disease on the host

Question 5

what is virulence

Answer 5

the relative ability of a pathogenic organism to cause disease

Question 6

what is the ability of an organism to inflict damage on the host?

Answer 6

pathogenicity

Question 7

what is the mechanism of disease production

Answer 7

pathogenesis

Question 8

what are virulence factors

Answer 8

genes/molecules/structures that contribute to virulence

Question 9

organisms that live in harmony with us? (colonisers)

Answer 9

commensals

Question 10

organisms that can cause disease in healthy subjects?

Answer 10

primary pathogens

Question 11

organisms that behave as pathogens when given the right opportunity in a compromised host?

Answer 11

opportunist pathogens

Question 12

organisms that live in the environment?

Answer 12

saprophytes

Question 13

organisms associated with animals?

Answer 13

zoonoses

Question 14

2 parts of immune system

Answer 14

innate (early response, no memory)
acquired (modern, has memory)

Question 15

physical defences?

Answer 15

physical barriers - deny entry
mechanical defences - remove pathogens from potential site of infection
microbiome - compete with pathogens for binding sites and nutrients

Question 16

physiological defences?

Answer 16

temperature
low pH
chemical mediators

Question 17

phagocytic/endocytic barriers

Answer 17

endocytosis - cells internalise and break down foreign material
phagocytosis - specialised cells internalise, kill and digest whole organisms

Question 18

inflammatory barriers?

Answer 18

tissue damage and infection causes leakage of fluid containing serum proteins with antibacterial activity

Question 19

bacterial virulence factors?

Answer 19

cytosolic
cell membrane associated
secreted

Question 20

most common bacterial cause of community acquired pneumonia?

Answer 20

streptococcus pneumoniae

Question 21

gram negative organism which can be carried as part of the microbiome in the bowel?

Answer 21

uropathogenic Escherichia coli (UPEC)

Question 22

antimicrobial prophylaxis of household contacts with infectious disease is recommended

Answer 22

neisseria meningitidis

Question 23

gram positive bacteria which is a very common cause of skin and soft tissue infections?ro

Answer 23

staphylococcus aureus

Question 24

what colour is gram negative/positive

Answer 24

negative - pink
positive - purple

Question 25

s. aureus virulence factors?

Answer 25

biofilm sticky making clearance difficult capsule reduces ability to be phagocytosed cell surface factors coagulase - secreted, prothrombin->thrombin exoenzymes (lipases, nucleases, proteases)

Question 26

how does S aureus cause skin infection

Answer 26

infects through break in skin to subcutis neutrophils recruited to consume s. aureus formation of fibrous capsule localising this

Question 27

how does S aureus infect mucosal surfaces

Answer 27

attaches closely to surface with lock and key mechanisms

Question 28

what must successful pathogens do to infect the respiratory tract

Answer 28

adhere to epithelial cell surfaces inhibit ciliary action avoid destruction by alveolar macrophages

Question 29

streptococcus pneumoniae gram +/-? where does it colonize?

Answer 29

gram positive (purple) colonization of nasopharynx and throat

Question 30

what can streptococcus pneumoniae cause

Answer 30

pneumonia mucosal infections (eg sinusitis) invasive infections (bacteraemia, meningitis)

Question 31

features of streptococcus pneumoniae

Answer 31

capsule - survives in mucous, reduces phagocytosis risk pili - type 1 & 2 which bind to receptors on host epithelium

Question 32

barriers to infection in the gi tract

Answer 32

stomach - acid pH small intestine - bile and lymphoid tissue large intestine - protective microbiota flora

Question 33

urinary tract barriers to infection?

Answer 33

bladder regular flushing action acidity of urine protective mucus covering urothelial cells

Question 34

what causes the majority of community acquired UTIs?

Answer 34

uropathogenic E. Coli

Question 35

uropathogenic E. Coli gram +/-?

Answer 35

gram negative (pink)

Question 36

uropathogenic E. Coli colonisation?

Answer 36

colonises periurethral area then ascends to the bladder and adheres to wall

Question 37

name for infection of bladder?

Answer 37

cystitis

Question 38

what can happen if uropathogenic E. Coli ascends further than the bladder

Answer 38

reaches kidneys via ureters causing pyelonephritis (kidney infection), and sepsis may occur as a result

Question 39

uropathogenic E. Coli features

Answer 39

2 types of fimbriae allow it to adhere to host cell surface flagellum allow mobility lipopolysaccharide (LPS) allows colonisation of bladder, formation of reservoirs, induces innate/adaptive immune responses capsule outer membrane vesicles deliver toxins

Question 40

what toxins does uropathogenic E. Coli secrete

Answer 40

alpha-haemolysin siderophores

Question 41

neisseria meningitidis gram +/-?

Answer 41

gram positive

Question 42

diseases associated with meningitis

Answer 42

neisseria meningitidis meningococcaemia meningoencephalitis pneumonia arthritis urethritis

Question 43

where does neisseria meningitidis colonize

Answer 43

nasopharynx

Question 44

neisseria meningitidis highest carriage rates?

Answer 44

school age children young adults lower socioeconomic groups

Question 45

neisseria meningitidis toxic effects?

Answer 45

hyperproduction of lipooligosaccharide (LOS) endotoxin (can cause sepsis)

Question 46

how does lipooligosaccharide (LOS) work

Answer 46

binds to cells in innate immune system cytokine release endothelial damage and capillary leakage

Question 47

what does neisseria meningitidis have the ability to cross? can all pathogens do this?

Answer 47

blood brain barrier. not all pathogens can cross this.

Question 48

2 most common causes of bacterial meningitis?

Answer 48

S. pneumoniae N. meningitidis

Question 49

what causes hospitalized patients to be at greater risk for new infections

Answer 49

immunocompromised breach in physical defences (eg urinary catheterisation) prosthetic material loss of microbiome (antibiotics) loss of cellular immunity (eg chemo)