Lecture 9 - Pathogenicity of bacteria

Question 1

what type of bacteria is pseudomonas aurginosa and what does it cause

Answer 1

oppurtunistic pathogen

infects severe burns patients
and
infects lungs of cystic fib patients

Question 2

what effects can staphylococcus epidermis cause and how

Answer 2

can form biofilm on catheter
because
blood plasma proteins coat the catheter
and then bacteria multipies on the plasma proteins

and this is antibiotic resistant oh dear

Question 3

why is s.epidermis on a catheter antibiotic resistant

Answer 3

it can form extracellular polymers
which is like sticky
and antibiotics cant penetrate the biofilm it forms

Question 4

what can cause risk of neisseria meningitis causing disease

Answer 4

usually is commensal
but smoking, having a cold can cause risk of disease

Question 5

what causes the shift from neisseria meningitidis to meningococcal septicemia

Answer 5

bact spreads through bloodstream into whole body
causing systemic infection
only 10-20% surivive

Question 6

where to m.tuberculosis replicate and what does this form

Answer 6

in alveolar macrophages (cuz is obligate intracellular pathogen) in the lung to form granulomas (Ghon complex)

Question 7

why is TB worse now

Answer 7

new strains emerged that are more drug resistant (XXDR-TB etc.)

Question 8

whats an example of a disease that causes diseases in different phases

Answer 8

treponema pallidum
ie syphillis

Question 9

waht are stages of syphillis

Answer 9

• primary lesion (2 weeks after infection)= chancres (sores)
• secondary stage (after 10 weeks) = bacteria spreads, rash
• latent phase (many years later) = 40% will develop tertiary syphillis
  insanity and death
  steven has syphillis

Question 10

what is a kochs postulates

Answer 10

swabbing things like lesions
then grown outside in a lab
and then given back to an organism (usually sheep)
then reisolated

Question 11

what are 3 problems encoutered with Kochs postulates

Answer 11

• some diseases cant be grown on lab media e.g. leprosy
• ethical problems
• sometimes no suitable animal model

Question 12

what is virulence

Answer 12

measure of pathogenicity

Question 13

what is viruelence measured by

Answer 13

LD50
lethal dose
does to kill 50% of animals in given time

Question 14

what is virulence determinants for anthrax

Answer 14

capsule
and
toxins

Question 15

what is capsule made of

Answer 15

poly-D-glutamic acid
forms mucoid colonies

Question 16

how does a capsule inhibit phagocytosis

Answer 16

similar charge to phagocytes
so repels them

Question 17

what are 2 functions of toxins

Answer 17

supresses immune cell responses
and later on, induces toxic shock and death

Question 18

how do bacteria adhere to host

Answer 18

attach via fimbriae
which have adhesins on the ends of it
and attach to mannose receptors on surface of epithelial cells

Question 19

how can adhesion be seletive

Answer 19

diff fimbriae bind to diff things

Question 20

what fimbriae do pathogenic e.coli use, and where does this attach

Answer 20

CFA fimbria
attach to duodenal mucosa
release toxins

Question 21

examples of diseases caused by non-fimbrial adhesins

Answer 21

streptococcal pyogenes
causes sore throat and rheumatic fever

Question 22

what does this non-fimbrial bacteria use instead to bind to surfaces

Answer 22

M protein