Gram Positive Pathogens L1

Question 1

what are facultative anaerobes

Answer 1

bacteria that grow anaerobically and aerobically

Question 2

what shape are cocci

Answer 2

round cells

Question 3

what shape are bacilli

Answer 3

rod

Question 4

examples of cocci anaerobic and aerobic bacteria

Answer 4

staphylococcus

streptococcus

Question 5

examples of cocci anaerobic bacteria

Answer 5

pepstreptococcus

magnus

Question 6

examples of bacilli anaerobic and aerobic

Answer 6

bacillus

listeria

Question 7

examples of bacilli anaerobic

Answer 7

clostridium

lactobacillus

Question 8

what colour is gram positive bacteria in blue dye

Answer 8

blue as thick peptidoglycan cell wall - when stain with the dye, the blue dye stuck here

Question 9

what colour is gram negative bacteria in blue dye

Answer 9

thinner layer peptidoglycan, have outer membrane. When stained with dye, blue dye easily washed out

Question 10

what colour is gram negative bacteria in pink dye

Answer 10

will take up pink dye so stained

Question 11

what is staphylococcus

Answer 11

facultative anaerobe and grow well on most media
non-motile
non-sporing
catalase-positive

Question 12

why do you test for coagulase positive or negative

Answer 12

coagulase test:

positive coagulase test has a strong correlation with pathogenicity

Question 13

how do you do a catalase test

Answer 13

Catalyse +ve have an enzyme in cell that can break down hydrogen peroxide into water and oxygen, fizzing – ONLY STAPHYLOCOCCI FIZZ

Question 14

examples of staphylococcus aureus causing clinical infections

Answer 14

sepsis
pneumonia
TSS

Question 15

what types of infection can staphylococcus aureus cause

Answer 15

endogenous - from persons own flora (usually from nose to cut)
exogenous - catch off someone else

Question 16

where is staphylococcus aureus found

Answer 16

healthy people (carriers) frequently colonised in anterior nares, axillae and groin

Question 17

how many people carry staphylococcus aureus

Answer 17

20% persistant carriers
30% intermittent carriers
50% never carry

Question 18

if you carry staphylococcus aureus when is it a problem

Answer 18

if move from that site to another acting as opportunistic pathogen causes problem

Question 19

what can be done against staphylococcus aureus

Answer 19

no vaccines
methicillin resistant staphylococcus aureus (MRSA)
methicillin sensitive staphylococcus aureus (MSSA)

Question 20

what is staphylococcus epidermis

what does it do

Answer 20

normal commensal of skin, gut, respiratory tract

acts as opportunistic pathogen - readily colonises implants as a biofilm e.g. joint replacements, intravenous devices

Question 21

how is staphylococcus epidermis treated

Answer 21

difficult as often resistant to anti-staphylococcal agents, produce glycocalyx - sticky surface layer made of polysaccharides, DNA and proteins
sticky surface biofilm prevent antibiotics

Question 22

what is staphylococcus saprophyticus

Answer 22

usually non-pathogenic

may cause urinary tract infection

Question 23

what is streptococci

Answer 23

gram positive cocci in short or long chains
non-motile
sometimes capsulate
catalase negative

Question 24

what do some streptococci require for growth

Answer 24

CO2

Question 25

how are streptococci species separated

Answer 25

ability to haemolyse blood, by serology and biochemical tests

Question 26

streptococci appearance on alpha-haemolysis

Answer 26

greenish partial Strep. pneumoniae

Question 27

streptococci appearance on beta-haemolysis

Answer 27

complete | Strep. pyogenes

Question 28

streptococci appearance on gamma hemolysis

Answer 28

non-haemolytic | Enterococcus faecalis

Question 29

streptococci main serotyping method

Answer 29

Lancefield grouping

Question 30

how many groups are there in the Lancefield grouping

Answer 30

20

Question 31

what is streptococcus pyogenes

Answer 31

major human pathogen present in nasopharynx of healthy

Question 32

what lansfield group is streptococcus pyogenes in

Answer 32

A

Question 33

how are streptococcus pygoenes subdivided

Answer 33

into Griffith | based on serology of three surface protein antigens M, R, T

Question 34

which streptococcus pygoenes have the M strain

Answer 34

those that are virulent | inhibit phagocytosis

Question 35

what does streptococcus pyogenes produces

Answer 35

many toxins enzymes e.g.haemolysins break down clots so molecules can move

Question 36

what does streptococcus pyogenes cause

Answer 36

suppurative infections: sore throats, tonsillitis, pharyngitis, scarlet fever, etc. invasive disease e.g necrotizing fasciitis and Streptococcal toxic shock syndrome Non‑suppurative infections: rheumatic fever, glomerulonephritis

Question 37

which lansfield group is streptococcus agalactiae in

Answer 37

B

Question 38

where is streptococcus agalactiae present

Answer 38

carried by some women in gential tract

Question 39

what does streptococcus agalactiae cause

Answer 39

important pathogen of neonates (meningitis, sepsis) also septic abortions, gynaecological sepsis may be transferred to newborn during birth, may cause infection in mother after baby born

Question 40

where is streptococcus pneumoniae found

Answer 40

important pathogen found as commensal of upper respiratory tract ‑ found in mouth and pharynx of carriers

Question 41

what does streptococcus pneumoniae cause

Answer 41

Commonly causes pneumonia | Also causes meningitis

Question 42

what is viridans streptococci | what does it look like on blood agar

Answer 42

A heterogeneous group of commensal streptococci which show greening on blood agar, but many show no haemolysis

Question 43

where is viridans streptococci

Answer 43

mouth and oropharynx — normally of low virulence

Question 44

what does viridans streptococci cause

Answer 44

dental caries and periodontal disease and endocarditis

Question 45

what is infective endocarditis caused by

Answer 45

always preceded by a bacteraemia (bacteria present in blood – tooth extraction may be one cause of bacteraemia)

Question 46

what is infective endocarditis

Answer 46

organisms may lodge in damaged or abnormal heart valves, found in rheumatic or congenital heart disease vegetations form and valve function further impaired — high mortality rate

Question 47

what lancefield group is enterococci

Answer 47

D

Question 48

what is enterococci

Answer 48

non haemolytic or β-haemolytic gram +ve cocci in pairs

Question 49

where is enterococci present

Answer 49

human and animal gut, occasionally in mouth | can grow in 40% bile salts

Question 50

what type of bacteria is enterococci

Answer 50

pathogenicity ‑ opportunist in urinary tract infections

Question 51

what are bacilli

Answer 51

commonly found as spores in environment e.g. soil

Question 52

what is bacillus anthracis like

Answer 52

``` large non-motile grows on all ordinary media forms 'medusa head' encapsulated produces plasmid encoded toxin complex ```

Question 53

what does bacillus anthracis cause

Answer 53

anthrax in humans and domestic animals

Question 54

what are coryneforms

Answer 54

average size 3x0.3 um phemorphic gram+ve bacillus snap and bend on division

Question 55

what does corynebacterium diphtheriae cause

Answer 55

diphtheria -may be lethal infection occurs in throat by inhaling infected aerosol =

Question 56

what does corynebacterium diphtheriae do

Answer 56

produce white plaque where growing produces a powerful toxin, spreads through body, intoxication may lead to myocarditis and peripheral neuritis interferes with proteinsynthesis in cells

Question 57

how is corynebacterium diphtheriae cured

Answer 57

effective vaccine based on inactivated toxin

Question 58

how is corynebacterium diphtheriae detected

Answer 58

ELEK test used to detect toxin. | PCR now also used to detect toxin gene

Question 59

what is listeria monocytogenes

Answer 59

short gram positive bacilli tumbling motility at 25 degrees C some strains are beta-haemolytic

Question 60

what does listeria monocytogenes cause

Answer 60

may cause neonatal meningitis and sepsis — in pregnancy may lead to abortion and stillbirth

Question 61

how can listeria monocytogenes frow

Answer 61

intracellularly in macrophages | grow well on all ordinary media