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Microorganisms + Disease > Gram Positive Pathogens L1 > Flashcards

Gram Positive Pathogens L1 Flashcards

1
Q

what are facultative anaerobes

A

bacteria that grow anaerobically and aerobically

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2
Q

what shape are cocci

A

round cells

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3
Q

what shape are bacilli

A

rod

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4
Q

examples of cocci anaerobic and aerobic bacteria

A

staphylococcus

streptococcus

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5
Q

examples of cocci anaerobic bacteria

A

pepstreptococcus

magnus

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6
Q

examples of bacilli anaerobic and aerobic

A

bacillus

listeria

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7
Q

examples of bacilli anaerobic

A

clostridium

lactobacillus

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8
Q

what colour is gram positive bacteria in blue dye

A

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

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9
Q

what colour is gram negative bacteria in blue dye

A

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

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10
Q

what colour is gram negative bacteria in pink dye

A

will take up pink dye so stained

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11
Q

what is staphylococcus

A

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

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12
Q

why do you test for coagulase positive or negative

A

coagulase test:

positive coagulase test has a strong correlation with pathogenicity

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13
Q

how do you do a catalase test

A

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

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14
Q

examples of staphylococcus aureus causing clinical infections

A

sepsis
pneumonia
TSS

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15
Q

what types of infection can staphylococcus aureus cause

A

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

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16
Q

where is staphylococcus aureus found

A

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

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17
Q

how many people carry staphylococcus aureus

A

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

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18
Q

if you carry staphylococcus aureus when is it a problem

A

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

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19
Q

what can be done against staphylococcus aureus

A

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

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20
Q

what is staphylococcus epidermis

what does it do

A

normal commensal of skin, gut, respiratory tract

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

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21
Q

how is staphylococcus epidermis treated

A

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

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22
Q

what is staphylococcus saprophyticus

A

usually non-pathogenic

may cause urinary tract infection

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23
Q

what is streptococci

A

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

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24
Q

what do some streptococci require for growth

A

CO2

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25
Q

how are streptococci species separated

A

ability to haemolyse blood, by serology and biochemical tests

26
Q

streptococci appearance on alpha-haemolysis

A

greenish
partial
Strep. pneumoniae

27
Q

streptococci appearance on beta-haemolysis

A

complete

Strep. pyogenes

28
Q

streptococci appearance on gamma hemolysis

A

non-haemolytic

Enterococcus faecalis

29
Q

streptococci main serotyping method

A

Lancefield grouping

30
Q

how many groups are there in the Lancefield grouping

A

20

31
Q

what is streptococcus pyogenes

A

major human pathogen present in nasopharynx of healthy

32
Q

what lansfield group is streptococcus pyogenes in

A

A

33
Q

how are streptococcus pygoenes subdivided

A

into Griffith

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

34
Q

which streptococcus pygoenes have the M strain

A

those that are virulent

inhibit phagocytosis

35
Q

what does streptococcus pyogenes produces

A

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

36
Q

what does streptococcus pyogenes cause

A

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

37
Q

which lansfield group is streptococcus agalactiae in

A

B

38
Q

where is streptococcus agalactiae present

A

carried by some women in gential tract

39
Q

what does streptococcus agalactiae cause

A

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

40
Q

where is streptococcus pneumoniae found

A

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

41
Q

what does streptococcus pneumoniae cause

A

Commonly causes pneumonia

Also causes meningitis

42
Q

what is viridans streptococci

what does it look like on blood agar

A

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

43
Q

where is viridans streptococci

A

mouth and oropharynx — normally of low virulence

44
Q

what does viridans streptococci cause

A

dental caries and periodontal disease and endocarditis

45
Q

what is infective endocarditis caused by

A

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

46
Q

what is infective endocarditis

A

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

47
Q

what lancefield group is enterococci

A

D

48
Q

what is enterococci

A

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

49
Q

where is enterococci present

A

human and animal gut, occasionally in mouth

can grow in 40% bile salts

50
Q

what type of bacteria is enterococci

A

pathogenicity ‑ opportunist in urinary tract infections

51
Q

what are bacilli

A

commonly found as spores in environment e.g. soil

52
Q

what is bacillus anthracis like

A 
large
non-motile
grows on all ordinary media
forms 'medusa head'
encapsulated
produces plasmid encoded toxin complex
53
Q

what does bacillus anthracis cause

A

anthrax in humans and domestic animals

54
Q

what are coryneforms

A

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

55
Q

what does corynebacterium diphtheriae cause

A

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

56
Q

what does corynebacterium diphtheriae do

A

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

57
Q

how is corynebacterium diphtheriae cured

A

effective vaccine based on inactivated toxin

58
Q

how is corynebacterium diphtheriae detected

A

ELEK test used to detect toxin.

PCR now also used to detect toxin gene

59
Q

what is listeria monocytogenes

A

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

60
Q

what does listeria monocytogenes cause

A

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

61
Q

how can listeria monocytogenes frow

A

intracellularly in macrophages

grow well on all ordinary media

Microorganisms + Disease (16 decks)

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