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Microbiology spot test > Background 1 > Flashcards

Background 1 Flashcards

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Biology 101 flashcards
1
Q

Microorganisms that can cause disease in the human host and are rarely part of the normal flora are

A

pathogens

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2
Q

microorganisms which are often present on or in the human host and usually do not cause disease are called

A

normal flora or commensals

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3
Q

disruption of the normal flora can lead to pathogens becoming the predominant flora resulting in

A

infection

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4
Q

antibiotic associated diarrhoea occurs due to the use of broad spectrum oral antibiotics such as

A

cephalosporins

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5
Q

cephalosporins alter the normal flora in the gi resulting in overgrowth of which bacteria

A

clostridium difficile

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6
Q

toxins produced by c.difficile in the gi causes

A

explosive diarrhoea

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7
Q

what life threatening condition can be caused by c.difficile

A

toxic megacolon

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8
Q

post threatment thrush can result from the use of broad spectrum antibiotics such as

A

beta lactams - amoxycillin

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9
Q

what can beta lactams such as amoxycillin usually be used for

A

UTI

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10
Q

Altering normal flora within the vaginal tract results in the proliferation of

A

candida sp. (yeast) resulting in thrush

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11
Q

contaminating a sterile device with the patients normal flora during insertion causes

A

prosthetic joint infections

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12
Q

prosthetic joint infections usually require removal of the

A

infected joint, removal of surrounding tissue and long term antimicrobial therapy

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13
Q

suseptibility testing is done using

A

antimicrobials

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14
Q

each lab has definite times in which they expect results to be completed and issued, these are called

A

turn around times

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15
Q

all positive reports are forwarded to the

A

consultant microbiologist

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16
Q

laboratory turn over time for urine culture is

A

<24 - 48 hours

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17
Q

laboratory turn over time for wound swab culture is

A

48 - 72 hours

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18
Q

laboratory turn over time for faeces culture is

A

38 - 96 hours

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19
Q

laboratory turn over time for throat swab culture is

A

24-48 hours

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20
Q

diagnostic molecular techniques can only that that a target organism is

A

present. not whether it is viable or what antibiotic the organism is suseptible to

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21
Q

lab based identification has changed from a system based on organisms biochemical profile to one that is molecular in nature, an example is

A

MALDI-TOF

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22
Q

maldi tof has revolutinaised what aspect of microbiology

A

the timescale in which an organism is identified

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23
Q

traditionally it takes 18 hours to identify an organism, MALDI TOF takes

A

minutes

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24
Q

the role of media is still important in MALDI TOF because

A

the organism has to be isolated first

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25
Q

new technologies mean disadvantages

A

increased cost per test and less skilled workforce

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26
Q

solid media used agar which is derived from

A

seaweed as a support matrix for bac to grow on. metabolites such as glucose, blood etc, added to aid growth

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27
Q

before agar is used in lab it is sterilised at

A

121 degrees for 15 minutes and allowed to cool

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28
Q

agar is poured into petri dishes in approx

A

20mL volumes

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29
Q

liquid media does not contain

A

agar

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30
Q

liquid media enriches big or small numbers of bacteria due to the contained peptone, protein, glucose

A

small

31
Q

two of the main agars used contain blood, these are called

A

blood agar and chocolate agar

32
Q

blood agar contains

A

horse blood

33
Q

chocolate agar is the same as blood agar but after adding blood to the molten agar it is heated

A

to 80 degrees for 15 minutes

34
Q

heating blood on the agar to 80 degrees for 15 minutes does what?

A

denatures but not lyses the red blood cells

35
Q

the denaturing of blood releases

A

more nutrients for bacteria to utilise

36
Q

if an organism grows on blood agar it will grow

A

better on chocolate agar

37
Q

some species such as Haemophilus species require the extra nutrients provided by

A

chocolate agar to grow

38
Q

organisms that require media richer than blood are called

A

fastidious

39
Q

chocolate agar is more difficult to make so it is only used when fastidious organisms are

A

potential pathogens

40
Q

some organisms such as streptococci produce enzymes that

A

lyse red blood cells

41
Q

alpha haemolysis is

A

partial lysis of the red blood cells

42
Q

alpha haemolysis results in which colour

A

green discolouration

43
Q

beta haemolysis is

A

total lysis of red blood cells

44
Q

beta haemolysis results in which colour change

A

a clear halo around the colony

45
Q

is alpha or beta haemolysis seen better on chocolate agar

A

alpha

46
Q

is beta haeolysis seen on chocolate agar

A

no

47
Q

many organisms look similar when they grow on blood agar so to aid in identification what is used?

A

an indicator media

48
Q

give two examples of indicator media

A

macconkey or cled

49
Q

what media do cled and macconkey contain as the indicator substrate ?

A

lactose

50
Q

which ph indicator is used in macconkey?

A

phenol

51
Q

which ph indicator is used in cled?

A

bromothymol blue

52
Q

macconkey agar lactose fermenters change the indicator to which colour

A

dark pink/red

53
Q

macconkey agar lactose non fermenters change the indicator to which colour

A

pale pink/ remain colourless

54
Q

organisms that ferment lactose produce acid which ____ the ph of the surrounding media changing the colour to dark pink/red

A

lowers

55
Q

incubation conditions include which three things

A

atmosphere, temperature and incubation duration

56
Q

aerobic is

A

oxygen at atmospheric air concentration

57
Q

anaerobic is

A

no air

58
Q

microaerobic is

A

low concentrations of oxygen

59
Q

some bacteria only grow when oxygen is present they are called

A

obligate aerobes

60
Q

an example of an obligate aerobe is

A

pseudomonas

61
Q

obligate anaerobes can only grow

A

without oxygen

62
Q

an exmaple of an obliagte anaerobe is

A

clostridium

63
Q

most bacteria grow optimally in the presence of oxygen but will grow in anaerobic conditions these are called

A

facultative anaerobes

64
Q

bacteria that grow in low o2 levels are

A

microaerophilic

65
Q

what temperature does listeria grow at

A

5 degrees

66
Q

what temperature does campylobacter grow at

A

42 degrees

67
Q

what are the main temperatures in the lab

A

35-37 degrees normal body temp and 30 degrees external skin temp

68
Q

the majority of organisms will grow after

A

18-24 hours incubation

69
Q

which species grow between 18-24 hours

A

e.coli, salmonella, s.aureus

70
Q

which bacteria grow at 24 hrs incubation

A

alpha and beta haemolytic streptococci

71
Q

which bacteria grow at 48-72 hours (fastidious)

A

haemophilus, campylobacter and anaerobes

72
Q

which bacteria grow after 5 days

A

nocardia species

73
Q

which bacteria grow after 6-8 weeks incubation and are extremely fastidious

A

mycobacterium tuberculosis

74
Q

what is a fastidious organism

A

A fastidious organism is any organism that has a complex nutritional requirement

Microbiology spot test (8 decks)

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