Background 1

Question 1

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

Answer 1

pathogens

Question 2

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

Answer 2

normal flora or commensals

Question 3

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

Answer 3

infection

Question 4

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

Answer 4

cephalosporins

Question 5

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

Answer 5

clostridium difficile

Question 6

toxins produced by c.difficile in the gi causes

Answer 6

explosive diarrhoea

Question 7

what life threatening condition can be caused by c.difficile

Answer 7

toxic megacolon

Question 8

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

Answer 8

beta lactams - amoxycillin

Question 9

what can beta lactams such as amoxycillin usually be used for

Answer 9

UTI

Question 10

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

Answer 10

candida sp. (yeast) resulting in thrush

Question 11

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

Answer 11

prosthetic joint infections

Question 12

prosthetic joint infections usually require removal of the

Answer 12

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

Question 13

suseptibility testing is done using

Answer 13

antimicrobials

Question 14

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

Answer 14

turn around times

Question 15

all positive reports are forwarded to the

Answer 15

consultant microbiologist

Question 16

laboratory turn over time for urine culture is

Answer 16

<24 - 48 hours

Question 17

laboratory turn over time for wound swab culture is

Answer 17

48 - 72 hours

Question 18

laboratory turn over time for faeces culture is

Answer 18

38 - 96 hours

Question 19

laboratory turn over time for throat swab culture is

Answer 19

24-48 hours

Question 20

diagnostic molecular techniques can only that that a target organism is

Answer 20

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

Question 21

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

Answer 21

MALDI-TOF

Question 22

maldi tof has revolutinaised what aspect of microbiology

Answer 22

the timescale in which an organism is identified

Question 23

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

Answer 23

minutes

Question 24

the role of media is still important in MALDI TOF because

Answer 24

the organism has to be isolated first

Question 25

new technologies mean disadvantages

Answer 25

increased cost per test and less skilled workforce

Question 26

solid media used agar which is derived from

Answer 26

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

Question 27

before agar is used in lab it is sterilised at

Answer 27

121 degrees for 15 minutes and allowed to cool

Question 28

agar is poured into petri dishes in approx

Answer 28

20mL volumes

Question 29

liquid media does not contain

Answer 29

agar

Question 30

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

Answer 30

small

Question 31

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

Answer 31

blood agar and chocolate agar

Question 32

blood agar contains

Answer 32

horse blood

Question 33

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

Answer 33

to 80 degrees for 15 minutes

Question 34

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

Answer 34

denatures but not lyses the red blood cells

Question 35

the denaturing of blood releases

Answer 35

more nutrients for bacteria to utilise

Question 36

if an organism grows on blood agar it will grow

Answer 36

better on chocolate agar

Question 37

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

Answer 37

chocolate agar to grow

Question 38

organisms that require media richer than blood are called

Answer 38

fastidious

Question 39

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

Answer 39

potential pathogens

Question 40

some organisms such as streptococci produce enzymes that

Answer 40

lyse red blood cells

Question 41

alpha haemolysis is

Answer 41

partial lysis of the red blood cells

Question 42

alpha haemolysis results in which colour

Answer 42

green discolouration

Question 43

beta haemolysis is

Answer 43

total lysis of red blood cells

Question 44

beta haemolysis results in which colour change

Answer 44

a clear halo around the colony

Question 45

is alpha or beta haemolysis seen better on chocolate agar

Answer 45

alpha

Question 46

is beta haeolysis seen on chocolate agar

Answer 46

no

Question 47

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

Answer 47

an indicator media

Question 48

give two examples of indicator media

Answer 48

macconkey or cled

Question 49

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

Answer 49

lactose

Question 50

which ph indicator is used in macconkey?

Answer 50

phenol

Question 51

which ph indicator is used in cled?

Answer 51

bromothymol blue

Question 52

macconkey agar lactose fermenters change the indicator to which colour

Answer 52

dark pink/red

Question 53

macconkey agar lactose non fermenters change the indicator to which colour

Answer 53

pale pink/ remain colourless

Question 54

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

Answer 54

lowers

Question 55

incubation conditions include which three things

Answer 55

atmosphere, temperature and incubation duration

Question 56

aerobic is

Answer 56

oxygen at atmospheric air concentration

Question 57

anaerobic is

Answer 57

no air

Question 58

microaerobic is

Answer 58

low concentrations of oxygen

Question 59

some bacteria only grow when oxygen is present they are called

Answer 59

obligate aerobes

Question 60

an example of an obligate aerobe is

Answer 60

pseudomonas

Question 61

obligate anaerobes can only grow

Answer 61

without oxygen

Question 62

an exmaple of an obliagte anaerobe is

Answer 62

clostridium

Question 63

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

Answer 63

facultative anaerobes

Question 64

bacteria that grow in low o2 levels are

Answer 64

microaerophilic

Question 65

what temperature does listeria grow at

Answer 65

5 degrees

Question 66

what temperature does campylobacter grow at

Answer 66

42 degrees

Question 67

what are the main temperatures in the lab

Answer 67

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

Question 68

the majority of organisms will grow after

Answer 68

18-24 hours incubation

Question 69

which species grow between 18-24 hours

Answer 69

e.coli, salmonella, s.aureus

Question 70

which bacteria grow at 24 hrs incubation

Answer 70

alpha and beta haemolytic streptococci

Question 71

which bacteria grow at 48-72 hours (fastidious)

Answer 71

haemophilus, campylobacter and anaerobes

Question 72

which bacteria grow after 5 days

Answer 72

nocardia species

Question 73

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

Answer 73

mycobacterium tuberculosis

Question 74

what is a fastidious organism

Answer 74

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