Background 3 GI

Question 1

why is direct microscopy of no use with stool samples

Answer 1

heavy growth of normal flora

Question 2

why is blood agar plate not used for stool samples

Answer 2

not possible to distinguish pathogen from normal flora

Question 3

what type of media is used for stool samples

Answer 3

indicator media such as macconkey

Question 4

samlonella and shigella are both

Answer 4

non lactose fermenters on macckoney agar

Question 5

e.coli is usually a

Answer 5

lactose fermenter on macconkey

Question 6

name a media which contains more inhibitory substances than macconkey

Answer 6

xld

Question 7

on xld salmonella is a

Answer 7

red colony with a black centre

Question 8

why does salmonella have a black centre in xld

Answer 8

becuase it produces H2s

Question 9

what does shigella loook like on xld

Answer 9

red colony

Question 10

e.coli looks like what on xld

Answer 10

it doesnt grow on xld

Question 11

which pathogens are associated with gi infection in the uk?

Answer 11

salmonella, shigella and campylobacter

Question 12

which pathogens are important to search for if the patient has travelled to an area where cholera is endemic?

Answer 12

vibrio

Question 13

overseas travel would require the stool to be examined for

Answer 13

ova, cysts and parasites

Question 14

campylobacter selective media is incubated for how many hours before it is examined?

Answer 14

48 hours

Question 15

non lactose fermenters on the macconkey plate are picked off for biochemical testing such as the

Answer 15

oxidase test

Question 16

the organisms that are oxidase negative are further tested biochemically e.g. a ____ test

Answer 16

urea

Question 17

all urea negative isolates are

Answer 17

identified biochemically overnight

Question 18

with the xld plate the red colonies are tested using

Answer 18

oxidase first

Question 19

all oxidase negative isolates are tested further (from the xld plate) using

Answer 19

urea

Question 20

the campylobacter selective media is examined for the presnece of colonies showing the

Answer 20

typical morphology of campylobacter species

Question 21

suspicious colonies on the campylobacter are

Answer 21

gram stained and checked biochemically (oxidase)

Question 22

if biochemistry identified salmonella and shigella colonies which tests are performed

Answer 22

agglutination tests to confirm the result using specific anti-sera

Question 23

the most common subspecies of salmonella in the uk are

Answer 23

salmonella enteritidis and salmonella typhimurium

Question 24

describe salmonella

Answer 24

gram negative rods, oxidase negative, non lactose fermenters on macconkey agar

Question 25

typhoid is caused by

Answer 25

salmonella typhi

Question 26

how is typhoid transmitted

Answer 26

contaminated water or by an asymptomatic carrier

Question 27

shigella is also known as

Answer 27

bacillary dysentery

Question 28

shigella is caused by

Answer 28

shigellae

Question 29

the infective dose of shigellae is very

Answer 29

small

Question 30

transmission of shigella is by

Answer 30

direct contact

Question 31

what are the most common types of shigella in the uk?

Answer 31

shigella sonnei and shigella flexneri

Question 32

describe shigellae

Answer 32

gram negative rods, oxidase neg, non lactose fermenters on macconkey agar

Question 33

most common cause of gastro enteritis in the uk

Answer 33

campylobacter jejuni

Question 34

what is the usual source of infection of campylobacter

Answer 34

poorly cooked poultry , contact with young animals

Question 35

campylobacter enteritis usaully occurs in

Answer 35

adults and older children

Question 36

symptoms of campylobacter enteritis are

Answer 36

severe bloody diarrhoea

Question 37

describe campylobacter jejuni

Answer 37

microaerobic organism, thin curved gram neg rod, oxidase positive

Question 38

verotoxin producing e.coli causes

Answer 38

haemorrhagic colitis and HUS Hemolytic uremic syndrome

Question 39

what is e.coli usually tansmitted by

Answer 39

raw meat

Question 40

e.coli O157 plated on sorbital macconkey doesnt ferment sorbitol so forms

Answer 40

colourless colonies

Question 41

other e.coli colonies not o157 produce which colour colonies on sorbitol macconkey

Answer 41

dark pink

Question 42

describe e.coli O157

Answer 42

gram negative rod, oxidase negative

Question 43

what causes cholera

Answer 43

vibrio cholerae 01 or 01239

Question 44

v cholerae produces a toxin causing secretions of fluids into intestine causes

Answer 44

severe diarrhoea

Question 45

transmission by

Answer 45

water or food

Question 46

vibrio cholera is isolated on which type of agar and which colour does it grow as

Answer 46

TCBS agar and grows as yellow colonies

Question 47

describe v.cholera

Answer 47

gram neg curved rod and oxidase positive

Question 48

rota virus causes 30-60% of GI infections in

Answer 48

infants

Question 49

rota virus is rare in

Answer 49

children and adults

Question 50

how is rotavirus transmitted

Answer 50

in nurseries and playgroups poor hand washing and hygiene

Question 51

what is the most common waterborne disease in the uk?

Answer 51

cryptosporidiosis

Question 52

what causes cryptosporidiosis and what exactly is it

Answer 52

cryptosporidium parvum is a parasite

Question 53

how is cryptosporidium parvum excreted from a host

Answer 53

as a chemical resistant oocyst

Question 54

how is cryptosporidium seen in the lab

Answer 54

by examining stool samples using ZN stain