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Flashcards in Microbiology Deck (101):
1

Host risk factors for GI infections (5)

Age - young and elderly
Reduced acid secretion
Reduced gut motility
Colonic microflora
Intestinal immunity

2

What is the definition of diarrhoea?

three or more looses stools in a 24 hour period

3

What is the source or reservoir for an infection?

This is the original source of the infection e.g. animal gut

4

What is the vehicle of the infection?

The means by which the infection is transmitted from one person to another

5

Describe campylobacter

Curved gram negative bacillus

6

What is the incubation period of campylobacter?

3-10 days

7

What is the mechanism of action of campylobacter?

Causes inflammation of the colon and rectum (presents as blood diarrhoea) and can invade and get into the blood stream

8

what is the source of campylobacter?

farm animals

9

What is the vehicle of campylobacter?

uncooked poultry, water and unpasteurised milk

10

What are the symptoms of campylobacter?

abdominal pain and diarrhoea with or without blood

11

What is the treatment for campylobacter?

Erythromycin or Ciprofloxacin for 5 days if they develop systemic illness

12

What is the species name for food poisoning?

Salmonella Enterica

13

What is the incubation period for salmonella?

12 - 48 hours

14

What is the mechanism of action for salmonella?

Causes inflammation of ileum and colon, it multiplies in the gut and causes mucosal damage, decreasing fluid absorption and increasing fluid excretion. Can also invade and reach blood stream

15

What is the source of salmonella?

farm animals

16

What is the vehicle of salmonella?

undercooked poultry

17

what are the symptoms of salmonella?

Abdominal pain, diarrhoea, sometimes bloody and vomiting

18

what is the treatment for salmonella?

Ciprofloxacin for 5 days if at risk of systemic illness

19

What is the incubation period of shigella spp?

1 - 9 days

20

what is the mechanism of action of shigella spp?

Invades intestinal mucosa causing severe inflammation, does not invade any further i.e. not in blood. Pus and blood seen in stool

21

what is the source of shigella spp?

humans

22

What is the vehicle for shigella spp?

person to person

23

what are the symptoms of shigella spp?

Abdominal Pain, diarrhoea and occasionally blood

24

what is the management for shigella spp?

Symptomatic treatment – other species, caught abroad, cause a more sever infection, treat with ciprofloxacin

25

What is the source of action of Escherichia coli (E. Coli)?

Produces a toxin that damages red cells and the kidneys causing haemolytic-uraemic syndrome which increases blood urea, red cell haemolysis and thrombocytopenia

26

what is the source of E. Coli?

normal gut flora of cattle

27

What is the vehicle of E. Coli?

beef - mainly burgers and mince

28

What are the symptoms of E. Coli?

Abdominal pain and bloody diarrhoea

29

What is the management of E. Coli?

symptomatic treatment

30

What are verotoxins?

Bind to receptors found on renal cells, RBC and others in the body. They inhibit protein synthesis and cause cell death

31

How does haemolytic ureamic syndrome present?

abdominal pain, fever, pallor, petechiae (haemorrhages in the skin) and decreased urine production (oliguria)

32

What indications show on a blood test fro HUS?

High white cells
Low platelets
Low HB
Red cell Fragments
Lactate dehydrogenase increased

33

What is typhoid caused by?

salmonella typhi/Salmonella paratyphi A & B

34

How does typhoid initially present?

Initially present as headaches, flu-like symptoms and then diarrhoea three weeks later

35

When does salmonella typhi become typhoid fever?

when it reaches the blood stream

36

what is the incubation period for typhoid fever?

14 - 21 days

37

what is the mechanism of action of typhoid?

Organism invades from the gut lumen, to the lymphatic system and blood stream. It is then in the reticuloendothelial system and call bladder and back to the gut lumen

38

what is the source of typhoid?

Human only

39

What is the vehicle for typhoid fever?

person-person and contaminated water

40

what are the symptoms of typhoid fever?

Fever, rash on abdomen (rose spots) and Diarrhoea

41

what is the management of typhoid fever?

Antibiotics as required – resistance to ciprofloxacin is common

42

what is cholera caused by?

Vibrio Cholerae – a small curved gram negative bacillus

43

what is the incubation period of cholera?

1 - 9 days

44

what is the mechanism of action of cholera?

The organism produces an exotoxin which cause an outpouring of fluid from the small intestine creating sever watery diarrhoea

45

what is the source of cholera?

human only

46

what is the vehicle for cholera?

person-person

47

what are the symptoms of cholera?

water diarrhoea (rice water) causing rapid dehydration

48

what is the management of cholera?

Fluid and electrolyte replacement – no antibiotics

49

Which GI infections are associated with the ingestion of pre-formed toxins?

Staph aureus
Clostridium perfringens
Bacillus cereus

50

What do the toxins of staph aureus act on?

vagus nerve and vomiting centre

51

what is cryptosporidium?

parasite

52

what is the mechanism of action of cryptosporidium?

Occurs when the cysts are ingested which hatch into the trophozoites in the small intestine and invade cells

53

what is the source of cryptosporidium?

domestic animals

54

what is the vehicle for cryptosporidium?

water supply and swimming pools

55

what are the symptoms of cryptosporidium?

diarrhoea - sever in HIV patients

56

what is the management of cryptosporidium?

symptomatic treatment

57

What is Giardia lamblia?

A protozoal infection - a single celled parasite

58

what is the mechanism of action of Giardia lamblia?

Infection occurs when cysts are ingested which “hatch” into trophozoites that invade the cells of the upper small intestine

59

what is the source of Giardia lamblia?

human only

60

what is the vehicle for Giardia lamblia?

person-person

61

what are the symptoms of Giardia lamblia?

diarrhea, malabsorption syndrome, anorexia, abdominal pain and flatulance

62

what is the management of Giardia lamblia?

Oral metronidazole

63

What is Enterobius vermicularis?

white threadworm which passes in stool

64

what is the mechanism of action of the tapeworm?

ova eggs are ingested and hatch in the intestine. They live in the caecum and colon, adult females come out on the perianal skin at night and lay the ova which cause and itch

65

what is the source of a tapeworm?

human only

66

what is the vehicle for a tapeworm?

person-person

67

what are the symptoms of having a tapeworm?

Perianal itch and worms in stool

68

what is the management of a tapeworm?

Oral mebendazole. Often have to treat all members of family at once

69

What is required when sending a stool sample to microbiology?

one pea sized specimen for each for microscopy, toxin test and culture
do not fill the container to the top
Give a separate specimen for virology

70

What is the commonest cause of healthcare-associated diarrhoea?

Clostridium difficile - C. Diff

71

What is the source of C. Diff?

Part of the normal gut flora in the elderly and infants

72

What is C. Diff's mechanism of action?

organsim produces 2 toxins - an enterotoxin and a cytotoxin

73

How does infection occur in C. diff?

when antibiotics prescribed kill off normal gut flora allowing c. diff to overgrow and produce spores which are more resistant

74

what are the symptoms of C. Diff?

Diarrhoea, sometimes bloody, abdominal pain. Severe cases may progress to pseudomembranous colitis or bowel perforation

75

what is the management for c. diff?

less severe = oral metronidazole
more severe = oral vancomycin

76

describe c. diff in terms of on a gram stain?

gram positive spore bearing bacilli

77

what is present on the surface of the colon in c. diff?

pseudo-membrane

78

what tests can be done which would suggest c. diff?

Screening for GDH
If GDH positive then test for toxin A&B
Culture can be done - not routine

79

if the screening test and toxin test for c. diff is positive what does this suggest?

Positive result

80

If the screening test for c. diff is positive but the toxin test is negative, what does this suggest?

indeterminate result - repeat specimen

81

what are the two main viruses which cause diarrhoea?

Rotavirus
Norovirus

82

when will most children contract the rotavirus?

By aged 5

83

How is the rotavirus spread?

person-person either direct or indirect

84

What are the symptoms of the rotavirus?

diarrhoea without blood

85

how is dehydration caused in the rotavirus?

decreased absorption of fluids and an increased secretion in the bowel

86

what complications can occur in children post-infection of rotavirus?

malabsorption causing diarrhoea

87

how is the rotavirus diagnosed?

PCR test on faeces

88

What is the management of the rotavirus?

oral rehydration

89

when is the rotavirus vaccination given and how often?

Twice - once at 2 months old and once at 3 months old

90

why is the rotavirus not given to children older than 24 weeks?

There is an increased risk of intussusception

91

what is intussusception?

One bit of bowel pushes into the other and cuts off the blood supply

92

How is the norovirus spread?

faecal oral/droplet routes person to person

93

what is the norovirus more commonly known as?

winter vomiting bug

94

what are the symptoms of the norovirus?

sudden onset of explosive diarrhoea and vomiting which lasts 2-4 days

95

How is norovirus diagnosed?

faeces specimen or vomit swab for PCR

96

What is the treatment for norovirus?

rehydration - especially in the elderly or very young

97

when are patients at their most infectious?

when vomiting or have diarrhoea

98

other than diarrhoea organisms, which other ones are spread the faecal-oral route?

hepatitis A&E
Resistant bacteria in the GI tract

99

what are the standard infection controls for diarrhoea in hospitals?

patients placed in a single room
cohort nursing in bays
ward closures
Increased ward cleaning

100

what contact precautions are used for the control of diarrhoea in hospital?

hand washing - not alcohol gel
gloves and apron
single use of equipment
disinfecting items with hypochlorite
report exposure of contamination

101

why is hand gel not as effective a soap when dealing with a patient for c. diff?

the spores are resistant to the alcohol hand gel