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Study Notes - Gastroenterology > Microbiology 1 (Dr Orange) > Flashcards

Microbiology 1 (Dr Orange) Flashcards

1
Q

What host factors affect your risk of gastrointestinal infection? (5)

A 
Age (very young and elderly)
Decreased gastric acid secretion
Decreased gut motility
Influence of colonic microflora
Intestinal immunity
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2
Q

What bacterias seen in the UK cause Gastrointestinal infections? (8)

A 
Campylobacter coli/ jejuni
Salmonella enterica
E coli O157
Shigella sonnei
Staph aureus/ Clostridium perfingens/ Bacillus cereus
C difficile
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3
Q

What viruses seen in the UK cause gastrointestinal infections? (2)

A

Norovirus

Rotavirus

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4
Q

What parasites seen in the UK cause gastrointestinal infections? (2)

A

Cryptosporidium sp

Giardia lamblia

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5
Q

What bacterias, usually imported from abroad, case gastrointestinal infections?

A

Vibrio cholerae/ parahaemolyticus
Salmonella typhi/ paratyphi
Aeromonas sp.
Shigella dysenteriae/ flexneri/ boydii

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6
Q

What parasite, usually imported from abroad, can cause GI infections?

A

Entamoeba histolytica

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7
Q

What is diarrhoea?

A

3 or more loose stools in 24 hours

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8
Q

What is the source/ reservoir of infection?

A

The original source of the infection e.g. animal gut, another human’s gut, etc.

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9
Q

What is the vehicle of infection?

A

The means by which the infection is transmitted from one person to another (e.g. contaminated food/ water)

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10
Q

What is the source and vehicle of infection of E. coli O157

A

Source = cattle GI tract

Vehicle of infection = undercooked hamburger

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11
Q

What shape is camplobacter (C. jejune, C. coli)?

A

Curved gram negative bacilus

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12
Q

What is the commonest cause bacterial GI infection in the UK?

A

Campylobacter

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13
Q

Incubation period of campylobacter?

A

3-10 days

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14
Q

How does campylobacter make you unwell?

A

Causes inflammation of the colon and rectum leading to bloody diarrhoea
Can invade and occasionally get into bloodstream (patients get systemically unwell with flu like symptoms)

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15
Q

What is the main source/ vehicle of infection of campylobacter?

A

Undercooked poultry + other farm animals, water and unpasteurised milk (person to person spread is rare - outbreaks usually because consumed the same chicken)

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16
Q

Symptoms of campylobacter?

A

Abdo pain

Diarrhoea =/- blood

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17
Q

Management of campylobacter?

A

Usually self limiting but give ERYTHROMYCIN or CIPROFLOXACIN for 5 days if patient develops systemic illness

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18
Q

What does “enteric” in Salmonella enterica mean?

A

It is the agreed species name for all food poisoning i.e. non-typhoidal salmonella (often still called by species name e.g. S. enteritiditis, S. typhimurium, etc.

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19
Q

What is the incubation period for Salmonella enterica?

A

12 - 48 hours

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20
Q

What is the mechanism of action of Salmonella enterica?

A

Causes inflammation of the ileum and colon - multiply in gut and cause mucosal damage, decreased mucosal damage and increased fluid excretion
Can invade and occasionally get into bloodstream

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21
Q

What is the source/ vehicle of infection of salmonella enterica?

A

Undercooked poultry + other farm animals (much less common since immunisation of poultry against Salmonella spp.)

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22
Q

Symptoms of salmonella enterica?

A

Abdo pain
Diarrhoea (occasionally bloody)
Vomiting

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23
Q

Management of salmonella?

A

Usually ciprofloxacin for 5 days if patient at risk of or develops systemic illness

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24
Q

What type of Shigella is seen in the UK?

A

Shigella sonnei (most benign type) - outbreaks occur every few years amongst cohorts of vulnerable children

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25
Q

Incubation period for Shigella sonnei?

A

1-9 days

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26
Q

Mechanism of action of Shigella sonnei?

A

Invades intestinal mucosa causing severe inflammation, but does not invade further (never seen in blood cultures)

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27
Q

What is seen in the stools of a patient with Shigella?

A

Blood and pus cells

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28
Q

Source/ vehicle of infection of Shigella?

A

Human only infection

Often spread person- person amongst young children in schools, etc.

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29
Q

Symptoms of shigella Sonnei?

A

Abdo pain

Diarrhoea (occasionally blood)

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30
Q

Management of Shigella sonnei?

A

Usually self-limiting - symptomatic treatment only
Other species of Shigella (dysenteriae, etc.) acquired abroad, usually require Ciprofloxacin due to more severe infection

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31
Q

What strain of E coli produces a toxin that damages red blood cells and the kidneys?

A

The O157:H7 strain (and a few other serotypes)

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32
Q

What type of toxin does E coli O157 produce and what does this do?

A

verotoxin (VTEC)
Damages red cells and the kidney, causing haemolytic-uraemic syndrome (HUS)
(increased blood urea, red cell haemolysis and thrombocytopenia)

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33
Q

Who are most at risk of developing HUS?

A

Children

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34
Q

What is the source/ vehicle of infection of E coli O157?

A

Carried as part of the normal gut flora in cattle
Beef becomes contained on the outside at slaughter = increased risk from minced meat and hamburgers than from a steak
Nursery/ school visits to farm
Private (untreated) water supplies = run off water from fields
Low infecting dose, so person-person spread causes 2y cases

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35
Q

Symptoms of E coli O157?

A

Abdo pain

Bloody diarrhoea is common

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36
Q

Management of E coli O157?

A

Symptomatic and supportive treatment only
Antibiotics contraindicated as may increase release of toxin
Check bloods for HUS 1 week after onset of symptoms

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37
Q

What does verotoxin do?

A

Binds to receptors found on renal cells, RBC and others
Inhibits protein synthesis
Causes cell death

38
Q

Clinical presentation of HUS?

A 
Abdo pain
Fever
Pallor
Petechiae
Oliguria (decreased urine production)
Bloody diarrhoea in 90% of cases
Mostly in under 16s
39
Q

When is the peak presentation of HYS?

A

7-10 days after onset of diarrhoea

40
Q

What does blood tests show which indicates HUS? (5)

A 
High white cells
Low platelets
Low Hb
Red cell fragments
Lactate dehydrogenase (increased 1.5 times normal)
41
Q

Appearance of Salmonella, Shigella and E coli O157 on gram film?
What is used to differentiate between these?

A

Gram negative bacilli

Biochemical tests, then serological tests

42
Q

What bacteria causes typhoid and paratyphoid fever?

A

Salmonella typhi/ salmonella paratyphi A and B

43
Q

What are the symptoms of typhoid/ paratyphoid fever?

A

Initially a febrile illness (bacteria circulating in bloodstream) causing headache, flu-like symptoms followed by diarrhoea 2 weeks later

44
Q

When is typhoid/ paratyphoid seen in the UK?

A

When it has been imported from abroad

45
Q

Incubation period of typhoid/ paratyphoid fever?

A

14 - 21 days

46
Q

Mechanism of action of typhoid/ paratyphoid?

A

Organism invades from gut lame -> lymphatic system -> bloodstream -> reticuloendothelial system and gall bladder -> gut lumen and invades Peyer’s patches

47
Q

In chronic carriers of typhoid/ parathyroid, where does the bacteria reside?

A

The gallbladder

48
Q

What can happen during the bacteraemic phase of typhoid/ paratyphoid?

A

Distant sites can become infected e.g. ostemyelitis

49
Q

Source of salmonella typhi/ paratyphi?

A

Human only infection
Spread person-person or from drinking contaminated water/ eating contaminated food/ poor sanitation (different from entericas which are associated with animals)

50
Q

Symptoms of typhoid/ paratyphoid?

A

Fever
Rash on abdomen (“rose spots”)
Diarrhoea

51
Q

Management of Typhoid/ paratyphoid?

A

Antibiotics are required, choice depends on sensitivities. Resistance to ciprofloxacin

52
Q

What causes cholera?

A

Vibrio cholerae (“the comma bacillus”)

53
Q

What is the appearance of Vibrio cholera?

A

Small curved gram negative baciluus

54
Q

Where are outbreaks of cholera common?

A

In disaster/ war stricken situations

55
Q

Incubation period of cholera?

A

1-9 days

56
Q

Mechanism of action of cholera?

A

Organism produces an exotoxin that causes active outpouring of fluid from cells of small intestine resulting in severe watery diarrhoea

57
Q

Source/ vehicle of infection of Vibrio cholerae

A

Human only infection - spread person-person or from drinking contaminated water/ poor sanitation

58
Q

Symptoms of cholera?

A

Watery diarrhoea “rice water stools” causing rapid dehydration

59
Q

Management of cholera?

A

Fluid and electrolyte replacement

Antibiotics NOT indicated

60
Q

What causes GI infections associated with ingestion of pre-formed toxin? (3)

A

Staph aureus
Clostridium perfingens
Bacillus cereus

61
Q

What is an enterotoxin?

A

A protein exotoxin released that targets the intestine

62
Q

What is the typical scenario where Staph aureus is passed on through food?

A

Bakery worker with infected finger touches cream cake
Staph aureus multiplies producing enterotoxin (exotoxin)
Customer ingests enterotoxin

63
Q

What does ingestion of staph aureus enterotoxin cause?

A

Acts directly on vagus nerve and vomiting centre inducing vomiting within 1 - 2 hours

64
Q

What is the appearance of clostridium perfingens?

A

Large gram positive anaerobic bacillus

65
Q

Where is clostridium profanens normally found?

A

Part of the normal gut flora in humans and animals

66
Q

How does clostridium perfringens cause infection?

A

Spores survive cooking, then turn into vegetative organism some strains of which produce enterotoxin (an exotoxin)

67
Q

What is clostridium perfringens infection associated with?

A

Inadequately refrigerated re-heated meat gravy

68
Q

What is the appearance of bacillus cereus?

A

Large gram positive aerobic bacillus

69
Q

How can a patient contract bacillus cereus?

A

Exotoxin can be ingested as pre-formed toxin in food
Organism can multiply in intestine, producing toxin that is absorbed from the gut
Spores survive cooking, then turn into vegetative organisms that produce toxin

70
Q

What is bacillus cereus infection associated with?

A

Contaminated inadequately refrigerated reheated rice

71
Q

What 2 bacterias have short incubation periods? (1-6 hours)

A

Staph aureus

72
Q

What 2 bacterias have a medium incubation period? (12-48hours)?

A

Salmonella

Cl perfrigens

73
Q

What 2 bacteria have a long incubation period? (2-14 days)

A

Campylobacter

E coli O157

74
Q

Cryptosporidium and Giardia lamblia are both protozoal infections - true/ false?

A

True

75
Q

Mechanism of action of cryptosporidium?

A

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

76
Q

Source/ vehicle of infection of cryptosporidium?

A

Domestic animals, especially calves
Person-person spread
Outbreaks associated with contaminated water supplies and swimming pools (cysts resistant to chlorine)

77
Q

Symptoms of cryptosporidium?

A

Diarrhoea

Particularly severe in HIV pos patients

78
Q

Management of Cryptosporidium?

A

Symptomatic treatment only

79
Q

What type of stain can be used to identify cryptosporidium cysts?

A

Ziehl-Neelson stain (pink cysts against blue background)

80
Q

Mechanism of action of Giardia lamblia?

A

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

81
Q

Source/ vehicle of infection of Giardia lamblia?

A

Human only infection
?person to person spread
Outbreaks associated with contaminated water supplies

82
Q

Symptoms of Giardia lamblia?

A 
Diarrhoea
Malabsorption syndrome
Anorexia
Abdominal pain
Flatulence
83
Q

Management of Giardia lamblia?

A

Oral metronidazole

84
Q

What is the more commonly used name for Enterobius vermicularis?

A

Threadworms

85
Q

Pathogenesis of thread worms?

A

Ova (egg) ingested -> hatch in intestine and live in caecum and colon -> adult females come out on to perianal skin at night and lay ova -> ova cause perianal itch -> child scratches bottom -> puts fingers in mouth

86
Q

Source/ vehicle of transport of enterobius vermicularis?

A

Human only infection

Person-person spread (poor hygiene)

87
Q

Symptoms of Enterobius vermicularis?

A

Perianal itch

Worms seen in stool

88
Q

What is the treatment for Enterobius vermicularis?

A

Oral mebendazole (often have to treat all members of family at once)

89
Q

What must be done if blood is seen in the patients stool?

A

Stool must be sent to ref lab for E coli verotoxin detection

90
Q

When sending a stool sample to the lab for testing, what must you tell the lab if the patient has been abroad?

A

Where they were

Study Notes - Gastroenterology (42 decks)

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