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Gastroenterology Year 1 > Microbiology > Flashcards

Microbiology Flashcards

1
Q

What is the definition of “intestinal flora”?

A

The symbiotic bacteria occurring naturally in the gut

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2
Q

What is the definition of GI colonisation?

A

The establishment of a microorganism on or within a host

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3
Q

What is the definition of a pathogen?

A

Any micro-organism that has the potential to cause disease

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4
Q

What is the definition of virulence?

A

The likelihood of causing disease

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5
Q

What are enterobacteriacaea?

A

Gram negative, non-spore forming, facultative anaerobes which are able to ferment sugars
They are pathogens

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6
Q

How do enterobacteriacaea cause disease?

A

Fimbriae helps them colonise by binding tight to tissue

They produce an endotoxin and an enterotoxin

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7
Q

What are some enterobacteriacaea coccobacilli?

A

H. Influenzae

B. pertussis

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8
Q

What are some enterobacteriacaea cocci?

A

Neisseria meningitis

Neisseria gonnorhoea

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9
Q

What are some lactose negative enterobacteriacaea bacilli?

A

Oxidase positive - Vibrio cholera, P. aeruginosa

Oxidase negative - H. pylori, Salmonella

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10
Q

What are some lactose positive enterobacteriacaea bacilli?

A

Klebsiella
E. coli
Enterobacter

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11
Q

What does clostridium difficile commonly cause?

A

Hospital- associated diarrhoea

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12
Q

What toxins does clostridium difficile produce?

A

Toxin A - enterotoxin

Toxin B - cytotoxin

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13
Q

What are the symptoms of a clostridium difficile infection?

A

Diarrhoea - sometimes bloody

Abdominal pain

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14
Q

What is the management of a moderate clostridium difficile infection?

A

Oral metronidazole

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15
Q

What is the management of a severe clostridium difficile infection?

A

Oral vancomycin

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16
Q

How can we prevent a clostridium difficile infection?

A

Avoid the 4C antibiots
Use narrow spectrum antibiotics
Isolation of patients

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17
Q

Describe a rotavirus infection

A 
Person to person spread
Commoner in the winter
Self-limiting - lasts about a week
Causes dehydration - so rehydration is key in management
Vaccine at 2 and 3 months old
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18
Q

Which is the commonest cause of diarrhoea and vomiting in children?

A

Rotavirus

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19
Q

Describe a norovirus infection

A

Can affect all ages
Faecal-oral / droplet routes of spread and person to person
Short incubation - less than 24 hours
Lasts 2-4 days

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20
Q

What are some GI infection risk factors?

A 
Malnutrition
Closed communities
Exposure to contaminated food/water
Age <5 and not breastfed
Age >65
Acid suppression
Immunosuppresion
Genetic susceptibility
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21
Q

What is the definition of diarrhoea?

A

More than 3 unformed stools per fay or a noticeable change in bowel habit

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22
Q

What is dysentery?

A

Inflammation of the intestine usually associated with fever, abdominal pain and rectal tenesmus causing diarrhoea with blood and mucus

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23
Q

What are some ways of contamination/transmission of gastroenteritis?

A

Cross contamination of raw and cooked food
Preparation of food too far in advance
Inadequate heating and cooling of food
Contaminated environment/equipment

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24
Q

What are some pathogens with an incubation time of 1-2 hours?

A

Staph aureus - preformed toxin in food that acts quickly on the vomiting centre in the brain

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25
Q

What are some pathogens with an incubation time of 1-6 hours?

A

Bacillus cereus - found in starchy foods, reheated rice etc that leads to profuse vomiting due to heat-resistant spores

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26
Q

What are some pathogens with an incubation time of 12-48 hours?

A

Salmonella enterica - found in poultry, raw meat and raw egg
C. perfrigens
Norovirus
Listeria monocytogenes - unpasteurised milk products and deli meats, mother to child and food borne transmission

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27
Q

What are some pathogens with an incubation time of a few hours to 5 days?

A

Vibrio cholera

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28
Q

What are some pathogens with an incubation time of 1-3 days?

A

Rotovirus

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29
Q

What are some pathogens with an incubation time of 1-4 days?

A

Enterotoxigenic E. Coli - produces a heat stable toxin and is usually travel related

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30
Q

What are some pathogens with an incubation time of 1-9 days?

A

Shigella - produces shiga toxin, binds to receptors found on renal cells, RBCs and others, inhibits protein synthesis and causes cell death

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31
Q

What are some pathogens with an incubation time of 3-10 days?

A

Campylobacter - poultry and raw milk

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32
Q

What are some pathogens with an incubation time of 7-21 days?

A

Giardia

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33
Q

What are some pathogens with an incubation time of 14-21 days?

A

Salmonella typhi

Salmonella parathyphi

34
Q

What are some pathogens with an incubation time of up to 21 days?

A

E. coli 0157

35
Q

What is enteric fever?

A

An infection most commonly caused by Salmonella typhi or paratyphoid in people returning from the Indian subcontinent and SE Asia.

36
Q

What is the incubation period of enteric fever?

A

7 to 18 incubation period

37
Q

What are some of the symptoms of enteric fever?

A

Fever, constipation/diarrhoea, dry cough, headache

38
Q

What is the treatment (if severe) of enteric fever?

A

IV Ceftriaxone

39
Q

What is amoebiasis?

A

A disease caused by entamoeba histolytic (a protozoa_

40
Q

How is amoebiasis transmitted?

A

Faecal oral spread

41
Q

What are some symptoms of amoebiasis?

A

Abdominal pain, fever, bloody diarrhoea, peritonism

42
Q

What can amoebiasis cause?

A

A liver abscess

Management for that is metronidazole

43
Q

What is giardiasis?

A

An illness caused by giardia intestinalis

44
Q

What is the incubation period for giardiasis?

A

About a week

45
Q

What are some symptoms of giardiasis?

A

Watery, malodorous diarrhoea

Abdominal cramps

46
Q

What is the treatment for giardiasis?

A

Metronidazole

47
Q

Name the 3 different types of Helminths

A

Nematodes - roundworms
Trematodes - flukes - fresh water exposure
Cestodes - tapeworms - undercooked beef/pork

48
Q

What is chagas disease caused by?

A

Kissing bug (triatome)

49
Q

What does chagas disease cause?

A

Parasympathetic denervation affecting the colon and the oesophagus

50
Q

What is the definition of an antibiotic?

A

A drug that kills or inhibits the growth of microorganisms

51
Q

What is the definition of a resistant microorganism?

A

An organism which will not be inhibited by an antibiotic at clinically achievable concentrations

52
Q

What is the definition of a susceptible microorganism?

A

An organism that is inhibited by antibiotics

53
Q

What is the definition of a multi-drug resistant (MDR) organism?

A

Non-susceptibility to at least 1 agent in 3 or more antimicrobial categories

54
Q

What is the definition of an extremely drug resistant (XDR) organism?

A

Non-susceptibility to at least 1 agent in all but 2 or fewer antimicrobial categories

55
Q

What is the definition of a pan-drug resistant (PDR) organism?

A

Non-susceptibility to all agents in all antimicrobial categories

56
Q

What is meant by “vertical transmission” of antimicrobial resistance?

A

A bacterium accumulated errors or mutations in its genome during replication
Some of these give the ability to resist antibiotics

57
Q

What is meant by “horizontal transmission” of antimicrobial resistance?

A

Resistant genes are swapped from one microbe to another

58
Q

What are some causes of antimicrobial resistance?

A

Human or animal antimicrobial misuse or overuse

Prior hospitalisation or invasive procedures

59
Q

What are some consequences of antimicrobial resistance?

A

Increased mortality and morbidity

Increased healthcare costs

60
Q

What are some solutions for reducing antimicrobial resistance?

A

Preventing infections/spread of disease
Improvement of antibiotic prescribing and use
Development of new antimicrobials

61
Q

How is Hepatitis A transmitted?

A

Faecal oral spread and poor hygiene/overcrowding

62
Q

What is the clinical presentation of Hepatitis A?

A

Acute presentation only

Peak incidence in older children/young adults

63
Q

What investigations confirm the diagnosis of Hepatitis A?

A

Clotted blood for serology - Hepatitis A IgM

64
Q

How is the spread of Hepatitis A controlled?

A

Hygiene

Vaccine prophylaxis

65
Q

How is Hepatitis B transmitted?

A

Sex
Mother to child
Blood to blood

66
Q

What is the clinical presentation of Hepatitis B?

A

Acute and chronic infections

67
Q

What investigations confirm the diagnosis of Hepatitis B?

A

Hep B surface antigen (HBsAg) - present in all infectious individuals
- Present for more than 6 months is chronic

Hepatitis B e antigen (HBeAg) - usually also present in highly infectious individuals

Hep B DNA - usually also present in highly infectious individuals

Hep B IgM - recently infected cases

Anti-HBs - present in immunity

68
Q

How is the spread of Hepatitis B controlled?

A

Minimize exposure - safe sex, safe needle exchange, prevention of needlestick injuries

Pre-exposure vaccines

Post-exposure prophylaxis

69
Q

How is Hepatitis C transmitted?

A

Sex
Mother to child
Blood to blood

70
Q

What is the clinical presentation of Hepatitis C?

A

75% of infected cases result in chronic infection

71
Q

What investigations confirm the diagnosis of Hepatitis C?

A

HCV serology:

  • Negative - patient is unlikely to have HepC
  • Positive - patient has been infected

HCV RNA assay:

  • Negative - past infection and no treatment needed
  • Positive - active infection
72
Q

How is the spread of Hepatitis C controlled?

A

Minimize exposure

No vaccine

73
Q

What is Hepatitis D?

A

An infection that is only found in individuals with a Hep B infection - exacerbated Hep B

74
Q

Which hepatitis is Hepatitis E similar to in transmission and clinical presentation?

A

Hep A

75
Q

Is there a vaccine for Hepatitis E?

A

No

76
Q

Is spontaneous cure common in chronic Hep B infections?

A

Yes

77
Q

Is spontaneous cure common in chronic Hep C infections?

A

No

78
Q

What is the management of acute viral hepatitis?

A

Monitor for encephalopathy or resolution
Immunisation of contacts
Vaccinate against other infections if at risk

79
Q

How long does a chronic hepatitis infection take to cause cirrhosis?

A

20 years

80
Q

How long does a chronic hepatitis infection take to cause hepatocellular carcinoma?

A

30 years

81
Q

What are the therapy options for chronic Hep B?

A
  1. Suppressive antiviral drug e.g. entecavir, tenofovir
    • Safe but only causes suppression not cure
  2. Peginteferon therapy
    • Sustained cure is possible but there’s serious side effects
82
Q

What are the therapy options of chronic Hep C?

A

Use of antivirals e.g. ledipasvir, sofosbuvir

Gastroenterology Year 1 (8 decks)

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