15) Microbiology of GI Tract Flashcards

1
Q

What are obligate aerobes?

Give an example

A

Must have oxygen to survive e.g Pseudomonas and Mycobacterium TB

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2
Q

What are obligate anaerobes?

Give an example

A

Die in the presence of oxygen e.g. Bacteroides fragilis, clostridial organisms

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3
Q

What are facultative anaerobes?

Give an example

A

Prefer oxygen but can live without it e.g. many gram-negative enteric bacteria such as E. Coli and gram-positive skin-dwellers such as Staphylococcus

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4
Q

What can clostridial organisms do to survive in oxygen?

A

Produce spores

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5
Q

What are the anaerobic zones of the GIT?

A

Parts of mouth - deep in taste buds, between teeth, gingival crevice areas
Small bowel
Colon

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6
Q

Why are human colonic bacteria important?

A

Synthesize and excrete vitamins that are absorbed by host e.g vit K, B12 and thiamine
Prevent colonisation by pathogens
Kill non-indigenous bacteria
Stimulate development of GALT (caecum and Peyer’s patches)
Stimulate production of natural antibodies

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7
Q

What are some features of bacteria that can allow them to survive and infect the GIT?

A

Endospores e.g. bacillus anthrax, clostridum tetani
Pili - adhere to epithelia
Biofilm

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8
Q

Why are biofilms on a prosthetic surface particularly dangerous?

A

No bloody supply close so difficult to get drugs to surface

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9
Q

What shape are the endospores of C. tetani?

A

Terminal drumstick

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10
Q

Give some examples of gram positive aerobic cocci:

A

Staphylococci, streptococci and enterococci

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11
Q

Give some examples of gram negative aerobic cocci:

A

Neisseria meningitidis and gonorrhoeae

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12
Q

Give some examples of gram positive aerobic bacilli:

A

Corynebacterium (diphtheria)
Bacillus (anthrax)
Lactobacillus
Mycobacterium TB

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13
Q

Give some examples of gram positive anaerobic bacilli:

A

Clostridia (tetani, perfringens, difficile)

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14
Q

Give some examples of gram negative enteric bacilli:

colon normal flora

A
E.coli, pseudomonas, klebsiella, salmonella, shigella, camplylobacter, helicobacter pylori 
Bacteroides fragilis (anaerobic)
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15
Q

Give some examples of gram negative non-enteric bacilli:

all aerobic

A

H. influenza, bordetella pertussis (whooping cough), brucella

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16
Q

What are the majority of mouth bacteria?

A

Anaerobes

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17
Q

What is noma/cancrum oris?

A

Bacteria causing tissue destruction, if individual is malnourished, dehydrated or immunocompressed

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18
Q

What causes oral thrush and how can it be treated?

A

Candida albicans

Amphotericin lozenges

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19
Q

What risk factors are there for oral thrush?

A
Newborns (immune system not developed)
Diabetes 
Antibiotics
Steroids
Immune deficiency
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20
Q

What is dental caries and what organism causes it?

A

Teeth colonised by mouth bacteria and Strep. mutans

Causes cavities and teeth to break down

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21
Q

What bacteria causes parotitis?

A

S. aureus

22
Q

What is Ludwig’s angina and what causes it?

A

Potentially life-threatening cellulitis or connective tissue infection of the floor of the mouth
Streptococci

23
Q

What are the three swab sites for MRSA screening?

A

Nose, throat and perineum

24
Q

What are the main bacteria found in the nose?

A

Staphylococcus and streptococcus

25
Q

What are some of the main bacteria found in the throat?

A

Strep viridans
Strep pyogenes
Staphylococci
Neisseria meningitidis

26
Q

When can Strep. viridans become a problem?

A

Dental procedures and teeth brushing where it can enter blood stream and stick to prosthetic surfaces

27
Q

What percentage of tonsillitis is caused by viruses?

A

70% - adenovirus and rhinovirus

28
Q

Which bacteria can cause tonsillitis?

A

Strep. pyogenes

29
Q

What is quinsy?

A

Abscess between tonsil and wall of throat making eating and breathing hard

30
Q

What are the main bacteria of the colon?

A

Anaerobes, particularly bacteroides and clostridial species, E. coli and enterococcus faecalis

31
Q

Why is there a high risk of infection in gut surgery?

A

Abnormal numbers of bacteria

32
Q

What prophylactic antibiotics can be given to reduce wound infections?

A

Metroniadazole and broad spectrum antibiotic (gentamicin or cephalosporin)
Co-amoxiclav

33
Q

What is faecal peritonitis?

A

Faeces in peritoneal cavity, bacteria can enter blood

High mortality

34
Q

What is a perianal abscess?

A

Glands in anal canal infected causing abscess around anus

35
Q

What is an example of a normal vaginal commensal?

A

Lactobacillus

36
Q

How does lactobacillus stop other micro-organisms from growing?

A

Converts glycogen into lactic acid, providing acidic environment

37
Q

What happens if antibiotics kills lactobacillus?

A

Vaginal thrush

38
Q

What organism is the most common cause of UTIs?

What is the next most common?

A

E. coli

Enterococcus faecalis

39
Q

What would you be looking for on a MSU gram stain?

A

Gram neg bacilli (E. coli)

Gram pos cocci (Enterococci)

40
Q

What is bacteraemia?

A

Bacteria rapidly cleared from bloodstream by liver/spleen macrophages, no symptoms

41
Q

What is septicaemia?

A

Bacteria aren’t cleared and multiply in bloodstream

42
Q

What does clostridium tetani cause?

A

Tetanus

43
Q

What does clostridium dificile cause?

A

Pseudomembranous colitis

44
Q

What does clostridium perfringes cause?

A

Gas/wet gangrene

45
Q

What causes gastroenteritis?

A

Consumption of contaminated food or drink

46
Q

What organisms can cause gastroenteritis?

A

Salmonella, campylobacter, listeria

47
Q

What are the symptoms of gastroenteritis?

A

Vomiting and diarrhoea

48
Q

What cause cholera and what are the symptoms?

A

Vibrio cholera leading mass movement of water and salt into lumen by secretion
Rice water diarrhoea and dehydration

49
Q

What can helminth infestations cause?

A

Malabsorption

50
Q

What can protozoal infections cause?

A

Giardia and cryptosporidium cause gastroenteritis

51
Q

What cause traveller’s diarrhoea?

A

E. coli

52
Q

What is the pathogenesis of traveller diarrhoea?

A

Heat stable or labile toxins released by E. coli resulting in watery diarrhoea
Usually self limiting