15) Microbiology of GI Tract Flashcards Preview

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Flashcards in 15) Microbiology of GI Tract Deck (52)
1

What are obligate aerobes?
Give an example

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

2

What are obligate anaerobes?
Give an example

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

3

What are facultative anaerobes?
Give an example

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

4

What can clostridial organisms do to survive in oxygen?

Produce spores

5

What are the anaerobic zones of the GIT?

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

6

Why are human colonic bacteria important?

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

7

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

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

8

Why are biofilms on a prosthetic surface particularly dangerous?

No bloody supply close so difficult to get drugs to surface

9

What shape are the endospores of C. tetani?

Terminal drumstick

10

Give some examples of gram positive aerobic cocci:

Staphylococci, streptococci and enterococci

11

Give some examples of gram negative aerobic cocci:

Neisseria meningitidis and gonorrhoeae

12

Give some examples of gram positive aerobic bacilli:

Corynebacterium (diphtheria)
Bacillus (anthrax)
Lactobacillus
Mycobacterium TB

13

Give some examples of gram positive anaerobic bacilli:

Clostridia (tetani, perfringens, difficile)

14

Give some examples of gram negative enteric bacilli:
(colon normal flora)

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

15

Give some examples of gram negative non-enteric bacilli:
(all aerobic)

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

16

What are the majority of mouth bacteria?

Anaerobes

17

What is noma/cancrum oris?

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

18

What causes oral thrush and how can it be treated?

Candida albicans
Amphotericin lozenges

19

What risk factors are there for oral thrush?

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

20

What is dental caries and what organism causes it?

Teeth colonised by mouth bacteria and Strep. mutans
Causes cavities and teeth to break down

21

What bacteria causes parotitis?

S. aureus

22

What is Ludwig's angina and what causes it?

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

23

What are the three swab sites for MRSA screening?

Nose, throat and perineum

24

What are the main bacteria found in the nose?

Staphylococcus and streptococcus

25

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

Strep viridans
Strep pyogenes
Staphylococci
Neisseria meningitidis

26

When can Strep. viridans become a problem?

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

27

What percentage of tonsillitis is caused by viruses?

70% - adenovirus and rhinovirus

28

Which bacteria can cause tonsillitis?

Strep. pyogenes

29

What is quinsy?

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

30

What are the main bacteria of the colon?

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

31

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

Abnormal numbers of bacteria

32

What prophylactic antibiotics can be given to reduce wound infections?

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

33

What is faecal peritonitis?

Faeces in peritoneal cavity, bacteria can enter blood
High mortality

34

What is a perianal abscess?

Glands in anal canal infected causing abscess around anus

35

What is an example of a normal vaginal commensal?

Lactobacillus

36

How does lactobacillus stop other micro-organisms from growing?

Converts glycogen into lactic acid, providing acidic environment

37

What happens if antibiotics kills lactobacillus?

Vaginal thrush

38

What organism is the most common cause of UTIs?
What is the next most common?

E. coli
Enterococcus faecalis

39

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

Gram neg bacilli (E. coli)
Gram pos cocci (Enterococci)

40

What is bacteraemia?

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

41

What is septicaemia?

Bacteria aren't cleared and multiply in bloodstream

42

What does clostridium tetani cause?

Tetanus

43

What does clostridium dificile cause?

Pseudomembranous colitis

44

What does clostridium perfringes cause?

Gas/wet gangrene

45

What causes gastroenteritis?

Consumption of contaminated food or drink

46

What organisms can cause gastroenteritis?

Salmonella, campylobacter, listeria

47

What are the symptoms of gastroenteritis?

Vomiting and diarrhoea

48

What cause cholera and what are the symptoms?

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

49

What can helminth infestations cause?

Malabsorption

50

What can protozoal infections cause?

Giardia and cryptosporidium cause gastroenteritis

51

What cause traveller's diarrhoea?

E. coli

52

What is the pathogenesis of traveller diarrhoea?

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