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Flashcards in GI Session 9 Deck (42):
1

What are obligate anaerobes?

Microbes that will die in the presence of oxygen e.g. Bacteroides fragilis, clostridia

2

What do clostridia have that can enable them to survive in oxygen containing environments?

They can form spores

3

What are facultative anaerobes?

Prefer oxygen but can live without it e.g. G-ve enteric bacteria like E.coli and G+ve skin dwellers like staph

4

Where are the anaerobic zones of the GI tract?

Deep in taste buds
Biofilm between teeth and gingival crevice areas
Small bowel
Colon

5

Where do anaerobic bacteria live in pts with periodontal disease?

Periodontal pockets

6

Why are human colonic bacteria necessary?

Synthesise and secrete vitamins e.g. K, B vitamins, thiamine
Prevent colonisation by pathogens
Kill non-indigenous bacteria
Stimulate development of MALT in caecum and Peyer's patches
Stimulate production of natural antibodies

7

What defence mechanisms do bacteria have against the GI tract?

Endospores
Bacterial pili and slime for adhesion

8

Why is bacterial slime particularly effective at a prosthetic surface?

No blood supply so Abx cannot be delivered to lowest layers of film

9

What are obligate aerobes?

Microbes that must have oxygen e.g. Pseudomonas, M.TB

10

What microbes are found in the mouth?

Anaerobes:
Streptococci
Staphylococci
Candida
Lactobacillus
Enterococcus

11

When can mouth flora cause tissue destruction?

If an individual is malnourished, dehydrated, immunocompromised or systemically unwell

12

What diseases can result from imbalance of mouth flora?

Noma/cancrum oris
Oral thrush
Dental caries
Gingivitis

13

What commensals are found in the nose?

Staph
Strep
Lots more

14

Where in the body is good for MRSA screening?

Nose
Throat
Perineum

15

What are the throat commensals?

Strep viridans
Strep pyogenes
Strep pneumoniae
Staph
Neisseria meningitidis
H.influenzae
Lactobacillus

16

Which spthroat commensals are universally found in the population?

Strep viridans
Staph
Neisseria meningitidis

17

How can strep throat lead to asphyxiation?

Lymph node infection --> cellulitis --> Ludwig's angina --> compressed larynx

18

What happens after brushing your teeth duets thelresende of strep viridans?

Temporary bacteraemia

19

Describe the aetiology of tonsillitis.

70% viral - adenovirus, rhinovirus, EBV
30% bacterial - strep pyogenes

20

What is quinsy?

When an abscess develops on the tonsils --> stridor and deviated uvula

21

What percentage of the world's population are infected with H.pylori in the stomach?

50%

22

What are the colon commensals?

Bacteroides fragilis/oralis/melaninogenicus
E.coli
Enterococcus faecalis
Pseudomonas
Proteus
Klebsiella
Salmonella
Shigella
Vibrio cholera
Campylobacter
Lactobacillus
Clostridial sp.

23

Why is all gut surgery 'dirty surgery'?

Because the gut is only ever operated on when the bacterial content is abnormal

24

What is the possible consequence of all gut surgery being 'dirty'?

Wound infection, dehiscence

25

What must prophylactic Abx used in GI surgery be active against?

Anaerobes
G+ve
G-ve

26

What are the universal colon commensals?

Bacteroides fragilis/oralis/melaninogenicus
E.coli
Enterococcus faecalis

27

What is faecal peritonitis?

Faeces in peritoneum which has no defence mechanism --> 50% mortality

28

What is the pathogenesis of Perianal abscess formation?

Blockage of anal gland --> passage of faeces impaired --> abscess formation

29

Why must bacteroides remain in the rectum?

Cannot survive in oxygen

30

What causes 75% of UTI?

E.coli

31

What is the second commonest cause of UTI?

Enterococcus faecalis

32

What is lactobacillus?

Normal vaginal commensal which converts glycogen--> lactic acid to prevent other bacteria and Candida albicans from growing

33

How do broad spectrum Abx lead to development of vaginal thrush?

Kill lactobacillus so Candida albicans can grow

34

Why do pts with lower abdominal pain need urgent MSU gram stain?

To determine whether they have a UTI of appendicitis

35

What does each possible outcome of the MSU gram stain of a pt with lower abdominal pain indicate?

G-ve bacilli --> E.coli --> UTI or appendicitis
G+ve bacilli --> lactobacillus --> contamination from vagina
G-ve cocci --> gonococcus --> contamination from urethritis
G+ve cocci --> enterococcus --> UTI or appendicitis

36

What causative agent is characterised by green pus formation?

Pseudomonas aeruginosa

37

What environment does pseudomonas aeruginosa favour?

Moist or fluid

38

What do all clostridia species produce?

Spores

39

What are the consequences of clostridia tetani infection?

Lock jaw --> risus sardonicus
Opisthotonos
Resp muscle spasm (larynx) --> death

40

What results from clostridia difficile infection?

Pseudomembranous colitis

41

What results from clostridia perfringens infection?

Gas or wet gangrene due to anaerobic digestion of glucose --> ethanol and carbon dioxide

42

Why does gas gangrene indicate immediate amputation?

Very dangerous cardiac endotoxins are released simultaneously