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Semester 3 > GI Session 9 > Flashcards

GI Session 9 Flashcards

1
Q

What are obligate anaerobes?

A

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

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2
Q

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

A

They can form spores

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3
Q

What are facultative anaerobes?

A

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

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4
Q

Where are the anaerobic zones of the GI tract?

A

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

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5
Q

Where do anaerobic bacteria live in pts with periodontal disease?

A

Periodontal pockets

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6
Q

Why are human colonic bacteria necessary?

A

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

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7
Q

What defence mechanisms do bacteria have against the GI tract?

A

Endospores

Bacterial pili and slime for adhesion

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8
Q

Why is bacterial slime particularly effective at a prosthetic surface?

A

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

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9
Q

What are obligate aerobes?

A

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

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10
Q

What microbes are found in the mouth?

A 
Anaerobes:
Streptococci
Staphylococci
Candida
Lactobacillus
Enterococcus
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11
Q

When can mouth flora cause tissue destruction?

A

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

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12
Q

What diseases can result from imbalance of mouth flora?

A

Noma/cancrum oris
Oral thrush
Dental caries
Gingivitis

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13
Q

What commensals are found in the nose?

A

Staph
Strep
Lots more

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14
Q

Where in the body is good for MRSA screening?

A

Nose
Throat
Perineum

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15
Q

What are the throat commensals?

A 
Strep viridans
Strep pyogenes
Strep pneumoniae
Staph
Neisseria meningitidis
H.influenzae
Lactobacillus
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16
Q

Which spthroat commensals are universally found in the population?

A

Strep viridans
Staph
Neisseria meningitidis

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17
Q

How can strep throat lead to asphyxiation?

A

Lymph node infection –> cellulitis –> Ludwig’s angina –> compressed larynx

18
Q

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

A

Temporary bacteraemia

19
Q

Describe the aetiology of tonsillitis.

A

70% viral - adenovirus, rhinovirus, EBV

30% bacterial - strep pyogenes

20
Q

What is quinsy?

A

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

21
Q

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

A

50%

22
Q

What are the colon commensals?

A 
Bacteroides fragilis/oralis/melaninogenicus
E.coli
Enterococcus faecalis
Pseudomonas
Proteus
Klebsiella
Salmonella
Shigella
Vibrio cholera
Campylobacter
Lactobacillus
Clostridial sp.
23
Q

Why is all gut surgery ‘dirty surgery’?

A

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

24
Q

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

A

Wound infection, dehiscence

25
Q

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

A

Anaerobes
G+ve
G-ve

26
Q

What are the universal colon commensals?

A

Bacteroides fragilis/oralis/melaninogenicus
E.coli
Enterococcus faecalis

27
Q

What is faecal peritonitis?

A

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

28
Q

What is the pathogenesis of Perianal abscess formation?

A

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

29
Q

Why must bacteroides remain in the rectum?

A

Cannot survive in oxygen

30
Q

What causes 75% of UTI?

A

E.coli

31
Q

What is the second commonest cause of UTI?

A

Enterococcus faecalis

32
Q

What is lactobacillus?

A

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

33
Q

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

A

Kill lactobacillus so Candida albicans can grow

34
Q

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

A

To determine whether they have a UTI of appendicitis

35
Q

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

A

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
Q

What causative agent is characterised by green pus formation?

A

Pseudomonas aeruginosa

37
Q

What environment does pseudomonas aeruginosa favour?

A

Moist or fluid

38
Q

What do all clostridia species produce?

A

Spores

39
Q

What are the consequences of clostridia tetani infection?

A

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

40
Q

What results from clostridia difficile infection?

A

Pseudomembranous colitis

41
Q

What results from clostridia perfringens infection?

A

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

42
Q

Why does gas gangrene indicate immediate amputation?

A

Very dangerous cardiac endotoxins are released simultaneously

Semester 3 (50 decks)

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