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Gastro-intestinal System > GI Infections > Flashcards

GI Infections Flashcards

0
Q

What is an obligate anaerobe? Give an example.

A

Organism which dies in the presence of oxygen

e.g. Bacteroides fragilis, Clostridium spp. (but these form spores which allow them to survive)

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1
Q

What is an obligate aerobe? Give an example.

A

Organism which must have oxygen to survive

e.g. Pseudomonas, Mycobacterium tuberculosis

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2
Q

What is a facultative anaerobe? Give an example.

A

Organism which prefers to utilise oxygen but can survive without it

e.g Gram-ve enteric bacteria (E. coli), Gram+ve skin bacteria (Staph.)

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3
Q

What anaerobic zones are present in the GI tract?

A

Parts of the mouth

  • deep in the taste buds
  • biofilm between teeth
  • gingival crevice areas (gingiva = gums)
  • peridontal pockets in people with peridontal disease (surrounding or encasing a tooth)

Small bowel

Colon

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4
Q

What are some functions of human colonic bacteria?

A

Synthesise and excrete vitamin K, B12, thiamine, more B vitamins

Prevent colonisation by pathogens

Kill non-indigenous bacteria

Stimulate development of MALT (caecum & Peyer’s patches)

Stimulate production of natural antibodies

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5
Q

Give some examples of spore-forming bacteria.

A

Bacillus anthrax

Clostridium tetani

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6
Q

Give examples of bacteria which can form biofilms.

A

Staphylococcus spp.

Streptococcus spp.

E. coli

Enterococcus spp.

Klebsiella pneumoniae

Pseudomonas aeruginosa

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7
Q

Name some aerobic cocci found in the GI tract.

A

Gram+ve:

  • Staphylococcus
  • Streptococcus
  • Enterococcus

Gram-ve:

  • Neisseria meningitidis
  • Neisseria gonorrhoea
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8
Q

Name some anaerobic bacilli found in the GI tract.

A 
Gram+ve:
Clostridia spp. 
- tetani (endospores)
- perfringens (gas gangrene)
- difficile (pseudomembranous colitis)

Gram-ve:
Bacteroides fragilis

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9
Q

Name some aerobic bacilli found in the GI tract.

A

Gram+ve:

  • Corynebacterium diptheria
  • Bacillus anthrax
  • Lactobacillus
  • Mycobacterium tuberculosis

Gram-ve:

  • Enteric bacteria (Escherichia coli, Pseudomonas, Proteus, Klebsiella, Salmonella, Shigella, Vibrio cholera, Campylobacter, Helicobacter pylori)
  • Non-enteric bacteria (Haemophilus influenze, Bordetella pertussis, Brucella)
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10
Q

Name some types of microbes found in the mouth.

A

Lots of anaerobes e.g. Streptococcus, Staphylococcus, Candida, Lactobacillus, Enterococcus

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11
Q

What is noma/cancrum oris?

A

Severe ulcerative gingivitis which causes a gangrenous infection of the mouth which spreads to involve the face

Causes:

  • systemically unwell
  • malnourished
  • dehydrated
  • immunocompromised
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12
Q

What are some risk factors for oral thrush? What is the treatment?

A 
Newborns 
Diabetics (glycosuria)
Antibiotics 
Inhaled steroids 
Immune deficiency

Treatment:

  • amphotericin lozenges
  • nystatin suspension
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13
Q

What is the main bacterium implicated in dental caries and gingivitis?

A

Dental caries = Streptococcus mutans + lactobacilli (progression of dental decay)

note: S. mutans only causes caries in the presence of sugars (metabolises sucrose to lactic acid -> acid erosion of enamel)

Gingivitis =

  • Porphyromonas gingivalis
  • Aggregatibacter actinomycetemcomitans
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14
Q

What is Ludwig’s angina?

A

Severe inflammation caused by infection of both sides of the floor of the mouth (upper respiratory infection)

Infection colonises cervical lymph nodes -> ascending & descending cellulitis

-> massive swelling of the neck -> obstruction of airways -> larynx closes (-> do tracheostomy)

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15
Q

Where are the swab sites for MRSA?

A

Nose

Throat

Perineum

16
Q

What is infective mononucleosis?

A

“glandular fever”

Epstein-Barr virus infection (10% due to cytomegalovirus infection)

Transmitted via saliva - “kissing disease”

  • fever
  • pharyngitis
  • adenopathy
17
Q

What microbes are found in the throat?

A

100% of patients:

  • Streptococcus viridians
  • Staphylococcus
  • Neisseria meningitidis

<100% of patients:

  • Streptococcus pyogenes
  • Streptococcus pneumoniae
  • Haemophilus influenzae
  • Lactobacilli
  • Corynebacterium diptheriae
  • Candida albicans
18
Q

What is the difference between bacteraemia and septicaemia?

A

BACTERIAEMIA = bacteria are rapidly cleared from the bloodstream by liver and spleen macrophages (no symptoms produced)

SEPTICAEMIA = bacteria are not cleared and multiply in the bloodstream -> sepsis develops

19
Q

What are the common microbes implicated in tonsillitis?

A

70% viral:

  • adenovirus
  • rhinovirus
  • Epstein-Barr virus

30% bacterial
- Streptococcus pyogenes (beta-haemolytic)

20
Q

What is quinsy? How is it treated?

A

Pus in the space between the tonsil and the wall of the pharynx, causing severe pain, difficulty swallowing, and trismus (difficulty opening mouth)

  • antibiotics
  • surgical incision of abscess to release pus and aid breathing (!carotid artery behind tonsil)
21
Q

What are the majority of the bacteria found in the colon?

A

95%-99% anaerobes

95%-99% of anaerobes are Bacteroides fragilis

Others:

  • Escherichia coli
  • Enterococcus faecalis
22
Q

What is dirty surgery? How can this be combatted?

A

High risk of wound infection

e. g.
- colon (organisms present before procedure)
- old traumatic wounds/devitalised tissue
- existing infection/perforation (presence of bacteria is likely if we are operating on the small bowel in the first place)

Give prophylactic antibiotics for surgery on the colon
= metronidazole for anaerobes + broad spectrum (gentamicin, cephalosporins) for Gram-ve bacilli & Gram+ve cocci/

OR co-amoxiclav

23
Q

What are the microbes implicated in perianal abscesses?

A

Infection of (mucous) anal gland

Bacteroides, E. coli, Enterococcus faecalis, Lactobacillus

24
Q

What organism is implicated in vaginal thrush?

A

Candida albicans

Lactobacillus is a normal vaginal commensal which converts glycogen to lactic acid (reduced pH prevents Candida from growing)

Broad spectrum antibiotics -> kill Lactobacilli -> colonisation of Candida albicans

25
Q

What is the characteristic appearance of Pseudomonas aeruginosa infection?

A

Green slime

26
Q

What are the key characteristics of tetanus?

A

Clostridia tetani

  • “lock jaw” -> risus sardonicus (involuntary prolonged contraction of facial muscles, causing abnormal grinning expression)
  • opisthotonos (extreme hyperextension causing arching of the head, neck, and spine)
  • respiratory spasm -> death
27
Q

What is gas gangrene? How is it treated?

A

Anaerobic digestion of glucose -> releases ethanol (wet) and carbon dioxide (gas)

Risk factor is diabetes (peripheral neuropathy)

Treatment: urgent amputation to prevent spread of cardiotoxin to the heart (cardiac arrest)

28
Q

Define traveller’s diarrhoea. What is it commonly caused by?

A

Passage of 3+ unformed stools per day in resident of industrialised country travelling in a developing nation

Entero-toxigenic E.coli (secretory, watery diarrhoea)
- HS toxin binds to receptor, activating c.GMP —> protein kinases activated —> inhibition of Na+ & Cl- absorption —> Cl- secretion —-> water follows

+ Shigella spp.
+ Salmonella spp.

Gastro-intestinal System (16 decks)

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