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Microbiology Flashcards

1
Q

H Pylori is often acquired at age ——

Around ——–% of world population infected.

A

Acquired at young age (consequences later in life)

50% of world population infected.

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2
Q

H Pylori - routes of contraction

A

Direct contact, oral-oral, feacal-oral

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3
Q

H Pylori infection increases risk of:

A

Duodenal ulcer, gastritis.
Gastric ulcer.
Gastric carcinoma.
Gastric lymphoma.

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4
Q

Why does H Pylori produce ammonia?

A

To increase the pH and protect itself from highly acidic environments.

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5
Q

How does H Pylori produce ammonia?

A

By producing UREASE

H2O + H+ &raquo_space;» ammonium bicarbonate

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6
Q

Gastroenteritis

A

illness caused by eating foods contaminated with microorganisms, toxins and poisons

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7
Q

Dysentery

A

Inflammation of intestine, causing diarrhoea associated with blood and mucus
(associated with tenesmus - cramping in rectal area)

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8
Q

Dysentery is commonly caused by ——-

A

shigella and campylobacter

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9
Q

Diarrhoea

A

> 3 unformed stools in a day when the subject has taken no laxatives

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10
Q 
Bacillus cereus 
(key points)
A

REHEATING STARCHY FOOD (e.g. rice)
Short incubation (1-6hrs)
Vomiting
Lasts 24hrs

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11
Q 
Staph aureus 
(key points)
A

FOOD LEFT AT ROOM TEMP (milk, meat, fish)
short incubation (1-6hrs)
Lasts 1-2 days

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12
Q

Both bacillus cereus and staph aureus usually cause {upper/lower} GI symptoms.

A

upper (e.g. vomiting)

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13
Q

Staph aureus has a preformed toxin called ———— causing ———–

A

enterotoxin B causes rapid absorption

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14
Q

Most common cause of food poisoning is ————

A

campylobacter

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15
Q

Campylobacter

key points

A

RAW POULTRY/RAW MILK (unpasteurised)
D&V (may be bloody), abdo pain, fever.
Lasts 2-10 days
**risk of Guillain Barre syndrome.

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16
Q

You are more likely to get ——– from raw chicken than salmonella

A

campylobacter

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17
Q

———— is the most common strain of campylobacter

A

Campylobacter jejuni

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18
Q

Salmonella is serotyped according to ———

A

O-antigen

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19
Q

Salmonella

key points

A 
OUTBREAKS
RAW MEAT, RAW EGG, RAW MILK.
(can be transmitted from reptiles)
D&V (unlikely to be bloody), abdo pain, fever.
Lasts 2-7 days
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20
Q

Shigella

key points

A

CONTAMINATED food/water with lots of HAND CONTACT (salad/sandwiches/raw veg)
BLOODY DIARRHOEA/mucous, vomiting, abdo cramps, fever…
Lasts 2-7 days

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21
Q

Shigella toxin =

A

shiga toxin - type 1 and type 2

TYPE 2 IS WORSE

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22
Q

Shigella toxin - method of action

A

Toxin binds to receptors on renal cells, RBC’s and other cells&raquo_space; inhibits protein synthesis&raquo_space; cell death

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23
Q

E.coli (0157)

A

CATTLE/BEEF, RAW MILK - usually undercooked beef
Rare - outbreaks
BLOODY DIARRHOEA (may have vomiting, abdo pain)
Lasts 5-10 days
**risk of HUS

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24
Q

E.coli toxin =

A

verotoxin

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25
Why do you not give antibodies for E. coli infection?
Increases risk of HUS
26
Verotoxin - method of action
binds to enterocytes >> inhibition of protein synthesis >> cell death >> provides verotoxin route to bloodstream >> cause death of vascular endothelial cells >> clots form within small vessels >> clots + verotoxin carried to kidneys >> renal cell death >> renal failure >> HUS
27
What is HUS?
Haemolytic-uremic syndrome group of blood disorders characterized by low RBCs, acute kidney failure, and low platelets - caused by E. coli infection. Most < 16 yrs old.
28
HUS - symptoms
Abdo pain, fever, pallor, petechiae (purple spots on the skin due to damaged blood vessels), oliguria. Bloody diarrhoea but it may have stopped.
29
Why should antibiotics be avoided in the treatment of food poisoning?
Possibly E. coli - risk of HUS Risk of antibiotic resistance Illness is usually self-limiting
30
HUS may be precipitated by ----------
Antibiotics, antimotility, and NSAIDS.
31
Gastroenteritis + urinary symptoms suggesting kidney involvement =
HUS
32
HUS - investigations/management
Any patient with bloody stools gets tested FBC, U&E’s, LFT, urine samples Lactate dehydrogenase – chemical released from damaged cells Must notify relevant health boards of any HUS cases. Treatment is supportive
33
Must notify health protection unit of any ------ infections
E. coli (0157)
34
----------- and ---------- infection both result in bloody diarrhoea
shigella and E. coli (0157) | *campylobacter may also cause bloody diarrhoea
35
Listeria | key points
THE FRIDGE ORGANISM - soft cheeses, deli meats, unpasteurised milk. Fever, stiff neck, confusion, vomiting - pregnant women and immunocompromised at risk. Incubation 3-70 days, lasts WEEKS.
36
C. Diff most commonly occurs when ------
the patient has been given hospital antibiotics | antibiotics kill normal competitive bowel flora, allowing C. diff overgrowth
37
C. diff can progress to -------
pseudomembranous colitis or bowel perforation
38
Risk of C. diff is increased by ---------
As well as hospital antibiotics, anything that reduces the acidity of the stomach can increase risk e.g. PPI’s carry a risk
39
C. diff toxin =
``` Toxin A (enterotoxin) and Toxin B (cytotoxin) ```
40
What antibiotics increase the risk of C. Diff?
``` 4Cs Cephalosporin Ciprofloxacin Co-amoxiclav Clindamycin ```
41
C. diff - symptoms
Watery diarrhoea. | Abdo pain and fever.
42
C. diff - treatment
Non-severe = Metronidazole oral (10 days). | Severe: Vancomycin oral + Metronidazole IV (10 days).
43
Rotavirus | key points
Usually children in nurseries (most common cause of diarrhoea in kids under 3) Mild, watery profuse diarrhoea (bloody = RED FLAG) - rehydrate Incubation 48hrs, lasts a week
44
Norovirus | key points
CRUISE SHIPS, WARDS, NURSING HOMES (can be contracted from shellfish) Highly infectious. Explosive D&V (no blood) - rehydrate Incubation 48hrs, lasts 1-3 days
45
In gastroenteritis, all stool samples get tested for ------------
salmonella, shigella, campylobacter, E.coli 0157 and cryptosporidium
46
Gastroenteritis - investigations
stool culture, stool microscopy, stool toxin and stool PCR
47
In gastroenteritis, if suspected bacteria - investigation = if suspected virus - investigation = if suspected protozoa - investigation =
bacteria = stool culture ( or stool toxin for c. diff or E. coli) virus = stool PCR protozoa = stool microscopy (for cysts)
48
In gastroenteritis, do a stool culture if -------- are suspected, and do a stool toxin if ---- are suspected.
Stool culture = salmonella, campylobacter | Stool toxin = c. diff, E. coli
49
Gastroenteritis - treatment
No antibiotics - except to treat c. diff. | Rehydration = key
50
Someone who has been at a BBQ and thought the burgers looked funny
E.coli
51
Someone who had been at a Chinese buffet/had reheated a takeaway with rice
Bacillus cereus
52
Someone remembers eating a cream cake that had been left out
Staph aureus
53
Care home where many of its residents have diarrhoea and some aren’t urinating
HUS - E.coli
54
Tropical gastroenteritis - causes
Someone travelling + doing one of the following: Swimming in lakes Drinking water from local taps Sexual activity Insect bites Did they get vaccinations before they left
55
Acute travellers diarrhoea
3 loose stools in 24hrs on the back of travelling (1/3rd have fever also)
56
Acute travellers diarrhoea - causative organism
Usually enterotoxigenic e. coli | If returned from cruise ship = noro/rotavirus
57
Acute travellers diarrhoea - management
Stool culture Rehydration Current travellers = single dose of ciprofloxacin
58
Cholera
Drinking water contaminated with faeces Profuse watery diarrhoea (RICE-WATER STOOLS) Massive fluid loss Toxin mediated
59
Enteric fever
``` Common Fever, headache, abdo pain (also GI bleeding and perforation) Either TYPHOID (salmonella typhi - most severe) or PARATYPHOID (s. paratyphi) ```
60
Enteric fever usually occurs in what scenario?
patients who are returning from SE Asia and the Indian subcontinent
61
Enteric fever - clinical findings
Abdominal tenderness | Hepatosplenomegaly
62
Enteric fever - management
Patients need isolated immediately If unstable (septic) = IV ceftriaxone Otherwise use oral ciprofloxacin Resistant cases = azithromycin in fluoroquinolone
63
Amoebiasis
Protozoa - POOR SANITATION Protozoa lives in cysts >> once ingested. emerge. multiply. Can often cause liver abscesses Intermittent diarrhoea, upper abdo pain/discomfort, fever, sweats, nausea, headaches
64
Amoebiasis - investigations
Stool MICROSCOPY Abdominal x-ray (for toxin mega colon) CXR (may show raised right hemi-diaphragm) May need endoscopy, biopsy
65
Amoebiasis - management
Metronoidazole | Paramomycin (used to clear gut lumen of parasites)
66
Giardiasis
Protozoa Affects duodenum/proximal jejunum Watery, malodourous diarrhoea, bloating, flatulence, abdo cramps, weight loss
67
Giardiasis - investigation
Stool microscopy for cysts | PCR in developed countries
68
Giardiasis - treatment
Metronidazole/Tinidazole
69
Helminth Infections
Parasitic infection | Associated with eosinophilia
70
Parasite contracted from swimming in lake Malawi
Schistosomiasis (Flukes)
71
Parasite contracted from eating undercooked meat
Tape worms (Cestode)
72
Helminth Infections - diagnosis
Usually diagnosed by the passage of adult worm or eggs in the stool

GI (9 decks)

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