GI Infections Flashcards
1
Q
Describe the stages of pathogenic infection?
A
- Exposure
- Adhesion
- Invasion
- Colonization
- Toxicity
- Tissue damage and disease
2
Q
What is the difference between colonisation and infection?
A
Colonisation
- establishment of a microorganism on or within a host which does not cause symptoms
Infection
- invasion of a host causing the patient to be symptomatic
3
Q
What is virulence?
A
likelihood of a pathogen to cause disease
4
Q
What normal bacterial flora is found in the mouth?
A
Strep. “viridans” Neisseria sp. Anaerobes Candida sp. (few) Staphylococci
5
Q
Why are the stomach and duodenum usually sterile?
A
- Low (acidic) pH
- Few Candida & Staphylococci may survive
6
Q
What normal bacterial flora are found in the small intestine?
A
Lactobacilli
E-Coli
Enterococcus
7
Q
The colon normally contains what types of bacteria?
A
Large numbers of coliforms and anaerobes
8
Q
The bile ducts are usually sterile. TRUE/FALSE?
A
TRUE
9
Q
How are GI infections caused in the community?
A
- Cross-contamination of work surfaces/utensils
- Undercooking (insufficient heat to kill pathogens/ inadequate defrosting of frozen food)
- Improper storage of food (inadequate refrigeration)
- Poor reheating of food
10
Q
Describe how CDiff infection is caused?
A
- C diff. is present in small numbers in bowel
- Infection occurs when antibiotics kill off normal competitive bowel flora
=> C diff overgrows - Organism produces spores that are more resistant to disinfectants
11
Q
What symptoms do patients experience with C Diff?
A
- Diarrhoea (sometimes bloody)
- abdominal pain
- Severe cases may progress to pseudomembranous colitis or bowel perforation
12
Q
How is C Diff usually managed?
A
Less severe = oral metronidazole
Severe = oral vancomycin
13
Q
How is C Diff. prevented?
A
- Use narrow spectrum antibiotics where possible
- Avoid the “4Cs”
- Isolation of patients
- HandWASHING (not alcohol gel)
- Cleaning of the environment
14
Q
If there is not one good lab test for CDIff, how can it be confirmed?
A
- Screening test for presence of the organism (GDH)
- If GDH positive, test for Toxins (A&B)
Culture can be done if strain needs to be typed:
- Only used if an outbreak is expected OR if hyper toxin-producing strains
15
Q
What viruses commonly cause diarrhoea?
A
Rotavirus
Norovirus
16
Q
Rotavirus usually presents in patients of what age?
A
- commonest cause of diarrhoea in patients under 3
- most cases occur in children <5 years
17
Q
How is rotavirus spread?
A
- Person-person spread
- direct or indirect
18
Q
Patients with rotavirus diarrhoea often have blood in their stool. TRUE/FALSE?
A
FALSE
no blood is seen
19
Q
What complications can rotavirus cause?
A
Children may develop post-infection malabsorption
=> causing more diarrhoea
20
Q
How is rotavirus diagnosed?
A
PCR test on faeces
21
Q
How is rotavirus managed?
A
Rehydration is key (orally where possible)
- vaccines given at 2 and 3 months of age
22
Q
Why should the rotavirus vaccine not be given >3 months of age?
A
Risk of intussusception
23
Q
How is norovirus spread and when does it normally present?
A
- “winter diarrhoea and vomiting disease”
SPREAD VIA: - faecal-oral/droplet
- person to person (or on contaminated food/water)
24
Q
Exposure to a low dose can infect patient’s with norovirus. TRUE/FALSE?
A
TRUE
25
Describe the disease course of norovirus
- Short incubation – often <24 hours
| - Sudden onset explosive D and V, lasts 2-4 days
26
How is norovirus diagnosed?
- Faeces specimen or vomit swab for PCR test
27
How is norovirus treated?
- Rehydration is key, esp. in the young and elderly
28
Patients can spread norovirus after their symptoms have disappeared. TRUE/FALSE?
Asymptomatic shedding occurs for up to 48 hours post cessation of symptoms
29
Where are outbreaks of norovirus common?
- Hospitals,
- Schools
- Cruise ships
- Nursing Homes
30
Which infections need patients to be contained in a side room?
C difficile and norovirus
31
Which infections require patients to be admitted to the infectious diseases unit?
Salmonella
| E-Coli 0157
32
What puts patients at a higher risk of developing a GI infection?
- Malnutrition
- Exposure to contaminated food/water /travel
- Winter congregating/ summer floods
- Age <5 or elderly
- not breastfeeding
- Acid suppression
- Immunosuppression
33
What is the definition of diarrhoea?
>3 unformed stools/day
From no other cause (laxatives etc)
Stool holds the shape of container
Departure from normal bowel habit
34
What pathogens are known to cause "dysentry" i.e inflammation of the colon?
- Shigella, Campylobacter
35
What symptoms do patients experience with gastroenteritis?
- inflames intestine
- diarrhoea associated with blood and mucus
- fever
- abdominal pain
- rectal tenesmus (sense of incomplete defaecation).
36
How long does gastroenteritis normally last?
Acute is duration < 2 weeks
37
What can go wrong in the kitchen that may cause a gastroenteritis?
- cross contamination of raw and cooked food
- preparation of food too far in advance
- inadequate heating and cooling
- contaminated environment/ equipment
- poor personal hygiene
38
What factors should be asked about in a gastroenteritis infection history?
- foreign travel
- antibiotics
- camping
- raw seafood
- anal receptive sex (MSM)
- HIV status
- cruise ship
39
What infections have a short incubation period?
Bacillus cereus (Gm +ve bacillus)
- forms Heat resistant spores
- usually from Reheated rice
Staph. Aureus (Gm +ve coccus)
- preformed toxin in food
- found in foods left at room temp. (Milk/ meat/fish)
40
What infections are tested for on a normal stool sample?
- All stools get Salmonella/Shigella/Campylobacter/ E-Coli 0157 & cryptosporidium
- All > 4 yrs stools get C Diff
41
Shigella infection produced Shiga Toxin, but what does this do?
- Binds to receptors found on renal cells, RBC's & others
- Inhibits protein synthesis
- Causes cell death
42
Type 2 is more potent than type 1 in Shigella. TRUE/FALSE?
TRUE
43
Shiga-like toxins have been discovered in other types of bacteria. TRUE/FALSE?
TRUE
| >30 serotypes of E- coli produce Shiga –like toxins
44
How do shiga-like toxins produced by ecoli cause damage?
- inhibit protein synthesis
| - kill enterocytes
45
What happens after shiga-like toxins attack the bowel?
- toxins are carried to the kidneys
- causes haematuria and renal failure (Haemolytic Uraemic Syndrome)
- shiga-like toxin 2 causes this
46
What symptoms/exposure would make you consider EColi 0157 infection?
- bloody diarrhoea
- exposure to beef (raw milk/water)
- animal contact
- children + elderly
47
HOw does haemolytic uraemic syndrome usually present?
- Abdo pain
- fever
- pallor
- petechiae
- oliguria
- bloody diarrhoea in 90% of cases
- 85 of cases occur in those under 16 years old
48
Describe how a patient's blood results may look in haemolytic uraemic syndrome?
- High white cells
- Low platelets
- Low Hb
- LDH>1.5 x normal
49
How is haemolytic uraemic syndrome investigated?
- stool culture (all Pts with bloody faeces)
- FBC, U+E, Blood film, Clotting
- LFT
- urine (dipstick/micro)
- lactate
50
What drugs should NOT be given if you suspect a patient has haemolytic uraemic syndrome?
NO antibiotics: may precipitate HUS
NO anti-motility agents
NO NSAIDS
51
What can be used to "type" EHEC? (a strain of EColi which produces shiga-like toxin)
- McConkey agar/ Sorbitol McConkey agar
- Antisera for serotypes
- ELISA identifies toxins
52
What tropical infections can present in the GI tract?
- Acute traveller’s diarrhoea
- Enteric fever
- Fever and Jaundice
- Protozoan infections
- Helminthic Infections
53
What questions should you remember to ask a returned traveller if you suspect a Tropical GI infection?
- Where have they been? (Rural/urban area)
- Accommodation? (air conditioning)?
- When did they get back?/ When did symptoms start?
- Insect/Tick bites
- Symptoms?
- Anyone else unwell?
- Activities whilst away? (Swimming/water sports/animal contact/bat caves/walking in bush/sex/work)
- Precautions? (Vaccinations/malaria prophylaxis/bite protection/condoms)
54
What signs should you look for on examination of a returned traveller?
- Fever
- Rash
- Hepatosplenomegaly
- Lymphadenopathy
- Insect bites
- Wounds
55
Which infections of the returned traveller can cause a fever?
- Respiratory tract infections – pneumonia/influenza
- Traveller’s diarrhoea
- Malaria
- Enteric fever (typhoid/paratyphoid fever)
- Arboviruses – e.g. Chikungunya/Zika
56
What is the definition of Traveller's diarrhoea?
3 loose stools in 24 hrs
| - usually associated with fever
57
What can cause Traveller's diarrhoea?
- Ecoli most common
- salmonella, campylobacter and shigella
- on Cruise Ships Norovirus/Rotavirus = common
58
What is the most likely cause of profuse watery diarrhoea as opposed to the bloody diarrhoea usually experienced in Ecoli infection?
Cholera
| - common in refugee camps
59
How is Acute Traveller's diarrhoea investigated?
- Stool culture
| - Stool wet prep on recently passed stool for amoebic trophozoites
60
How is Traveller's Diarrhoea treated?
- Supportive – fluid rehydration (oral/IV)
- In those travelling a fluoroquinolone (ciprofloxacin) single dose can stop worsening
- Antibiotic resistance – now very common (if pt has been travelling in Asia, a macrolide e.g. azithromycin may be useful)
61
What are the causes of enteric fever?
Typhoid or paratyphoid fever
| Salmonella typhi or paratyphi
62
Patients with enteric fever usually return from travelling in what part of the world?
Most common in those returning from Indian subcontinent and SE Asia
63
What is the normal incubation period for enteric fever?
7-18 days (though occasionally up to 60 days)
64
Patients with enteric fever usually present with what symptoms?
- Fever
- Headache
- Constipation or diarrhoea
- Dry cough
65
What are the potential complications of enteric fever?
- GI bleeding
- GI perforation
- Encephalopathy
- Bone and joint infection
66
How is enteric fever treated empirically if the patient has signs of sepsis?
IV Ceftriaxone
67
What antibiotics can be used to treat enteric fever and how long do they take to clear the fever?
Ciprofloxacin <4 days (70% of cases are now resistant!)
Azithromycin 4.4 days
Ceftriaxone 6.2 days
68
What infections can cause pre-hepatic (haemolytic) jaundice?
(i. e. jaundice from breakdown of red blood cells)
- Malaria
- HUS as complication of diarrhoea – E.coli 0157
- Sickle cell crisis triggered by infection
69
What infections can cause hepatic jaundice?
- Hepatitis A and E – acute (occasionally Hep B)
- Leptospirosis – Weils diseases
- Malaria
- Enteric fever
- Rickettsia (scrub typhus, Rocky Mountain spotted fever etc)
- Viral haemorrhagic fever
70
How is fever and jaundice investigated in a returned traveller?
- Malaria blood film and rapid antigen
- Blood film for red cell fragmentation
- Blood tests and cultures
- US abdomen
- Serology for viruses
71
How is fever and jaundice treated in a returned traveller?
- Appropriate isolation and infection control procedures
- Supportive – possible dialysis if AKI
- Acute liver failure – hepatology/transplant unit
72
What is a Amoebiasis infection caused by and how is this spread?
- caused by a protozoa
- faecal-oral spread
- strong association with poor sanitation
73
Patients can carry amoebiasis infection asymptomatically. TRUE/FALSE?
TRUE
| - may not be symptomatic but protozoa chronically sheds cysts in stools
74
What symptoms are caused by amoebiaisis infection?
- Abdominal pain/ Peritonism
- Fever
- Bloody diarrhoea / colitis (can perforate)
75
What investigations are used for suspected amoebiasis?
- Stool microscopy for trophozoites/ cysts
- AXR if you suspect toxic megacolon
- Endoscopy for biopsy (not if evidence of toxic dilatation)
76
What complication can amoebiasis infection cause?
Liver abscesses
77
How long do amoebic liver abscesses take to present and in which gender are they most common?
- more common in men
- incubation period 8-20 weeks
- usually present sub-acutely over 2-4 weeks
78
What symptoms are caused by an amoebic liver abscess?
- Fever, sweats
- Upper abdominal pain
- Sometimes history of GI upset (dysentery)
- Hepatomegaly
- Point tenderness over right lower ribs
79
What investigations are used to diagnose amoebic liver abscesses?
- Abnormal LFTs
- CXR – raised right hemi-diaphragm
- USS/CT scan
- Serology
- Stool microscopy - often negative
80
How are amoebic liver abscesses treated?
- Metronidazole or Tinidazole
- If pyogenic abscess, Tx with empirical antibiotics
- Clear the gut lumen of parasites (Paramomycin/ Diloxanide)
81
What causes giardiasis and how is it spread?
- flagellated protozoa
- Invades duodenum and proximal jejunum
- Faecal-oral spread (contaminated water)
- Incubation ~ 7 days
82
How does giardiasis present?
- Watery, malodorous diarrhoea
- Bloating, flatulence
- Abdominal cramps
- Weight loss
83
How is giardiasis investigated?
- Stool microscopy for cysts
- PCR tests (in developed countries)
- OGD for duodenal biopsy (rarely necessary)
84
How is giardiasis treated?
- Metronidazole
| - Tinidazole
85
Helminth infections are caused by what?
Parasites!
86
Helminth infections are associated with an increase in which type of white blood cell?
Eosinophilia
87
What are the different types of Helminth infections?
Nematodes (Roundworms)
=> Intestinal roundworms
=> Tissue roundworms (filariasis)
Trematodes (Flukes)
Cestodes (Tapeworms)
=> Intestinal or Larval
88
Give an example of a Trematode (Fluke) infection?
Schistosomiasis – from fresh water exposure
89
What sources of Tapeworm can give rise to infection?
- Eating undercooked meat containing infectious larval cysts
- Either PORK or BEEF
90
What is Chagas disease caused by and how is it transmitted?
Trypanosmiasis
| - Transmitted by the kissing bug (Triatome)
91
How does Chagas disease affect the body?
- Causes parasymphathetic denervation affecting the colon and/or oesophagus
- May cause Megaoesophagus
