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GI infections Flashcards

1
Q

Gastroenteritis - DEFINITION

A

A rapid onset diarrhoeal illness, lasting LESS THAN < 2 weeks, usually one week, with diarrhoea (loose and unformed stool), 3 or more times a day

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2
Q

DEFINITION Diarrhoea

A
  • Loose or watery stools passed AT LEAST 3 times in 24 hours which can be acute, chronic or persistent
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3
Q

o Acute, persistent, chronic diarrhoea time frames

A

o Acute- lasting < 14 days often due to either viral or bacterial pathogens

o Persistent- between 14-29 days

  • entameboa histolytica
  • giardia lamblia
  • cryptosporidium

o Chronic- lasting > 30 days, may be due to parasites or (often) non-infectious aetiology- IBD/neoplastic causes

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4
Q

small bowel vs large bowel diarrhoea

A

-Small bowel diarrhoea:
o Large volume
o Often watery
o crampy abdominal pain with bloating and gas
o RARELY any fever, inflammation, blood, mucus

Large bowel diarrhoea:
oSmall volume
opainful stool
ooften with blood, mucus, inflammatory cells found in the stools
oaccompanying fever
oPatients complain more about blood and mucus than diarrhoea itself

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5
Q

main people vulnerable to gastroenteritis

A

infants, elderly, MSM- shigella

Patients with haemochromatosis or haemoglobinopathy

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6
Q

secretory vs inflammatory vs enteric fever

A
  • Secretory diarrhoea does NOT tend to have a fever or WBCs in the stool- profuse watery diarrhoea
  • If there is a fever, it is an inflammatory diarrhoea. with WCC, blood, mucus in stool
  • enteric fever: fever but with relatively little/no change in stools- these infections are often more severe.
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7
Q

GI infection causes within incubation within 1 day

A 
staph aureus 
bacillius cereus 
Clostridium perfringens 
Listeria 
Norovirus 
viruses: rotavirus and enteric adenovirus

usually have preformed toxins

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8
Q

GI infection causes within incubation after day 1

A

think about enteric fever:

shigella, Campylobacter, salmonella, enterotoxigenic E. coli

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9
Q

GI infection causes within incubation after day 4-6 or weeks

A 
think about parasites + C.difficile 
o	Cryptosporidium parvum 
o	Giardia 
o	Yersnia 
,
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10
Q

how does cholera produce profuse diarrhoea

A

toxin production&raquo_space;> - cAMP will open Cl- channels in the apical membrane of enterocytes

leading to Cl- efflux into the lumen and loss of water and electrolytes

They get shock due to fluid loss

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11
Q

what type of diarrhoea does cholera produce

A

Cholera is a classic example of secretory diarrhoea

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12
Q

how many stool samples needed in parasitic infections

A

In parasitic infections, intermittent shedding occurs so need to send THREE stool samples to see if it can be found

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13
Q

which organisms cause Aortitis, Osteomyelitis, deep tissue infection

A

salmonella, Yersinia

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14
Q

what organisms cause haemolytic anaemia

A

Campylobacter, Yersinia- this one is longer lasting

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15
Q

what organisms cause haemolytic uraemic syndrome

A

**shiga toxin producing E-coli, shigella dysenteriae serotype 1

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16
Q

which organisms cause erythema nodosum

A

**Yersinia, **Campylobacter, Salmonella, Shigella

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17
Q

which organisms cause Reactive arthritis

A

Salmonella, Shigella, **Campylobacter, Yersinia, rarely Giardia and Cyclospora cayetanensis

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18
Q

which organisms can cause Meningitis

A

***Listeria, Salmonella (infants ≤ 3 months of age are at high risk

Viral enteroviruses pathogens can also give meningitis

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19
Q

staph aureus- mode of transmission and type of bacteria + treatment + presenting symptoms

A

skin contact, shedding of bacteria from skin when handling food.

prominent VOMITTING, watery non bloody diarrhoea

gram positive, coagulase positive cocci in clusters /tetrads

  • Catalase

self limiting: fluid hydration and electrolyte replacement

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20
Q

Interleukins produced by staph aureus

A

IL1 and IL2

S. aureus produces an enterotoxin, an exotoxin that can act as a superantigen in the GIT, releasing IL-1 and IL-2.

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21
Q

staph aureus appearance on blood agar

A

golden colonies

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22
Q

Bacillus cereus - mode of transmission and type of bacteria + treatment + presenting symptoms

A

transmission: reheated fried rice
gram positive rods, spore forming

presenting symptoms: watery non bloody diarrhoea
treatment: self limiting

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23
Q

toxins produced by bacillus cereus

A
  • Heat stable emetic toxin- not destroyed by reheating

- Heat labile diarrhoeal toxin- when food is not cooked at a high enough temperature (destroyed by heat)

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24
Q

complications (2) of bacilllus cereus

A

o cause bacteraemia in vulnerable people

o Can cause cerebral abscesses

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25
Q

Clostridia- name the different types

A

clostridium botulinum, clostridium difficile, clostridium perfringens

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26
Q

clostridium botulinum - mode of transmission + treatment + presenting symptoms

A

transmission: honey (paediatirc/infants) /vaccum packed canned foods

Blocks ACh release from peripheral nerve synapses presenting symptoms: botulinism: paralysis

Treatment: antitoxins + can be inactivated by cooking

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27
Q
  • Clostridium perfringens - mode of transmission + treatment + presenting symptoms
A

transmission: reheated meat
(Normal flora of colon but not small bowel, where the enterotoxin acts (superantigen))

presenting symptoms: watery diarrhoea, abdominal cramps, little vomiting lasting 24 hours. Prolonged symptoms may be suggestive of gut infarction and necrosis

Treatment: self limiting but can cause severe disease requiring removal or part of colon

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28
Q

Clostridium difficile: type of infection and what does it cause

A

causes Pseudomembranous colitis

hospital acquired infection

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29
Q

toxins produced by C.difficile and significance of this

A

Toxin A (enterotoxin), Toxin B (cytotoxin)

o Toxin A- causes inflammation of gut with intestinal fluid secretion and damage to the mucosa

o Toxin B- more potent than toxin A, acts as a virulence factor

If PCR +ve but toxin -ve&raquo_space;> need adequate infection control but may not need treatment depending on if symptomatic or not

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30
Q

which group of people are most vulnerable to C.difficile

A

common in hospitalised patients (30%)

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31
Q

what causes C. difficile with specific examples

A

antibiotic related Collitis (4Cs)

  • cephalosporins
  • coamoxiclav
  • ciprofloxacin
  • clindamycin

any of the beta-lactams can be associated with C. difficile too

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32
Q

does C.difficile require infection control + prevention

A

Infection prevention and control precautions are required
o Need to be in a side room with gloves + apron.
o Need to handwash as gel does not kill spores

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33
Q
  • TREATMENT for C.difficile
A

o stop antibiotics
o 1st line: PO Metronidazole
o PO Vancomycin

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34
Q

what gram staining is clostridium species

A

gram positive anareobes

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35
Q

listeria monocytogenes- gram staining, transmission, presenting symptoms, complications + treatment

A

listeria: gram positive rods, beta haemolytic, tumbling motility , aesculin +ve
transmission: refrigerated food + unpasteruised dairy

presenting symptoms: GI watery diarrhoea, abdominal cramps, headache, fever, little vomiting

complication: meningitis in elderly and neonates- pregnant woman are very vulnerable
treatment: Amoxicillin

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36
Q

Enterobacteriaceae - type of bacteria and characteristics of bacteria

A
  • Facultative anaerobes
  • Glucose/ lactose fermenters (LF)
  • Oxidase negative
37
Q

one major example of enterobacteracae + transmission, + toxins produced by them + where do they act in the gut + treatment

A

E-coli: travellers diarrhoea: food/ water contaminated with human faeces

Enterotoxins:
 Heat labile- stimulates adenyl cyclase and cAMP
 Heat stable- stimulates guanylate cyclase
Acts on the small bowel: jejunum and ileum, but NOT the large bowel, colon

treatment: Should NOT treat with antibiotics

38
Q

types of E-coli

A

Enterotoxigenic E. coli (ETEC) toxigenic- main cause of traveller’s diarrhoea

Enteropathogenic E. coli (EPEC) pathogenic- infantile diarrhoea

Enteroinvasive E. coli (EIEC) invasive- dysentery-like illness

Enterohaemorrhagic E. coli (EHEC)- also called Shiga-toxin-producing E. coli or STEC
known as E. coli O157:H7 EHEC- the shiga-like verocytotoxin causes Haemolytic Uraemic Syndrome

39
Q

salmonellae - characteristics + colour on agar + antigens + transmission

A
  • Non lactose fermenters- looks clear on plate
  • Pale on blood agar
  • Antigens- the presence of different combinations of the antigens help to differentiate what subspecies it is. Salmonellae has:
    o Cell wall O (groups A-I)
    o Flagellar H
    o Capsular Vi (virulence antiphagocytic)

transmission: various but can also get this from pet reptiles e.g. turtle, lizard, snake

40
Q

difference between salmonellae and enterbacteriae

A
  • Glucose/ lactose fermenters (LF)- enterobacteriae

- non lactose fermenters- salmonellla

41
Q

species of salmonella that is of worry

A
  • salmonella typhi + paratyphi
  • salmonella enteritidis
  • salmonella cholerasuis
42
Q

S. enteritidis- presentation+ transmission + invasion in which part of the bowel + treatment + risk of bacteraemia + investigation

A

o Transmitted from poultry, eggs, meat

invasion: Invasion of the epi- and subepithelial tissue of the small AND large bowel

presentation: CLASSIC GASTROENTERITIS: Self-limiting non-bloody diarrhoea resolves in 4-7 days with abdominal pain.
o Nausea, vomiting and fever usually resolves in 48-72 hours

treatment: self resolving and no treatment
investigation: stool culture positive

Infrequent bacteraemia rate < 5%

43
Q

S. typhi- presentation+ transmission + treatment + risk of bacteraemia + investigation

A

transmission: Transmitted ONLY by humans

presentation:
- slow onset
- typhoid enteric fever (no diarrhoea): fever + constipation (after first or second week)
- Extra-intestinal manifestations can occur: splenomegaly, rose spots, anaemia, leukopaenia, aortitis, osteomyelitis (due to peyers patch enlargement)

  • Signs: bradycardia, haemorrhage and perforation of the bowel
  • Bacteraemia occurs

investigations:

  • Blood culture- positive 40-80%
  • Stool culture- positive 30-40%
  • bone marrow: if negative stool + blood cultures + remains positive until >5 days after antibiotic treatment

TREATMENT: Ceftriaxone

44
Q

Shigellae - characteristics + antigens + classical groups of shigella

A

non lactose fermenter
non motile

  • Antigens:
    o Cell wall O antigens
    o Polysaccharide (groups A-D):

o Classic groups are:
S. sonnei - Very resistant
S. dyseneteriae
S. flexneri (MSM)

45
Q

why is shigella similar to salmonella + different

A

-both are Non-lactose fermenters but shigella does not produce hydrogen sulphide like salmonella

46
Q

shigella: presentation+ transmission + carrier state + treatment + investigation + which toxin does it produce

A

human to human transmission + no carrier state

produces shiga toxin - enterotoxin

presenting symptoms: causes dystentry: diarrhoea with blood and mucus
:Abdominal pain, watery diarrhoea which proceeds to bloody diarrhoea, fever, vomiting

treatment: Disease is SELF-LIMITING to around 7 days: often do NOT recommend antibiotics.

47
Q

difference between salmonella typhi and salmonella entertidis

A

typhi- 3% are carriers- low compared to S. enteritidis

entertidis: quicker onset and self resolving + transmitted by poultry, eggs, meat
typhi: needs ceftriaxone and entra intestinal manifestations and transmitted only by humans , increased risk of bacteraemia

48
Q

define dystentry

A

Dysentery (infection of the intestines resulting in severe diarrhoea with the presence of blood and mucus in the faeces)

49
Q

what are the indications for treating shigella with antibiotics

A

immunosuppressed or if MSM (to prevent onward transmission of the S. flexneri)

50
Q

Vibrios- transmission and specific type of agar plate do you need

characteristical features:

A
  • Handling shellfish, deep sea diver, scuba diving, cutting self on coral
  • need specific salty agar plate

characteristics:
- comma shaped
- lactose fermenters
- oxidase positive

51
Q

3 types of vibrio

A

o Vibrio cholerae - cholera
o Vibro parahaemolyticus
o Vibro vulnificus: cause diarrhoea, seen in septic patients and those with liver disease

52
Q 
Vibrio cholerae
2 groups 
transmission 
presentation 
colonises which part of the bowel
A
  • O1 group: epidemics
  • Non O1 group: sporadic or non-pathogens
  • Transmission: contamination of water and food from human faeces (shellfish, oysters, shrimp

MASSIVE DIARRHOEA (rice water stool) WITHOUT inflammatory cells

small bowel: secretion of enterotoxin with A and B subunit&raquo_space;» constant stimulation of adenylate cyclase

53
Q

Vibrio parahaemolyticus
- transmission
- prevalence in which countries
treatment

A

RAW or UNDERCOOKED seafood e.g. oysters

  • Major cause of diarrhoea in Japan or when cruising in the Caribbean
  • SELF-LIMITED for 3 days
54
Q

Vibrio vulnificus

  • transmission and what type of hazard causes it
  • presenting symptoms + who is vulnerable
  • treatmet
A
  • Cellulitis in shellfish handlers
  • occupational hazard
  • Can cause FATAL SEPTICAEMIA with D+V in HIV/immunosupressed patients
    treatment: doxycycline
55
Q

Campylobacter

characteristics

A
  • Curved, comma or S-shaped
  • Microaerophilic- does not require much oxygen to grow
  • C. jejuni grows at 42oC

oxidase +ve, MOTILE organism

56
Q

which two organisms are curved comma shaped

A

vibrio and campylobacter

57
Q

Campylobacter:
transmission
symptoms
treatment

A
  • Transmitted via contaminated food and water with animal faeces (poultry, meat, unpasteurised milk). - Undercooked poultry (chicken at a BBQ)
  • Symptoms: watery, foul smelling diarrhoea, bloody stool, fever, severe crampy abdominal pain
  • Loose stools occur > 10 x day

treatment: self limiting and lasts for ~ 7 days
- Only treat if immunosuppressed with MACROLIDE

58
Q

when would you treat Campylobacter

A
  • Only treat if immunosuppressed with MACROLIDE

- TREATMENT: erythromycin or ciprofloxacin if in the first 4-5 days

59
Q

what indicates severe disease in Campylobacter

A
  • Stools may become bloody from 2-3rd day onwards in those with the plasmid PVir which correlates with more SEVERE disease
60
Q
  • Extra-intestinal manifestations of Campylobacter
A 
o	Guillain-Barre syndrome - main one 
o	Reactive arthritis
o	Reiter’s
o	Erythema nodosum 
o	Glomerulonephritis
61
Q
  • Yersinia entercolitica- characteristic + transmission + presentation
A

o Non-lactose fermenter
prefers 4oC “cold enrichment

o Transmitted via food contaminated with domestic animals’

Causes:
 Enterocolitis
 Mesenteric adenitis

62
Q

what conditions is yersnia associated with

A

**reactive arthritis
**Reiter’s,
Glomerulonephritis,
Haemolytic anaemia

63
Q

which Protozoa causes GI infections

A
  • Entamoeba histolytica
  • Giardia lamblia
  • Cryptosporidium parvum
64
Q
  • Entamoeba histolytica: characteristic features in terms of protozoa

how is it killed

who is at risk of Entamoeba histolytica

A

o Motile trophozoite in diarrhoea
o Non-motile cyst in non-diarrhoeal illness
o Has 4 nuclei- easy to identify down the microscope

o Killed by boiling, removed by water filters

o More common in MSM

65
Q

presentation of Entamoeba histolytica
classic symptoms
chronic symptoms

A

flask shaped’ ulcer in ileum

CLASSIC symptoms: dysentery, flatulence, tenesmus

Chronic symptoms: weight loss +/- diarrhoea

liver abscess which requires imaging and further investigations

66
Q

diagnosis of Entamoeba histolytica

A

 Stool microscopy (wet mount, iodine + trichrome)

 Serology in invasive disease

67
Q

treatment of Entamoeba histolytica

A

TREATMENT: Metronidazole + paromomycin in luminal disease

68
Q
  • Giardia lamblia
    characteristic features

transmission

symptoms

A

o Ghost-like trophozoite that is pear-shaped
o Has 2 nuclei + 4 flagellae + suction disk

transmission: faecally contaminated water and food
cruises or resource poor settings
Occurs in travellers, hikers, day care, mental hospitals, MSM

symptoms: No invasion occurs BUT malabsorption of protein and fat lead to symptoms (flatulence, bloating, diarrhoea)

foul-smelling non bloody diarrhoea, cramps, flatulence, NO fever

69
Q

Giardia lamblia- diagnosis

A

 Stool microscopy
 ELISA
 “String-test”: Swallow a capsule containing some string

70
Q

Giardia lamblia- treatment

A

o TREATMENT: Metronidazole

71
Q
  • Cryptosporidium parvum
    who is at risk
    and where does it affect

diagnosis:

A

immunosuppressed

Infects the jejunum

seen in stool by modified Kinyoun acid fast stain

72
Q
  • Cryptosporidium parvum- symptoms
A

o Symptoms: severe diarrhoea in the IMMUNOCOMPROMISED (e.g. HIV

73
Q

which stain is used for Cryptosporidium parvum-

A

in stool by modified Kinyoun acid fast stain

74
Q

o TREATMENT for Cryptosporidium parvum-

A

 Self-limiting so no other treatment

 Reconstitution of the immune system

75
Q

common cause of gastroenteritis outbreaks in hospitals

A

Norovirus

76
Q

do you get long term immunity with norovirus

A
  • NO long-term immunity – once you’ve had it, can get it again
77
Q

how can you remove norovirus

A

it is very resistant to cleaning

78
Q

what is the infectious disease criteria/ dose of norovirus

A

very LOW infectious disease criteria/ dose

79
Q

viruses that cause GI infections and which population do they infect

A
  • norovirus- common outbreaks in hospital
  • adenovirus: immunocompromised and non bloody diarrhoea <2. years of age
  • rotavirus: children aged 6 months to 2 years but can affect the elderly

others:
- Poliovirus
- Enteroviruses (coxsackie, ECHO) - meningitis esp in neonates
- Hepatitis A

80
Q
  • Rotavirus
A

o children aged 6 months to 2 years but can affect the elderly
o occasionally cause diarrhoea in the elderly

SYMPTOMS: secretory diarrhoea, NO inflammation

81
Q

do you get lifelong immunity in rotavirus

A

o Exposure to natural infection TWICE confers lifelong immunity

82
Q

adenovirus - who does it affect

A

Types 40 and 41 cause non-bloody diarrhoea < 2 years of age

Any type in immunocompromised

83
Q

diagnosis of adenovirus

A

o Diagnosis:
 Stool electron microscopy
 Antigen detection
 PCR

84
Q

MOST IMPORTANT Infection Prevention and Control

A

o Good handwashing

85
Q

how should D+ V be managed in hospital

A
  • In hospital- D+V should be isolated
86
Q

vaccines

A
  • Cholera- INACTIVATED
  • Campylobacter
  • ETEC - in trial
  • Salmonella typhi- live vaccine
  • Rotavirus- given to children: Age of vaccine is 6-12 weeks can be offered this
87
Q

public health notifiable diseases

A 
o	Campylobacter
o	Clostridium sp.
o	Listeria monocytogenes
o	Vibrio
o	Yersinia
o	Salmonella

-

88
Q

Which virus is commonly associated with outbreaks?

A
  • Norovirus

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