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Microbiology - Gastrointestinal Infections Flashcards

(78 cards)

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1
Q

Risk Factors

A 
Lack of clean water, poor sanitation
Overcrowding
Poor hygiene 
Poor food preparation/storgae
Seasonal factors
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2
Q

Host Factors

A 
Age (very young/elderly)
Decreased gastric acid secretion 
Decreased gut motility
Influence of colonic microflora
Intestinal immunity
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3
Q

Define Diarrhoea

A

Three or more loose stools in 24 hours

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4
Q

Define Source/Reservoir of Infection

A

Original source of infection

E.g. animal gut, human gut

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5
Q

Define Vehicle of Infection

A

Means by which the infection is transmitted from one person to another
E.g. contaminated food/water

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6
Q

Campylobacter - Classification

A

Curved gram negative bacillus

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7
Q

Campylobacter - Incubation Period

A

3-10 days

DAYS - WEEK

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8
Q

Campylobacter - Mechanism of Action

A

Causes inflammation of colon and rectum = bloody diarrhoea

Can invade bloodstream

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9
Q

Campylobacter - Source and Vehicle of Infection

A

Farm animals

Undercooked poultry, water, unpasteurised milk

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10
Q

Campylobacter - Symptoms

A

Abdo pain

Diarrhoea +/- blood

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11
Q

Campylobacter - Management

A

Usually self limiting

Systemic illness = erythromycin or ciprofloxacin for 5 days

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12
Q

Salmonella enterica - Incubation Period

A

12-48 hours

HOURS - DAY

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13
Q

Salmonella enterica - Mechanism of Action

A

Causes inflammation of ileum and colon
Multiply in gut and cause mucosal damage, decreased fluid absorption and increased fluid excretion
Can invade bloodstream

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14
Q

Salmonella enterica - Source and Vehicle of Infection

A

Farm animals
Undercooked poultry
Less common since immunisation of poultry against salmonella

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15
Q

Salmonella enterica - Symptoms

A

Abdo pain
Diarrhoea (occasionally bloody)
Vomiting

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16
Q

Salmonella enterica - Management

A

Usually self limiting

Systemic illness = ciprofloxacin for 5 days

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17
Q

Shigella - Incubation Period

A

1-9 days

DAYS - WEEK

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18
Q

Shigella - Mechanism of Action

A

Invades intestinal mucosa causing severe inflammation
Does not invade bloodstream
Pus cells and blood seen in stools

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19
Q

Shigella - Source and Vehicle of Infection

A

Human only

Associated with schools and nurseries

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20
Q

Shigella - Symptoms

A

Abdo pain

Diarrhoea (occasionally bloody)

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21
Q

Shigella - Management

A

Usually self limiting
S sonnei = only symptomatic treatment
Other species = ciprofloxacin

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22
Q

E coli O157 - Mechanism of Action

A

Produces a toxin that damages red cells and the kidney

Leads to haemolytic-uraemic syndrome

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23
Q

E coli O157 - Source and Vehicle of Infection

A 
Gut flora in cattle
Beef contaminated at slaughter 
Nursery school visits to farms
Untreated water supplies 
Person to person causes secondary cases
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24
Q

E coli O157 - Symptoms

A

Abdo pain

Commonly bloody diarrhoea

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25
E coli O157 - Management
Symptomatic and supportive treatment only Antibiotics contraindicated Check for HUS after 1 week
26
Clinical Presentation of HUS
``` Abdo pain Fever Pallor Petechiae (skin haemorrhages) Oliguria (decreased urine) Bloody diarrhoea Mostly in under 16s Peak presentation 7-10 days after diarrhoea onset ```
27
HUS Blood Tests
``` High white cells Low platelets Low HB Red cell fragments Lactate dehydrogenase increased ```
28
Salmonella, Shigella and E coli O157 - Classification
Gram negative bacilli | Further classify through serology
29
Salmonella typhi/paratyphi - Background Info
Cause tyhpoid/paratyphoid fever | Seen in UK when imported from abroad
30
Salmonella typhi/paratyphi - Incubation Period
14-21 days | WEEKS
31
Salmonella typhi/paratyphi - Mechanism of Action
Organism invades from gut lumen to lymphatics, blood stream, reticuloendothelial system and gall bladder Some people become chronic carriers (gallbladder)
32
Salmonella typhi/paratyphi - Source and Vehicle of Infection
Human only | Person to person or contaminated water, food and poor sanitation
33
Salmonella typhi/paratyphi - Symptoms
Initially systemic headache/flu like symptoms Fever Abdo rash (rose spots) 3 weeks later, diarrhoea
34
Salmonella typhi/paratyphi - Management
Antibiotics needed Depends on sensitivities Ciprofloxacin resistance common in developing countries
35
Cholera - Causative Organism
Vibrio cholerae | Small curved gram negative bacillus
36
Cholera - Incubation Period
1-9 days | DAYS - WEEK
37
Cholera - Mechanism of Action
Organism produces exotoxin that causes active outpouring of fluid from small intestine cells
38
Cholera - Source and Vehicle of Infection
Human only Person to person or contaminated water and poor sanitation Outbreaks common in "disaster" or war situations
39
Cholera - Symptoms
``` Watery diarrhoea (rice water stools) Rapid dehydration ```
40
Cholera - Management
Fluid and electrolyte replacement | No antibiotics
41
GI Infections Associated with Ingestion of Pre-formed Toxin
Staph aureus Clostridium perfringens Bacillus cereus Generally have much shorter incubation periods
42
Staphylococcus aureus
Some strains produce enterotoxin Generally spread via contaminated food Absorbs quickly, acts directly on vagus nerve and vomiting centre, vomiting within 1-2 hours
43
Clostridium perfringens
Part of normal gut flora Spores survive cooking, turn into vegetative organisms, some strains produce enterotoxin Associated with poorly stored food
44
Bacillus cereus
Exotoxin ingested as pre-formed toxin in food or organism multiplies in intestine, producing toxin that is absorbed from gut Spores survive cooking, turn into vegetative organisms which produce toxin Associated with poorly stored reheated rice
45
Cryptosporidium
Single celled parasite
46
Cryptosporidium - Mechanism of Action
Cysts ingested which hatch and invade small intestine cells
47
Cryptosporidium - Source and Vehicle of Infection
Domestic animals, especially calves Person to person Outbreaks associated with contaminated water and swimming pools (resistant to chlorine)
48
Cryptosporidium - Symptoms
Diarrhoea | Severe in HIV patients
49
Cryptosporidium - Management
Symptomatic treatment only
50
Giardia lamblia
Single celled parasite | Probably under diagnosed in Scotland
51
Giardia lamblia - Mechanism of Action
Cysts ingested which hatch and invade upper small intestine cells
52
Giardia lamblia - Source and Vehicle of Infection
Human only Possible person to person Outbreaks associated with contaminated water
53
Giardia lamblia - Symptoms
``` Diarrhoea Malabsorption syndrome Anorexia Abdo pain Flatulence ```
54
Giardia lamblia - Management
Oral metronidazole
55
Enterobius vermicularis - Pathogenesis
Ingested ova Hatch in intestine and live in caecum & colon Adult females lay ova on perianal skin at night Ova cause perianal itch Child scratches then puts fingers into mouth
56
Enterobius vermicularis - Source and Vehicle of Infection
Human only Person to person Poor hygiene
57
Enterobius vermicularis - Symptoms
Perianal itch | Worms in stool
58
Enterobius vermicularis - Management
Oral mebendazole | Treat all family at once
59
C.diff - Mechanism of Action
Organism produces two toxins: A (enterotoxin) and B (cytotoxin)
60
C.diff - Source and Vehicle of Infection
Part of normal gut flora Antibiotics kill normal gut flora, but C.diff survives due to spores Patient to patient spread
61
C.diff - Symptoms
Diarrhoea, sometimes bloody Abdo pain Severe cases = pseudomembranous colitis or bowel perforation
62
C.diff - Management
Less severe = oral metronidazole | Severe = oral vancomycin
63
C.diff - Prevention
Stewardship = Narrow spectrum antibiotics where possible and avoidance of 4 Cs Isolation of patients Hand washing Cleaning of environment
64
C.diff - Classification
Gram positive, spore bearing, bacillus
65
C.diff - Lab Diagnosis
Screening test for positive organism (GDH) Toxin test if GDH positive Culture is strain needs to be typed Screening -ve = -ve Screening +ve, toxin +ve = +ve Screening +ve, toxin -ve = indeterminate Indeterminate = reassess and repeat. If still indeterminate, clinical judgement (smells of horse dung)
66
Rotavirus - Typical Presentation
Commonest in children
67
Rotavirus - Vehicle of Infection
Person to person spread Direct or indirect Low infective dose Survives in the environment
68
Rotavirus - Symptoms
Mild to severe diarrhoea No blood Dehydration Children may develop post infective malabsorption
69
Rotavirus - Treatment
``` Self limiting (~ 1 week) Oral rehydration where possible ```
70
Rotavirus - Diagnosis
PCR test on faeces
71
Rotavirus - Prevention
Live attenuated vaccine 2 doses at 2 and 3 months Not given to children over 24 weeks because of increased risk of intussusception
72
Norovirus - Route of Spread
``` Faecal/oral droplets Person to person Contaminated food/water High environmental survival Low infective dose ```
73
Norovirus - Incubation Period
Often
74
Norovirus - Symptoms
Sudden onset explosive D&V | Lasts 2-4 days
75
Norovirus - Diagnosis
Faeces specimen or vomit swab for PCR
76
Norovirus - Treatment
Rehydration
77
Hospital Control of Infectious Diarrhoea
Single room with own toilet/commode Cohort nursing bays during outbreaks Wards closed to new admissions Increased ward cleaning/disinfection
78
Doctors and Diarrhoea
Infectious diarrhoea, stay off work until 48 hours after symptoms have stooped Inform line manager and Occ Health

GI (24 decks)

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