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GI Infections Flashcards

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1
Q

What is the concern in developing countries?

A

Outbreaks such as cholera.
No access to clean drinking water and sanitation
Most vulnerable children and elderly

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2
Q

What are the reportable infections?

A

Campylobacter, salmonella, shigella, E. coli 0157, listeria, norovirus

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3
Q

What age group tend to be the most infected but not the most vulnerable?

A

15-45

Self limiting

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4
Q

What is the first clinical syndrome?

A

No fever, low grade, no WBC in stool.
Cholerae, ETEC, EAggEC, EPEC, EHEC.
Secretory diarrhoea

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5
Q

What is the second clinical syndrome?

A

Fever, WBC in stool
Campylobacter, shigella, non typhoid all salmonella, EIEC
Inflammatory diarrhoea

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6
Q

What is the 3rd clinical syndrome?

A

Fever, WBC in stool (mononuclear)
Typhoidal salmonella, enteropathogenic yersinia, brucella
Enteric fever

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7
Q

Incubation and duration for campylobacter?

A

1-10 days incubation
2-20 days duration
Poultry

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8
Q

Incubation and duration for E. coli?

A

1-5 days incubation
1-4 days duration
HUS, verotoxin

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9
Q

Incubation and duration for shigella?

A

12-96 hours incubation
5-7 days duration
Small infective dose, outbreaks

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10
Q

Incubation and duration for non typhoidal salmonella?

A

8-48 hours incubation
4-7 days duration
Rare cause of systemic disease

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11
Q

Incubation and duration for vibrio parahaemolyticus?

A

24-72 hours incubation
2-10 days
Shellfish

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12
Q

Incubation and duration for cholera?

A

1-5 days incubation
Variable duration
Ricewater, endemic

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13
Q

Incubation and duration for b cereus?

A

1-6 hours incubation
Less than1 day duration
Heat stable emetic toxin (rice)

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14
Q

Incubation and duration for staph aureus?

A

2-7 hours duration
Less than one day duration
Preformed toxin

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15
Q

Mechanism for cholera- secretory diarrhoea

A

Toxins bind to units
Opening up of chloride channels at the apical membrane of enterocytes by cAMP
Effluent of chloride into the lumen with loss of water and electrolytes

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16
Q

Mechanism of disease with secretory diarrhoea- super antigen

A

Antigen binds to T cell receptors and MHC molecules
Outside the peptide binding site
Massive cytokine production by CD4 cells ie systemic toxicity and suppression of adaptive response

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17
Q

Who tends to get an exudative or inflammatory response?

A

Immunocompromised patients

Septic shock

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18
Q

What happens with interstitial inflammation/enteric?

A

Immunocompetent, no septic shock.

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19
Q

Facts about s aureus leading to food poisoning?

A

1/3 chronic carriers, 1/3 transient
Spread by skin lesion on food handlers
Catalase, coagulase, gram positive coccus
Appears in tetrads, clusters on gram stain
Yellow colonies

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20
Q

What is the mechanism of s aureus?

A

Produces an enterotoxin, an exotoxin that can act as a super antigen, releasing IL 1 and 2.
Causing prominent vomiting and watery non bloody diarrhoea
Self limiting
No heat inactivation

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21
Q

Mechanism for b cereus?

A 
Gram positive rod, spore forming 
Spores germinate in reheated fried rice 
Heat stable emetic toxin 
Heat labile diarrhoeal toxin 
Watery non bloody diarrhoea 
Self limited 
Rare cause of bacteraemia
Can cause cerebral abcess
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22
Q

Facts about clostridium botulinum?

A

Gram positive anaerobes
Source is canned or vacuumed food
Ingestion of preformed toxin, inactivated by Heat
Blocks ACH release from peripheral nerve synapses
Tx is with antitoxin

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23
Q

Mechanism for clostridium pefringens?

A 
Reheated food/meat
Affects normal flora of colon but not small bowel, where super antigen acts 
8-16 hours incubation
Watery diarrhoea 
Cramps
Vomiting 24 hours
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24
Q

C diff?

A

Pseudo membranous colitis
3% population 30% hospital
Abx related colitis mainly, cephalosporin, Citroen and clindamycin
Monitor albumin, renal function and white cells
Tx with oral metro, vanco.

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25
Listeria monocytogenes?
Outbreaks of febrile gastroenteritis Pregnant ladies, perinatal infection B haemolytic, aesculin positive with tumbling motility Refridgerated food, grows at 4 degrees Celsius Watery diarrhoea, cramps, headache, fever, little vomiting Tx with ampicillin, ceftriaxone, cotrimoxazole
26
What are enterobacteriae?
Facultative anaerobes, glucose/lactose fermenters, oxidase negative
27
E. coli?
Travellers diarrhoea Food/water contaminated with human faeces Enterotoxins- Heat labile stimulates adenyl cyclase, and cAMP Heat stable stimulates guanylate cyclase Act on jejenun and ileum NOT colon
28
What is ETEC?
Toxigenic | Travellers diarrhoea
29
What is EPEC?
Pathogenic | Infantile diarrhoea
30
What is EIEC?
Invasive | Dysentry
31
What is EHEC?
Haemorrhagic O157 Shiga like verocytotoxin causes HUS Avoid abx
32
Why are infections underreported?
Most are self limiting, under 24 hours, patients do not seek healthcare
33
What are salmonellae?
They are non lactose fermenters, they produce hydrogen disulphide They produce antigens
34
What are the antigens from salmonellae?
Cell wall O(groups a-I) Flagellar H Capsular Vi (virulence and antiphagocytic)
35
What are the 3 salmonellae species?
S typhi S enteritidis S cholerasuis
36
What does s enteritidis cause?
``` Enterocolitis, poultry, eggs, meat Invasion of epi and sub epithelial tissue of small and large bowel Bacteraemia is infrequent Self limited, non bloody diarrhoea Give cipro after 3-5 days Stool positivity ```
37
What does s typhi cause?
``` Enteric fever, South East Asia, humans Multiples in payers patches Often bacteriaemic Slow, fever, constipation Splenomegaly Rose spots Anaemia, leucopenia, bradycardia, haemorrhage Blood culture positive (abcess.mycotic aneurysm) Treat with ceftriaxone ```
38
What is shigellae?
Gram negative anaerobes, non motile
39
What are the shigellae antigens?
Cell wall O | Polysaccharide groups a-d
40
What are the 3 shigellae species?
S sonnei, s dysenteriae, s flexneri (msm, faecal) The most effective enteric pathogen low ID 50 No animal reservoir No carrier state
41
What does shigella cause?
``` Dysentery, invading cells of mucosa of distal ileum and colon Producing enterotoxin (shigatoxin) Avoid abx (ciprofloxacin to prevent onward spread) ```
42
What are vibrios?
Gram negative rod shaped, late lactose fermenters, oxidase positive
43
What is vibrio cholera?
O1 group causes epidemics Non O1 group is sporadic or non pathogens Transmitted by contamination of water and food from human faeces (shellfish, oysters and shrimp)
44
How does v cholera work?
Colonisation of the small bowel, secretion of enterotoxin with A and B subunit, causing persistent stimulation of adenylate cyclise Massive diarrhoea without any white cells
45
How does vibrio parahaemolyticus work?
Ingestion of raw or undercooked seafood Major cause of diarrhoea in Japan, or cruising Self limiting for 3 days Grows in salty conditions
46
How does vibrio vulnificus work?
Causes cellulitis in shellfish handlers, waterborne. Can cause fatal septicaemia if immunosuppressive (HIV) Treat with doxycycline
47
What is campylobacter?
Gram negative, microaerophilic Grows at 42 degrees Motile, oxidative positive Self limiting but symptoms can last for 20 days Lives in poultry gut Only treat with immunocomprimise does with macrolide
48
How is campylobacter transmitted?
Contaminated food and water with animal faeces (poultry, meat, birds pecking on milk) Enterotoxin, watery diarrhoea Fever, abdo pain Not sure if it invades blood (f one does) Treat with erythromycin or cipro in first 4-5days
49
What syndrome can campylobacter cause?
GBS Reactive arthritis Reiters disease
50
What is yersinia enterocolitica?
Gram negative rod shaped Non lactose fermenters, prefers cold 4 degrees Transmitted via food contaminated with domestic animal poo Can cause enterocolitis, mesenteric adenitis, assoc reactive arthritis, reiters
51
What is entamoeba histolytica?
``` Protozoa Motile trophozoite in diarrhoea Non motile in non diarrhoeal Killed by boiling, removed by water filter 4 nuclei, no animal reservoir ```
52
How does e histolytica work?
``` Ingestion of cysts, trophies in ileum, colonise caecum, causes flask shaped ulcer Dysentery and flatulence Tenesmus Chronic weight loss, plus diarrhoea Liver abscess ```
53
How would you diagnose e histolytica?
``` Stool microbiology (wet mount, iodine, trichrome) Serology in invasive disease ```
54
How do you treat e histolytica?
Metro plus paromomycin in luminal disease
55
What is giardia?
Protozoa, trophozoite Pear shaped 2 nuclei, 4 flagella, suction disk
56
How is giardia passed?
Ingestion of cyst from faecally contaminate water, food Excystation at the duodenum Tropho attaches No invasion but malabsorption of protein or fat Travellers hikers, day care, mental hospital people can't look after themselves msm.
57
What are the symptoms of giardia?
Foul smelling non bloody diarrhoea stool floats Cramps Flatulence No fever
58
How can you diagnose giardia?
Stool microscopy ELISA String test- capsule with string into stomach Treat with metro
59
What is cryptosporidium parvum?
Protozoa, infects the jejenum Severe diarrhoea in the immunocompromised Oocysts seen in stool, modified by kinyoun acid fast stain Treatment- reconstitution of immune system Picked up from swimming
60
What is norovirus?
``` Causes outbreaks Low ID (18-1000 viral particles) Resilient up to 60 degrees celcius No long term immunity G2.4 is the currently predominant strain Vomiting and diarrhoea ```
61
What is rotavirus?
``` Wheel like virus, dsRNA Replicates in mucosa of small intestine Secretory diarrhoea No inflammation Can get watery diarrhoea by stimulation of enteric nervous system ```
62
Who gets rotavirus?
Age 6 kids most have it | Exposure to natural infection twice confers lifelong immunity
63
What can adenovirus cause?
Types 40, 41 cause non bloody diarrhoea, usually less than 2 years of age Any type in immunocompromised
64
How do you diagnose adenovirus?
Stool em, antigen detection, PCR
65
What are the targets for prevention promotion?
Breast feeding, improved weening practice Clean water for drinking Safe disposal of stools of young children Precautions when travelling Food handling Public health notification Good handwashing
66
What is the cholera vaccine?
Inactivated whole cell, contains serogroups O1 and O139 Plus beta unit of toxin Live is not recommend
67
What about campylobacter vaccine?
One available for military, infant and travellers | Candidate vaccines exist only for high risk
68
Are there any ETEC vaccines?
Inactivated and live vaccines in trials
69
Is there a salmonella vaccine?
Yes, vi capsular ps (IM) and oral live
70
What are the rotavirus vaccines?
Rotarix- live attenuated human strain, 2 oral doses Rotateq- pentavalent, 3 oral doses, one bovine, 4 human strains 6-12 weeks , UK don't get it really
71
What are the notifiable diseases?
Camp, clostridium, listeria, vibrio, yersinia, shigella, salmonella? Identify outbreaks in areas

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