GI Infections- I have started reordering these cards, will finish soon. daniel Flashcards
1
Q
Anaerobic organism responsible for GI infections
A
Clostridia (Gram +ve rod)
2
Q
3 subspecies of clostridium responsible for GI infections
A
Botulinum Perfringens Difficile
3
Q
Name of disease caused by Clostridium botulinum
A
Botulism
4
Q
Clostridium botulinum: microscopic features
A
Gram +ve Rod-shaped Anaerobic Spore-forming Motile Produces the neurotoxin botulinum
5
Q
How is Clostridium botulinum transmitted?
A
Botulinum toxin can be produced by the bacteria if present in canned/vacuum packed foods. Botulism is contracted if the toxin is ingested without inactivation by cooking. EMQ keywords: child eating honey, student eating beans from a dented can
6
Q
How does botulism present?
A
Botulinum toxin blocks ACh release from peripheral nerves, causing a *descending* paralysis *The descending nature of paralysis differentiates from Guillain-Barré (differential diagnosis)
7
Q
What is the treatment for botulism?
A
Botulism antitoxin
8
Q
Clostridium perfringens: microscopic features
A
Gram +ve Rod-shaped Anaerobic Spore-forming
9
Q
How does Clostridium perfringens cause GI infection?
A
Main culprit is reheated meat The “superantigen” clostridium perfringens enterotoxin (CPE) binds directly to the TCR and MHC outside the peptide binding site. The subsequent massive cytokine production by CD4 causes systemic toxicity and suppression of adaptive response
10
Q
How does a clostridium perfringens infection present?
A
Acts on small bowel 8-16 hours incubation Watery diarrhoea Cramps Symptoms usually last 24 hours Can cause “gas gangrene” (gas producing muscle necrosis)
11
Q
Clostridium difficile: microscopic features
A
Gram +ve Spore-forming Anaerobic Motile Long, irregular (often drumstick- or spindle-shaped) cells with a bulge at their terminal ends
12
Q
How does C.diff cause GI infection?
A
Via 2 exotoxins, A and B
13
Q
What is the name for the bowel inflammation caused by Clostridium difficile?
A
Pseudomembranous colitis
14
Q
What iatrogenic factor can make a C.diff infection more likely?
A
Use of antibiotics, specifically cephalosporins and fluorquinolones
15
Q
How is Clostridium difficile treated?
A
Metronidazole or vancomycin PO
16
Q
2 aerobic organisms responsible for GI infections
A
Bacillus cereus (Gram +ve rod) Staphylococcus (Gram +ve)
17
Q
How is bacillus cereus commonly ingested?
A
Reheated rice. Spores germinate while rice is at room temperature, then may not be killed by reheating
18
Q
What is the incubation period for bacillus cereus?
A
Diarrhoeal form: 6-15 hours (related to raised cAMP level) Emetic form: 30 minutes to 6 hours (related to superantigen)
19
Q
How does bacillus cereus infection present?
A
Either sudden vomiting or watery, non-bloody diarrhoea
20
Q
What is the treatment for bacillus cereus?
A
None, self limiting
21
Q
Subspecies of staphylococcus responsible for GI infections
A
Staph aureus
22
Q
Staphylococcus microscopic features
A
Gram +ve Cocci Catalase +ve Coagulase +ve Appears in tetrads/clusters on Gram stain Beta haemolytic on blood agar
23
Q
How does Staph aureus cause GI infection? (mode of action)
A
Produces enterotoxin - exotoxin that acts as a superantigen, releasing IL1 and IL2 which stimulate diarrhoea
24
Q
What is the main virulence factor of Staph. aureus?
A
Protein A
25
How does Staph aureus infection present?
Prominent vomiting and watery, non-bloody diarrhoea
26
What is the treatment for Staph aureus?
None, self limiting
27
Lactose fermenting organism in Enterobacteriaceae family, responsible for GI infections
E(-scherichia) coli (Gram -ve, facultative anaerobe, oxidase -ve)
28
4 subspecies of E. coli
Enterotoxigenic E. coli (ETEC) Enteroinvasive E. coli (EIEC) Enterohemorrhagic E. coli (EHEC) Enteropathogenic E. coli (EPEC)
29
What does ETEC stand for?
Enterotoxigenic E. coli (Can also remember T=travellers)
30
How does ETEC cause travellers diarrhoea? (mode of action)
Produces 2 enterotoxins: heat-labile enterotoxin (LT) and heat-stable enterotoxin (ST) LT stimulates adenyl cyclase and cAMP ST stimulates guanylate cyclase
31
Which parts of the GI system do the ETEC entertoxins (LT and ST) act upon?
Jejunum and Ileum NOT the colon
32
What does EIEC stand for?
Enteroinvasive E. coli
33
What is the name of the disease caused by EIEC?
Invasive dysentery
34
What does EHEC stand for?
Enterohemorrhagic E. coli
35
What is the name of the toxin produced by EHEC?
Verotoxin
36
What does EPEC stand for?
Enteropathogenic E. coli (Can also remember P=paeds)
37
What paediatric disease is caused by EPEC?
Infantile diarrhoea
38
What is HUS and how is it caused?
Haemolytic-uremic syndrome Disease characterized by hemolytic anemia, acute kidney failure (uremia) and thrombocytopenia Usually caused by E. coli toxin O157:H7, a particularly infamous strain of the EHEC subspecies
39
What is the source of E. coli?
Human faeces - contaminated food/water
40
What is the treatment for E coli?
Usually self limiting and should avoid antibiotics. Occasionally ciprofloxacin may be rquired
41
3 non-lactose fermenting organisms in Enterobacteriaceae family, responsible for GI infections
Salmonella (Gram -ve rod) Shigella (Gram -ve, facultative anaerobe, non-spore-forming, non-motile, rods) Yersinia enterocolitica (Gram -ve, bacillus-shaped)
42
3 subspecies of salmonella
Typhi Paratyphi Enteritides
43
In relation to salmonella, what does Vi Ag stand for?
Vi (Virulence) antigen. Present on pathogenic strains of salmonella
44
What is the Kauffman–White classification?
A system that classifies the genus Salmonella into serotypes, based on their surface antigens
45
How many types of surface antigen can salmonella be classified by, and what are they?
3 types: O, H and Vi
46
Which gas is produced by salmonella and can therefore be used for detection?
Hydrogen sulphide (H2S)
47
Which compound should salmonella be grown on to encourage H2S production, and in which test is this used?
Ferrous sulfate Used in the triple sugar iron test
48
Name 3 media used for the selective growth of salmonella
Triple sugar iron (TSI) agar Xylose lysine deoxycholate (ZLD) agar Selenite F broth
49
Which 2 subspecies of salmonella cause enteric fever?
Typhi Paratyphi
50
Can enteric fever be carried by animals?
No, only human-human transmission (spread by eating or drinking food or water contaminated with the feces of an infected person)
51
What is enteric fever also known as?
Typhoid
52
Where in the body do salmonella typhi and paratyphi multiply?
Peryer's patches (aggregations of gut associated lymphoid tissue, found in the ileum)
53
What percentage of the population are salmonella carriers and whereabouts in the body is it carried?
3% Carried in the gallbladder where salmonella is able to form a robust biofilm on gallstones
54
Give 2 symptoms of enteric fever
Slow onset fever Constipation
55
Give 6 clinical signs of enteric fever
Slow onset fever Relative bradycardia Splenomegaly Rose spots Anaemia Leukopaenia
56
What is the treatment for enteric fever (and salmonella enteritides if required)?
Ceftriaxone or ciprofloxacin
57
How is salmonella enteritides transmitted?
Poorly cooked poultry, eggs and meat
58
Which parts of the body are typically infected by salmonella enteritides?
Small and large bowel (Bacteraemia infrequent)
59
What is the main symptom of salmonella enteritides?
Self limiting non-bloody diarrhoea
60
Which parts of the GI system are affected by shigella, and how are they affected?
Distal ileum and colon Mucosal inflammation
61
Give 3 symptoms of shigella
Fever Pain Bloody diarrhoea
62
What is the name of the toxin that causes the symptoms of shigella?
Shiga enterotoxin
63
What is the treatment for shigella
Usually self limiting Antibiotics should be avoided, but ciprofloxacin if required
64
What is the disease caused by shigella also known as?
Dysentery
65
What is the name of the disease caused by yersinia enterocolitica?
Yersiniosis
66
What inflammatory affects does yersiniosis have on the GI system?
Enterocolitis Mesenteric adenitis w/necrotising granulomas
67
Give 2 potential complications of yersiniosis
Reactive arthritis Erythema nodosum
68
How is yersinia enterocolitica transmitted?
Food contaminated with animal faeces (many animals are a natural reservoir/carrier)
69
What is the preferred temperature of yersinia enterocolitica?
4C (cold enrichment)
70
3 "miscellaneous" bacterial organisms responsible for GI infections
Vibriosis (Gram -ve, comma shaped, late lactose fermenters, oxidase +ve) Campylobacter (Gram -ve, curved/comma/S-shaped/spiral, microaerophilic, oxidase-positive, catalase-positive, nonfermentative) Listeria monocytogenes (Gram +ve, facultative anaerobe, V/L shaped, beta haemolytic, aesculin +ve, tumbling motility)
71
3 protozoan organisms responsible for GI infections
Entamoeba histolytica Giardia lamblia Cryptosporidium parvum
72
Can mycobacteria cause GI infections?
Yes, especially in HIV +ve pts eg Mycobacterium tuberculosis, mycobacterium avium complex
73
5 viruses responsible for GI infections
Rotavirus Adenovirus Norovirus Poliovirus Enteroviruses - coxsackie, ECHO/echovirus (Enteric Cytopathic Human Orphan)
74
3 subspecies of vibriosis
Cholera Parahaemolyticus Vulnificus
75
Subspecies of campylobacter
Jejuni
76
Vibrio cholerae - microscopic features
Gram-negative comma-shaped bacterium Lives in brackish or saltwater.
77
What is the name of the disease caused by pathogenic strains of Vibrio cholerae?
Cholera
78
What is the pathomnemonic presenting feature of cholera?
Rice-water stool
79
How is cholera transmitted?
Via human faeces - therefore often involves shellfish (because they feed on sewage)
80
Describe the process by which Vibrio cholerae acts on the gut to cause diarrhoea
- Increase in cAMP - Opens Cl channels at the apical membrane of enterocytes - Efflux of Cl ions to the lumen, causing loss of H2O and electrolytes - Result is massive diarrhoea but no inflammation of the gut
81
What is the treatment for cholera?
Supportive
82
Vibrio parahaemolyticus - microscopic features
Gram-negative Curved Rod-shaped Found in brackish saltwater
83
How is vibrio parahaemolyticus often transmitted to humans?
Ingestion of raw/undercooked seafood Common in Japan
84
How does vibrio parahaemolyticus present?
3 days of diarrhoea Often self-limiting
85
Vibrio vulnificus - microscopic features
Gram-negative Motile Curved Rod-shaped
86
Who is likely to catch Vibrio vulnificus?
Shellfish handlers
87
How does Vibrio vulnificus usually present?
Cellulitis
88
How can Vibrio vulnificus present in HIV patients?
Fatal septicaemia with D+V
89
What is the treatment of choice for both Vibrio parahaemolyticus and Vibrio vulnificus?
Doxycycline
90
Campylobacter jejuni - microscopic features
Gram-negative Oxidase +ve Curved Helical/S-shaped Non-spore forming Microaerophilic Sensitive to nalidixic acid
91
How is Campylobacter jejuni ingested?
Drinking unpasteurised milk and from certain undercooked foods eg poultry
92
What does the Campylobacter jejuni prodrome include?
Headache and fever
93
What are the main GI symptoms of Campylobacter jejuni?
Abdo cramps Bloody foul-smelling diarrhoea
94
Give 2 serious complications associated with Campylobacter jejuni
Guillain Barre Reiter's reactive arthritis
95
What is the treatment for Campylobacter jejuni?
Antibiotic use controversial - unclear whether benefit If required, erythromycin or ciprofloxacin in first 4-5 days
96
Listeria monocytogenes - microscopic features
Facultative anaerobe V or L shaped Beta haemolytic Aesculin +ve Tumbling motility
97
What is the name of the disease caused by Listeria monocytogenes?
Listeriosis
98
Give 5 symptoms of listeriosis
Watery diarrhoea Cramps Headache Fever Little vomiting
99
Name a serious complication of listeriosis
Meningitis
100
In which foods is Listeria monocytogenes commonly found?
Unpasteurised ready-to-eat food eg pate and soft cheese
101
Which 2 groups of people should especially avoid the foods at risk of Listeria monocytogenes infection?
Pregnant women and immunocompromised
102
What is the treatment for listeriosis?
Ampicillin (generally first choice) OR Ceftriaxone OR Cotrimoxazole
103
Entamoeba histolytica - microscopic features
Anaerobic Parasitic protozoan
104
Which group is particularly at risk of Entamoeba histolytica infection?
MSM (faeco-oral transmission)
105
What does "histolytica" literally mean?
Tissue destroyer
106
As well as GI infection, where else can Entamoeba histolytica cause abscesses?
Liver
107
Entamoeba histolytica can exist in 2 forms, what are they?
Trophozoite (active, motile stage) Cyst (non-motile)
108
Which form of Entamoeba histolytica exists outside the host and allows the parasite to be transmitted?
Cyst
109
Which form of Entamoeba histolytica only exists within the host or in fresh loose stool and causes the symptoms of infection?
Trophozoite stage
110
How many nuclei exist in the mature Entamoeba histolytica cyst?
4
111
What can be seen on histology in an Entamoeba histolytica infection?
A flask-shaped ulcer
112
List 5 symptoms of Entamoeba histolytica
Dysentery Wind Tenesmus Chronic weight loss RUQ pain (due to liver abscesses)
113
How is Entamoeba histolytica investigated/diagnosed?
Stool microscopy
114
What is the treatment for Entamoeba histolytica?
Metronidazole + paromycin (if luminal disease)
115
In EMQ land, which patient groups are more likely to be infected with the protozoan Giardia lamblia?
Travellers Hikers MSM Psychiatric inpatients (?because they eat poo?)
116
Fun fact: what is giardiasis also known as (in the US)?
Beaver fever
117
What are the two stages of the giardia life cycle?
Trophozoite (active form) and cyst (resistant, most likely to be the form that's ingested, causing infection)
118
Microscopic features of the giardia trophozoite
Anaerobic, flagellated and pear-shaped
119
How is giardia transmitted?
Commonly from drinking water contaminated with faeces containing cysts
120
How does giardiasis affect GI function?
Causes malabsorption of protein and fat This leads to foul smelling non-bloody diarrhoea
121
How is Giardia lamblia identified?
Stool microscopy ELISA String test (gelatin capsule with an attached thread is swallowed then withdrawn. If present, trophozites may be released)
122
Which part of the GI system does the protozoan Cryptosporidium parvum infect?
Jejunum
123
Who is most likely to be infected with Cryptosporidium parvum?
Immunocompromised Fun fact: Cryptosporidium parvum is the organism most commonly isolated in HIV-positive patients presenting with diarrhoea
124
What is the test for Cryptosporidium parvum?
Modified Kinyoun acid fast stain (other stains also used) Oocytes can then be seen on microscopy of the stool
125
What is the name of the disease caused by Cryptosporidium parvum infection?
Cryptosporidiosis
126
What is the treatment for cryptosporidiosis?
Paromycin OR Nitazoxanide (in children)
127
Which 2 viruses cause secretory diarrhoea in children?
Rotavirus Adenovirus
128
Which strains of adenovirus cause non-bloody diarrhoea
Types 40 and 41
129
What is the difference between secretory and inflammatory diarrhoea?
Secretory - no white cells in stool sample Inflammatory - Neutrophils in sample
130
List 4 bacteria that cause \*secretory\* diarrhoea
Vibrio cholerae Enterotoxigenic E. coli (ETEC) Enterohemorrhagic E. coli (EHEC) Enteropathogenic E. coli (EPEC)
131
List 4 bacteria that cause \*inflammatory\* diarrhoea
Campylobacter jejuni Enteroinvasive E. coli (EIEC) Non typhoidal salmonella serotypes Shigella species
