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Path - Microbiology > GI Infection > Flashcards

GI Infection Flashcards

1
Q

list some reportable GI infections?

A

Campylobacter, Salmonella, Shigella, E.Coli 0157, Listeria, Norovirus

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2
Q

patient with gastroenteritis. No/ low fever . No WCC in stool. what are the possible organisms?

name this type of diarrhoea?

A

secretory diarrhoea

Virbio cholera
ETEC
EPEC + EHEC

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3
Q

patient with gastroenteritis. Fever . WCC in stool - neutrophils. what are the possible organisms?

name this type of diarrhoea?

A

campylobacter
shigella

non-typhoid salmonella
EIEC

Inflammatory diarrhoea

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4
Q

patient with Fever . WCC in stool - mononuclear cells. what are the possible organisms?

name this?

A

Enteric fever

salmonella para/typhi
yersinia spp
brucella spp

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5
Q

list these in order of incubation period from longest to shortest;

E.Coli 0157
Campylobacter
Bacillus cereus
Shigella
Staph aureus
A 
Bacillus cereus
Staph aureus
Shigella
E.Coli 0157
Campylobacter
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6
Q

which organism produces verotoxin?

A

E.Coli 0157

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7
Q

which organism produces Heat stable emetic toxin?

A

Bacillus cereus

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8
Q

which organism produces Preformed toxin

enterotoxin, an exotoxin that can act as a superantigen in the GI tract ?

A

staph aureus

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9
Q

How do organisms causing secretory diarrhoea cause disease?

A

produce toxins

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10
Q

the cholera toxin induced efflux of which ion into lumen causing loss of H2O and electrolytes?

A

chloride

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11
Q

what does the cholera toxin bing to?

A

GM1 peptide binding site on cell membrane

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12
Q

where do super antigens bind?

A

Superantigens bind directly to
T-cell receptors and MHC molecules;

outside the peptide binding site

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13
Q

what reactions do superantigens induce after binding

A

> > massive cytokine production by CD4 cells ie systemic toxicity and suppression of adaptive response

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14
Q

name a bacterial superantigen?

A

tsst1

Toxic shock syndrome toxin-1

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15
Q

why do the host responses in Inflammatory (exudative ) diarrhoea lead to septic shock?

A

detection of LPS by Monocytes expressing TLR4

release of IFN-y, TNF leads to septics shock

concomitant neutrophilia

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16
Q

which organism appears in tetrads, clusters on Gram stain?

A

staph aureus

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17
Q

which organism produces Yellow colonies on blood agar?

A

staph aureus

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18
Q

staph enterotoxin leads to the release of which cytokines?

A

releasing IL1 and IL2

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19
Q

why is reheating rice not useful?

A

the emetic toxin released by bacillus cereus is heat stable

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20
Q

name 2 types of clostridia and their resulting infection and source?

A

Clostridium botulinum : botulism
Source : canned or vacuum packed food (honey / infants)

Clostridium pefringens : food poisoning
Source : reheated food (meat)

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21
Q

Clostridium pefringens is normal flora where?

where does it have an effect?

A

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

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22
Q

what is the MOA of botulism toxin?

A

Blocks Ach release from peripheral nerve synapses

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23
Q

which Abx are most implicated in c diff colitis?

A

cephalosporins - eg ceftriaxone
ciprofloxacin
clindamycin

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24
Q

Rx C diff colitis?

A

(PO) metronidazole OR

vancomycin

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25
what is an aesculin test?
The bile aesculin agar is streaked and incubated at 37 °C (99 °F) for 24 hours.
26
what indicates a positive aesculin test?
The presence of a dark brown or black halo indicates that the test is positive. positive cultures produce blackening agar
27
the following is classic of which orgnaism; ß haemolytic, aesculin positive with tumbling motility
Listeria monocytogenes
28
source of Listeria monocytogenes?
refrigerated food (“cold enhancement”),i.e. unpasteurised dairy, vegetables It grows at 4 degrees C
29
rx for listeria?
Ampicillin
30
which go infection is common in pregnancy?
listeria
31
define 'oxidase negative'
the oxidase negative result just means that these organisms do not have the cytochrome c oxidase that oxidizes the test reagent.
32
Which part of the GI tract do e.coli enterotoxins target?
Jejunum Ileum NOT colon
33
Heat Stable e.coli enterotoxins stimulates which enzyme ?
guanylate cyclase
34
Heat labile enterotoxins stimulates ?
adenyl cyclase and cAMP
35
which e.coli is the main cause of traveller’s diarrhoea?
ETEC ; Enterotoxigenic Escherichia coli
36
what is dysentry?
Dysentery is an intestinal inflammation, primarily of the colon. It can lead to mild or severe stomach cramps and severe diarrhea with mucus or blood in the feces.
37
which e.coli is the main cause of dysentry?
EIEC Enteroinvasive Escherichia coli
38
Rx for e.coli?
AVOID Abx
39
which is a human pathogen responsible for outbreaks of bloody diarrhea and hemolytic uremic syndrome (HUS) worldwide?
O157:H7 EHEC
40
Salmonellae are grown on which type of agar?
TRIPLE SUGAR IRON AGAR - TSI agar XLD agar enriched with selenite F broth
41
list 3 salmonella antigens?
cell wall O (groups A-I) - flagellar H - capsular Vi (virulence, antiphagocytic)
42
what is the difference in transmission between S.enteritidis and S.typhi ?
s. typhi - only get from humans | s. enteritis - from meat
43
which organism multiplies in Payer’s patches?
S.typhi
44
you will get stool positive with which salmonella?
S. enteritidis
45
pt presents from se Asia with hx of ; ``` Slow onset fever and constipation, splenomegaly, anaemia, leucopaenia, bradycardia, haemorrhage and perforation ``` diagnosis and rx?
diagnosis; typhoid fever - constipaition! rx - ceftriaxone
46
what is the most effective enteric pathogen ? WHY?
SHIGELLAE low ID 50 - median infectious dose
47
what is the MOST common cause of dysentry?
shigella
48
how does shigella cause dysentry? mention; region of GI tract impacted name of toxin
By invading cells of mucosa of DISTAL ileum and COLON | -producing enterotoxin (Shiga toxin)
49
rx for shigella?
Avoid antibiotics
50
Curved, comma shaped, late lactose fermenters, oxidase positive organisms are which?
v. cholerae
51
which v cholera serogroup cause epidemics?
O1 GROUP
52
list 3 serotypes in the 01 serogroup of v cholerae
Ogawa, Inaba, Hikojima
53
rice water stool) without inflammatory cells is from which infection?
cholera
54
cellulitis in shellfish handlers is caused by\?
Vibrio vulnificus
55
rx for vibrio; 1. cholerae ; 2. parahaemolyticus ; 3. vulnificus ; ?
1. cholerae ; treat losses i.e. fluids 2. parahaemolyticus ; self limiting 3. vulnificus ; doxycycline
56
campylobacter can have which shape?
Curved, comma or S shaped
57
rx campylobacter?
Only treat if immunocompromised (macrolide)
58
pt presents with foul smelling diarrhoea, bloody stool, fever and severe abdo pain condition?
campylobacter
59
possible consequences of campylobacter infection?
Guillaine barre syndrome, reactive arthritis, Reiter’s
60
which go infection can cause mesenteric adenitis?
Yersinia enterocolitica
61
UPon MCS, you see 4 nuclei. this is suggestive of?
Entamoeba histolytica
62
what colonizes the cecum, colon causing a “flask shaped” ulcer
Entamoeba histolytica
63
patient presents with dysentery,flatulence, tenesmus -chronic : wt loss,+/- diarrhoea -liver abscess dx?
Entamoeba histolytica
64
ivx for Entamoeba histolytica?
stool micro (wet mount, iodine and trichrome ) serology if invasive
65
which trophozoite is “pear shaped” 2 nuclei | 4 flagellas and a suction disk
Giardia lamblia
66
which trophozoite cause malabsorption of protein and fat
Giardia lamblia
67
list ddx for; 1. foul smelling, bloody stool, fever 2. foul smelling, non-bloody stool, no fever
1. campylobacter | 2. giardiasis
68
ivx for giardiasis?
stool micro, ELISA, “string test” - only if other tests can't detect giardia ; examined under microscope for parasites
69
rx giardia?
metronidazole
70
diagnostic test for Cryptosporidium parvum?
Oocysts seen in stool by | modified Kinyoun acid fast stain
71
what is the most predominant norovirus strain?
GII.4 currently predominant strain
72
Exposure to natural infection twice confers lifelong immunity to which pathogen?
rotavirus
73
which pathogen causes non bloody diarrhoea in those <2yrs of age?
adenovirus types 40,41
74
which go infections can you get vaccines for?
Cholera - inactivated Campylobacter Salmonella typhi Rotavirus
75
when are rotavirus vaccines given?
6-12 weeks

Path - Microbiology (27 decks)

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