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Path - Microbiology > GI Infection > Flashcards

GI Infection Flashcards

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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
Q

what is an aesculin test?

A

The bile aesculin agar is streaked and incubated at 37 °C (99 °F) for 24 hours.

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26
Q

what indicates a positive aesculin test?

A

The presence of a dark brown or black halo indicates that the test is positive.

positive cultures produce blackening agar

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27
Q

the following is classic of which orgnaism;

ß haemolytic, aesculin positive with tumbling motility

A

Listeria monocytogenes

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28
Q

source of Listeria monocytogenes?

A

refrigerated food (“cold enhancement”),i.e. unpasteurised dairy, vegetables

It grows at 4 degrees C

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29
Q

rx for listeria?

A

Ampicillin

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30
Q

which go infection is common in pregnancy?

A

listeria

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31
Q

define ‘oxidase negative’

A

the oxidase negative result just means that these organisms do not have the cytochrome c oxidase that oxidizes the test reagent.

32
Q

Which part of the GI tract do e.coli enterotoxins target?

A

Jejunum
Ileum

NOT colon

33
Q

Heat Stable e.coli enterotoxins stimulates which enzyme ?

A

guanylate cyclase

34
Q

Heat labile enterotoxins stimulates ?

A

adenyl cyclase and cAMP

35
Q

which e.coli is the main cause of traveller’s diarrhoea?

A

ETEC ; Enterotoxigenic Escherichia coli

36
Q

what is dysentry?

A

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
Q

which e.coli is the main cause of dysentry?

A

EIEC

Enteroinvasive Escherichia coli

38
Q

Rx for e.coli?

A

AVOID Abx

39
Q

which is a human pathogen responsible for outbreaks of bloody diarrhea and hemolytic uremic syndrome (HUS) worldwide?

A

O157:H7 EHEC

40
Q

Salmonellae are grown on which type of agar?

A

TRIPLE SUGAR IRON AGAR - TSI agar

XLD agar enriched with selenite F broth

41
Q

list 3 salmonella antigens?

A

cell wall O (groups A-I)

	- flagellar H
	- capsular Vi (virulence, 	antiphagocytic)
42
Q

what is the difference in transmission between S.enteritidis and S.typhi ?

A

s. typhi - only get from humans

s. enteritis - from meat

43
Q

which organism multiplies in Payer’s patches?

A

S.typhi

44
Q

you will get stool positive with which salmonella?

A

S. enteritidis

45
Q

pt presents from se Asia with hx of ;

Slow onset fever and constipation,
splenomegaly, 
anaemia, leucopaenia,
bradycardia, haemorrhage and
perforation

diagnosis and rx?

A

diagnosis; typhoid fever
- constipaition!

rx - ceftriaxone

46
Q

what is the most effective enteric pathogen ?

WHY?

A

SHIGELLAE

low ID 50 - median infectious dose

47
Q

what is the MOST common cause of dysentry?

A

shigella

48
Q

how does shigella cause dysentry?

mention;
region of GI tract impacted
name of toxin

A

By invading cells of mucosa of DISTAL ileum and COLON

-producing enterotoxin (Shiga toxin)

49
Q

rx for shigella?

A

Avoid antibiotics

50
Q

Curved, comma shaped, late lactose fermenters, oxidase positive organisms are which?

A

v. cholerae

51
Q

which v cholera serogroup cause epidemics?

A

O1 GROUP

52
Q

list 3 serotypes in the 01 serogroup of v cholerae

A

Ogawa, Inaba, Hikojima

53
Q

rice water stool) without inflammatory cells is from which infection?

A

cholera

54
Q

cellulitis in shellfish handlers is caused by\?

A

Vibrio vulnificus

55
Q

rx for vibrio;

  1. cholerae ;
  2. parahaemolyticus ;
  3. vulnificus ;

?

A
  1. cholerae ; treat losses i.e. fluids
  2. parahaemolyticus ; self limiting
  3. vulnificus ; doxycycline
56
Q

campylobacter can have which shape?

A

Curved, comma or S shaped

57
Q

rx campylobacter?

A

Only treat if immunocompromised (macrolide)

58
Q

pt presents with foul smelling diarrhoea, bloody stool, fever and severe abdo pain

condition?

A

campylobacter

59
Q

possible consequences of campylobacter infection?

A

Guillaine barre syndrome, reactive arthritis, Reiter’s

60
Q

which go infection can cause mesenteric adenitis?

A

Yersinia enterocolitica

61
Q

UPon MCS, you see 4 nuclei. this is suggestive of?

A

Entamoeba histolytica

62
Q

what colonizes the cecum, colon causing a “flask shaped” ulcer

A

Entamoeba histolytica

63
Q

patient presents with dysentery,flatulence,
tenesmus
-chronic : wt loss,+/- diarrhoea
-liver abscess

dx?

A

Entamoeba histolytica

64
Q

ivx for Entamoeba histolytica?

A

stool micro (wet mount, iodine and trichrome )

serology if invasive

65
Q

which trophozoite is “pear shaped” 2 nuclei

4 flagellas and a suction disk

A

Giardia lamblia

66
Q

which trophozoite cause malabsorption of protein and fat

A

Giardia lamblia

67
Q

list ddx for;

  1. foul smelling, bloody stool, fever
  2. foul smelling, non-bloody stool, no fever
A
  1. campylobacter

2. giardiasis

68
Q

ivx for giardiasis?

A

stool micro,
ELISA,
“string test” - only if other tests can’t detect giardia ; examined under microscope for parasites

69
Q

rx giardia?

A

metronidazole

70
Q

diagnostic test for Cryptosporidium parvum?

A

Oocysts seen in stool by

modified Kinyoun acid fast stain

71
Q

what is the most predominant norovirus strain?

A

GII.4 currently predominant strain

72
Q

Exposure to natural infection twice confers lifelong immunity to which pathogen?

A

rotavirus

73
Q

which pathogen causes non bloody diarrhoea in those <2yrs of age?

A

adenovirus types 40,41

74
Q

which go infections can you get vaccines for?

A

Cholera - inactivated

Campylobacter

Salmonella typhi

Rotavirus

75
Q

when are rotavirus vaccines given?

A

6-12 weeks

Path - Microbiology (27 decks)

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