gi pathogens Flashcards

1
Q

what is colonisation ?

A

the establishment of microorganism on or within a host

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2
Q

what is a pathogen ?

A

any organism that has the potential to cause diseases

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3
Q

how can we diagnose infection via microbiology ?

A
blood
stool
urine 
wound 
tissue cultures
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4
Q

describe the process in which pathogens invade

A
  • invasion by pathogen
  • incubation period (pathogen replicates in host)
  • which leads to subclinical infection / the prodromal period ( early signs and symptoms )
  • illness period ( clinical signs and symptoms )
  • convalescent period ( reduction of symptoms )
  • host may become a chronic carrier of infectious agent
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5
Q

what do phagocytes target ?

A

bacteria and fungi

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6
Q

what do T lymphocytes target ?

A

viruses, fungi, protozoa

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7
Q

what do antibodies and B lymphocytes target ?

A

viruses

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8
Q

what do eosinophils target ?

A

fungi protozoa worms

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9
Q

what do mast cells target ?

A

worms

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10
Q

what does the complement system target ?

A

bacteria

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11
Q

what do the macroscopic investigations include ?

A

colony size
shape
pattern
haemolysis

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12
Q

what do the microscopic investigations include ?

A

gram stain
organism shape
antigenic properties

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13
Q

why do gram + bacteria stain darker (purple/blue) ?

A

they have a much thicker peptidoglycan layer and so traps the crystal violet better

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14
Q

what are the main differences between gram + and - ?

A

gram + bacteria have a thick peptidoglycan layer, have no outer membrane and stain purple

gram - bacteria have a thin peptidoglycan layer, have an outer membrane and stain pink

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15
Q

what are the lactose fermenting gram - rods (enterobacteriacea) ?

*most common for causing infection in the gi tract

A

e. coli
citrobacter spp
klebsiella spp
enterobacter

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16
Q

what are the lactose non-fermenting gram - rods ?

A
morganella 
proteus 
providencia 
salmonella 
shigella
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17
Q

what are the gram - anaerobic bacilli ?

A

bacteroides
prevotella
porphyromonas
fusobacterium

18
Q

what are the gram - anaerobic cocci ?

A

veillonella

19
Q

what are the microbiological tests for enterobacteriaceae ?

A
  • ferment glucose
  • oxidase
  • blood agar
  • MacConkey agar (lactose fermenters turn it pink)
  • CLED agar (Cysteine Lactose Electrolyte Deficient)
  • chromogenic agar
20
Q

characteristics of enterobacteriacea ?

A
gram -
non spore forming 
grow on a variety of media
ferment sugars (- produce lactase and lack oxidase) 
mostly facultative anaerobes 
increasing resistance !
21
Q

how do enterobacteriacea cause disease ?

A

motility - flagella are motile (shigella and klebsiella are not motile though)
colonisation factors (fimbriae can tightly bind)
endotoxin (part of the outer membrane of the LPPs)
enterotoxin

22
Q

what is MALDI-TOF mass spectrometry ?

A
  • it analyses the protein composition of bacterial cell wall
  • uses a database
  • discriminates between highly genetically similar organisms with identical 16s rRNA
  • pathogenic vs non-pathogenic E.coli may be difficult to differentiate
  • some species are difficult for MALDI-TOF to differentiate between ie e.coli and salmonella
23
Q

what is 16s rRNA ?

A

another molecular method to determine bacteria

  • whole genome sequencing
  • pulsed field gel electrophoresis
  • multilocus sequence typing (MLST)
  • multiple locus variable number tandem
24
Q

what is serotyping ?

A

determining the immunoreactivity of various antigens

25
Q

what types of bacteria can penicillin kill ?

A

enterococcus faecalis
streptococcus
clostridium
meningitis

26
Q

what can amoxicillin kill ?

A

e. faecalis
strept.
clostridium
haemophilus influenza

27
Q

what can co-amoxiclav kill ?

A

much wider range…

MSSA
enterococcus (both)
strept.
clostridium.
bacteriodes 
meningitis 
h. influenza 
moraxella 
e.coli
klebsiella
proteus mirabilis
28
Q

flucloxacillin ?

A

s. epidermis
staphy.
strept.

29
Q

clindamycin ?

A

MRSA
MSSA
strept. / clostridium / bactericiodes (anaerobes)

30
Q

azithromycin / erythromycin ?

A

legionella

31
Q

rifampicin ?

A
MRSA 
s.epidermis 
staph. 
h. influenza 
moraxella
32
Q

fusidic acid ?

A
MRSA
MSSA
staph/s.epidermis 
e.faecalis 
meningitis
33
Q

metronidazole ?

A

clostridium

bacteriodes

34
Q

vancomycin / teicoplanin ?

A

gram + cocci

MRSA MSSA staph/s.epidermis clostridium enterococcus (both)

35
Q

co-trimoxazole ?

A
MRSA MSSA staph/s.epidermis 
e.faecalis 
strept. 
clostridium 
bacteriodes 
meningitis 
influenza 
moraxella 
e.coli 
klebsiella
36
Q

gentamicin ?

A
MRSA
MSSA
enterococcus 
e.coli
klebsiella
proteus mirabilis 
pseudomonas
37
Q

ceftriaxone ?

A
MSSA 
strept. 
clostridium 
meningitis 
haemophilus influenza 
moraxella 
e.coli
klebsiella
38
Q

what is the normal flora of the mouth ?

A
strep. viridans
neisseria sp. 
anaerobes 
candida spp
staphylococci
39
Q

normal flora of the stomach / duodenum ?

A

low pH

usually sterile

40
Q

normal flora of the intestines ?

A

coliforms, anaerobes

and enterococcus faecalis in the colon