Intro Flashcards

1
Q

define pathogen

A

Organism that causes or is capable of causing disease

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2
Q

define commensal

A

Organism which colonises the host but causes no disease in normal circumstances

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3
Q

define opportunist pathogen

A

Microbe that only causes disease if host defences are compromised

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4
Q

define virulence/ pathogenicity

A

The degree to which a given organism is pathogenic

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5
Q

define asympomatic carriage

A

Disease is carried harmlessly at a tissue site

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6
Q

what is bacterial nomenclature

A

genus then species

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7
Q

what is round bacteria called

A

coccus

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8
Q

what is rod like bacteria called

A

bacillus

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9
Q

two main groups of bacteria

A

gram positive
gram negative

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10
Q

gram positive colour?

A

purple

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11
Q

gram negative colour?

A

pink

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12
Q

what is diplococcus

A

two cocci that grow together

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13
Q

structure of basic bacteria cell

A

cell envelope- phsopholipid membrane w layer of peptidoglycan
capusle
inner membrane
outer membrane

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14
Q

purpose of flagella/ pilli

A

to stick to host cells
swim / movement

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15
Q

what bacteria does not show up with GRAM staining and what would you use isntead

A

TB
Ziehl- neelsen stain

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16
Q

structure of gram + bacteria

A

Has a capsule with
Thick peptidoglycan linked to phospholipid membrane

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17
Q

structure of gram - bacteria

A

two phospholipid membrane
perisplamsic space- thin phosphilipid layer
endotoxin-

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18
Q

what is endotoxin

A

Component of the outer membrane of bacteria, eg lipopolysaccharide in Gram negative bacteria

19
Q

what is exotoxin

A

Secreted proteins of Gram positive and Gram negative bacteria

20
Q

characteristics of exotoxin

A

protein
specific
labile to heat
strong antigenicity
produced by gram + & -

21
Q

methods of gene transfer

A

transformation
transduction
conjugation

22
Q

what does gram staining do

A

seperates bacteria into gram positive and negative depending on the thickness of peptidoglycan

23
Q

what structure does staph usually appear

A

clusters

24
Q

what structure does strep usually appear in

A

chains

25
Q

what does the catalase test show

A

differentiates between staphylcoccus and streptococcus genus

26
Q

what would catalase + show

A

staph

27
Q

what would catalase -ve show

A

strep

28
Q

3 types of haemolysis and what they show

A

alpha- partial
beta- complete
gamma- none

29
Q

what does mackonkey agar show

A

bacteria that can digest lactose

30
Q

examples of bacteria that are non- fermenters gram -ve

A

salmonella, shigella, pseudomonas aurerginosa

31
Q

optochin -ve and +ve would show

A

-ve = strep viridans
+ve= strep pneumonia

32
Q

which strep is susceptible to optochin

A

s pneumoniae

33
Q

structure of c difficile

A

gram +ve bacilli

34
Q

what does the coagulase test do

A

differentiates staph aureus which produces the enzyme coagulase from S epidermis and S saprophyticus which do not produce coagulase

35
Q

what would coagulase +ve show

A

staph aureus

36
Q

what would coagulase -ve indicate

A

staph epidermis or sapro

37
Q

method for the coagulase test

A

apply rabbit plasma to a small sample or pure colony, observe for fibrin clot clumps

38
Q

what does the lancefield grouping rely on ?

A

relies on the different group specific carbohydrates antigen present on the bacterial cell wall

39
Q

what group in the lancefield classification would s.pyogenes be

A

GROUP A

40
Q

what agar would you use for streptocuccus

A

blood

41
Q

what agar would you use for fastidious neisseria

A

chocolate

42
Q

what agar would you use for differentiating lactose status

A

MacConkey

43
Q

what agar would you use to isolate salmonella and shigella

A

XLD AGAR- xylose lysine deoxycholate agar

44
Q

What diseases does s pyogenes cause

A

Tonsillitis
Pharyngitis
Impetigo
Cellulose of the foot