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Year 1: Principles > Microbiology > Flashcards

Microbiology Flashcards

1
Q

difference between sterilisation and disinfection?

A

disinfection is reducing or eliminating harmful microorganisms to levels considered safe (some bacteria, spores and viruses remain), whilst sterilisation is getting rid of all microorganisms (even spores)

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2
Q

describe fungi

A

higher plant like organisms

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3
Q

describe bacteria

A

small, single celled prokaryotes

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4
Q

describe viruses

A

v small obligate parasites, non-living

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5
Q

are the ribosomes different in prokaryotes and eukaryotes?

A

yes

They are 70S in prokaryotes (e.g. bacteria) and 80S in eukaryotes e.g. humans

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6
Q

Gm+ve and Gm-ve bacteria both have peptidoglycan layer in their cell wall. What’s the difference?

A

Gm+ve have a thick multi layer and Gm-ve have a single layer

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7
Q

Which Gm bacteria contain lipopolysaccharide in their outer membrane?

A

Gm-ve
LPS are endotoxins, and are released on cell lysis. They can lead to disseminated intravascular coagulation and septic shock

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8
Q

Which Gm bacteria contain lipopolysaccharide in their outer membrane?

A

Gm-ve
LPS are endotoxins, and are released on cell lysis. They can lead to disseminated intravascular coagulation and septic shock

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9
Q

which type of prokaryote (psycrophiles/ thermophiles/ mesophiles) grows at body temperature?

A

mesophiles

psycrophiles grow at low temp, thermophiles grow at high temp

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10
Q

can strict anaerobes survive in the presence of O2?

A

no - they die

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11
Q

can facultative anaerobes grow in presence of O2?

A

yes, but they grow better with O2 - but can grow without O2

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12
Q

can aerotolerant anaerobes grow in presence of O2?

A

yes, they tolerate it

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13
Q

what are the 4 phases of the bacterial growth curve?

A
  • lag phase
  • exponential
  • stationary
  • decline
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14
Q

biofilm

A

microorganisms sticking to each other and the cells adhering to a surface e.g. catheter

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15
Q

what are some organisms that don’t gram stain well, and why don’t they?

A
  • mycobacterium TB (has a lipid rich/ waxy cell wall that doesn’t take up the stain)
  • treponema pallidum (spirochaete that causes syphilis, an STI)
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16
Q

selective media?

A

the presence of specific substances permits growth of one organism over another

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17
Q

differential media?

A

incorporates chemicals that give visible changes and allow identification

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18
Q

how can Streptococci be differentiated?

A

Which type of haemolysis occurs

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19
Q

example of a protozoan disease?

A

malaria

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20
Q

what shape are Gm-ve cocci?

A

diplococci
Relevant species are:
-Neisseria meningitides
-Neisseria gonorrhoeae

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21
Q

describe coliforms

A

Gm-ve bacilli that look like E coli on Gm film and when cultured on blood agar

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22
Q

What is the 1st line antibiotic for treatment of coliform infection?

A

gentamicin

23
Q

why do patients with coliform infection become v unwell quickly (hint: Gm-ve)

A

due to the endotoxin released when the bacteria die

24
Q

what do endotoxins (LPS) cause to happen in the body when they are released?

A
  • bind to macrophages, B cells and other cells that stimulate release of acute phase cytokines
  • cytokines travel to brain (anterior hypothalamus)
  • effects of sepsis
  • PG E released, increasing thermal set point
  • body shivers = fever
25
Q

what happens in sepsis?

A
  • small vessels become leaky and lose fluid into tissues
  • lower blood volume requires heart to work harder to maintain oxygenation
  • poor tissue perfusion means blood supply to less essential organs is shut down to try to maintain supply to brain
  • clotting system activated causing clots in tiny blood vessels - using up all clotting factors and increasing risk of haemorrhage
26
Q

5 ways infection can spread? (5 Is)

A 
inhalation
ingestion
inoculation
mother to Infant
intercourse
27
Q

which areas of the hand are most frequently missed during handwashing?

A

thumb and finger tips

28
Q

orange waste bags are for what waste?

A

clinical waste

29
Q

black bin bags are for what kind of waster?

A

domestic waste

30
Q

what are precautions against infection via droplet inhalation?

A

single room
gloves, apron, mask
eye protection
vaccination

31
Q

what are airborne microorganism precautions?

A

negative pressure room
gown, gloves, apron, eye protection, filter mask
vaccination

32
Q

disinfection methods?

A

cleaning - hot water and detergent, rinse and dry
heat
ultrasound
chemicals

33
Q

sterilisation methods?

A

heat (autoclave kills by coagulating and denaturing enzymes and proteins)
chemicals
radiation
filtration

34
Q

what are some antibiotic targets?

A 
cell wall
protein synthesis
bacterial DNA (replication)
DNA gyrases
metabolic pathways
35
Q

why don’t glycopeptides (e.g. vancomycin) work on Gm-ves?

A

they are too large to get across the outer membrane of Gm-ves

36
Q

what’s a common use for rifampicin?

A

in combination therapy for mycobacteria

37
Q

what are antibiotics that we try to avoid using? (hint: the 4 Cs)

A 
cephalosporins
co-amoxiclav
ciprofloxacin
clindamycin
(these are broad spectrum and are particularly associated with increased risk of Clostridium difficile infection)
38
Q

persistor cells are resistant to antimicrobials. True/ False?

A

False

They are TOLERANT (very slow growth, dormant)

39
Q

what are three ways in which bacteria can acquire new genes which may confer resistance?

A

transformation
transduction
conjugation

40
Q

what are the three mechanisms of resistance?

A

altered antibiotic binding site
destroy the antibiotic (e.g. B-lactamases)
increased efflux of antibiotic from bacteria cell (before it has time to act)

41
Q

what is ESBL (extended spectrum B-lactamase) resistant to?

A

all penicillins

extends to third generation cephalosporing and monobactams

42
Q

what are prion proteins?

A

infectious proteins that have no DNA or RNA
responsible for mad cow disease
cannot be reliably removed by sterilisation or disinfection - surgical instruments have to be destroyed after use

43
Q

why do some bacteria make us ill?

A

they produce toxins
exotoxins from mainly Gm+ves (produced inside cell and exported from it)
endotoxins from mainly Gm-ves (part of Gm-ve cell wall)
the toxins interact with cells of the immune system causing release of cytokines - leading to sepsis and septic shock

44
Q

what is serology?

A

detection of antibodies in blood

45
Q

how long does a TB culture take to come back?

A

4-12 weeks

46
Q

do viruses contain DNA/ RNA?

A

either one (never both)

47
Q

what does adenovirus infection usually infect?

A

respiratory system

48
Q

what does Herpes simplex virus usually infect?

A

a type can cause oral herpes (cold sores) and another type can also cause genital herpes

49
Q

what is the pathogenesis of viral infection?

A

cell death due to lysis or hijacking of cell machinery
cell death due to immune system (cytotoxic T cells)
causes cell proliferation (can lead to cancer)

50
Q

what are examples of virally induced cancer?

A

HPV - cervical cancer
Hep B and Hep C - hepatocellular cancer
Epstein Barr virus - lymphoma
Herpes type 8 - Kaposi’s sarcoma

51
Q

do Ig play a role in immunity against viruses?

A

yes

52
Q

what is chronic infection by viruses?

A

when the virus remains active for years (e.g. HIV, Hep C). These patients remain asymptomatic but infectious for decades before getting life threatening complciations

53
Q

how can viruses be detected?

A

PCR
antigen detection
mass spectrometry

Year 1: Principles (2 decks)

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