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243: Medical Microbiology > Things I Struggle With > Flashcards

Things I Struggle With Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
1
Q

How can we detect growth in lactose medium

Note: not macconkey that’s somet else

A

pH changes and oxygen is produced

Solution turns from red -> yellow

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2
Q

What infection is known to produce insoluble hydrogen sulphide

A

Salmonella

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3
Q

What do bile salts in macconkey agar prevent the growth of

A

Gram positives

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4
Q

What type of bacteria contain endospores

A

Gram positives

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5
Q

What are the 3 components of a gram-negative cell wall

A

Lipopolysaccharide
Porin
Periplasm

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6
Q

What is a heterotroph

A

A bacteria that fix their carbon using sugars

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7
Q

What are autotrophs

A

Bacteria that fix inorganic carbon

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8
Q

Give an example of a autotroph

A

Guild F = green & purple sulphur bacteria

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9
Q

Give an example of a heterotroph

A

Guild B = gliding bacteria

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10
Q

Where do organotrophs source electrons

A

Organic matter

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11
Q

Where do lithotrophs source electrons

A

Inorganic compounds

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12
Q

What are guild D bacteria used for

A

Used to leach materials & oxidise iron

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13
Q

What are pathobionts

A

Normal flora that become pathogenic

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14
Q

Draw the difference between laminar flow and turbulent flow

A

Straight lines = laminar Flor

Turbulent flow = lots of mixing, no discrete lines

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15
Q

What provides structure and integrity to the biofilm matrix

A

Exopolymeric substances

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16
Q

What are 3 components of exopolymeric substances

A

Lipids
Polysaccharides
Proteins
Extracellular DNA

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17
Q

Name 3 examples of biofilms

A

Skin
Teeth (plaque)
Mucosa (respiratory tract)

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18
Q

What sloughs cells from a biofilm

A

Phagocytes (amoeba) grazing on the surface

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19
Q

What does lux R and lux I do

A

Lux R = recruits rna polymerase to transcribe the operon when conc of autoinducer is high

Lux I = produces autoinducer

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20
Q

What do the police of Neisseria gonorrhoea bind to

A

Galactose

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21
Q

What bacteria uses collagenase

A

Clostridium

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22
Q

Give an example of a cytolytic toxin

A

Staph aureus alpha toxin

- inserts into host membrane forming a pore which cell contents flow out of

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23
Q

Give an example of a A-B toxin

A

Clostridium botulinum

- binds to pre synaptic membrane preventing ach release

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24
Q

What do B subunits bind to in A-B toxin

A

Glycans in cell wall

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25
Q

Give an example of a superantigen

A

Staph aureus toxic shock syndrome toxin 1

- secretion of fluids and electrolytes

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26
Q

How do superantigens work

A

Stimulate immune cells to produce cytokines = severe inflammation, shock and organ failure

27
Q

How does the gastroenteritis toxin work

A

Toxin is endocytosed into the cell where it is transported to the ER via phagosome

Causes CAMP increase and electrolyte imbalance

= water leaves causing dehydration & diarrhoea

28
Q

Give 3 examples of PAMPs

A

Adhesions
O antigens of LPS
Peptidoglycan

29
Q

What type of receptors do amoeba have

- how do they work?

A

Pattern recognition receptors

- binding directly induces phagocytosis 

30
Q

How do bacteria avoid ingestion;

A

Altering PAMPS

Offensive & defensive virulence factors

31
Q

How do bacteria avoid digestion

A
  • Leave food vacuole and divide in cytoplasm
  • Produce chaperonins that re-fold incorrectly folded polypeptides
  • Produce protease that disrupts host superoxide anion generation
32
Q

What do aminoglycosides target

A

Mainly gram negative bacteria

33
Q

Name two ribosomal protection proteins

A

Tet M

Tet O

34
Q

How do ribosomal protection proteins work

A

Find to the ribosome changing its confirmation, prevents tetracycline from binding without stopping synthesis

35
Q

What does Tet X gene do

A

Produces a protein that chemically modifies tetra cycling in the presence of oxygen and NADPH

36
Q

Name three mechanisms of tetracycline resistance

A

Tetracycline efflux
Ribosomal protection proteins
Tetracycline inactivation

37
Q

What are the two types of resistance to antibiotics

A

Intrinsic resistance which is naturally occurring

Acquired resistance e.g. genetic transfer

38
Q

How do bacteria biofilm resist antibiotics

A

Covered in polymeric substance that prevents antibiotic penetration

39
Q

How can a phage induce antibiotic resistance in a population

A

Bacteriophage infect bacterial cells and break down the host chromosome

Sometimes host DNA is repackaged into the phage genome

Phage is released and reinfects another cell where recombination occurs (lysogenic life cycle)

40
Q

What do beta lactams bind to which weakens the cell wall

A

Bind to penicillin binding proteins = weakening cell wall

41
Q

What gene confers resistance in MRSA

A

Mec A

42
Q

What is the mortality rate for postsplenectomy sepsis

A

50-70%

43
Q

How can we prevent aspergillus

A

Filter hospital air

Give respiratory protection to vulnerable patients

44
Q

How can we prevent legionella

A

Prohibit showers = sponge baths
Monitor the water supply
Surveillance on cases

45
Q

Why does diabetes affect necrotising fasciitis

A

Reduce blood flow to extremities means it’s harder to mobilise the immune system

46
Q

How many organisms are Manuka honey effective against

A

80

47
Q

Describe the new properties of teixobactin 

A

New antibiotic that treats gram-positive infections (via disturbing cell wall synthesis)

Effective at low-dose, not yet approved

48
Q

Describe the life cycle of leishmaniasis

A

Sandfly ejects infected stage
Promastigotes phagocytosed by macrophage
Transform into amastigotes = multiply
Infected macrophages are consumed in blood meal

49
Q

What test can be used to diagnose L. Donovani & L. Infantum

A

Immunochromatographic strip
= nitrocellulose with antigens that detects any antibodies

X - lots of false positives

50
Q

What happens to ingested giardia cysts

A

Excyststion in small intestine
= trophozoites which multiply

Encystation towards the colon
= cysts pass in faeces

51
Q

Life cycle of cryptosporidium

A

Ingest oocyst & excystation
Sporozoites parasitise epithelial cells of gut
2 types of oocysts produced = thick walled excreted from host

52
Q

Gold standard for detecting cryptosporidium

A

Direct fluorescence assay

Antigen & conjugated antibody

53
Q

What are subunits that make a capsid called

A

Capsomers

54
Q

Describe the replication cycle of a virus

A

Adhesion, entry and uncoating

Viruses with ssRNA form ds intermediate using RNA polymerase = allows mRNA to be formed

Translation occurs using host machinery

Assembly of new virus in the nucleus

Pinches off by budding

55
Q

What did Fraenkel find

A

RNA is the genetic material of TMV

56
Q

Average latent period for covid-19

A

5.6 days

57
Q

Describe measles

A

R0 = 15

Respiratory disease that can spread to the rest of the body

58
Q

Describe the stages of HIV infection

A

Flu like symptoms

CD4 T cells decline and immune system declines anti-HIV antibodies rise

anti-HIV can no longer be produced virus becomes prevalent and can survive outside of T cells

Virus reproduces uncontrollably = fatal

59
Q

How does Dicer work

A

Double stranded RNA genomes are recognised by DICER proteins

These are cleaved into pieces and catalysed further by RISC or Argonaut

60
Q

How do PAMPs work

A

Detect infection and recruit adaptor molecules

Phosphorylation of Irf3 forms a dimer that binds to the promoter region and causes gene expression

Process encodes interferons

61
Q

What do interferons do

A

Bind to receptors in adjacent cells activating STAT pathway

Priming the cells to fight viruses that have not yet arrived

62
Q

What produces interleukin 4, what does it do

A

T-helper type 1 cells

Converts naive t helper cells into t helper type 2 cells
Negative inhibition= prevents cytokine storm

63
Q

Since 2000 how many cases of polio in 21 cases

A

760

Most being vaccine derived polio

64
Q

What does acyclovir do

A

Inhibits viral DNA synthesis

243: Medical Microbiology (27 decks)

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