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My Principles > Microbiology > Flashcards

Microbiology Flashcards

1
Q

What does S. pyogenes cause?

A

haemolysis

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2
Q

What are the features of eukaryotes?

A
  • complex
  • multi-cellular
  • linear chromosomes with histones
  • introns
  • 80S ribosomes
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3
Q

What are the features of prokaryotes?

A
  • simple
  • single-celled
  • circular chromosome
  • 70S ribosomes
  • cell wall
  • rapid cell cycle
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4
Q

What is the structure of the cell wall in prokaryotes?

A
  • made of peptidoglycan or murein
  • rigid barrier
  • for gram +ve there is a multi-layer
  • for gram -ve there s an outer membrane, periplasm and thinner PG layer
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5
Q

What are the special features of the gram negative organisms?

A

many lipopolysaccharides (LPS) which have a structural role and role in antigens and bacterial toxins

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6
Q

What are the differing structures added on to gram positive or negative organisms?

A

gram +ve have fimbriae which are non-flagella protein appendages
gram -ve plus aren’t a motor and have piling repeat unit

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7
Q

What are the differences in ribosomes between eukaryotic and prokaryotic organisms?

A

70S in prokaryotes
80S in eukaryotes
these are very different so drugs can tailor their effect to the ribsome

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8
Q

What are the different factors needed for prokaryotic growth?

A
  • Food= C, O, H, salts, vitamins
  • Temperature (mesophiles work at body temperature)
  • [H+]
  • Osmotic protection
  • Oxygen
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9
Q

What are the phases of bacterial growth?

A
  • lag
  • exponential
  • stationary
  • decline
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10
Q

How can microorganisms be classified?

A
  • appearance
  • growth requirements
  • enzyme/metabolic tests
  • molecular tests
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11
Q

What structures can cocci form?

A

division in one plane to make chains

division in three planes to make clumps

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12
Q

What are curved rods always?

A

gram negative

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13
Q

What can spiral shaped bacteria be?

A
  • rigid spirillum

- flexible spirochaete

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14
Q

What colours do gram negative and positive stain?

A
  • gram negative stain pink with LPS on outer membrane

- gram positive stain purple with multi-layered peptidoglycan

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15
Q

What are obligate aerobes, obligate anaerobes and facultative aerobes?

A
  • obligate aerobes need oxygen
  • obligate anaerobes are killed by oxygen
  • facultative aerobes tolerate oxygen
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16
Q

What are selective and differential media?

A
  • selective permits growth of one organism over another

- differential allows adding of chemicals to produce changes that help with identification

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17
Q

What haemolysis does streptococcus give?

A
  • green alpha partial haemolysis
  • complet beta haemolysis
  • no gamma haemolysis
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18
Q

What makes up a microbiome?

A

endogenous and exogenous mircroorganisms

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19
Q

What is virulence?

A

the capacity of a microbe to cause damage to the host so its pathogenicity

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20
Q

What is commensal bacteria?

A

part of the normal flora, endogenous, mutualistic

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21
Q

What is an example of a protozoa and fungus?

A

malaria = protozoa

yeast and candida = fungus

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22
Q

What is an example of gram -ve cocci?

A

neisseria meningitides

neisseria gonorrhoeae

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23
Q

What are coliforms and what are they treated with?

A

gram -ve bacilli like E.coli which are aerobes

treated with Gentamicin

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24
Q

What type of membrane do endotoxins have?

A

gram -ve

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25
Q

How does endotoxic shock come about?

A
  • endotoxin binds to macrophage receptors and B cells

- acute cytokines cause endotoxic shock and fever

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26
Q

How is fever brought about?

A
  • cytokines to anterior hypothalamus
  • prostaglandin E increases the body’s thermal set point
  • this causes fever
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27
Q

What happens in sepsis?

A
  • leaky small blood vessels
  • decreased blood volume so increased HR
  • poor perfusion
  • blood clotting so increases risk of haemorrhage
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28
Q

What are streptococcus, enterococcus and staphylococcus?

A

gram +ve

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29
Q

What is streptococcus pneumonia?

A

gram +ve

alpha haemolytic cocci

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30
Q

Are enterococci haemolytic?

A

no they are non-haemolytic

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31
Q

What is the gram state of staph aureus and epidermis and what is their coagulase state?

A
  • staph aureus is gram +ve and coagulase +ve
  • staph epidermis is gram +ve and coagulase -ve
  • both are in clusters
32
Q

What are the features of clostridium?

A

gram +ve
anaerobic bacilli
produce exotoxins

33
Q

What are the key gram -ve organisms?

A 
Neisseria spp (STI and meningitis)
Escherichia coli (GI)
34
Q

What are the key gram +ve organisms?

A

Streptococcus, Staphylococcus and C. diff

35
Q

How do viruses infect cells?

A
  • attach ligand to receptor on a cell
  • viral and cell envelope fuse which can be mediated by a viral enzyme
  • viral uncaring to realise viral nucleic acid then host ribosomes used to make nucleic acids and proteins
36
Q

How can viruses be released?

A
  • enveloped viruses release by budding

- other viruses release by lysis

37
Q

How do antibiotics target bacteria?

A
  • ribosomes
  • growing bacterial cell wall
  • enzymes
38
Q

How do anti-viral drugs work?

A
  • target viral nucleic acid polymerase
  • other viral enzymes
  • uncoating
  • attachment
  • release
39
Q

How is antiviral resistance analysed?

A

genotypical not phenotypically

40
Q

How does a virus cause pathogenesis?

A

cells can die due to lysis/hijacking of cell, immune system or proliferation

41
Q

How do cytotoxic T lymphocytes work?

A
  • recognise cell-surface proteins as foreign

- start cell death

42
Q

How does viral persistence work?

A
  • virus can either remain latent then reactivate or remain active and only cause complications later on
43
Q

What are the ways to detect a virus?

A

detect either the virus itself of the antibody against the virus

44
Q

What are the antibodies produced in repose to infection?

A
  • IgM initially but then levels of this will drop to 0

- IgG will be produced after and levels will remain low after rise in the blood

45
Q

What will be blood components of recent infection?

A

IgM, rising titre of IgG and very high IgG

46
Q

How can virus detection be done?

A

PCR or antigen detection

47
Q

What is bacteriostatic?

A

inhibit the growth of bacteria

48
Q

What is bactericidal?

A

kill bacteria

49
Q

What are the features of the ideal antibiotic?

A

remains for a long time
minimal toxicity to host
kills bacteria

50
Q

What are the groups of cell wall antimicrobials?

A
  • Penicillins (beta lactam)
  • Cephalosporins (beta lactam)
  • Carbapenems (beta lactam)
  • Glycopeptides (not beta lactam)
51
Q

What do beta lactams target?

A

Penicillin Binding Proteins (PBPs)

52
Q

How do beta lactam antibiotics work?

A

beta lactam ring on penicillin binds to bacteria to unhurt cross-linking and its ability to make new cell walls

53
Q

What are the features of Penicillins?

A 
\+ few side effects
 \+ safe in pregnancy
 - resistance
 - patients can be allergic
 - few side effects
54
Q

What are the common types of penicillins and their features?

A
  • Amoxicillin: safe, oral, good tissue perfusion, works on gram +ve and -ve
  • Co-amoxiclav: IV/oral, beta lactam and beta lactase inhibitor, works on gram -ve and +ve
  • Flucloxacillin: narrow spectrum, staph and strep, gram +ve
  • Temocillin: gram -ve, beta-lactamase resistant, active against coliforms and ESBL-producing organisms
55
Q

What do Cephalosporins do?

A
  • inhibit cell wall synthesis
  • bactericidal
  • more resistant to beta lactamases
  • broad spectrum
  • cause C. diff
  • kidney and urine excretion
  • eg Cephoxitin
56
Q

What do Glycopeptides do?

A
  • bactericidal
  • not beta lactam
  • act on substrate so enzyme can’t attach
  • reduced cross-linking
  • weakened cell wall
  • only active on gram +ve
  • IV only
57
Q

How do antibiotics that inhibits protein synthesis work?

A

attach to ribosomes

bacteriostatic as synthesis resumes when antibiotics are stopped (with the exception of aminoglycosides)

58
Q

What are the main types of antibiotics that inhibit protein synthesis?

A
  • Aminoglycosides: IV, binds to ribosomes, bactericidal, gram -ve, urine excretion eg Gentamicin
  • Tetracyclines: bacteriostatic, bind to ribosomes, broad spectrum, eg doxyclycine
  • Macrolides: liver excretion, eg clarithromycin, azithromycin and azithromycin
59
Q

What is the side effect of Gentamicin?

A

damage to cranial nerve VIII

damage to kidneys

60
Q

What are the main antibiotics that affect nucleic acids?

A
  • Metronidazole: against anaerobes, rare resistance
  • Quinolones: bactericidal, indirectly inhibit DNA synthesis
  • Fluoroquinolones: bactericidal, good orally, gram -ve and +ve
61
Q

What is the main class of antibiotics that affects folic acid synthesis?

A
  • Timethoprim: gram -ve and +ve, used in UTIs

folic acid is needed for the synthesis of key cellular components

62
Q

What is the side effect of Ciprofloxacin?

A

tendonitis

63
Q

What is the side effect of Metronidazole?

A

alcohol interaction

64
Q

What are the 4 Cs to avoid?

A
  • Cephalosporins
  • Co-amoxiclav
  • Cirprofloxacin
  • Clindamycin
65
Q

What are biofilms?

A

organisms behaving as part of a multi-cellular community that are resistant to antimicrobial agents and host defences

66
Q

What are the features of persister cells?

A

tolerance not resistance
very slow growth
enriched in biofilms

67
Q

What are the main steps of resistance transfer?

A

variation –> selective pressure –> evolution resistance –> gene transfer

68
Q

How can horizontal gene transfer occur?

A

bacterial transformation
transduction
conjugation

69
Q

What are the antimicrobial drug resistance mechanisms?

A
  • altered permeability (altered efflux or influx)
  • inactivation (beta lactamases)
  • altered target site
  • replacement of a sensitive pathway
70
Q

What are the types of beta lactamase?

A

penicillinase
extended spectrum beta lactamases
carbapenemase

71
Q

What does SICPs stand for?

A

standard infection control procedures

72
Q

What is the chain of infection?

A
  • infectious microbe
  • reservoir
  • portal of exit
  • modes of transmission
  • portal of entry
  • susceptible host
  • infectious microbe
  • repeat
73
Q

What are the five Is of infection spread?

A 
Inhalation
Ingestion
Inoculation
Intercourse
(mother to) Infant
74
Q

What is disinfection?

A

reducing the number of microorganisms to a level which is safe

75
Q

What is sterilisation?

A

killing the microorganisms so they are incapable of causing infection

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