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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
How does endotoxic shock come about?
- endotoxin binds to macrophage receptors and B cells | - acute cytokines cause endotoxic shock and fever
26
How is fever brought about?
- cytokines to anterior hypothalamus - prostaglandin E increases the body's thermal set point - this causes fever
27
What happens in sepsis?
- leaky small blood vessels - decreased blood volume so increased HR - poor perfusion - blood clotting so increases risk of haemorrhage
28
What are streptococcus, enterococcus and staphylococcus?
gram +ve
29
What is streptococcus pneumonia?
gram +ve | alpha haemolytic cocci
30
Are enterococci haemolytic?
no they are non-haemolytic
31
What is the gram state of staph aureus and epidermis and what is their coagulase state?
- staph aureus is gram +ve and coagulase +ve - staph epidermis is gram +ve and coagulase -ve - both are in clusters
32
What are the features of clostridium?
gram +ve anaerobic bacilli produce exotoxins
33
What are the key gram -ve organisms?
``` Neisseria spp (STI and meningitis) Escherichia coli (GI) ```
34
What are the key gram +ve organisms?
Streptococcus, Staphylococcus and C. diff
35
How do viruses infect cells?
- 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
How can viruses be released?
- enveloped viruses release by budding | - other viruses release by lysis
37
How do antibiotics target bacteria?
- ribosomes - growing bacterial cell wall - enzymes
38
How do anti-viral drugs work?
- target viral nucleic acid polymerase - other viral enzymes - uncoating - attachment - release
39
How is antiviral resistance analysed?
genotypical not phenotypically
40
How does a virus cause pathogenesis?
cells can die due to lysis/hijacking of cell, immune system or proliferation
41
How do cytotoxic T lymphocytes work?
- recognise cell-surface proteins as foreign | - start cell death
42
How does viral persistence work?
- virus can either remain latent then reactivate or remain active and only cause complications later on
43
What are the ways to detect a virus?
detect either the virus itself of the antibody against the virus
44
What are the antibodies produced in repose to infection?
- 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
What will be blood components of recent infection?
IgM, rising titre of IgG and very high IgG
46
How can virus detection be done?
PCR or antigen detection
47
What is bacteriostatic?
inhibit the growth of bacteria
48
What is bactericidal?
kill bacteria
49
What are the features of the ideal antibiotic?
remains for a long time minimal toxicity to host kills bacteria
50
What are the groups of cell wall antimicrobials?
- Penicillins (beta lactam) - Cephalosporins (beta lactam) - Carbapenems (beta lactam) - Glycopeptides (not beta lactam)
51
What do beta lactams target?
Penicillin Binding Proteins (PBPs)
52
How do beta lactam antibiotics work?
beta lactam ring on penicillin binds to bacteria to unhurt cross-linking and its ability to make new cell walls
53
What are the features of Penicillins?
``` + few side effects + safe in pregnancy - resistance - patients can be allergic - few side effects ```
54
What are the common types of penicillins and their features?
- 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
What do Cephalosporins do?
- inhibit cell wall synthesis - bactericidal - more resistant to beta lactamases - broad spectrum - cause C. diff - kidney and urine excretion - eg Cephoxitin
56
What do Glycopeptides do?
- 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
How do antibiotics that inhibits protein synthesis work?
attach to ribosomes | bacteriostatic as synthesis resumes when antibiotics are stopped (with the exception of aminoglycosides)
58
What are the main types of antibiotics that inhibit protein synthesis?
- 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
What is the side effect of Gentamicin?
damage to cranial nerve VIII | damage to kidneys
60
What are the main antibiotics that affect nucleic acids?
- Metronidazole: against anaerobes, rare resistance - Quinolones: bactericidal, indirectly inhibit DNA synthesis - Fluoroquinolones: bactericidal, good orally, gram -ve and +ve
61
What is the main class of antibiotics that affects folic acid synthesis?
- Timethoprim: gram -ve and +ve, used in UTIs | folic acid is needed for the synthesis of key cellular components
62
What is the side effect of Ciprofloxacin?
tendonitis
63
What is the side effect of Metronidazole?
alcohol interaction
64
What are the 4 Cs to avoid?
- Cephalosporins - Co-amoxiclav - Cirprofloxacin - Clindamycin
65
What are biofilms?
organisms behaving as part of a multi-cellular community that are resistant to antimicrobial agents and host defences
66
What are the features of persister cells?
tolerance not resistance very slow growth enriched in biofilms
67
What are the main steps of resistance transfer?
variation --> selective pressure --> evolution resistance --> gene transfer
68
How can horizontal gene transfer occur?
bacterial transformation transduction conjugation
69
What are the antimicrobial drug resistance mechanisms?
- altered permeability (altered efflux or influx) - inactivation (beta lactamases) - altered target site - replacement of a sensitive pathway
70
What are the types of beta lactamase?
penicillinase extended spectrum beta lactamases carbapenemase
71
What does SICPs stand for?
standard infection control procedures
72
What is the chain of infection?
- infectious microbe - reservoir - portal of exit - modes of transmission - portal of entry - susceptible host - infectious microbe - repeat
73
What are the five Is of infection spread?
``` Inhalation Ingestion Inoculation Intercourse (mother to) Infant ```
74
What is disinfection?
reducing the number of microorganisms to a level which is safe
75
What is sterilisation?
killing the microorganisms so they are incapable of causing infection

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