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Foundations in Medicine 1 > Microbiology > Flashcards

Microbiology Flashcards

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1
Q

What are the three most common shapes of bacteria

A

cocci, bacili, and spiral

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2
Q

What are examples of cocci bacteria

A

staphylococcus (clump) and streptococcus (chain)

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3
Q

What are bacillus bacteria

A

rod shaped bacteria

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4
Q

What are fusiform bacteria

A

long slender rods

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5
Q

what type of bacteria is a curved rod

A

gram-negative pathogens such as vibrio cholerae

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6
Q

What are spores

A

single-celled reproductive units often produced by fungi, bacteria algae etc (inert structures resistant to physical and chemical challenge

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7
Q

what distinguishes gram -ve from gram +ve

A

their cell wall (-ve has a thin peptidoglycan layer with an outer membrane containing LPS and +ve has a thick peptidoglycan layer with no outer layer )

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8
Q

What colour does gram -ve stain

A

pink because it’s thin wall does not retain the stain/dye

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9
Q

Gram +ve stains pink, true or false?

A

false, it stains purple because it’s thin wall can retain the stain/dye

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10
Q

What are examples of gram-negative bacteria?

A

E.coli and salmonella

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11
Q

What is selective media?

A

The presence of one substance permits the growth of one colony over another

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12
Q

Give an example of selective media

A

mannitol sugar agar - salts allow preferential isolation of staphylococci
salmonella shigella - bile salts inhibit growth of coliforms

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13
Q

What is differential media?

A

media that selects for the growth of specific prokaryotes - clearly distinguishable colonies

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14
Q

what are examples of differential media

A

McConkay agar selects for gram -ve and inhibits gram +ve) and eosin methylene blue (allows for lactose fermenters such as e.coli)

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15
Q

Which bacteria is involved in hemolysis

A

streptococci

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16
Q

what is hemolysis

A

breakdown of RBCs causing the release of haemoglobin

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17
Q

What are the different types of hemolysis and examples of bacteria that perform this?

A

alpha - partial breakdown of RBCs, the colonies stain green (streptococcus pneumonia)
beta - full breakdown and release of haem in the RBCs so the colonies appear clear (streptococcus pyogenes) these are more virulent
gamma - no hemolysis occurs (enterococcus)

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18
Q

what antibody activity can you test in vitro

A

agglutination (have antibodies attached to a latex bead)

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19
Q

What DNA technology is useful in sequencing the genetic material of bacteria/viruses?

A

qPCR

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20
Q

What is MALDI-TOF

A

a type of mass spectrometry used to identify molecules/proteins based on their mass-charge ratio

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21
Q

What is a pathogen

A

harmful organism that produces pathology

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22
Q

What is meant by commensal/symbiosis

A

an organism part of the natural flora that has a mutualistic relationship

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23
Q

What is an opportunistic pathogen

A

one that causes infection upon opportunity such as immunocompromised individual

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24
Q

Give examples of protozoan derived diseases?

A

malaria and toxoplasma

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25
give examples of fungal infections
aspergillus (moulds)
26
Give two examples of gram-negative cocci
Neisseria meningitis and gonorrhoeae
27
What are the three groups of enterobacteriaceae
ferment lactose rapidly, variable or slow lactose fermentation and another group that the majority do not ferment lactose
28
What are coliforms
gram-negative rod-shaped bacteria
29
what is the first-line antibiotic for coliforms (gram-negative) ?
gentamicin
30
what endotoxin causes sepsis from coliform infection?
LPS
31
What is sepsis?
host response to severe infection mediated by LPS /endotoxin from a bacteria
32
What is fever?
increase of the body temperature above 38 degrees
33
What are the four groups of gram-positive pathogens
streptococcus enterococcus staphylococcus clostridia
34
What is the most common bacteria to cause UTIs
enterococci
35
Which gram-positive bacteria has spores central to its spread and ability to avoid antimicrobials?
clostridioles
36
Why are spores resistant to antibiotics
antibiotics generally need a cell to be metabolically active and spores are not
37
what is a facultative anaerobe
a bacteria that can switch between anaerobic and aerobic respiration
38
What are the two broad classes of antibiotics
beta-lactams and glycopeptides
39
What is the difference between bacteriostatic and bactericidal
bactericidal kills the bacteria and the former just inhibits the growth
40
What are 5 ideal factors of an antibiotic
minimal toxicity to the host (no adverse side effects) kills the bacteria oral administration long half-life (not having to give multiple times throughout the day etc) appropriate tissue distribution (pro drug)
41
what are beta-lactams
group of antibiotics that are analogues to d-ala-d-ala and bind to the penicillin-binding protein active site, therefore targeting the bacterial cell wall
42
what are the two main groups of beta-lactams
penicillins and cephalosporins
43
what do beta-lactams do
impairs the cell division by binding to the penicillin-binding protein
44
What are the limitations of penicillins?
rapid excretion by the kidney patients often allergic resistance
45
What is a good broad antibiotic for primary care?
amoxicillin
46
How does beta lactam based resistance develop?
the production of beta lactamases by bacteria can degrade the drug
47
what is co-amoxiclav a combination of?
amoxicillin and clavulanic acid (a beta-lactamase inhibitor)
48
What is flucloxacillin?
this has had the structure altered so that beta lactamase cannot degrade it so allows it to persist and is useful for streptococci and staphylococci and replaced methicillin works on gram positive
49
what is temocillin used for?
gram-negative organisms and used in IV in secondary care
50
What are cephalosporins?
broad-spectrum antibiotics that significantly affect the gut flora
51
Which of these is not an advantage of cephalosporins? A broad spectrum B reduced hypersensitivity C a variety of spectrums and targets D excreted rapidly in the urine
D
52
What are glycoproteins?
restricted to gram-positive because of the size of the cell wall in gram-negative - this binds to the d-alanine d-alanine (the substrate itself) preventing the cross-linking important for resistant staph aureus
53
what are two examples of glycoproteins drugs?
vancomycin and teicoplanin
54
Name the three groups of protein synthesis inhibitors
aminoglycosides tetracyclines macrolides
55
What are the 6 components of a cell that serve as antibiotic targets
cell wall ribosomes DNA replication DNA gyrases metabolic pathways cell membrane
56
What are aminoglycosides?
bacteriocidal usually long half life
57
What is an example of an aminoglycoside?
gentamycin
58
What are the properties of gentamycin?
Must be given IV inhibits protein synthesis by irreversible binding and kills the bacteria mainly gram-negative aerobic organisms side effects include damage to the kidney - must be monitored
59
What are tetracyclines?
bacteriostatic broad spectrum GI flora risk
60
What are macroslides?
bacteriostatic intracellular pathogens Often used in cases of penicillin allergy very safe as has in increased rate of absorption
61
What is an example of a macroslide?
erythromycin
62
What is trimeprothim?
antibiotic that targets nucleic acids, primarily used in UTIs
63
Name the three types of antibiotics that target nucleic acids
Fluoroquinolones metronidazole trimeprothim
64
What are quinolones?
bind to the A subunit of DNA gyrase preventing replication
65
What is an example of quinolones?
ciprofloxacin - broad spectrum IV and oral
66
Which antibiotics are used for C.difficile
quinolones/ciprofloxacin
67
What does metronidazole target?
anaerobes (and parasites/protozoa)
68
What antibiotics target folic acid synthesis?
trimeprothim and sulphonamides
69
what is meant by empiric prescribing?
uncertainty of what is causing the infection so one prescribes what is most likely to have a positive effect without damaging the host
70
What is natural resistance?
the microorganism is more resistant to the the mode of action of the antibiotic
71
What are the four different ways of natural resistance?
target not present target not accessible developmental structure/state metabolism
72
What is a biofilm?
A structured community of microbes that adhere to surfaces making them more resistant to environmental stress
73
What are persistor cells?
dormant non growing cells that downregulate their metabolism to tolerate antimicrobials
74
What is clinical resistance?
the tolerance gained by bacteria upon continual exposure to an antimicrobial/antibiotic
75
What causes clinical resistance?
mutation or gene transfer
76
How does resistance provide a selective advantage?
They are able to persist despite mechanisms to limit their survival so can go on to reproduce etc
77
What factors create resistance?
variation (HGT eg) and the selective pressure (antibiotic)
78
What are the three methods of horizontal gene transfer?
natural competence bacteriophage (viruses or phages transfer bacterial DNA between cells) bacteria conjugation (sex pili)
79
What bacterial infection engages in bacteriophage HGT
MRSA
80
Where is HGT most common and why?
in the gut because bacterial cells are present in close proximity
81
What are the mechanisms of AMR
altered permeability (changes to the outer membrane, reduced OmpF) and inactivation (beta-lactamases) and altered target site
82
Give three types of b lactamases
penicillinase extended spectrum beta lactamase (ESBL) carbapenemase (CPE)
83
Give an example of an altered target site
84
How does MRSA acquire its resistance?
Through multiple mechanisms; HGT of a gene that alters the PBP which allows it to continue cell wall synthesis in the presence of a drug, it also has efflux pumps
85
What is a drug that can treat MRSA?
vancomycin
86
What antibiotic is used against VRE
daptomycin
87

Foundations in Medicine 1 (11 decks)

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