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Foundations in Medicine 1 > Microbiology > Flashcards

Microbiology Flashcards

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
Q

give examples of fungal infections

A

aspergillus (moulds)

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26
Q

Give two examples of gram-negative cocci

A

Neisseria meningitis and gonorrhoeae

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27
Q

What are the three groups of enterobacteriaceae

A

ferment lactose rapidly, variable or slow lactose fermentation and another group that the majority do not ferment lactose

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28
Q

What are coliforms

A

gram-negative rod-shaped bacteria

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29
Q

what is the first-line antibiotic for coliforms (gram-negative) ?

A

gentamicin

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30
Q

what endotoxin causes sepsis from coliform infection?

A

LPS

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31
Q

What is sepsis?

A

host response to severe infection mediated by LPS /endotoxin from a bacteria

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32
Q

What is fever?

A

increase of the body temperature above 38 degrees

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33
Q

What are the four groups of gram-positive pathogens

A

streptococcus
enterococcus
staphylococcus
clostridia

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34
Q

What is the most common bacteria to cause UTIs

A

enterococci

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35
Q

Which gram-positive bacteria has spores central to its spread and ability to avoid antimicrobials?

A

clostridioles

36
Q

Why are spores resistant to antibiotics

A

antibiotics generally need a cell to be metabolically active and spores are not

37
Q

what is a facultative anaerobe

A

a bacteria that can switch between anaerobic and aerobic respiration

38
Q

What are the two broad classes of antibiotics

A

beta-lactams and glycopeptides

39
Q

What is the difference between bacteriostatic and bactericidal

A

bactericidal kills the bacteria and the former just inhibits the growth

40
Q

What are 5 ideal factors of an antibiotic

A

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
Q

what are beta-lactams

A

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
Q

what are the two main groups of beta-lactams

A

penicillins and cephalosporins

43
Q

what do beta-lactams do

A

impairs the cell division by binding to the penicillin-binding protein

44
Q

What are the limitations of penicillins?

A

rapid excretion by the kidney
patients often allergic
resistance

45
Q

What is a good broad antibiotic for primary care?

A

amoxicillin

46
Q

How does beta lactam based resistance develop?

A

the production of beta lactamases by bacteria can degrade the drug

47
Q

what is co-amoxiclav a combination of?

A

amoxicillin and clavulanic acid (a beta-lactamase inhibitor)

48
Q

What is flucloxacillin?

A

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
Q

what is temocillin used for?

A

gram-negative organisms and used in IV in secondary care

50
Q

What are cephalosporins?

A

broad-spectrum antibiotics that significantly affect the gut flora

51
Q

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

A

D

52
Q

What are glycoproteins?

A

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
Q

what are two examples of glycoproteins drugs?

A

vancomycin and teicoplanin

54
Q

Name the three groups of protein synthesis inhibitors

A

aminoglycosides
tetracyclines
macrolides

55
Q

What are the 6 components of a cell that serve as antibiotic targets

A

cell wall
ribosomes
DNA replication
DNA gyrases
metabolic pathways
cell membrane

56
Q

What are aminoglycosides?

A

bacteriocidal
usually long half life

57
Q

What is an example of an aminoglycoside?

A

gentamycin

58
Q

What are the properties of gentamycin?

A

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
Q

What are tetracyclines?

A

bacteriostatic
broad spectrum
GI flora risk

60
Q

What are macroslides?

A

bacteriostatic
intracellular pathogens
Often used in cases of penicillin allergy
very safe as has in increased rate of absorption

61
Q

What is an example of a macroslide?

A

erythromycin

62
Q

What is trimeprothim?

A

antibiotic that targets nucleic acids, primarily used in UTIs

63
Q

Name the three types of antibiotics that target nucleic acids

A

Fluoroquinolones
metronidazole
trimeprothim

64
Q

What are quinolones?

A

bind to the A subunit of DNA gyrase preventing replication

65
Q

What is an example of quinolones?

A

ciprofloxacin - broad spectrum IV and oral

66
Q

Which antibiotics are used for C.difficile

A

quinolones/ciprofloxacin

67
Q

What does metronidazole target?

A

anaerobes (and parasites/protozoa)

68
Q

What antibiotics target folic acid synthesis?

A

trimeprothim and sulphonamides

69
Q

what is meant by empiric prescribing?

A

uncertainty of what is causing the infection so one prescribes what is most likely to have a positive effect without damaging the host

70
Q

What is natural resistance?

A

the microorganism is more resistant to the the mode of action of the antibiotic

71
Q

What are the four different ways of natural resistance?

A

target not present
target not accessible
developmental structure/state
metabolism

72
Q

What is a biofilm?

A

A structured community of microbes that adhere to surfaces making them more resistant to environmental stress

73
Q

What are persistor cells?

A

dormant non growing cells that downregulate their metabolism to tolerate antimicrobials

74
Q

What is clinical resistance?

A

the tolerance gained by bacteria upon continual exposure to an antimicrobial/antibiotic

75
Q

What causes clinical resistance?

A

mutation or gene transfer

76
Q

How does resistance provide a selective advantage?

A

They are able to persist despite mechanisms to limit their survival so can go on to reproduce etc

77
Q

What factors create resistance?

A

variation (HGT eg) and the selective pressure (antibiotic)

78
Q

What are the three methods of horizontal gene transfer?

A

natural competence
bacteriophage (viruses or phages transfer bacterial DNA between cells)
bacteria conjugation (sex pili)

79
Q

What bacterial infection engages in bacteriophage HGT

A

MRSA

80
Q

Where is HGT most common and why?

A

in the gut because bacterial cells are present in close proximity

81
Q

What are the mechanisms of AMR

A

altered permeability (changes to the outer membrane, reduced OmpF) and inactivation (beta-lactamases) and altered target site

82
Q

Give three types of b lactamases

A

penicillinase
extended spectrum beta lactamase (ESBL)
carbapenemase (CPE)

83
Q

Give an example of an altered target site

A
84
Q

How does MRSA acquire its resistance?

A

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
Q

What is a drug that can treat MRSA?

A

vancomycin

86
Q

What antibiotic is used against VRE

A

daptomycin

87
Q
A

Foundations in Medicine 1 (11 decks)

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