Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

PHARMACOLOGY FRCA > antimicrobials and antifungals > Flashcards

antimicrobials and antifungals Flashcards

1
Q

what different types of pathogens do you know?

A

pathogen is a micro-organism that causes disease
may be bacterial, virus, fungi, protazoa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is the difference between gram positive and negative bacteria?

A

depends on structure of cell wall
gram staining includes applying stain to bacteria and washing it off. Gram positive bacterial retains the stain and appears purple, gram negative does not hold the stain and appears pink

gram negative - thin peptidoglycan wall, outer and inner membrane , lipopolysaccharides

gram positive - thick peptidoglycan wall

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

describe the structure of a bacteria..

A

cell wall
cell membrane
naked DNA , no nucleus
plasmids
30s and 50s ribosomes (40s and 60s in eukaryotes)
no mitochondria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

describe the structure of a virus

A

genetic material - positive/ negative RNA, DNA
proteins
contained in protein shell = capside
sometimes enveloped

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

can you classify different bacteria

A

gram staining + rods/ cones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

causes of atypical pneumonias..

A

mycoplasm
legionella
mycobacterium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

can you classify viruses

A

DNA/ RNA, enveloped and non-enveloped

DNA enveloped = herpes, hep B
DNA non-enveloped = adenovirus
RNA enveloped = Measles, mumps , rubella
RNA non-env = polio, hep A

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

describe the general structure of fungi

A

eukaryotic cells
membranes differ from ours - contain ergosterol (not cholesterol)
have cell walls made of chitin

2 main groups - yeast (candida) and moulds (Asperigillus)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is the size of bacteria, virus and eukaryotes

A

virus less than 0.3um
bacteria 2um
erykaryotes - 10-100um

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what fungal infections do you know

A

candida albicans - thrush of mouth, vagina. can also cause disseminated disease in immunocompromised

asperigillus - lung infection in immunocompromised

cryptococcus - fungal menigitis assoicated with HIV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

how can the antibiotics be classified?

A

By target
Cell wall
* B lactams
* glycopeptides

Protein synthesis
* 30S - aminoglycosides , tetracyclines
* 50S - macrolides, clindamycin, linezolid, chloramphenicol

Nucleic acid synthesis
* folate synthesis - trimethroprim, sulphonamides
* DNA gyrase - quinolones
* RNA polymerase - rifampicin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is the difference between bacteriostatic and bacteriocidal.
can you give examples

A

some Abx work by killing bacterial = bacteriocidal e.g. B lactam and glycopeptides and aminoglycocides

others inhibit growth - macrolides, sulphonamides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is meant by minimum inhibitory concentration and minimum bacteriocidal concentration?

A

MIC = lowest Abx conc to inhibit bacterial growth
MBC = lowest conc to kill bacteria in vitro

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what pharmacokinetic parameters are important when assessing Abx efficiency

A

peak serum level
Trough serum level
Area under serum conc time curve

some Abx work via conc dependant killing - in this case the peak serum / MIC ratio shuld be high and the 24h AUC / MIC ratio should be high
(MIC = minimum inhibitory conc)

some Abx work via time dependant killing e.g. efficacy is determined by time above MIC. for these the time above MIC i.e percentage time spent above MIC during dose period, should be high.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

give an example of Abx which are dose dependant and time dependant killing..

A

time dependant = b lactams

conc dependant e..g aminoglycosides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is the general structure of a penicillin

A

B lactam ring + Thiazolidine ring + acyl chain

acyl chain varies between different penicillins

previous Q asked to draw this

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

which bacteria are penicillin used for?

A

gram positive - inhibit thick peptidoglycan wall
e.g. cellulitis, respiratory tract infection (streptococcus, pseudomonas)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

how do penicillins work

A

bacteriocidal Abx
inhibition of cell wall synthesis
through inhibiting transpeptidase enzyme - normally responsible for cross linking peptidoglycan wall and hence allowing strength to develop
without this strength, weak wall and bacteria cell bursts due to osmotic damage.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what are the pharmacodynamics of the penicillins?

A

GI - diarrhoea and cholestatic jaundice
immune - anaphylaxis and hypersensitivity.
CNS - some can be pro convulsant (benzylpenicillin)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what are the pharmacokinetics of penicillins?

A

A: oral, IV. some only can be given IV e.g. benzylpenicillin and amoxicillin only oral
some can penetrate BBB when it is inflammed e..g benzylpenicillin

20% metabolised
mostly excreted unchanged by kidneys
hence renal adjustments necessary
short half life

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

tell me about penicillin resistance..

A

bacteria can develop resistance in a number of ways

B lactamases can be priduced by bacteria which breaks down B lactam ring, preventing penicillins acting.

altering transpeptidase target

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

how can the penicillins be classified?

A

classified depending on their spectrum of uses….

narrow spec = flucloxacillin. NOT inhibited by B lactamases. good for staphylococcus

Broad spec = benzylpenicillin. howeever destroyed by B lactams and poor GI absorption. can cover gram positive and negative cocci

extended spec = amoxicillin. destroyed by B lactamases. good GI absorption. same as broad spec PLUS increased gram neg cover - bacilli too.

anti-pseudomonal = piperacillin, destroyed by B lactamases, poor GI absorption. broad spec PLUS pseudomonas

23
Q

how can B lactamase resistance be over come?

A

combining penicillin with B lactamase inhibtor
e.g. co-amoxiclav = amoxicillin + clauvanic acid
e.g. Tazocin = piperacillin + tazobactam

24
Q

what are the cephalosporins

A

bacteriocidal, B lactam antibiotics
B lactam ring like penicillin but no thiazolidine ring instead dihydrothiazine ring
mostly good for gram positive infections….

5 generations , each with improved spectrum of activity. common ones include cefuroxime (2nd gen) and cefotaxime and ceftriaxone (3rd gen). 5th generation ones have MRSA cover.

lipid solubility gives them good BBB penetration for CNS infections.

25
Q

what abx belong to B lactam group

A

penicillins e.g. amoxicillin
cephalosporins e.g. ceftriaxone
carbapenems e.g. meropenem

26
Q

which Abx should be used in caution in those with penicillin allergy?

A

cephalosporins - cross reactivity
both have B lactam ring

27
Q

tell me about the carbopenems

A

bacteriocidal Abx in B lactam group
similar to penicillins and cephalosporins as all have B lactam ring.
broader spectrum, gram positive and negative and anerobic cover.
not susceptible to B lactamases

28
Q

tell me about the glycopeptides..

A

glycopeptides are a class of Abx that work via inhibiting cell wall synthesis (non B lactams)
includes vancomycin, teicoplanin

they work by inhibiting the transpeptidase enzyme which is responsible for cross linking bacterial peptidoglycan cell wall. hence bacteria killed by osmotic pressure - bacterocidal.

can be used for both aerobic and anerobic gram positive.

pharmacodymanics
* nephrotoxic
* ototoxic
* histamine release - red man syndrome + hypotension
* allergy - teicoplanin is highest (NAP6)

pharamcokinetics
* no GI absorption - hence acts locally for C diff. can give intrathecally for CNS infection
* excreted unchanged in urine
* needs monitoring to maintain levels between 10-15mg/l

29
Q

common uses of glycopeptides

A
  • oral vancomycin for C diff
  • endocarditis
  • MSRA
30
Q

how does ciprofloxacin work?

A

quinolone Abx
DNA gyrase inhibition
prevents DNA synthesis

good for gram negative

31
Q

which Abx penetrate BBB well

A

3rd gen cephalosporins
rifampicin
ciprofloxacin

32
Q

how does rifampicin work and when is it used?

A

TB infection
inhibits DNA dependant RNA polymerase - transcription
bacteriocidal

33
Q

Mechanism of metronidazole?

A

breakdown of bacterial DNA
mostly works in anaerobes - mechanism involves free radical production that destroys DNA

34
Q

which Abx should be avoided with alcohol?

A

metronidazole - nausea vomitting, headache (hangover)

35
Q

how do macrolides work?

A

bacteriostatic
50S inhibition
prevent protein synthesis

36
Q

give an example of a macrolide

A

erythromycin
clarithromycin
azithromycin

37
Q

what precautions should be taken with macrolides?

A

prolong QTc
risk of rhabdo with statins
cyp450 inhibitor - increases warfarin
prokinetics - diarrhoea, N&V

38
Q

give examples of aminoglycosides

A

gentamicin
streptomicin

39
Q

what bacteria are aminoglycosides most effective against. how do they work?

A

gram neg
30S inhibition

40
Q

what precautions should be taken with aminoglycosides?

A

ototoxic and nephrotoxic
can also cause muscle weakness by inhibiting nACHR presynaptically - bad for myasthenia gravis (prolong NMBA)
needs monitoring - initially dose via height and weight and then by levels
narrow therapeutic index

hence contraindicated in MG

41
Q

which Abx belong to tetracyclines. how do these work?

A

doxycycline
30S inhibition
good for intracellular bacteria e.g. chlamydia

42
Q

what are the side effects of tetracyclines

A

photosensitivity
shouldnt be given to children - due to teeth and bone development

43
Q

mechanism of clindamycin

A

50S inhibition

44
Q

mechanism of trimethroprim

A

dihydrofolate reductase inhibitor - prevents folate and nucleic acid synthesis

45
Q

what is meant by antimicrobial stewardship?

A

coordinated programme that promotes correct use of antibiotics to reduce risk of resistance devloping and improve patient outcomes.

methods include
- only when clinically indicated
- use local guidelines
- correct dose and duration
- collect samples and target therapy to sensitivity - de-escalate from broad to narrow spec when possible
- stop spread - PPE

46
Q

what is meant by antimicrobial resistance

A

microbes are rapidly dividing
within the population mutations will develop and some of these will be beneficial and provide resistance to Abx. these will be selected for and resistance will develop
plasmids can also share resistance genes in the population

mechanisms for mutation include
- enzymes that destroy Abx - b lactamases
- altering bacterial target
- pumping Abx out of the cell

47
Q

what factors are considered when starting Abx

A

patient factors
* age e.g. avoid gentamicin in older people
* allergies
* renal function
* pregnancy

infection factors
* culture and sensitivities
* gram staining
* location of infection - BBB needs penetrating

local policies

48
Q

what antivirals do you know?

A

viruses replicate within host cells
hence hard to target without killing host.
antivirals work by targeting virally infected cells selctively
they may inhibit protein synthesis, viral release or DNA replication

examples include
aciclovir - inhibits nucleic acid syntheiss as it is a guanine analogue but only activated in virally infected cells.

Tamiflu
neuraminidase inhibitor prevents release of influenza

HIV antivirals act via targetting reverse transcriptase

49
Q

what antifungal agents do you know?

A

3 groups
azoles, polyenes, echinocandins

azoles = inhibit ergosterol synthesis - important component of fungal cell wall. e.g. fluconazole

polyenes = bind ergosterol and create a pore within membrane - intracellular contents leak. e..g amphotericin , nystatin

echinocandins - inhibit B1,3 glucan synthase - prevents synthesis of b-1,3 glucan which gives cell wall strength e.g. capsofungin

50
Q

do you know any other mechanisms of antifungals?

A

inhibit DNA and RNA synthesis

inhibit mitosis

51
Q

tell me about amphotericin

A

polyene antifungal agent
works via binding ergosterol and creating pores that allow leakage of fungal cell contents

given IV
for systemic fungal infections.

52
Q

what are the side effects of azoles and polyenes

A

polyenes
- nephrotoxic, electrolyte disturbance

azoles
* hepatic dysfunction
* prolonged QT
* CYP450 inhibitor

53
Q

when are antifungals given prophylactically

A

immunocompromised patients
e.g. transplanted patients, HIV

54
Q

what are the risk factors for developing fungal disease?

A

immunocompromisation
HIV, diabetes, chemo, transplant , long term steroid

resp compromise - bronchiectasis , CF , prolonged mechanical ventilation

PHARMACOLOGY FRCA (16 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions