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Infection > Antibiotics (2/2) > Flashcards

Antibiotics (2/2) Flashcards

1
Q

beta lactam antibiotics

A

This is an umbrella group that encompasses four families of antibiotics: penicillins, cephalosporins, carbapenems and monobactams.

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2
Q

most penicillins have the suffix

A

‘-cillin’

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3
Q

penicillins all interfere with the

A

third and final stage of bacterial cell wall synthesis

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4
Q

important penicillins to remember

A
  • benzylpenicillin (usually just referred to as penicillin)
  • amxoicillin
  • flucloxacillin
  • co-amoxiclav
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5
Q

which bacteria are penicillins affective against and why

A

gram positive (streptococci mainly)- have thicker and exposed cell wall

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6
Q

which penicillin has some activity against gram-negative bacteria?

A

amoxicillin

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7
Q

flucloxacillin is effective against

A

straphlococci and streptococci

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8
Q

co-amoxiclav is a

A

combination of amoxicillin and clavulanic acid ( a beta lactase inhibiter)

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9
Q

what can make amoxicillin less effective

A

bacteria such as staphylococcus aureus can excrete beta-lactamase reducing antibacterial efficacy as it breaks down the antibiotic. The clavulanic acid inhibits the beta-lactamase allowing amoxicillin to function for longer without being broken down

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10
Q

co-amoxiclav is effective against

A

Staphylococci, Streptococci, Gram-negative bacteria and gives it an effect on anaerobic bacteria as well.

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11
Q

cephalosporins

A

There are considered to be five generations of cephalosporins but each of them works by inhibiting cell wall synthesis. q

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12
Q

how are cephalosporins (a beta lactam) different to penicillins

A

cephalosporins have no activity against anaerobic bacteria but are otherwise quite broad spectrum.

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13
Q

name a cephalosporin

A

ceftriaxone

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14
Q

ceftriaxone is used to treat

A

meningitis - good level of activity in the cerebrospinal fluid (can cross BBB)

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15
Q

cephalosporins and clostridium difficile infection

A

C. diff is a commensal bacterium found in your normal gut microbiome that competes for nutrients with other flora. This constant competition prevents C. diff overgrowth. Cephalosporins can also eliminate some of the natural gut flora as well as the pathogenic organism in an infection. This reduces competition allowing for C.diff to proliferate and over grow causing disease.

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16
Q

carbapenems example

A

meropenem

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17
Q

what is meropenem active against

A

Alongside Gram-positive and Gram-negative bacteria, it is active against anaerobic bacteria

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18
Q

what is meropenem strongest against

A

strongest against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus, though it is not effective against MRSA.

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19
Q

why would you not prescribe meropenem to someone with a penicillin allergy

A

similar structure to penicillin

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20
Q

what the main glycopeptide (another class of antibiotic)

A

vancomycin

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21
Q

glycopeptides inhibit what

A

cell wall synthesis by preventing two subunits from being incorporated into the peptidoglycan matrix that is the core structural component of the cell walls of Gram-positive bacteria

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22
Q

vancomycin is active again

A

both aerobic and anaerobic bacteria

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23
Q

important to remember about vancomycin

A

does have a narrow therapeutic window, so the patient needs to have therapeutic drug monitoring to ensure that the dose does not become toxic.

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24
Q

why is vancomycin a last resort drug

A

still many bacteria that are not resistant to it, including multiresistant staphylococci and Clostridium difficile, so it is only given when absolutely necessary to prevent sudden overuse and resistance among bacteria

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25
Q

how is vancomycin delivered

A

given IV (esp for systemic infection) because it isn’t absorbed via the gut (except int he case of C .diff infection whereby it is given orally to target GI)

26
Q

other glycopeptide of note other than vancomycin

A

teicoplanin

27
Q

teicoplanin more poplar than vancomycin because

A

his has a larger therapeutic index and is therefore much easier to monitor with the risk of a toxic dose less likely.

28
Q

what are the two main tetracyclines

A

tetracycline and doxycycline

29
Q

mode of action of doxycycline and tetracycline

A

Both are bacteriostatic antibiotics through their action of inhibiting protein synthesis of the bacteria (this holds them in the stationary phase of their growth cycle instead of killing them outright (bactericidal)).

30
Q

both doxycycline and tetracycline are

A

broad spectrum antibiotics

31
Q

what sort of infections are doxycycline and tetracycline useful in treating

A

a good choice for patients with a penicillin allergy that you are treating for a Gram-positive bacterium.

32
Q

what sort of illnesses are doxycycline and tetracycline affective against

A

Chlamydia, rocky mountain spotted fever and typhoid fever

33
Q

what should doxycycline and tetracycline not be used to treat

A

Streptococcal infections as up to 44% of S. pyogenes and 74% of S. faecalis have been found to be resistant to tetracyclines. This is why they are decreasing in value except in a number of different illnesses or patients with penicillin allergies (e.g. in leptospirosis as an alternative to erythromycin).

34
Q

why can tetracycline not be given to children younger than 12 years old or pregnant women

A

as it causes yellowing of the teeth among other adverse effects.

35
Q

Bioavailability of tetracycline is

A

100% via IV, but only 40% via intramuscular (IM).

36
Q

macrolides work by

A

inhibiting protein synthesis

37
Q

name three macrocodes

A

erythromycin, clarithromycin and azithromycin

38
Q

macrolides have a similar spectrum of action as penicillins

A

which make them a good alternative in patients with a penicillin allergy (mild gram-positive)

39
Q

what is erythromycin used to treat

A

atypical pathogens in pneumonia, Legionnaires’ disease, early syphilis and Chlamydia.

40
Q

erythromycin does not have great activity against

A

Haemophilus influenza

A way to work around this is the combination of erythromycin with a sulphonamide which will result in activity against a number of strains of H. influenzae.

41
Q

side effects of erythromycin

A

tends to make patients nauseous, vomit or give them diarrhoea. If a patient has a mild infection then a lower dose can be prescribed, but when the infection is more serious (such as with a Legionella infection/pneumonia) then a higher dose needs to be prescribed.

42
Q

azithromycin can attack

A

H influenza and other gram-negative bacteria

43
Q

Clarithromycin dervived from erythromycin) treats

A

Helicobacter pylori infections (along with metronidazole and proton pump inhibitors)

44
Q

quinolones work by inhibiting

A

bacterial replication through inhibiting DNA gyrase.

45
Q

in the UK the only quinolones available to prescribe are

A

fluoroquinolones

46
Q

name a fluoroquinolone

A

ciprofloaxin

47
Q

ciprofloxacin is best against

A

Gram negative bacteria such as Escherichia coli, Salmonella and Shigella. It is only moderately active against Gram-positive bacteria such as Streptococcus, and a lot of Staphylococci are resistant to quinolones so make sure not to use them in MRSA infections.

48
Q

risk when taking quinolones

A

C.diff infection

49
Q

how can ciprofloxacin be used

A

an eye drop, ointment, orally and IV

50
Q

ciprofloxacin used to treat

A

UTIs, GI infections, Gonorrhoea and septicaemia due the bacteria that it affects.

51
Q

which other antibiotics not within the classes mentioned inhibit bacterial replication

A

trimethoprim and sulphonamides

52
Q

trimethoprim works by

A

works to inhibit dihydrofolate reductase, an enzyme that is important in the folic acid cycle. Dihydrofolate reductase’s normal role is the conversion of dihydrofolic acid to tetrahydrofolic acid in the thymidine synthesis pathway

53
Q

trimethoprim is often combined with

A

a sulphonamide, sulfamethoxazole, which are bacteriostatic antibiotics. As a side note, sulfamethoxazole acts on dihydrofolate synthetase, which is involved further upstream in the folic acid pathway

54
Q

what is trimethoprim and sulphonamide together called

A

co-trimoxazole- more effective than either of its standalone components.

55
Q

co-trimoxazol used to treat

A

uncomplicated pyelonephritis

COPD exacerbation

pneumocystis penumonia

56
Q

trimethoprim alone is commonly used to treat

A

UTIs, acne, prostatitis and shigellosis.

57
Q

trimethoprim should not be prescribed to

A

to a pregnant patient, particularly during the first trimester when folic acid supplements are often given to help with foetal development

58
Q

metronidazole main target

A

anaerobic bacteria and protozoa

59
Q

what sort of infections is metronidazole used to reeat

A

H. pylori

Fistulae in Crohn’s disease

Bacterial vaginosis

Pelvic inflammatory disease

Ulcerative gingivitis

Amoebiasis

Trichomoniasis

Giardiasis

Clostridium difficile.

60
Q

Normally for anaerobic infections metronidazole is prescribed for

A

7 days

61
Q

when a patient has C diff how long is metronidazole prescribed

A

10 to 14 days

62
Q

with C diff infection what is emtronidazole co-prescribed with

A

omeprazole/lansoprazole and clarithromycin/amoxicillin

Infection (36 decks)

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