Antibiotics (2/2)

Question 1

beta lactam antibiotics

Answer 1

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

Question 2

most penicillins have the suffix

Answer 2

‘-cillin’

Question 3

penicillins all interfere with the

Answer 3

third and final stage of bacterial cell wall synthesis

Question 4

important penicillins to remember

Answer 4

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

Question 5

which bacteria are penicillins affective against and why

Answer 5

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

Question 6

which penicillin has some activity against gram-negative bacteria?

Answer 6

amoxicillin

Question 7

flucloxacillin is effective against

Answer 7

straphlococci and streptococci

Question 8

co-amoxiclav is a

Answer 8

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

Question 9

what can make amoxicillin less effective

Answer 9

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

Question 10

co-amoxiclav is effective against

Answer 10

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

Question 11

cephalosporins

Answer 11

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

Question 12

how are cephalosporins (a beta lactam) different to penicillins

Answer 12

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

Question 13

name a cephalosporin

Answer 13

ceftriaxone

Question 14

ceftriaxone is used to treat

Answer 14

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

Question 15

cephalosporins and clostridium difficile infection

Answer 15

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.

Question 16

carbapenems example

Answer 16

meropenem

Question 17

what is meropenem active against

Answer 17

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

Question 18

what is meropenem strongest against

Answer 18

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

Question 19

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

Answer 19

similar structure to penicillin

Question 20

what the main glycopeptide (another class of antibiotic)

Answer 20

vancomycin

Question 21

glycopeptides inhibit what

Answer 21

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

Question 22

vancomycin is active again

Answer 22

both aerobic and anaerobic bacteria

Question 23

important to remember about vancomycin

Answer 23

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

Question 24

why is vancomycin a last resort drug

Answer 24

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

Question 25

how is vancomycin delivered

Answer 25

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)

Question 26

other glycopeptide of note other than vancomycin

Answer 26

teicoplanin

Question 27

teicoplanin more poplar than vancomycin because

Answer 27

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

Question 28

what are the two main tetracyclines

Answer 28

tetracycline and doxycycline

Question 29

mode of action of doxycycline and tetracycline

Answer 29

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)).

Question 30

both doxycycline and tetracycline are

Answer 30

broad spectrum antibiotics

Question 31

what sort of infections are doxycycline and tetracycline useful in treating

Answer 31

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

Question 32

what sort of illnesses are doxycycline and tetracycline affective against

Answer 32

Chlamydia, rocky mountain spotted fever and typhoid fever

Question 33

what should doxycycline and tetracycline not be used to treat

Answer 33

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).

Question 34

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

Answer 34

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

Question 35

Bioavailability of tetracycline is

Answer 35

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

Question 36

macrolides work by

Answer 36

inhibiting protein synthesis

Question 37

name three macrocodes

Answer 37

erythromycin, clarithromycin and azithromycin

Question 38

macrolides have a similar spectrum of action as penicillins

Answer 38

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

Question 39

what is erythromycin used to treat

Answer 39

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

Question 40

erythromycin does not have great activity against

Answer 40

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.

Question 41

side effects of erythromycin

Answer 41

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.

Question 42

azithromycin can attack

Answer 42

H influenza and other gram-negative bacteria

Question 43

Clarithromycin dervived from erythromycin) treats

Answer 43

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

Question 44

quinolones work by inhibiting

Answer 44

bacterial replication through inhibiting DNA gyrase.

Question 45

in the UK the only quinolones available to prescribe are

Answer 45

fluoroquinolones

Question 46

name a fluoroquinolone

Answer 46

ciprofloaxin

Question 47

ciprofloxacin is best against

Answer 47

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.

Question 48

risk when taking quinolones

Answer 48

C.diff infection

Question 49

how can ciprofloxacin be used

Answer 49

an eye drop, ointment, orally and IV

Question 50

ciprofloxacin used to treat

Answer 50

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

Question 51

which other antibiotics not within the classes mentioned inhibit bacterial replication

Answer 51

trimethoprim and sulphonamides

Question 52

trimethoprim works by

Answer 52

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

Question 53

trimethoprim is often combined with

Answer 53

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

Question 54

what is trimethoprim and sulphonamide together called

Answer 54

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

Question 55

co-trimoxazol used to treat

Answer 55

uncomplicated pyelonephritis COPD exacerbation pneumocystis penumonia

Question 56

trimethoprim alone is commonly used to treat

Answer 56

UTIs, acne, prostatitis and shigellosis.

Question 57

trimethoprim should not be prescribed to

Answer 57

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

Question 58

metronidazole main target

Answer 58

anaerobic bacteria and protozoa

Question 59

what sort of infections is metronidazole used to reeat

Answer 59

H. pylori Fistulae in Crohn’s disease Bacterial vaginosis Pelvic inflammatory disease Ulcerative gingivitis Amoebiasis Trichomoniasis Giardiasis Clostridium difficile.

Question 60

Normally for anaerobic infections metronidazole is prescribed for

Answer 60

7 days

Question 61

when a patient has C diff how long is metronidazole prescribed

Answer 61

10 to 14 days

Question 62

with C diff infection what is emtronidazole co-prescribed with

Answer 62

omeprazole/lansoprazole and clarithromycin/amoxicillin