Antibiotic classes

Question 1

Penicillins belong to which AB class?

What part of the bacteris do they target?

Answer 1

Beta-lactams

Target cell wall synthesis

Question 2

What ABx class does ciprofloxacin belong? How does it work?

Answer 2

(Flouro)quinolone class.

Acts by inhibiting DNA replication (acts on toboisomerases)

Question 3

Which ABx class (and examples) should never be used with statins? Why?

Answer 3

Macrolides - erythromycin, clarithromycin, azithromycin
They r both metabolised by the same liver enzyme resulting in increased statin bioavailability resulting in risk of myopathy/rhabdo

Question 4

What ABx class do cephalosporins belong?

Answer 4

Beta-lactams.

Eg ceftriaxone, cephalexin,

Question 5

What bad adverse reaction can you have to Vancomycin? What is the mechanism of this reaction?

Answer 5

Red man syndrome.
Driven by vancomycin directly activating mast cells to release histamine and cause skin reaction. Other Sx include Hypotension, Flushing and rarely Ototoxicity

Question 6

What class of ABx does vancomycin belong and how dies it kill bacteria?

Answer 6

Glycopeptide class.

Acts on the cell wall synthesis

Question 7

What class does erythromycin/azithromycin belong? How do they work?

Answer 7

Macrolides. Target the 50s subunit on ribosomes to prevent protein synthesis

Question 8

How does gentamicin work? What class idoes it belong to?

Answer 8

Inhibits 30s subunit of ribosomes preventing protein synthesis. Aminoglycosides

Question 9

How does Trimethoprim work?

Answer 9

DHFR inhibitor - interferes with folic acid synthesis in bacterial cells

Question 10

Name two ABx classes that act via inhibiting the 30s subunit of ribosomes

Answer 10

Tetracyclines (Doxycycline, Tetracycline) + Aminoglycosides (Gentamycin, Neomycin, Tobramycin)

Question 11

Daptomycin method of action

Answer 11

Loss of cell wall selective permeability

Note: binds to surfactant & cannot be used in lung infections

Question 12

Pt with MRSA pneumonia - what ABx can NOT be used and why?

Answer 12

Daptomycin. It binds to surfactant so cannot be used in lung infections

Question 13

Gold standard method for identifying osteomyelitis?

Answer 13

MRI

Question 14

Blood cultures are positive in __% of cases of osteomyelitis.
How frequently do swabs of wound correlate with bacteria at bone in osteomyelitis?

Answer 14

50%

superficial swabs rarely correlate with bacteria at bone in osteomyelitis therefore no need to do.

Question 15

No ABx therapy is recommended in persons with travellers diarrhoea unless..

Answer 15

Severe disease
Immunocomromised (HIV, … )
IBD
Have comorbidities that would be adversely affected by dehydration

Question 16

Treatment of travellers diarhhoea with ABx in A) normal, B) immunosuppressed Pt’s, reduces the duration of illness by how long?

Answer 16

A) nothing

B) 1-2days

Question 17

What complication can occur if Pt’s with uncomplicated gastro are treated with ABx?

Answer 17

Prolonged bacterial shedding = prolonged duration of bacteria in gut/stool ?prolonged contagious?

Question 18

What are the beta lactic antibiotics?

Answer 18

penicillins
cephalosporins
monobactams
Carbapenams - meropenem, ertapenem
Clavulinic acid
tazocin

Question 19

what drugs block folic acid synthesis?

Answer 19

trimethoprim

sulphonamides

Question 20

What are the 4 main mechanisms of antibiotic resistance

Answer 20

antibiotic inactivation
alteration of antibiotic target sites
decreased antibiotic permeability of cell wall
active antibiotic efflux

Question 21

what are the escappm bacteria, and how do you treat them?

Answer 21

Gram negatives with inducible chromosomal mediated beta lactase production, inactive 3rd gen cephalosporins
Need meropenum

enterobacter
serratia
citrobacter
acientobacter
pseudomonas
proteus
morganella

Question 22

How does flagyl / metronidazole work?

Answer 22

DNA damage

Question 23

What is the gene that encodes MRSA

Answer 23

MEC A gene

alters PBP therefore penicillin can’t bind

Question 24

ICU patient with resistant GNB on meropenum - what is it and how to treat?

Answer 24

Likely strentophonomonous maltophilia

Treat with bactrim

Question 25

what ABx inhibit 30s subunit ribosome and what bacteria d they target?

Answer 25

Aminoglycosides (gentamycin, tobramycin, neomycin) - gram neg including pseudomonas. No gram pos cover.
Tetracycline and Doxycycline - gram pos, limited gram neg + atypicals. All tetracyclines contraindicated in pregnancy, lactation

Question 26

Which ABx stains teeth in children and should never be given in those <8yo?

Answer 26

Tertracyclines/doxycycline

Question 27

In whom can tetracycline/doxycycline NOT be used?

Answer 27

Pregnant or lactating women. Kids <8yo (stains teeth + photosensitive rash)

Question 28

Gram positive cocci that are catalase + & coagulase + ?

Answer 28

Staph aureus

Question 29

bacteria class that are gram positive cocci catalase negative?

Answer 29

Streptococci

Question 30

Gram positive cocci catalase positive, coagulase negative?

Answer 30

Staph epidermidis / S saprophyticus

Question 31

Group B strep?

Answer 31

Strep agalactiae

Question 32

Group A strep?

Answer 32

Strep pyogenes

Question 33

gram pos cocci, catalase negative + complete haemolysis?

Answer 33

Strep agalactiae or Strep pyogenes