Antimicrobials

Question 1

What are some general mechanisms of action of antibacterials?

Answer 1

Disrupt cell wall synthesis
Disrupt protein synthesis
Disrupt cell membrane function
Disrupt nucleic acid synthesis

Question 2

Which classes of abx disrupt cell wall synthesis?

Answer 2

β-lactams

Glycopeptides

Question 3

Which classes of abx disrupt protein synthesis?

Answer 3

Tetracyclines
Aminoglycosides
Macrolides

Question 4

Which class of abx disrupt cell membrane function?

Answer 4

Polymixins

Question 5

Which class of abx disrupt nucleic acid synthesis?

Answer 5

Quinolones

Question 6

What are some examples of β-lactams?

Answer 6

Penicillins
Cephalosporins
Carbapenems
Monobactams

Question 7

What are some penicillins, and what are they active against?

Answer 7

Penicillin; mainly Streptococci

Amoxicillin; some gram -ve

Flucloxacillin; Staph and Strep

Co-amoxiclav; Staph, Strep, anaerobes and gram -ve

Question 8

What is an example of cephalosporin, and what is it active against?

Answer 8

Ceftriaxone

Broad spectrum, no anaerobe activity
Good activity in CSF (used for meningitis)

Question 9

What is an example of a carbapenem, and what is it active against?

Answer 9

Meropenem

V broad spectrum
Most gram -ve
Generally used in penicillin allergy
Empiric treatment for sepsis

Question 10

What is an example of a glycopeptide, and what is it active against?

Answer 10

Vancomycin

Active against most gram +ve
Requires therapeutic drug monitoring

Question 11

What is an example of a tetracycline, and what is it active against?

Answer 11

Doxycycline

Broad spectrum, used in penicillin allergy for gram +ve

Used against atypical pathogens in pneumonia, chlamydia and some protozoa

Question 12

What is an example of an aminoglycoside and what is it active against?

Answer 12

Gentamicin

Active against gram -ve
Reserved for gram -ve sepsis

Question 13

What is an example of a macrolide, and what is it active against?

Answer 13

Erythromycin

Alternative to penicillin for mild gram +ve infections
Atypical respiratory pathogens

Question 14

What is are examples of quinolones?

Answer 14

Ciprofloaxacin

Trimethoprim

Question 15

How does ciprofloxacin exert its actions?

Answer 15

Inhibits DNA gyrase

V active against gram -ve and atypical pathogens

Question 16

How does trimethoprim exert its actions?

Answer 16

Inhibits folic acid synthesis

Used for UTIs

Question 17

When are abx used for prophylaxis?

Answer 17

Peri-operative;
Prevention of surgical site infection
1 dose just before surgery to last duration of procedure

Short term;
For pts who have had contact w/ meningitis - gets rid of N. meningitidis colonising oropharynx

Long term;
Asplenia, immunodeficiency

Question 18

How are abx used to treat bacterial infections?

Answer 18

Empirical treatment for suspected infection

Treatment of culture proven infection

Question 19

How is the likely cause of infection determined?

Answer 19

Duration of illness 
PMH 
Occupational hx 
Travel hx 
Time of year 
Age 
Personal background 
Anatomical site

Question 20

How is an effective antibiotic determined?

Answer 20

Community or healthcare onset?
Severity of infection
Immune status of pt
Baseline rate of resistance

Question 21

How is antibiotic activity determined?

Answer 21

Disc sensitivity testing

Question 22

How do bacteria become resistant to abx?

Answer 22

Mutation of their own DNA

Acquiring resistance genes from other bacteria - horizontal transmission

Question 23

What are some adverse effects of abx?

Answer 23

Organ toxicity

Allergic reactions

Question 24

What are some specific abx toxicity, and the causative abx?

Answer 24

Nephrotoxicity - aminoglycosides, vancomycin
Hepatotoxicity - flucloxacillin
Ototoxicity - aminoglycosides

Question 25

What are mechanisms of and resistance?

Answer 25

Antibiotic inactivation;
β-lactamase

Alteration of target site;
Penicillin binding protein

Alteration of metabolic pathways

Reduced intracellular abx accumulation;
Active efflux, decreased permeability of cell membrane

Question 26

What is the minimum inhibitory concentration?

Answer 26

Minimum concentration of antibiotic required to inhibit growth of bacterium in vitro

Question 27

How can antibiotic resistance be prevented?

Answer 27

Infection control

Appropriate prescribing