Topical Antibacterial Agents

Question 1

Bacitracin MoA

Answer 1

Inhibits phospholipid receptors involved in peptidoglycan synthesis

Complexes with the carrier protein C55- prenol pyro phosphate which is involved in cell wall synthesis

Question 2

T/F

Bacitracin has good gram negative coverage

Answer 2

False
Minimal G-
Not active against pseudomonas , Nocardia, enterobacteriaceae, candida or cryptococcus

Question 3

T/F

Bacitracin is minimally effective at eliminating nasal carriage of S. Aureus

Answer 3

True

Question 4

T/F

Bacitracin is a frequent allergen in patients with chronic stasis derm or keratoconjunctivitis

Answer 4

True

Question 5

T/F

Anaphylaxis to bacitracin is possible with application to an ulcer bed

Answer 5

True

Question 6

Polymyxin B

MoA

Answer 6

Increases permeability of bacterial cell membrane , interacts with phospholipid components of membrane (detergent like mechanisms)!

Question 7

T/F

Polymyxin B is effective against fungi and gram positive organisms

Answer 7

False

Ineffective

Question 8

T/F

Bacitracin often co-reacts with neomycin such that patch testing to both may uncover neomycin allergy

Answer 8

T

Question 9

T/F

Bacitracin is bactericidal against G+ and Neisseria species

Answer 9

True

Question 10

Which organisms are Polymyxin B useful for treating ?

Answer 10

Gram negative Bacteria only

Effective against P.aeruginosa

Question 11

How does Polymyxin B work ?

Answer 11

Increased the permeability of bacteria cell wall membrane

Occurs by interacting with phospholipid components of membrane

Question 12

Neomycin MoA

Answer 12

Bactericidal
Inhibits protein synthesis
Occurs by binding to 30S subunit of ribosomal RNA

Question 13

What bacteria does neomycin cover

Answer 13

Bactericidal - most of clinically important G-
Some G+ including 
S. Aureus 
Proteus
H influenzae
E. coli
Klebsiella
Serratia

SPHECKS

Doesn’t cover p.aeruginosa or anaerobes (eg bacteroides)

Only weak activity against strep

Question 14

Neomycin adverse effects

Answer 14

Like aminoglycosides, ototoxicity and nephrotoxicity

Question 15

Mupirocin MoA

Answer 15

Bactericidal

Hinders bacterial RNA, protein and cell wall synthesis .

Inhibits bacterial isoleucyl t- RNA synthetase

Question 16

Mupirocin antibacterial coverage

Answer 16

S aureus
S epidermidis
S pyogenes
B-haemolytic strep
MRSA

NOT EFFECTIVE AGAINST ANAEROBES, FUNGI OR NORMAL SKIN

Question 17

T/F

Mupirocin ointment is equivalent to oral erythromycin in the treatment of impetigo

Answer 17

T

Question 18

Retapamulin MoA

Answer 18

Bacteriostatic
Inhibits protein synthesis via three mech
- binds to protein L3 on the 50s ribosomal subunit
- inhibiting ribosomal peptidyltransferase
- preventing translation initiation by blocking interaction of fmet-tRNA to p site of ribosome

Question 19

Retapamulin coverage

Answer 19

S pyogenes
Mupirocin resistant
MRSA
ANAEROBES

SpAMM

Question 20

Gentamicin topical MOA

Answer 20

Bactericidal

Inhibits protein synthesis by IRREVERSIBLE binding to 30S ribosomal subunits

Question 21

Gentamicin coverage

Answer 21

Some G+
Eg . s aureus

and -

Eg . E. coli
Proteus
P auruginosa

Question 22

Silver sulfadiazine MoA and coverage

Answer 22

Binds to bacterial DNA and inh replication

Gram + and - including p aeruginosa and MRSA

Most frequent use is in burns

Question 23

Iodoquinol

Coverage

Answer 23

Mechanism unknown 
Broad spectrum 
Eg. P. Acnes
P. Auruginosa 
Corynebacterium 
MRSA
Dermatophytes and yeasts 

PaPaCMDY

Question 24

Bacitracin is a polypeptide antibacterial agent produced by the Tracey I strain of bacillus subtilis

Answer 24

T

Question 25

What organisms is bacitracin active against ?

Answer 25

``` Minimal gram negative cover Effective against S. Aureus, S. Pneumoniae Neisseria H. Influenzae Treponema pallidum Actinomyces Fusobacterium ``` SapHATFuN

Question 26

When complexed with zinc , bacitracin becomes more water soluble and shelf life diminishes

Answer 26

False | Less water soluble and shelf life increases from 2-5 years

Question 27

Bacitracin can be combined with polymyxin B and possibly neomycin to provide a wider spectrum of bacterial coverage

Answer 27

T

Question 28

Bacitracin in combo with cetrimide or polymyxin B significantly reduces S aureus in wounds

Answer 28

T

Question 29

Bacitracin is minimally effective at eradicating nasal staph

Answer 29

T

Question 30

No systemic absorption of bacitracin occurs after bladder irrigation

Answer 30

T

Question 31

Neomycin is produced by strotomyces fradiae

Answer 31

T

Question 32

Neomycin may inhibit bacterial DNA polymerase

Answer 32

T

Question 33

Neomycin resistance has been reported in gram Neg and pos - therefore almost always used in combo

Answer 33

T Bacitracin typically added for gram positive coverage Polymyxin B added for pseudomonas coverage

Question 34

Neomycin is the most common cause of post op ACD and should be avoided

Answer 34

T

Question 35

Contact allergy to neomycin in patients with Rosacea is uncommon

Answer 35

T

Question 36

Mupirocin is formerly known as pseudomonic acid

Answer 36

T

Question 37

Mupirocin is a major metabolite of P. Fluorescens

Answer 37

T

Question 38

How protein bound is mupurocin?

Answer 38

95% | Therefore may be less effective on weeping wounds

Question 39

Iodoquinol is a halogenated quinolone derivative

Answer 39

T

Question 40

Sodium sulfacetamide inhibits bacterial dihydropteroate synthetase , preventing conversion of PABA to folic acid (Same mechanism as dapsone)

Answer 40

T

Question 41

Mupurocin cross reacts with gentamicin and neomycin.

Answer 41

F | Unique structure so does not cross react

Question 42

Metronidazole enhances cell mediated immunity

Answer 42

F | Suppresses