Antimicrobial stewardship

Question 1

Antimicrobial stewardship refers to
(AVMA)

Answer 1

the actions veterinarians take individually and as a profession to preserve the effectiveness and availability of antimicrobial drugs through conscientious oversight and responsible medical decision-making while safeguarding animal, public, and environmental health

Question 2

core principles of antimicrobial stewardship

Answer 2

• maintain animal health and welfare using preventative and management strategies to prevent common diseases
• using an evidence-based approach in making decisions to use antimicrobial drugs
• using antimicrobials judiciously, sparingly, and with continual evaluation of the outcomes of therapy, respecting the client’s available resources

Question 3

according to antimicrobial stewardship principles, when should we use antibiotics for dermatology cases?

Answer 3

only when topical therapy is expected to fail
- Many cases can resolve with topical treatment alone

Question 4

Highest Priority Critical Important (HPCIA) or Critically Important Antimicrobial (CIA) refer to what type of drugs?

Answer 4

an antimicrobial class authorized for use in both humans and animals

Question 5

what are the tier 1 antimicrobials?

Answer 5

• first generation cephalosporins (cephalexin),
• clindamycin,
• Amoxicillin-clavulanic acid

Question 6

what are the tier 2 antimicrobials?

Answer 6

(never use without a culture)
- Doxycycline,
- Minocycline,
- Fluoroquinolones (marbofloxacin, enrofloxacin),
- Chloramphenicol,
- Rifampin,
- Amikacin

Question 7

what are tier 3 antibiotics?

Answer 7

should be avoided since they are used in human medicine for patients with limited options
 Avoid in veterinary medicine with few exceptions
 Linezolid, Vancomycin
- never a need in veterinary dermatology
- 3rd gen cephalosprins will likely be upgraded to this tier

Question 8

can resistance to antibiotics spread from non-humans to humans?

Answer 8

There are human infections where evidence exists for the transmission of
resistant bacteria or resistance genes from non-human sources

Question 9

3 Ds of antimicrobial stewardship

Answer 9

De-escalate: reduce or minimize
systemic antibiotic usage

Decontaminate: clean-up site

Design – consider dose and duration to maximize delivery to the target site and killing of the organism (not just inhibiting)

Question 10

what does it mean to de-escalate antimicrobial use?

Answer 10

– reduce or minimize systemic antibiotic usage.
 Likely the most effective means to reducing resistance
 Question or confirm the need for systemic treatment
 Antimicrobials can be used if indicated – shorten duration

Question 11

what does decontamination mean for antimicrobial stewardship

Answer 11

– clean up the site. Topical therapy is the cornerstone of effective and judicious use of antimicrobials
 Reduce size of infection (fewer colonies, less drug needed) > Topical therapy
 Reduce biofilms (MICs may be 500X higher), remove barriers to blood supply > Topical therapy
 Reduce pre-disposing host factors (ex. inflammatory responses)
 Reduce potential spread in clinic and home

Question 12

what does ‘design’ mean as an antimicrobial stewardship principle?

Answer 12

– consider dose and duration to maximize delivery to the target site and killing of the organism (not just inhibiting)
 Avoid prescribing antibiotics prior to receiving culture results
 Choose a lower tier drug where possible
 Use the upper end of a dosing range (increased GI risk)
 Dead bugs don’t mutate (want to kill rather than inhibit)
 Dosing well above the MIC, trying to achieve MPC (mutant prevention concentration)
 Choose drugs with better penetration for deeper infections (Clindamycin, Fluoroquinolones)

Question 13

antibiotic treatment duration - what is it based, and will it change?

Answer 13

New guidelines may recommend a shorter duration (14 days) and emphasize reassessment.

According to ISCAID,
“Previous durations of treatment have no scientific basis and likely reflected convenience rather than thought. They are decades old and implemented before the insidious nature of resistance was understood.”

Question 14

should we use topical antibiotics if we are already using systemic?

Answer 14

antimicrobial shampoos or sprays should be used in all cases whenever possible, whether or not systemic drugs are used

Question 15

go- to products for pyoderma

Answer 15

chlorhexidine containing products

Question 16

contact time for shampoos in pyoderma cases

Answer 16

5-10 minutes contact time (BTC – by the clock!)

Question 17

shampoo and spray for pyoderma
- frequency and duration
- additional benefit of shampoos

Answer 17

• bathe the dog twice a week and use a topical chlorhexidine spray on non-shampoo days for the first two weeks,
  > slowly decreasing the shampoo frequency.
  > In this way I have a chlorhexidine containing product on the patients daily for the first two weeks.
  <><>
• Shampoos offer the additional benefit of rehydrating the skin and washing off allergens in the allergic patient.
• As with systemic treatments, topical treatments should continue until lesions are gone for at least 2 weeks; however, I find spray and shampoos to be a good control program for patients with recurrent pyoderma

Question 18

what is phovia?

Answer 18

• adjunct to antimicrobial therapy for pyoderma
• It uses fluorescent light energy and is promoted as a treatment to shorten antibiotic treatment courses and help wound

Question 19

what is the mutant prevention concentration?

Answer 19

(MPC) represents a threshold above which the selective proliferation of resistant mutants is expected to occur only rarely

Question 20

Therapy for the patient infected with Methicillin Resistant Staphylococcus Pseudintermedius
- treat based on what?
- which antibiotics should be our last resort and why

Answer 20

• should be treated as per culture test results
• Aminoglycosides and fluoroquinolones should be reserved for serious infections or when there are no other options
• MRSA seems to rapidly develop resistance to fluoroquinolones, as it is a one-step process, and this may be true for MRSP too.

Question 21

Therapy for the patient infected with Methicillin Resistant Staphylococcus Pseudintermedius
- good choice for antimicrobial, adverse effect with this drug

Answer 21

Trimethoprim sulfa (TMS)
- the period of time needed to resolve pyoderma with TMS increases the likelihood of inducing hypothyroidism with this sulfa drug
> breed sensitivities (eg. doberman)
- Patients on long term TMS should have their tear production checked regularly as KCS is another important potential side effect

Question 22

many MR cases are still sensitive to what drugs?

Answer 22

TMS and chloramphenicol

Question 23

MRSP infections are resistant to what drugs?

Answer 23

Resistant to all β-lactam antibiotics and are often resistant to many other antimicrobials

Question 24

MRSP infection - can we use clindamycin or erythromycin to treat? considerations for these drugs?

Answer 24

clindamycin can be a good choice
- look at culture and sensitivity
- MRSP cases that are sensitive to Clindamycin are best assessed for sensitivity to erythromycin
> avoid if not reported or resistant to erythromycin
> resistance may be induced > use D-test with adjacent erythromycin and clindamycin discs to predict inducible resistance
> In the absence of this test, one might consider alternate treatments when clindamycin is susceptible, but erythromycin is resistant

Question 25

MRSP infections - can we use tetra or doxycycline? another related drug to consider?

Answer 25

• many cases are susceptible, some are not
  > if resistant, consider minocycline as different genes confer resistance

Question 26

tetracycline resistance in staphylococci is determined by what? implications for drug choice?

Answer 26

Resistance to tetracyclines in staphylococci is mediated through tetracycline resistance genes
> tet (M) and tet (O), which confer resistance by ribosomal protection of the drug target,
> tet (K) and tet (L), which encode drug efflux pumps.
<><>
- tet (K) and tet (L) confer resistance to tetracycline and doxycycline, but not to minocycline
- Since tet (K) has been associated with a common MRSP clone, testing for minocycline in the face of resistance to tetracycline and doxycycline is a consideration.

Question 27

can we use chloramphenicol for MRSP infections? drawbacks?

Answer 27

• In some cases, chloramphenicol is the treatment of choice
  <><>
• However, chloramphenicol should be used with extreme caution, if at all, in patients with preexisting hematologic abnormalities, especially preexisting nonregenerative anemia.
  > Development of irreversible aplastic anemia (reported in humans) does not appear to be a significant problem for veterinary patients;
• however, a dose-related bone marrow suppression (reversible) is seen in all species, primarily with long-term therapy.
• Unfortunately, many of our patients need longer term therapy.
  > Accordingly, I check CBCs every two weeks. While I have not personally had a case of chloramphenicol induced myelosuppression, I have had cases of gastrointestinal irritation and especially hind end weakness; the latter seems to be more common in larger breed dogs.
  <><><><>
• GI side effects
• neurological side effects
• weakness?
• hematological?
  > owners must wear gloves
  > check CBC every 2 weeks

Question 28

MRSP infection therapy - is rifampin a good choice? adverse effects?

Answer 28

• Most of the MRSP cases I see are sensitive to rifampin on the antibiogram.
• In a study by Bajwa et al, there was a 2% fatality rate in dogs treated with rifampin, but may have died for unrelated reasons
• Adverse events were reported in 16% of the cases
• Increases in ALT were reported in 26.59% of cases
• most common time for adverse effects is 19-27 days into treatment
• Weekly serum biochemistry monitoring was recommended

Question 29

amikacin for MRSP pros and cons, considerations

Answer 29

• expensive
• only injectable available
• monitor renal panel and urine for casts weekly

Question 30

potentiated sulfonamide for MRSP use

Answer 30

• side effects limit usability when extended therapy is a consideration

Question 31

Topicals for treatment of MR infected patient

Answer 31

• chlorhexidine (available as 2% to 4% sprays, mousse, wipes, and shampoos)
• mupirocin
• fusidic acid
• dilute bleach
• pure oxygen shampoo
• phovia

Question 32

how long to continue treatment for MRSP recurrent pyoderma?

Answer 32

• treatment of the patient with recurrent pyoderma should continue for at least one to two weeks past clinical cure, which may mean more than three weeks for superficial pyoderma cases and two to three months for deep pyoderma
• Be sure to recheck the pet before the treatment is complete to be sure that there are no palpable lesions