Monday, April 13, 2015

What can you do to reduce antimicrobial resistance?

bearded dragon medication
Do you consider antimicrobial resistance when treating companion animals with antimicrobials? A bearded dragon has a topical antimicrobial applied to a nasal fistula. 
How much thought do you give to the problem of antimicrobial resistance when prescribing (or taking) antimicrobials?

The American College of Veterinary Internal Medicine (ACVIM) has released the “ACVIM consensus statement on therapeutic antimicrobial use in animals and antimicrobial resistance” and it’s a worthy read.

The statement highlights the dangers of willy-nilly antimicrobial use but also points to areas where evidence is lacking. While many expert panels blame the veterinary use of antimicrobials for the development of antimicrobial resistance, the committee holds that “antimicrobial use in a single animal species (or humans) is the main force behind development of AMR in bacteria affecting that species” but adds that “transmission of resistant bacteria from animals to humans is an important concern, albeit one that is inadequately understood.”(p488).

Phil with Love is the Best Medicine Dr Nick Trout
Phil reckons Love is the Best Medicine - but he's needed more than love to deal with previous dental infections. Antimicrobials have their place but need to be used carefully. And the underlying cause (in Phil's case, some teeth that needed to be removed) must be addressed.
As the paper states – ANY use of antimicrobials – prudent or not – exposes bacterial pathogens and normal flora to a drug which imposes selection pressure for resistance. Bacterial infections usually occur in the context of an inciting or underlying cause, so attending to the underlying cause – rather than simply changing antimicrobials or dishing out more – is important.

It’s a paper that anyone who uses antimicrobials should read. For me, the following points were most helpful:
  • Antimicrobial resistant organisms are not necessarily more virulent. Infection which such organisms can lead to poor clinical outcomes (including death) due to factors not related to virulence, for example, delayed diagnosis. Rapid laboratory identification of these organisms is therefore critical.
  • Prevention of disease in the first place – through good husbandry, vaccination, excellent care and attention to sterility - is more important than simply avoiding using antimicrobials. And indeed, the jury is out about whether prevention of prophylactic use of antibiotics will actually reduce resistance.
  • Over the counter supply of antimicrobials online and from pet and feed supply stores is likely to increase resistance and should be discouraged.
  • There is still very little evidence around the length of an antimicrobial course. There has been a trend to argue for longer treatment courses, but according to the statement a shorter treatment course means that normal flora or commensal bacteria have reduced exposure to antimicrobial drugs (there’s also likely to be better client compliance, reduced expense, reduced inconvenience to the client and animal, and reduced risk of adverse drug effects). There is no minimal duration of an antimicrobial drug dose to prevent resistance. According to the paper, “antimicrobials should never be continued once there is clinical and microbiological evidence that an infection has been eliminated or once an alternate diagnosis has been made” (p494).
  • There is no definitive distinction between “narrow-spectrum” and “broad- spectrum” drugs and the concept may be misleading. For example, some supposedly narrow-spectrum agents have a huge impact on commensal flora. So these terms are avoided by the committee.
  • Vets should encourage clients to dispose of leftover antimicrobials in the practice, as this reduces the likelihood that they will be used at the owner’s discretion at home.

Meanwhile if you are interested in pharmacology, the Centre for Veterinary Education is hosting a two day symposium with some of the best pharmacology brains in the world. You’ll need to be able to attend this Thursday and Friday. View the program here. You do not need to be a pharmacologist to go - in fact this is very clinically focused. I went to the last one and it was accessible and extremely practical.


Weese JS, Giguere S, GuardabassiL, Morley PS, Papich M, Ricciuto DR & Sykes JE (2015) ACVIM consensus statement on therapeutic antimicrobial use in animals and antimicrobial resistance. Journal of Veterinary Internal Medicine 29:487498.