Antimicrobial resistance (AMR) is a major problem in human and veterinary populations. A key way veterinarians can limit AMR is through reducing overall antimicrobial use (ACVIM consensus statement 2015). Culture and sensitivity testing (C&S) is recommended prior to commencing any antibiotics, but in primary-care practice where time and finances are frequently limited, this is often not possible.
We therefore aimed to evaluate the clinical need for antibiotics in a common condition where it is suspected primary-care veterinarians overuse antibiotics. We chose to study haemorrhagic diarrhoea in dogs, where two antibiotics are often administered as standard. Both amoxicillin-clavulanic acid and metronidazole are typically prescribed to severe cases of haemorrhagic diarrhoea, but there is no evidence that this is beneficial to the patient.
A clinical trial was designed to determine whether dogs with haemorrhagic diarrhoea had an improved clinical outcome when receiving both amoxicillin-clavulanic acid and metronidazole, or whether administration of amoxicillin-clavulanic acid alone was sufficient. Dogs presenting to a private primary-care veterinary hospital with haemorrhagic diarrhoea < 3 day duration were recruited to an ethically approved, prospective, placebo controlled, blinded treatment trial with owner consent. Cases were randomised to receive either metronidazole or saline in a blinded manner, in addition to receiving standard supportive therapy; amoxicillin-clavulanic acid, intravenous fluid therapy, analgesia and a gastroprotectant. Diagnostics were performed in accordance with the usual primary-care practice protocol; routine haematology and biochemistry but no faecal C&S. The efficacy of treatment was assessed by the duration of hospitalisation, and daily clinical progress was measured by a clinical scoring system.
Between Feb 2016 and Jan 2018, 34 dogs successfully completed the clinical trial. For cases receiving metronidazole, the average duration of hospitalisation was 29.6hr (SD 15.4hr). For the saline placebo this was 26.3hr (SD 11.5hr). There was no significant difference between the two patient groups. All dogs in the trial showed a significant improvement in daily clinical score between day 1 (admission) and day 2 (p < 0.001), but there was no statistically significant difference between the daily clinical scores when comparing the patient groups.
In summary, this clinical trial has two valuable conclusions. First, by demonstrating that two antibiotics are not necessary for treatment of haemorrhagic diarrhoea we have shown that antibiotic usage can be safely reduced in these patients. Second we have proven that rigorous clinical trials can be performed in primary-care practice in the absence of extensive diagnostics. It is hoped that similar trials examining possible overuse of antibiotics in other common conditions will be conducted in the future.
Post-doctoral research fellow
University of Cambridge
Sarah is a Diplomat of the American College of Veterinary Microbiology and has a PhD from Imperial College London. She divides her time between post-doctoral research into infectious disease at the University of Cambridge, and emergency small animal practice at a private hospital.
Thursday, June 14
5:00 PM – 5:15 PM
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