How do antimicrobial use and frequency of microbial identification testing differ between general practice and referral?

3 November 2025

Antimicrobial resistance (AMR) is considered one of the most significant global public health threats, and understanding patterns of antimicrobial prescription is crucial to reducing their use and slowing the rate of AMR. There is currently limited information on practice and geographical variation in antimicrobial prescribing and on the use of bacterial culture and sensitivity to guide prescriptions.

A new study published in the American Journal of Veterinary Research has described antimicrobial (AM) prescribing patterns in companion animals in general practice and referral in the UK, and compared the frequency of bacterial culture and sensitivity performed in both.¹

The study included 516 dogs and cats referred to the Internal Medicine Department of the Queen’s Veterinary School Hospital, University of Cambridge, over a 12-month period, who were assessed from presentation to discharge. Information collected for patients receiving AMs included AM class, specific drugs prescribed, total dose, frequency of administration, microbial identification tests performed (culture/sensitivity or PCR), and test results. The total number of prescriptions for each AM class, and the number of microbial identification tests performed both before and after referral were compared.

AM prescription rates were 23% before referral (23% of dogs and 24% of cats), and 22% at the time of discharge after referral (20% of dogs and 28% of cats). There was a tendency towards decreased odds of AM prescription before referral with increasing age, and older animals were also less likely to be discharged after referral on AMs. Animals receiving AMs before referral were 2.7 times more likely to be discharged from referral on AMs, suggesting that previously prescribed medications can influence subsequent treatment decisions.

Penicillins were the most commonly prescribed AMs in both dogs and cats, both before (69% and 72%, respectively) and after referral (87% and 63%, respectively). 8% of cases received a combination of 2 AMs at the time of referral, with the most common combination in dogs being a penicillin and metronidazole. After referral, 11% of cases were given a combination of 2 AMs, the most frequent combination being penicillin and a fluoroquinolone in both dogs and cats.

There was a notable difference in fluoroquinolone prescription rates between referral clinicians (13%) and GPs (7%) and in the frequency of microbial identification tests to guide fluoroquinolones use (used in 85% of cases prescribed a fluoroquinolone at referral and 13% of cases by GPs), despite guidelines that fluoroquinolones should only be used where culture and sensitivity have been performed. None of the fluoroquinolones prescribed by GPs were continued by referral clinicians, suggesting that their use was deemed inappropriate, possibly inferring poor AM stewardship.

Underdosing of AMs (defined as a prescription lower than that in the BSAVA Small Animal Formulary and ‘PROTECT ME’ guidelines) was more frequent by GPs (occurring in 16% of AMs prescribed by GPs compared to 3% by referral clinicians). In cases where AMs had been started by GPs and continued by the referral clinician, either the dose or AM agent was altered in 72% of cases, suggesting that optimal dosages were not initially used, or there were differences in clinician preference.

Microbial identification tests were more commonly performed after referral (72% of cases receiving AMs, of which 48% had a positive bacterial infection result) than before referral (17%, of which 4% had a positive result). Notably, although 6 cats were prescribed AMs by GPs for suspected urinary tract infections, only one had a positive urine bacterial culture result, yet current International Society for Companion Animal Infectious Diseases (ISCAID) guidelines recommend that all cats suspected of bacterial cystitis should undergo bacterial culture and sensitivity testing, suggesting poor adherence to guidelines. Of the cases discharged from referral on AMs, a bacterial etiology was found in 52%.

The most common disease organ system prescribed an AM by GPs was the urinary system (28%), and at referral was the respiratory system (47%) and the urinary system (33%). Post-referral respiratory, urinary cases, and haematology/immunology cases were 7.3 times, 4.4 times and 3.7 times more likely, respectively, to be discharged on AMs.

Limitations of the study are that only referred cases were included, which are likely to be more complex or critically ill cases, possibly increasing the chance of AM and HPCIA use, and may underrepresent AM prescribing cases in general practice. The study was also limited to cases referred within a restricted timeframe of one year and referred specifically to the internal medicine department.

Take home message

These findings highlight poor AM stewardship and adherence to stewardship guidance in GP practices, with inappropriate use of HPCIAs (including fluoroquinolones), AM underdosing, and a lack of bacterial culture and sensitivity testing. There’s a noticeable difference in the use of microbial identification tests and bacterial culture between general practitioners and referral clinicians.

Further resources

The Animal Medicines Amnesty is taking place throughout November. The aim is to encourage pet owners to return any unused or out-of-date pet medicines to veterinary practices. This will allow for correct and safe disposal of these medications, which will avoid contamination of the environment and help prevent medicines resistance due to inappropriate use or disposal.

Practices can sign up today to receive campaign updates and a full campaign toolkit is available to download from RUMA Companion Animal and Equine here: https://bit.ly/4nvEO3r

BSAVA/SAMSoc Guide to Responsible Use of Antibiotics: PROTECT ME

BSAVA/SAMSoc/RWA&F Guide to Responsible Use of Antibiotics in Rabbits

Antimicrobial stewardship library collection

Reference

1. Lord A, Russell O, Hodds C, Williams T & Skelly B (2025) Antimicrobial use differs between general practice and referral settings in United Kingdom companion animals: a 12-month prospective study. American Journal of Veterinary Research. https://doi.org/10.2460/ajvr.25.06.0229