While antibiotics are essential medicines for treating bacterial infections, it is important to remember that their use leads to selection of resistant strains of bacteria. Resistance may be intrinsic (chromosomal DNA changes) or acquired (by plasmid transfer).

The veterinary profession must use antibiotics responsibly to:

• Minimize the selection of resistant veterinary pathogens (safeguarding animal health)
• Minimize possible resistance transfer to human pathogens
• Retain the right to prescribe certain antibiotics.

Following guidelines will help maximize the therapeutic success of antibiotics while minimizing the development of antibiotic resistance. These guidelines should be read in conjunction with the individual drug monographs, updated BSAVA Guide to the Use of Veterinary Medicines  and the PROTECT ME guidance (www.bsavalibrary.com).

Following the PROTECT ME guidance can help combat AMR:

Prescribe only when necessary  Consider non-bacterial disease (e.g. viral infection), nutritional imbalance or metabolic disorders where antibiotic therapy would be redundant. Remember that some bacterial disease will self-resolve without antibiotics. Offer a non-prescription form to support a decision not to prescribe antibiotic therapy. Prophylactic antibiotics are not a substitute for surgical asepsis and their use around surgery should be carefully considered. Prophylactic antibiotics are only appropriate in a few medical cases (e.g. immunocompromised patients).

Replace with non-antibiotic treatments Consider therapeutic alternatives (e.g. lavage and debridement of infected material, analgesia, cough suppressants, fluid therapy or nutritional modification) and measures to address underlying conditions that may negate the need for antibiotics. Use topical preparations (ideally antiseptics) as these reduce the selection pressure on resident intestinal flora (the microbiome).

Optimize dosage protocols Use the shortest effective course and avoid underdosing. Treat until clinical resolution.

Treat effectively Before prescribing antibiotics, consider which bacteria are likely to be involved and how effectively the chosen drug will penetrate the target site (e.g. prostatitis, osteomyelitis). Consider pharmacokinetics and drug interactions with concurrent medication. Provide instructions, including demonstrations, on how to administer prescribed antibiotics. 

Employ narrow spectrum Selecting narrow-spectrum antibiotics limits the effects on commensal bacteria. Avoid antibiotic combination therapy. Use culture results to support de-escalation (switching to a narrower spectrum antibiotic) whenever possible.

Conduct cytology and culture Use cytology to demonstrate bacterial involvement and an inflammatory response consistent with infection (e.g. intracellular bacteria). A sample for culture should be collected before starting antibiotic therapy. Culture is essential when prolonged (>1 week) treatment courses are anticipated, when there are risk factors for resistance (e.g. healthcare associated infections, antibiotic treatment in the prior 60 days or multiple prior courses/repeated antibiotic use) and with life-threatening infections. If first-line treatment fails, do not use another antibiotic without culture and susceptibility results.

Tailor your practice policy A customized practice policy can guide antibiotic selection to address the bacterial infections and resistance patterns that you encounter, minimizing inappropriate use.

Monitor Track and record culture profiles and update your practice policy accordingly. Monitor for preventable infections (e.g. surgical site infections) and alter practice protocols if needed. Audit your own antibiotic use, particularly of EMA Restrict category antibiotics (fluoroquinolones/3rd generation cephalosporins).

Educate others Share this important message to reduce the threat from multi-resistant strains of bacteria and improve the health of pets and people. Encourage return of leftover antibiotics for safe disposal.

European Medicines Agency categorization of antibiotics

In 2019, the EMA launched a public consultation on its updated scientific advice on the categorization of antibiotics. The scientific advice ranks antibiotics by considering both the risk that their use in animals causes to public health through the possible development of antimicrobial resistance and the need to use them in veterinary medicine. It now addresses all classes of antibiotics, including those classified as critically important antimicrobials for human health by the World Health Organization (see Useful websites).

Readers are encouraged to check and consider the EMA’s updated scientific advice on the categorization of antibiotics when prescribing these medicines for animals in their care. The categorization can also be used as a tool for the preparation of treatment guidelines (see Useful websites). The classification comprises four categories:  

• Category A (Avoid) includes antibiotics that are currently not authorized in veterinary medicine in the European Union (EU). These medicines may not be used in food-producing animals and may be given to individual companion animals only under exceptional circumstances.
• Category B (Restrict) refers to quinolones, 3rd- and 4th-generation cephalosporins and polymyxins. Antibiotics in this category are critically important in human medicine and their use in animals should be restricted to mitigate the risk to public health.
• Category C (Caution) covers antibiotics for which alternatives in human medicine generally exist in the EU, but only few alternatives are available in certain veterinary indications. These antibiotics should only be used when there are no antibiotic substances in Category D that would be clinically effective.
• Category D (Prudence) includes antibiotics that should be used as first line treatments, whenever possible. These antibiotics can be used in animals in a prudent manner. This means that unnecessary use and long treatment periods should be avoided, and group treatment should be restricted to situations where individual treatment is not feasible.

Antibiotics in small mammals

Antibiotic therapy in several small mammal species poses a greater risk when compared with other species due to the suppression of normal bacterial flora, resulting in overgrowth of other species, notably Clostridium, resulting in enterotoxaemia and death. Mice, rats, ferrets and usually gerbils are fairly resistant, whereas hamsters, guinea pigs, chinchillas, degus and rabbits are more susceptible. The risk of enterotoxaemia is related to several factors, including the drug selected, the dose, the route of administration and the animal’s nutritional status  and general health. Antibiotics that have been associated with this problem when given orally include penicillins, lincosamides, cephalosporins and erythromycin. Some species appear more sensitive to certain drugs than others, while some medications appear welltolerated by alternative routes (e.g., injectable benzylpenicillin in rabbits). See individual monographs for more details.

References

Allerton F and Nuttall T (2021) Antimicrobial use: importance of bacterial culture and susceptibility testing. In Practice 43, 500–510

Sykes J (2022) Greene’s Infectious Diseases of the Dog and Cat, 5th edn. Saunders, Philadelphia