The International Society for Companion Animal Infectious Diseases (ISCAID) Antimicrobial Guidelines Working Group was formed to develop guidelines for antimicrobial drug use in dogs and cats, because of concerns that antimicrobial drug resistance has dramatically increased in prevalence among isolates from dogs and cats in the last decade. The founding members of the ISCAID Working Group are Scott Weese, Joseph Blondeau, Dawn Boothe, Edward Breitschwerdt, Luca Guardabassi, Andrew Hillier, Michael Lappin, David Lloyd, Mark Papich, Shelley Rankin, Jane Sykes, and John Turnidge. Input has also been obtained from panels of Diplomates of relevant specialty groups. It should be noted that members of the working group receive support from a variety of industry groups that provide funding for honoraria and research.

Guidelines for treatment of urinary tract disease in dogs and cats, respiratory disease and superficial pyoderma have been published and are available as open access documents for any individual to download (www.iscaid.org). During the course of guideline development, it became clear that there is a significant lack of objective, published information. Accordingly, recommendations are based on available data, whenever present, along with expert opinion, considering principles of infectious diseases, antimicrobial treatment, antimicrobial resistance, pharmacology, and internal medicine. Clinical trials that evaluate antimicrobial drug regimes for bacterial infections in dogs and cats are encouraged.

Because of the increased prevalence of antimicrobial drug resistance, the need to properly document the presence of an infection before initiating antimicrobial drug treatment is more important than ever. In veterinary medicine, this may be at odds with client financial resources. However, inappropriate use of antimicrobial drugs is wasteful of client resources when an infection is not present or a multidrug resistant pathogen is present, and risks selection for antimicrobial resistant bacteria that may be harmful to the pet, other animals, and also humans that are in contact with the animal. Clinicians should choose laboratories for culture and susceptibility (C&S) testing that follow protocols and use breakpoints published by the Clinical and Laboratory Standards Institute (CLSI), EUCAST or other internationally recognized institutions. The Working Group hopes that veterinarians will re-think the empiric use of antimicrobial drugs, especially when the underlying condition is not immediately life-threatening. An emphasis on rational antimicrobial treatment needs to be made to pet owners.

A selection of the basic recommendations within the respiratory and superficial pyoderma guidelines are summarized below and will be discussed. Doses of specific antimicrobial drugs are listed in the guidelines.^1-3 Updated urinary tract guidelines include information on bacterial prostatitis and urological procedures, and are covered elsewhere in these conference proceedings. In general, as the guidelines have evolved, there has been an emphasis on shortening the duration of antimicrobial therapy.

Recommendations for Superficial Pyoderma

The cause of most superficial bacterial folliculitis (SBF) in dogs is Staphylococcus pseudintermedius. Methicillin-resistant S. pseudintermedius (MRSP), which is often highly multiresistant, has now spread rapidly throughout the world. This has focused attention on the need to ensure that diagnosis and treatment of SBF is managed in an optimal way so as to resist the spread of this organism.

SBF only occurs when there is an underlying problem such as allergic dermatoses, hyperadrenocorticism, hypothyroidism, or demodicosis. These need to be differentiated from SBF.

Diagnosis of SBF should be supported by cytological examination and the demonstration of coccoid bacteria associated with inflammatory cells and within phagocytes. Cytology is also important for identification of co-infection with Malassezia pachydermatis.

SBF must be distinguished from other causes of folliculitis and pustular disease. It should be differentiated from demodicosis by deep skin scrapings and from dermatophytosis by fungal culture.

Culture is essential if there is a poor response to 2 weeks of appropriate systemic antimicrobial therapy, emergence of new lesions 2 weeks or more after the initiation of such therapy, presence of residual lesions after 6 weeks of therapy combined with cytology demonstrating infection with cocci, when cytology reveals intracellular bacterial rods, and when there has been a history of a multidrug resistant infection in the dog or a dog that shares the household. C&S testing is encouraged in cases of recurrent SBF infection or when there has been a history of treatment with antimicrobial drugs.

Specimens for culture should be taken from pustules. If pustules are not found, specimens may be taken from pus beneath crusts, and from papules or epidermal collarettes.

Contact with owners should be maintained to promote effective compliance and to determine if and when failure to respond to treatment, or recurrence, occurs.

Topical antimicrobials (ointments, gels and creams) should be considered, which can be applied to localised lesions 2 to 3 times daily. Such products may contain antibiotics (e.g., mupirocin), silver sulfadiazine, benzoyl peroxide and hydroxyl acids. More extensive areas of infection can be treated with shampoos, lotions, sprays and rinses. These contain antiseptics such as chlorhexidine, benzoyl peroxide, ethyl lactate, povidone iodine, triclosan and hydroxyl acids; they are commonly used 2 to 3 times weekly and until 7 days after lesions resolve, with contact times of 10 minutes before rinsing or conditioners. They can then be used for prophylaxis on a weekly or less frequent basis depending on response.

Empirical systemic drug therapy choices can be made in non-recurrent cases and when there has been no history of antimicrobial drug exposure. Otherwise, drug selection should be based on C&S tests. First-tier empirical drugs include clindamycin, first-generation cephalosporins, potentiated sulphonamides, and lincomycin. When first-tier drugs are not appropriate and topical therapy cannot be used, second-tier drugs may be chosen; these include fluoroquinolones, doxycycline, chloramphenicol and rifampin. Most of the Working Group members felt that third-generation cephalosporins should be second-tier drugs, but the evidence to support their placement in this category was lacking, and so they were listed as first- or second-tier drugs.

Systemic antimicrobial drugs given at subtherapeutic doses or as pulse therapy have been used to prevent or delay recurrence but such protocols are likely to promote the development of antimicrobial resistance and are discouraged.

Recommendations for Respiratory Disease

Acute Upper Respiratory Tract Disease (URTD)

Consider an observation period of up to 10 days without antimicrobial treatment for cats and dogs with acute URTD. Antimicrobial therapy should be considered if a mucopurulent nasal discharge is accompanied by fever, lethargy or anorexia. In the latter case, appropriate empiric therapy would be doxycycline (first choice) followed by amoxicillin. The duration should be 7–10 days.

Avoid performing C&S on nasal discharge from cats with acute URTD.

If empiric antimicrobial therapy is ineffective, a diagnostic workup is indicated.

Chronic Upper Respiratory Tract Disease in Cats

A diagnostic work-up is recommended. If treatable causes of nasal discharge are not identified, then nasal lavage or brushings could be submitted for C&S testing, and a nasal biopsy could be submitted for histopathology. Treatment should be based on these results.

Should nasal discharge recur, the previously effective antimicrobial drug should be used for a minimum of 48 hours; if this is ineffective, then switch to a different class should be considered, provided a diagnostic work-up to rule out other causes of nasal discharge (tumors, fungal infection, foreign bodies, etc.) has been performed.

Bacterial Bronchitis in Dogs and Cats

Airway lavage with cytologic examination and C&S testing is indicated if bacterial bronchitis is suspected.

While awaiting results of the above tests, empiric treatment is recommended with doxycycline for 7 to 10 days. If this results in clinical improvement, treatment should be continued for 1 week past resolution of clinical signs.

Pneumonia

Antimicrobial therapy for pneumonia should be initiated as soon as possible and within 1–2 hours if signs of sepsis exist.

Antimicrobial therapy should be parenteral while patients with pneumonia are hospitalized.

If there is no evidence of systemic sepsis, parenteral administration of a beta-lactam is recommended for empiric therapy; if signs of sepsis are present, then a combination of a fluoroquinolone and ampicillin or clindamycin is recommended pending the results of C&S if possible. Animals should be re-evaluated for possible discontinuation of antimicrobials no later than 10 to 14 days after starting treatment.

Pyothorax

Pyothorax should be treated with IV fluids and drainage of pus after placement of chest tubes. Surgical debridement may be required.

Empiric antimicrobial therapy pending the results of C&S should be with a parenteral combination of a fluoroquinolone and a penicillin or clindamycin.

It has been recommended that treatment continue for at least 3 weeks and ideally 4–6 weeks, but the optimum duration is unknown. Animals should be re-evaluated 10 to 14 days after starting treatment.

References

1.  Weese JS, Blondeau JM, Boothe D, et al. Antimicrobial Use Guidelines for treatment of urinary tract disease in dogs and cats: antimicrobial guidelines working group of the International Society for Companion Animal Infectious Diseases. Vet Med Int. 2011; Epub Jun 27.

2.  Hillier A, Lloyd DH, Weese JS, et al. Guidelines for the diagnosis and antimicrobial therapy of canine superficial bacterial folliculitis (Antimicrobial Guidelines Working Group of the International Society for Companion Animal Infectious Diseases). Vet Dermatol. 2014;25(3):163-e43.

3.  Lappin MR, Blondeau J, Boothe D, et al. Antimicrobial Use Guidelines for treatment of respiratory tract disease in dogs and cats: antimicrobial guidelines working group of the International Society for Companion Animal Infectious Diseases. J Vet Intern Med. 2017.