Urinary tract

If it is unclear whether culture will be positive, consider giving pain relief (if there are signs of pain) and await culture results rather than starting empirical antimicrobials straight away (see delayed prescribing technique).

If empirical antimicrobials are indicated, initial therapy should consist of amoxycillin or trimethoprim / sulphonamide.

Recommended treatment length is 3-5 days.

Treatment of intact male dogs with no evidence of prostatitis or animals with comorbidities not involving the urinary tract (e.g. pets with clinical UTI that receive immunosuppressives, are obese or have endocrinopathies) and with non-recurrent cystitis are included in the above recommendation.

There should be an adequate response to treatment within 48 hours (i.e. signs reduce/resolve) and if not, further investigation considered. DO NOT change antibiotics empirically (i.e. without culturing) if clinical signs persist.

Change antibiotics if initial culture results indicate resistance to empirical antimicrobial AND there is a lack of response. Do not change antibiotics if there was good clinical response (even if the bacteria are resistant in vitro).

If clinical signs resolve, follow-up culture is NOT recommended.

Treatment should be based on culture and susceptibility testing results. If required, empirical therapy can be initiated prior to results with amoxycillin or trimethoprim / sulphonamide. Preference should be given to drugs that are excreted in the urine in the active form (not macrolides).

Anecdotal evidence suggests that in mixed infections including Enterococcus spp., infection with this isolate will often resolve with effective treatment of other isolates, however ideally an antimicrobial that is effective against both pathogens should be selected. Note, there is no evidence that some drugs (ie clarithromycin) are effective at breaking down biofilms, these should be avoided as they are not excreted in the urine in active forms.

Treatment length may vary depending on the clinical signs/comorbidities; goal of treatment is clinical cure (i.e. no clinical signs) and no adverse effects (including antimicrobial resistance). Microbiological cure (i.e. negative culture) is desirable but not necessarily achievable.

Consider pain relief whilst awaiting culture results, in lieu to starting antimicrobials empirically straight away. If empirical therapy is started, first choice is as for sporadic cystitis

Short duration (3-5 days) should be considered, particularly if infection appears to be a reinfection (not relapse/persistence) and/or the animal has comorbidities that relate to organs other than the urinary tract

Recommendation for longer courses has now shortened to 7-14 days (used to be 4 weeks); these to be considered if there are urinary tract abnormalities (e.g. bladder mucosa abnormalities)

If there is likely tissue involvement (e.g. bladder wall mucosa infection, TCC) then antimicrobial type and dosing needs to achieve adequate concentration in tissue, i.e. amoxicillin-clavulanate is NOT recommended.

Culture during treatment not recommended if short duration of treatment chosen. Culture after 5-7 days is reasonable if there is a longer duration of treatment, but approach to culture result must be considered. Positive cultures indicate the need for evaluation of compliance and further diagnostic testing, to determine why the bacterium has not been eliminated, not simply a change in antimicrobial, particularly if clinical cure has been documented. Negative results could be used to help determine when to stop therapy if a long course of treatment is being used, but are not a guarantee of microbiological cure. Culture of urine specimens, ideally collected by cystocentesis, can be considered 5–7 days after cessation of antimicrobials in animals where clinical cure is documented. However, this should be used as part of the diagnostic process to help differentiate relapse, re-infection and persistent infection, and to guide potential future diagnostic testing, not as an indication of a need to treat. The presence of bacteriuria post-treatment should be approached as described under ‘Subclinical bacteri-uria’. If client compliance is deemed to have been adequate, referral to a specialist should be considered to explore reasons for microbial persistence or rapid re-infection.

Treatment of SBU with antimicrobials is discouraged, even if there is evidence of pyuria or the isolated organism is multidrug-resistant. If it is unclear whether the animal has SBU or clinical UTI a short course of treatment (3-5 days, as for sporadic cystitis) is recommended – if there is no discernable clinical improvement further treatment is discouraged.

In rare circumstances, treatment of SBU may be considered if there is concern of high risk of ascending or systemic infections. By extrapolation of data from humans, not many animals may be at risk of developing ascending or systemic infections when SBU is present.

In animals that cannot display clinical signs (e.g. paralysed) judgement must be made whether treatment is indicated.

If Corynebacterium urealyticum or Staphylococci are isolated short course treatment may be considered because of their associations with encrusting cystitis and struvite urolith formation, respectively. Because of the potential difficulties in treating these conditions, consideration of a single short course (3–5 days duration) of treatment, as per ‘Sporadic bacterial cystitis’, could be considered after confirming that bladder wall plaque or uroliths are not present. However, it is unknown whether this is a necessary or effective approach. Continued treatment of subclinical bacteriuria with these strains is likely not warranted.

There is currently no evidence that adjunctive treatment (e.g. cranberry extract) is effective but there is no contraindication to the use of supplements that are known to be safe.

If an animal subsequently develops clinical UTI or pyelonephritis, it must not be assumed that this is caused by the SBU strain. Approach these cases is as mentioned in other categories (i.e. recurrent cystitis, pyelonephritis).

Serum/soft tissue concentrations of the antimicrobial are the key determinant to potential drug efficacy rather than urine concentrations (i.e. chose antimicrobials that ‘reach’ tissue). Initial (empirical drugs) should be effective against Enterobacteriaceae (e.g. E. coli) e.g consider fluoroquinolones. If the animal is clinical unwell (dehydrated, anorexic, lethargic) consider parenteral administration

Review antimicrobial therapy when culture results are available (i.e. consider de-escalation if 2 antimicrobials used; consider change if resistance in vitro and no clinical response; if there is clinical response then same antimicrobial therapy may be continued despite in vitro resistance, if response is not explained by other treatment factors (e.g. fluids, pain relief).

Consult with specialist if multidrug resistance is encountered.

If there is no appropriate response to treatment within 72 hours of therapy then diagnosis needs to be re-considered, e.g. it could be possible that there is other disease explaining the signs and concurrent subclinical bacteriuria.

Treatment length recommendation is 10-14 days. Physical examination, clinicopathological examination (e.g. CBC/biochem) and urine culture 1-2 weeks after cessation of therapy.

However, if clinical signs and azotemia have resolved, consideration has to be given to the clinical relevance of microbiological failure, as it may represent subclinical bacteriuria and not indicate a need for treatment. Re-isolation of the same bacterial species as that identified initially should stimulate consideration of reasons for potential persistence, including antimicrobial resistance, urolithiasis, anatomic defects or immune deficiency. Management of positive urine cultures in animals that have responded clinically and hematologically should be as per ‘Subclinical bacteriuria’.

Prostatic abscesses should be drained because of the low likelihood of resolution with medical treatment alone. Surgical or ultrasound-guided percutaneous drainage can be performed. This should be performed after culture results are available, whenever possible, to facilitate proper perioperative antimicrobial therapy. Concurrent with drainage, treatment as for chronic prostatitis should be administered. Empirical treatment should target Enterobacteriaceae. Administration of a veterinary fluoroquinolone should be considered while awaiting culture and susceptibility testing results, particularly if brucellosis is suspected.

Trimethoprim-sulfonamide has a spectrum of activity that includes a broad range of potential pathogens.

Clindamycin and macrolides can effectively penetrate the blood-prostate barrier, but should only be used based on culture and susceptibility test results, and not for empiric therapy because of lack of efficacy against Gram-negative bacteria. The blood-prostate barrier reduces the penetration of many drugs, such as penicillins, cephalosporins, aminoglycosides and tetracyclines. This barrier is typically considered to be less intact in acute prostatitis; however, these drugs should be avoided, regardless of in vitro susceptibility data, particularly in cases of chronic prostatitis. If a bacterial isolate that is resistant to fluoroquinolones, trimethoprim-sulfamethoxazole, clindamycin and chloram- phenicol is present, consultation with a theriogenologist, veterinary microbiologist, pharmacologist or internist with expertise in infectious diseases or urology is recommended. Ciprofloxacin should not be used because of the unpredictable bioavailability in dogs and relatively poor prostate penetration compared to enrofloxacin.

Four weeks is typically recommended for acute prostatitis, with 4–6 weeks for chronic disease. Shorter durations might be effective in acute cases that are castrated and where there is quick clinical response; however, objective data are lacking. A longer duration of treatment may be required in some chronic cases, particularly when abscessation is present or when castration is not performed. Castration should be recommended in dogs that are not intended for breeding. Castration does not alter the recommended antimicrobial drug choice or duration, but should be performed as early as is possible. Other medical approaches to control underlying prostatic disease should be considered (e.g. finasteride, androgen receptor antagonists or GnRH agonists). These approaches are less successful when intraprostatic cysts or abscesses are present. Ultrasonographic re-evaluation of prostatic size and internal architecture is advised in dogs 8–12 weeks after treatment.

When initial treatment has failed and antimicrobial resistance or other correctable factors such as client compliance have not been implicated as the cause, resolution of infection is unlikely. In such cases, castration is strongly recommended, if not performed initially. Poor initial response to therapy should lead to re-assessment of the diagnosis and if prostatitis is still suspected. Collection of ultrasound-guided fine needle aspirate of prostatic cyst fluid or prostatic tissue core biopsy for culture and cytology or histopathology should be considered, and/or a BRAF test if not already performed. If further testing is not possible and prostatitis is still suspected, empirical change to a different antimicrobial can be considered because ejaculate culture does not always correlate with prostatic cyst fluid or prostate tissue core biopsy culture. A drug from a different drug class should be chosen if an empirical change is made. In dogs with persistent prostatic abnormalities (e.g. prostatomegaly) but no clinical signs consistent with prostatitis, subsequent treatment should focus on treatment of episodes of cystitis that develop. This should be managed as described under ‘Sporadic bacterial cystitis or “Bacterial prostatitis”, with the goal being elimination of clinical signs.

Prostatic size should be monitored by ultrasound transrectal palpation. Culture of prostatic fluid or urine can be performed during the course of therapy, but is not recommended. Clinical response and monitoring of prostatic size/architecture are better indicators of whether treatment is successful. Semen quality improves with resolution of bacterial prostatitis in most cases.

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