Page 1473 - Small Animal Internal Medicine, 6th Edition

CHAPTER 92 Practical Antimicrobial Chemotherapy 1445

aminoglycosides, tetracycline derivatives, and quinolones pyoderma involving methicillin-resistant staphylococcal
can be used successfully in those cats. infections, and empirical drug selection for systemic therapy
VetBooks.ir neonatally infected, transplacentally infected, and immuno- is always contraindicated when a methicillin-resistant staph-
Toxoplasma gondii occasionally causes pneumonia in
ylococcal infection is suspected due to the high prevalence
suppressed cats and dogs (see Chapter 98). Clindamycin or
agement of suspect cases should always be guided by anti-
potentiated sulfas should be used if toxoplasmosis is sus- of multidrug resistance within these strains. The case man-
pected. Azithromycin may also be effective for the treatment microbial sensitivity results.
of toxoplasmosis. Neospora caninum has occasionally been Other explanations for cutaneous and soft tissue infections
associated with pneumonia in dogs and should be treated that fail to respond to routine treatments include infections
with a combination of clindamycin and potentiated sulfas. with gram-negative bacteria, L-form bacteria, Mycoplasma
If pyothorax is attributable to penetration of foreign spp., Mycobacterium spp., systemic fungi, or Sporothrix spp.
material from an airway or esophagus into the pleural space, (see Fig. 99.3), These cases should undergo further diag-
thoracotomy is usually required for removal of devitalized nostic testing and appropriate treatments administered. If
tissue and the foreign body (see Chapter 24). Pyothorax not previously done, microscopic examination of tissue or
occasionally results from hematogenous spread of bacteria pustule aspirates should be performed for the presence of
to the pleural space; this may be common in cats. Pleural Sporothrix organisms and bacteria morphologically similar
lavage through chest tubes is the most effective treatment for to Mycobacterium spp. After surgical preparation of the skin,
patients with pyothorax and no obvious foreign material. deep tissues should be obtained for aerobic, anaerobic, Myco-
Most dogs and cats with pyothorax have mixed aerobic and plasma, fungal, and atypical Mycobacterium spp. culture (see
anaerobic bacterial infections. Animals with pyothorax and Chapter 91).
clinical signs of bacteremia should initially be administered
a combination of fluoroquinolones and a penicillin or
clindamycin, and then the antibiotic therapy should be UROGENITAL TRACT INFECTIONS
adjusted based on the culture, susceptibility results, and
clinical response (Lappin et al., 2017). Treatment duration is Antimicrobial use guidelines for treatment of urinary tract
determined by clinical responses and repeated thoracic disease in dogs and cats were recently published by the Anti-
radiographs, and is usually at least 4 weeks duration. microbial Guidelines Working Group of the ISCAID (Weese
et al., 2011; Weese et al., 2017). The Working Group rec-
ommended that amoxicillin or trimethoprim-sulfonamide
SKIN AND SOFT TISSUE INFECTIONS be prescribed to dogs or cats with uncomplicated infec-
tions (sporadic bacterial cystitis). Dogs or cats with com-
Staphylococcus pseudointermedius is the most common cause plicated infections should be administered amoxicillin or
of pyoderma in dogs and cats. Any organism, including trimethoprim-sulfonamide and then have the antimicrobial
gram-negative types, can induce deep pyoderma. Most soft therapy guided by results of culture and antimicrobial sus-
tissue infections, including open wounds and abscesses, are ceptibility results. Classically, antibiotics were administered
infected with a mixed population of bacteria; the aerobic and for 7 to 14 days to animals with simple urinary tract infec-
anaerobic flora from the mouth are often involved. Recom- tions. However, recent evidence suggests short-term proto-
mended empirical antibiotic choices for routine cases of pyo- cols could be effective. For example, in a recent study of dogs
derma and soft tissue infections are listed in Table 92.3. with simple urinary tract infections, administration of enro-
Guidelines for the diagnosis and treatment of superficial floxacin at 18 to 20 mg/kg PO q24h for 3 days or amoxicillin-
bacterial folliculitis have been published that discuss optimal clavulanic acid at 13.75 to 25 mg/kg PO q12h for 14 days
topical and systemic treatments (Hillier et al., 2014). When had similar microbiologic cure rates (Westropp et al., 2012).
systemic treatment is deemed appropriate, the first-tier There is no indication for repeat urinalysis or culture for
drugs recommended included clindamycin, lincomycin, simple infections if clinical signs resolve and the drugs are
first-generation cephalosporins, amoxicillin-clavulanate, or administered as prescribed (Weese et al., 2011; Weese et al.,
potentiated sulfas. Other drugs to be used as second and 2017). For cases with complicated infections, antimicrobial
third tiers (third-generation cephalosporins, doxycycline, therapy should be administered for at least 4 weeks with
minocycline, chloramphenicol, fluoroquinolones) should monitoring of clinical response, and urine culture and sus-
also be based on antimicrobial susceptibility results (Hillier ceptibility testing (usually 5 days after stopping treatment).
et al., 2014). Fluoroquinolones are often the antibiotic class It is possible that shorter duration of therapy for complicated
of choice for the treatment of gram-negative infections. cases could be considered.
The World Association for Veterinary Dermatology pub- All dogs and cats with urinary tract infection and azote-
lished recommendations for the approach to methicillin- mia should be assumed to have pyelonephritis and be treated
resistant staphylococcal infections (Morris et al., 2017). accordingly, even if further diagnostic procedures are not
Many key points were presented, including use of topical performed. The ISCAID Working Group recommends
therapy with known antistaphylococcal efficacy as the administration of a fluoroquinolone initially with adjust-
primary treatment modality for any surface or superficial ments based on susceptibility results. If Leptospira spp.