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The most prevalent microorganisms isolated from urine specimens of dogs (385) and cats (132) with clinical signs of urinary tract infections were Escherichia coli, Proteus spp., and Staphylococcus aureus. The results of quantitative urine-culturing methods showed 48.6% of the canine and 12.1% of the feline specimens had more than 10(5) organisms per ml of urine. The bacteria isolated appear to have a greater resistance to antibacterial agents than previously reported.

Swab specimens obtained from skin lesions of 45 cats were cultured bacteriologically for staphylococci. Thirty-two staphylococcal isolates were recovered from 30 cats and were biotyped, using biochemical tests contained in a staphylococcal identification system. Of 23 isolates considered coagulase-positive, 16 were identified as Staphylococcus aureus, 5 as S intermedius, and 2 as S hyicus. Of 9 isolates considered coagulase-negative, 6 were identified as S simulans, 2 as S epidermidis, and 1 as S xylosus. Antimicrobial susceptibility tests were done on all staphylococcal isolates, using a disk-diffusion method. Staphylococcal isolates were susceptible to clavulanic acid-amoxicillin, cloxacillin, cephalothin, chloramphenicol, gentamicin, erythromycin, and trimethoprim-sulfamethoxazole. Resistance to penicillin G, ampicillin, and tetracycline was frequent.

An attempt was made to reverse the antibiotic resistance of Proteus mirabilis used to induce experimental cystitis in cats and dogs. Results of in vitro studies on an oxytetracycline-resistant strain of P mirabilis, utilizing standard plate counts, indicated the organism became susceptible to oxytetracycline when it was treated with a solution of EDTA-tromethamine. In vivo experiments were conducted with cats and dogs in which 50% of the experimentally infected animals were treated with bladder lavage twice daily with EDTA-tromethamine solution and 50% with tromethamine buffer alone; all were given standard doses of oxytetracycline. Results of bacteriologic cultural examinations of urinary samples and urinalyses done each day, at the end of the experiments, indicated all animals had cystitis. Thus, although the organism's resistance to oxytetracycline was changed by EDTA-tromethamine in vitro, change in bacterial resistance did not occur in vivo in cats and dogs during clinical treatment.

A protruding nasal mass in a domestic shorthair cat with nasal discharge and recurrent fever was determined to be caused by infection with the fungus Trichosporon pullulans, as determined by cytologic, histologic, and fungal culture methods. Initially, the cat was treated orally with ketoconazole and the mass decreased in size. When signs of hepatotoxicosis developed, treatment was reduced to an alternate-day basis. However, the nasal mass increased in size with this regimen, and therapy with amphotericin B and 5-flucytosine was begun. It also was unsuccessful.