Treating UTIs with fluoroquinolones: A case study (Sponsored by Pfizer)
Aug 01, 2005
Florie is a 4-year-old, spayed female Labrador-shepherd crossbred dog. Until six months ago, Florie's medical history was unremarkable. At that time, she was diagnosed with a bacterial urinary tract infection (UTI) based on the presence of hematuria and pollakiuria; she received 500 mg cephalexin orally once daily by the referring veterinarian for five days. When the UTI was observed again by the referring veterinarian three months later, Escherichia coli was cultured but sensitivity results were not obtained. Florie was given 50 mg gentamicin subcutaneously three times daily for 10 days.
Three months later, Florie was referred to the University of Georgia Veterinary Medical Teaching Hospital (UGA-VMTH). At this time, she was exhibiting a recurrence of the same clinical signs (i.e., pollakiuria, dysuria, and hematuria). During this exam, the owner reported that Florie had actually experienced pollakiuria and hematuria intermittently for six months and had recently increased her water intake. Florie weighed 44 lbs and her physical examination findings were normal except that she was reluctant to allow caudal abdominal palpation and her urinary bladder appeared small. Because of her size, body conformation, and reluctance for abdominal palpation, Florie's kidneys could not be palpated. Rectal palpation of the distal urethra was normal.
Initial identification of UTI
Canine UTIs generally involve the lower urinary tract (bladder and urethra), where the inflammation caused by the infection produces obvious clinical signs such as pollakiuria, stranguria, and dysuria. These findings in Florie, typical of lower tract disease in general, led to the initial suspicion of a bacterial UTI. However, other causes of lower urinary tract inflammation, such as cystouroliths or neoplasia, may coexist with a UTI or cause lower tract signs in the absence of bacteria. In this case, the presumptive diagnosis of a bacterial UTI was reasonable because it's a common cause of lower tract signs in dogs, particularly young or middle-aged dogs with no other findings.
Origin of the infection
Most bacterial UTIs are caused by intestinal or cutaneous flora that ascend through the urethra to the bladder. The most common bacterial pathogens associated with UTIs in the dog are E. coli (as later found to be the case in Florie) and Staphylococcus, Streptococcus, Enterococcus, Enterobacter, Proteus, Klebsiella, and Pseudomonas species.
Common contributory causes of UTIs were apparently not factors in Florie, such as urethral catheter use, conditions that would cause local inflammation and prevent efficient urine flow from the bladder (e.g., prostate enlargement in males or uroliths), and urinary tract surgery. Nonetheless, a presumptive diagnosis of a UTI was made. The main reservoir for such a UTI is the bacterial flora of the gastrointestinal tract—this was presumed to be the source in Florie's case.