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Detection of an enzyme produced by red blood cells
3%
10/313
Direct detection of white blood cell surface proteins
7%
23/313
Detection of urinary nitrate conversion by gram-negative pathogens
75%
235/313
Detection of urinary nitrate conversion by gram-positive pathogens
4%
11/313
Detection of an enzyme produced by gram-negative pathogens
6%
18/313
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This patient presents with a urinary tract infection in the setting of acute urinary retention. Most urinary tract infections are caused by gram-negative pathogens, which would result in positive detection of nitrites on urinalysis. Elderly patients are susceptible to developing acute delirium in the setting of a urinary tract infection. Findings on dipstick urinalysis consistent with a urinary tract infection include the detection of blood, the detection of leukocyte esterase, and the detection of nitrites. The most common culprits are gram-negative pathogens such as Escherichia coli, Proteus spp., and Klebsiella pneumoniae. These gram-negative bacteria possess a nitrate reductase enzyme, which converts urinary nitrates into nitrites. Simati et al. review dipstick urinalysis for the diagnosis of acute urinary tract infections. They found that if nitrites and leukocyte esterase are not detected on dipstick urinalysis, the odds of a urinary tract infection decrease by 40 to 60 percent. The combination of positive leukocyte esterase and nitrites has been reported to have a sensitivity of 75 percent and a specificity of 82 percent in women. However, in symptomatic women with negative dipstick urinalysis results, a urine culture must be performed due to the possibility of false-negative dipstick urinalysis results. Yang et al. studied the influence of urinary pH on antibiotic efficacy against bacterial uropathogens. They found that commonly utilized antibiotics such as the fluoroquinolones, aminogylcosides, and macrolides functioned optimally in alkaline pH. In contrast, the tetracyclines, nitrafurantoin, and many beta-lactams functioned best in acidic pH urine. The consideration of urinary pH when choosing antibiotic therapy may assist in the treatment of complicated cases as well as reduce antibiotic resistance development if lower dosages and treatment durations are required. Incorrect Answers: Answer 1: Urine dipstick detects the presence of heme in red blood cells. Answer 2: Urine dipstick detects the presence of leukocyte esterase enzyme in white blood cells. Answer 4: Nitrites are produced by gram-negative pathogens possessing the nitrate reductase enzyme. Answer 5: Urine dipstick detects the presence of nitrites, not the nitrate reductase enzyme.
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