© The Canadian Journal of Urology™; 19(Supplement 1); October 2012
Mazzulli
44
uncomplicated cystitis. Little et al compared three
treatment strategies—empiric treatment without
urine culture; targeted treatment based on results of a
urine culture; and the use of UTI symptom scores to
make treatment decisions—and found no significant
differences in time to symptom improvement.
11
However, although empiric treatment was as effective
as the other two approaches, the study did not consider
the cost of overutilization of antibiotics (that would
be incurred by treating all patients presenting with
symptoms suggestive of a UTI) or the potential for
selective pressure for antibiotic-resistant bacteria. One
study estimates that empiric treatment of women with
acute cystitis might result in up to 40% of women with
urinary symptoms receiving unnecessary antibiotics,
since they would have had negative urine cultures.
12
A validated clinical decision aid to determine
whether a patient needs to be treated with antibiotics
for anuncomplicatedUTI has beendeveloped for use in
the setting of a community-based family practice. The
decision aid is based on the presence of three criteria:
symptoms suggestive of a UTI (especially burning or
pain on urination); urine leukocytes (detected by a
dipstick test based on leukocyte esterase; any amount
more than trace); and urine nitrites (detected by a
dipstick test that is a marker for bacteria; any amount
including trace).
13
Patients are assigned one point
for each criterion. Patients with one point should
provide a urine specimen for a culture before any
antibiotic treatment is initiated, since the likelihood
of a positive result is relatively low (between 26% and
38%).
Only patients with a positive urine culture for
a known uropathogen should receive treatment. For
patients with two or more points, empiric therapy
targeting
Escherichia coli
(
E. coli
)
should be prescribed
without waiting for the results of a urine culture,
because of the high likelihood of infection (> 70%
likelihood of a positive urine culture). The use of such
a clinical decision aid should help reduce the overuse
of antibiotics and thus alleviate some of the selection
pressure for antimicrobial resistance in the community.
Complicated UTIs
The extent of the work up and investigations required
for patients with uncomplicated pyelonephritis and
complicated UTIs depends onwhich underlying factors
associated with complicated urinary tract infections
(
listed in Table 1) are suspected or known to exist at
the time of clinical presentation. All patients with a
suspecteduncomplicated pyelonephritis or complicated
UTI should provide a urine specimen for culture and
antibiotic susceptibility testing.
7,14
As discussed later,
the predictability of the likely pathogen(s) is less clear
than in uncomplicated cystitis, and the likelihood of
detecting an antibiotic-resistant organism is increased.
Additional work up—such as abdominal ultrasound or
other imaging studies, or referral to an infectious diseases
specialist and/or urologist—should be determined on a
case-by-case basis. Thesepatients should receive empiric
antibiotic therapy pending the results of a urine culture,
based on consideration of local antimicrobial resistance
rates in addition to the patient’s recent antimicrobial use.
Recurrent UTIs
Determining whether a patient has a recurrent UTI
will also impact patient management. Reinfection,
which is the most common type of recurrent UTI,
occurs more than 2 weeks after a patient has completed
antimicrobial therapy and is generally due to infection
with a different organism (including a different
E.
coli
strain). Relapse occurs in 5% to 10% of women
within 2 weeks of completing antimicrobial therapy
and is caused by persistence of the same pathogen
in the urinary tract system, which suggests infection
with an antimicrobial-resistant pathogen.
15
Studies
suggest that women who have a recurrent UTI due to
reinfection should be treated with the same agent that
they received for their original UTI episode; however,
an alternative agent should be used if the re-infection
occurs within 6 months, especially if the original agent
was trimethoprim-sulfamethoxazole (TMP-SMX), due to
the high risk of developingmicrobial resistance to TMP-
SMX.
16,17
Patients with relapse may require additional
assessment and investigations to determine why they
did not respond to their initial therapy, and treatment
should be based on the results of their urine culture.
Etiology
Most uncomplicated UTIs are due to a single bacterial
pathogen, with
E. coli
isolated in 75% to 95% of cases.
7
Another 5% to 15% of cases may be due to the gram-
positive organism
Staphylococcus saprophyticus
(
which
is almost exclusively associated with uncomplicated
cystitis and not pyelonephritis), while the remaining
cases are usually due to other enteric gram-negative
bacteria such as
Klebsiella
species,
Proteus
species, and
others. The etiologyof complicatedUTIs is usuallymore
varied and is less predictable than uncomplicatedUTIs.
As well, the possibility of mixed infections with two or
more organisms may occur. Although
E. coli
remains
the most common pathogen isolated in complicated
UTIs, it is found in only 50% of cases. Other, generally
more resistant organisms such as
Proteus
species,
Klebsiella
species, enterococci,
Pseudomonas aeruginosa
,
and even yeast may be isolated.
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