ORIGINAL STUDIES

Asymptomatic Bacteriuria in
Institutionalized Elders in Israel
Raul Raz, MD, Diana Gronich, BS.c, Yoshua Ben-Israel, MD, and Lindsey E. Nicolle, MD
Objectives: To document the prevalence of asymptomatic bacteriuria in patients in one large long-term
care facility, and describe clinical outcomes in initially
bacteriuric and nonbacteriuric residents during prospective observation encompassing one year.
Methods: Patients enrolled in the study were residents of the Haim-Shoham Geriatric Center, a longterm care institute with 800 inhabitants. Twenty patients were related randomly for study enrollment on
each of the ten wards. A urine culture was obtained
from the enrolled patients. A second culture was obtained within one week if the initial culture grew Ն
105 colony-forming units per milliliter (cfu/ml) of at
least one uropathogen. Demographic data and comorbidities, as well as most recent laboratory results,
were recorded for all patients enrolled. Subjects were
followed prospectively for one year or until death.
Clinical events and usage of antibiotics were recorded.
In patients with asymptomatic bacteriuria, repeated
urine cultures were obtained every two months.
Results: Eighty-ﬁve (43.3%) of a total of 196 elder res-

There is a high prevalence of bacteriuria among institutionalized older people, with 25–50% of women and 15– 48%
of men bacteriuric at any time.1 Bacteriuria is usually asymptomatic,2 and the impact of asymptomatic bacteriuria on
patient outcomes has been controversial. Prospective studies
have reported similar survival between bacteriuric and nonbacteriuric institutionalized subjects, although the bacteriuric
group is consistently more functionally impaired.3,4 Where
increased mortality has been observed in bacteriuric subjects,
the association with bacteriuria has disappeared following
adjustment for covariates.5
Infectious Diseases Unit, Haemek Medical Center, Afula, and the Technion,
Faculty of Medicine, Haifa (R.R.); Haim Shoham Geriatrics Institute, Pardes
Hana (D.G. and Y.B.I.), Israel; and the Department of Internal Medicine, University of Manitoba, Canada (L.E.N.).
Address correspondence to: Raul Raz, MD, Director, Infectious Diseases Unit,
Haemek Medical Center, Afula, 18101, Israel.

Copyright ©2001 American Medical Directors Association
ORIGINAL STUDIES

idents screened presented asymptomatic bacteriuria.
There were no differences between patients with and
without asymptomatic bacteriuria in age, gender, and
underlying diseases. Patients with asymptomatic bacteriuria were signiﬁcantly more bed-ridden (91.7% vs.
82.1%, P ϭ 0.05); demented (78.8% vs. 59.8%, P ϭ
0.03); and incontinent of urine (93% vs. 71.4%, P Ͻ
0.0001) and bowel (85.8% vs. 59.3%). During one year
of prospective observation, bacteriuric patients had a
mortality rate of 25.9%, compared to 7.1% for nonbacteriuric (P Ͻ 0.0001). Mortality in the group with
bacteriuria was higher due to both urinary infection
and other causes.
Conclusions: In our population, asymptomatic bacteriuria was associated with increased functional impairment and increased mortality over 12 months. The increased mortality, however, was not fully attributable
to urinary infection. (J Am Med Dir Assoc 2001; 2: 275–
278)
Keywords: asymptomatic bacteriuria; bacteriuria in
the elderly; asymptomatic bacteriuria and death

Prospective, randomized studies have also shown no difference in clinical outcomes, including mortality, with treatment of asymptomatic bacteriuria.5–7 Older residents of longterm care facilities who have long-term indwelling catheters,
however, have been reported to have decreased survival
rates.8 This ﬁnding has been attributed to bacteriuria, but
patients with indwelling catheters are medically and functionally different than noncatheterized patients, and bacteriuria,
per se, has not been documented to be the direct cause of
mortality differences. Several studies have also postulated a
relationship between bacteriuria and hypertension or renal
failure,9 but none of these associations have been conﬁrmed
in prospective studies.
This study was undertaken to document the prevalence of
asymptomatic bacteriuria in patients in one large long-term
care facility, and describe clinical outcomes, including mortality, in initially bacteriuric and nonbacteriuric residents
during prospective observation for one year.
Raz et al. 275

MATERIAL AND METHODS
Institution and Study Design
Patients enrolled in the study were residents of the HaimShoham Geriatric Center, a long-term care institute with 800
inhabitants in Pardes Hana, Israel. This institution is funded
by the Ministry of Health in Israel, with 90% of the residents
Jewish, and the majority from middle or lower economic
classes. The residents are highly functionally impaired, with
two-thirds being fully bedridden. The study protocol was
reviewed and approved by the local Helsinki Committee, and
informed consent obtained from each patient or family.
There are approximately 40 patients in each ward, and we
decided to enroll randomly half from each ward–20 patients
per ward (approximately 200 patients). Patients were excluded if they had signs or symptoms suggestive of symptomatic urinary infection, or had taken antibiotics during the last
month. A urine culture was obtained from enrolled patients
by nurses according to an established protocol for collecting
urine. If the initial urine culture had Ն 105 colony-forming
units per milliliter (cfu/ml) of at least one organism, a second
sample was obtained within one week. Patients with initial
negative cultures did not have a repeat specimen obtained.
Demographic data and comorbidities, as well as most recent
laboratory results, were recorded for patients enrolled. Subjects were followed prospectively for one year, or until death.
Clinical events, including episodes of infection, antibiotic
use, and death were assessed and recorded at two-month
intervals. Patients with asymptomatic bacteriuria at the initial
survey had urine specimens for culture repeated at two-month
intervals; the nonbacteriuric group did not have subsequent
urine specimens obtained.
Laboratory Methods
Urine specimens were obtained by a clean catch method in
noncatheterized subjects. Study subjects with an indwelling
urethral catheter had a urine specimen collected immediately
following catheter replacement. Urine specimens were transported promptly to the laboratory, and culture was performed
using a dipstick method. Bacterial isolates present at Ն105
cfu/ml were identiﬁed using standard methods.10 Leukocyte
esterase and nitrate tests performed by dipstick were recorded
for each of the subsequent specimens collected at two
monthly intervals in the bacteriuric group.
Deﬁnitions and Data Analysis
Urinary tract infection was deﬁned microbiologically by
growth of Ն105 cfu/ml of one or more organisms. Asymptomatic bacteriuria was identiﬁed when two consecutive positive
urine cultures with the same microorganism(s) were obtained
in a patient free of urinary symptoms such as dysuria, frequency, burning sensation, or loin pain. In patients who were
unable to provide an accurate history, asymptomatic bacteriuria was identiﬁed by signs of urosepsis, such as fever, chills,
leukocytosis, or clinical deterioration. Patients with an initial
positive culture and repeat negative culture at initial screening were enrolled as negative for follow-up. Any positive
result (ie, 1ϩ or greater) was designated as a positive leuko276 Raz et al.

cyte esterase or nitrate test. The diagnosis of urosepsis was
made in the presence of one or more clinical signs and
symptoms, including fever, chills, hypothermia, or clinical
deterioration with no other source of infection, together with
leukocytosis or leukopenia, pyuria, and a positive urine
culture.
Standard parametric and nonparametric tests were used for
data analysis. The t test was used for means, the chi-squared
test or Fisher’s exact test for nominal values, and the Wilcoxon rank sum test for nonnormally distributed values. Life
table analysis used the Kaplan-Meier method with a log rank
test of difference.
RESULTS
One hundred and ninety seven patients were included in
the survey; asymptomatic bacteriuria was present at initial
screening in 85 (43.1%). Patients with and without asymptomatic bacteriuria were similar in age, gender, residence
duration, underlying diseases, and presence or absence of an
indwelling catheter (Table 1). However, patients with asymptomatic bacteriuria were more functionally impaired, with a
signiﬁcantly high proportion being bedridden, demented, or
experiencing urine and bowel incontinence. Escherichia coli
was the most frequent species, isolated in 54 (64%) patients.
Other organisms isolated included Klebsiella pneumoniae, 13
(15%); Providencia species (spp.), 9 (7.1%); Proteus mirabilis, 4
(4.7%); and 3 (3.5%) each of Pseudomonas spp., Enterobacter
spp., and Enterococcus spp. Staphylococcus epidermidis was
present in 8 (8.4%) bacteriuric residents. Ten patients (12%)
had polymicrobial bacteriuria.
The proportion of initially bacteriuric subjects who remained bacteriuric at the two monthly screening intervals was
100% during twelve months, 85% (63 had a persistent infection and 9 a new uropathogen), 90% (60 and 12), 88% (65
and 8), 86% (60 and 13) and 89% (67 and 9) at the following
two-months survey. Eighteen of the 57 patients who survived
one year had persistent bacteriuria with the same organism; 14
E coli and two each of Klebsiella spp. and Pseudomonas
aeruginosa.
For these subsequent urine specimens, the leukocyte esterase test had a sensitivity of 94.5%, speciﬁcity of 65.2%,
positive predictive value of 95.4%, and a negative predictive
value of 61% for bacteriuria. The nitrate test had a sensitivity
of 56%, speciﬁcity of 97%, positive predictive value of 98%,
and negative predictive value of 21%.
At one year, 22/85 (25.9%) initially bacteriuric residents
had died compared to 8/112 (7.1%) nonbacteriuric (P Ͻ
0.0001); (OR ϭ 4.5,95% CI [1.9, 10.8]) (Table 2). Other
characteristics explored in the univariant analysis that showed
a trend toward higher mortality included dementia (24/134,
17.9% vs. 6/63, 9.5%; P ϭ 0.1126), being bedridden (26/169,
15.4% vs. 3/27, 11.1%; P ϭ 0.410), and experiencing urine
(26/159, 16.4% vs.3/35, 8.6%; P ϭ 0.242) or bowel incontinence (24/146, 16.4% vs. 3/43, 7.0%; P ϭ 0.119). The proportion of antibiotic days were similar for the two groups (P ϭ
0.902). Twelve (14.1%) patients with bacteriuria had 15
episodes of symptomatic urinary infection and 8 (7.1%) of 112
without bacteriuria (P ϭ 0.1) experienced ten episodes. Nine
JAMDA – November/December 2001

Table 1. Demographic and Clinical Characteristics of the Patients With and Without Asymptomatic Bacteriuria
Asymptomatic bacteriuria
Yes ‫)%34( 58 ؍‬
Mean age (years)
Range
Male/Female
Duration residence (months)
Underlying Diseases
Diabetes Mellitus
IDDM
IHD
CVA
COPD
Malignancies
Mobility
Partially mobile
Bedridden
Mental Status
Dementia
Competent
Urine incontinence
Bowel incontinence
Chronic indwelling catheter
Laboratory
Hemaglobin
White blood cells
Serum albumin
Serum creatinine

84 Ϯ 7.9
66–99
11 (12.9%)/74 (87.1%)
19.3 Ϯ 5.2

P value
No ‫)%1.75( 211 ؍‬
83.4 Ϯ 9.1
63–92
18 (16.0%)/94 (83.9%)
21.1 Ϯ 6.4

N.S.

29 (34.1%)
5
43 (50.5%)
32 (37.6%)
3 (3.5%)
7 (8.2%)

43 (38.3%)
3
59 (52.6%)
44 (39.2%)
5 (4.4%)
10 (8.9%)

N.S.

7 (8.2%)
78 (91.7%)

20 (17.9%)
92 (82.1%)

P ϭ 0.05

67 (78.8%)
18 (21.1%)
79 (93%)
73 (85.8%)
15 (17.6%)

67 (59.8%)
45 (40.2%)
80 (71.4%)
73 (65.2%)
17 (15.1%)

P Ͻ 0.003

12.6 Ϯ 1.8 (8–14.8)
6.8 Ϯ 2.2 (4.0–12.8)
3.8 Ϯ 0.4 (2.4–4.8)
0.8 Ϯ 0.6 (0.3–3.0)

N.S.

12.1 Ϯ 1.5 (7.6–15.7)
7.1 Ϯ 2.1 (3.5–13.8)
3.9 Ϯ 0.6 (2.6–5.4)
0.9 Ϯ 0.3 (0.1–2.4)

N.S.
N.S.

P Ͻ 0.0001
P Ͻ 0.0001
N.S.

IDDM ϭ insulin dependent diabetes mellitus; IHD ϭ ischemic heart disease; CVA ϭ cerebrovascular accident; COPD ϭ chronic obstructive lung
disease; N.S. ϭ not signiﬁcant.

(41%) of 22 bacteriuric subjects died because of urosepsis, and
two (25%) of 8 without bacteriuria (Fisher’s exact test ϭ
0.470). The bacteriuric group also had increased mortality
from other causes, particularly cerebrovascular accidents and

myocardial infarction (Table 2), but we did not ﬁnd signiﬁcant statistical differences.
Figure 1 displays the differences in the proportion of survival rates between the residents with and without asymptomatic bacteriuria during the 12 months’ follow-up.
DISCUSSION

Table 2. Outcome in Residents With and Without Asymptomatic
Bacteriuria
Bacteriuria

All subjects

P value

Yes
(N ‫)58 ؍‬
Infections:
Symptomatic UTI
Upper respiratory
Pneumonia
Cellulitis
Decubitus ulcer
Fever, site unknown
Chronic osteomyelitis
Antibiotic courses
Days (%)
Deaths
Symptomatic UTI
Pneumonia
CVA/MI

No
(N ‫)211 ؍‬

95
15*
21
12
12
8
24
3
92
111 (10)
22 (25.9%)
9
3
10

90
10†
26
13
9
5
26
1
90
104 (6.4)
8 (7.1%)
2
3
3

0.1

0.9
Ͻ0.0001
0.4

CVA ϭ cerebrovascular accident/MI ϭ myocardial infarction;
UTI ϭ urinary tract infection.
*4 with bacteremia.
†
2 with bacteremia.
ORIGINAL STUDIES

The prevalence of bacteriuria in this long-term care facility
is similar to previous studies from other facilities that provide

Fig. 1. Life table analysis of long-term care residents initially
identiﬁed as bacteriuric or nonbacteriuric.
Raz et al. 277

care to a highly functionally impaired older population.1 Our
observation of a signiﬁcantly higher occurrence of bacteriuria
in patients with greater functional impairment, and the distribution of infecting organisms observed are also consistent
with other reports.1 There are, however, some unique aspects
of this study population. A much higher proportion was bedridden than in previous reports, suggesting a greater degree of
functional impairment. In addition, urosepsis and bacteremia
were identiﬁed more frequently than in other populations.6,7,10
Death from urosepsis is infrequent in other reports,11,12 but was
responsible for 37% of deaths in this population.
We observed an increased mortality during one-year follow-up in those identiﬁed as bacteriuric at initial screening,
compared to those who were not bacteriuric. This observation
is consistent with other studies that have reported decreased
survival in the bacteriuric institutionalized elder population.5,13 The bacteriuric and nonbacteriuric populations were
not similar in baseline characteristics, and the more functionally impaired bacteriuric subjects may be anticipated to have
decreased survival. A trend toward increased mortality with
increasing functional impairment was observed, and this is
consistent with other studies where the increased mortality
associated with bacteriuria did not persist when corrected
for covariates.5 Bacteriuric residents also had an increased
frequency of death from causes other than urosepsis, such as
myocardial infarction and cerebrovascular accident.
In addition, although numbers are small, the proportions of
bacteriuric and nonbacteriuric patients who experienced urosepsis and died from urosepsis, were not signiﬁcantly different.
This suggests bacteriuria is a marker for a more impaired
population, rather than a direct cause of increased mortality.
Even if mortality is directly attributable to asymptomatic
urinary infection, current evidence does not suggest antimicrobial treatment of bacteriuria can modify this outcome. Older institutionalized populations have a high recurrence rate of urinary infection following antimicrobial
therapy.5,7 Consequently, it is not realistic to expect that
these individuals can be maintained free of bacteriuria.
Prospective randomized trials of antimicrobial therapy
compared with no antimicrobial therapy in long-term care
residents with asymptomatic bacteriuria have not shown
any beneﬁts in patients treated with antimicrobials.5,7 In
fact, there was a trend to increased mortality with antimicrobial therapy for both men6 and women.7 Thus, an
observation of increased mortality in bacteriuric subjects

278 Raz et al.

should not be interpreted as an argument for treatment of
asymptomatic bacteriuria.
In our institutionalized population, we observed, as have
others, that individuals with a greater level of functional
impairment have a greater likelihood of bacteriuria. In addition, a very high prevalence of bacteriuria in the population
was conﬁrmed. Our observation of an increased mortality in
the group that was initially identiﬁed as having asymptomatic
bacteriuria requires further exploration14.
ACKNOWLEDGMENTS
We would like to thank Mrs. Frances Nachmani for her
secretarial assistance with this manuscript.
REFERENCES
1. Nicolle LE. Urinary tract infections in long-term care facilities. Infect
Control Hosp Epidemiol 1993;14:220 –225.
2. Nicolle LE. Asymptomatic bacteriuria in the elderly. Infect Dis Clinics
North Am 1997;11:647– 662.
3. Nicolle LE, Henderson E, Bjornson J, et al. The association of bacteriuria
with resident characteristics and survival in elderly institutionalized
males. Ann Intern Med 1987;106:682– 686.
4. Nicolle LE, Brunka J, McIntyre M, et al. Asymptomatic bacteriuria,
urinary antibody, and survival in the institutionalized elderly. J Am
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5. Abruptyn E, Mossey J, Berlin JA, et al. Does asymptomatic bacteriuria
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elderly institutionalized men. N Engl J Med 1983;309:1420 –1425.
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11. Nicolle LE, Strausbaugh LJ, Garibaldi RA. Infections and antibiotic
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13. Gross JS, Neufeld RR, Libow LS, et al. Autopsy study of the elderly
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