Vol.3, No.3, 146-150 (2011) Health
doi:10.4236/health.2011.33027
Copyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/HEALTH/
Effects of water flow volume on the isolation of bacteria
from motion sensor faucets
Yasutaka Nakamura1,2*, Masaharu Watanabe1,3, Etuko Kubo1,4, Akiko Suzuki1,5,
Hidetoshi Igari1,6, Mitsukazu Kitada2, Takeyuki Sato1,6
1 Infection Control Team, Chiba University Hospital, Chiba, Japan; *Corresponding Author:
2 Division of Pharmacy, Chiba University Hospital, Chiba, Japan;
3 Division of Laboratory Medicine, Chiba University Hospital, Chiba, Japan;
4 Division of Nursing, Chiba University Hospital, Chiba, Japan;
5 Department of Pathobiology, Graduate School of Nursing, Chiba University, Chiba, Japan;
6 Division of Control and Treatment of Infectious Diseases, Chiba University Hospital, Chiba, Japan.
Received 10 November 2010; revised 27 December 2010; accepted 22 January 2011.
ABSTRACT
Water outlets for washing hands and medical
equipment are essential for preventing hospital
infection. The present study clarified the effects
of water flow volume on the identification and
quantitative evaluation of bacteria found around
spouts in the 17 hand-washing stations. Pseu-
domonas aeruginosa was detected from 4 sta-
tions before adjustment and 2 after adjustment.
Although no significant difference was identi-
fied in the detection rate of P. aeruginosa (p =
0.368), when combining P. aeruginosa and glu-
cose non-fermentative Gram-negative bacilli
(NFB), the number of stations with P. aeruginosa
and/or NFB decreased significantly from 15 be-
fore adjustment to 9 af ter adjustment (p = 0.023).
Before adjustment, quantit y of bacteria w as “2+”
for 3 stations and “1+” for 7 stations, but was
“1+” for 3 stations and “2+” for 0 stations after
adjustment. These results show that quantity of
bacteria could be reduced from spouts by ad-
justing flow volume. These results were also
supported by experiments for cleanliness using
Adenosine 5’-triphosphate bioluminescence me-
thod.
Keywords: Infection Control; Water Flow Volume;
Motion Sensor Faucets
1. INTRODUCTION
Water outlets for washing hands and medical equip-
ment are essential for preventing hospital infection. In
our hospital, to prevent hospital infection via water out-
lets, non-contact faucets and bigger sinks have been in-
stalled to minimize splashing. However, spouts cannot
be easily removed, and spouts are difficult to clean be-
cause water is turned on and off automatically using a
motion sensor. Also, chlorine sterilization is insufficient
with mixing faucets. These factors can contribute to hos-
pital infection. In addition, Gram-negative bacteria have
been found around water outlets, and some hospital out-
breaks have been attributed to tap water contamination
[1-4]. In particular, Pseudomonas aeruginosa is a clini-
cally important Gram-negative bacteria that can be lethal
if sepsis results [5]. In recent years, problems surround-
ing multidrug-resistant P. aeruginosa have arisen as an
important social issue, and although various studies have
examined environmental infection, to our knowledge, no
studies appear to have investigated water flow volume.
The present study clarified the effects of water flow
volume on the identification and quantitative evaluation
of bacteria found around spouts.
2. METHODS
2.1. Hand-Washing St ati ons, Equipment and
Adjustment Period
Bacteria tests were conducted at 17 hand-washing sta-
tions located at nurse stations in 8 wards and used exclu-
sively and frequently by hospital staff. All hand-washing
stations had motion-sensor faucets, with a shell sink (L-
50G; INAX Corporation, Aichi, Japan; pressure of water
supply: 0.05~0.74 Mpa [0.5~7.5 kgf/cm3]) used at 13
stations and an integrated sink (AWL-76AM (P); INAX
Corporation; pressure of water supply: 0.08~0.74 Mpa
[0.8~7.5 kgf/cm3]) used at 4 stations. Water flow volume
was adjusted at the end of November 2007, and was ad-
justed for all 17 stations on the same day.
2.2. Water Flow Volume Adjustment
First, without any notification, water flow volume was

Y. Nakamura et al. / Health 3 (2011) 146-150
Copyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/HEALTH/
147
measured at each hand-washing station (pre-adjustment
flow volume). Next, based on sink size, flow volume
was adjusted at 120-200 mL/s (post-adjustment flow
volume). Flow volume per second was calculated by
measuring flow volume over a 10-s period twice. Also,
when adjusting flow volume, each floor was notified that
water flow volume would be adjusted as part of activi-
ties of Infection Control Team (ICT) and was instructed
to refrain from performing any action that could have
impacted the surveillance, such as changing flow volume
or contacting a cleaning service.
2.3. Sample Collection, Identification and
Quantity of Bacteria
Samples were collected by wiping the entire spout
using a cotton swab soaked in physiological saline be-
fore and after adjustment at intervals of 1 month. One
person collected all samples from all hand-washing sta-
tions before and after volume adjustment. Each sample
was inoculated using Drigalski improved medium (Eiken
Chemical, Tokyo, Japan) and tryptic soy agar II sup-
plemented with 5% sheep blood (Becton Dickinson, To-
kyo, Japan) and cultured at 35˚C for 72 h. Gram-positive
bacilli (GPB) were identified by Gram staining alone,
and Gram-positive cocci were biochemically divided
into Streptococcus, Staphylococcus aureus and coagu-
lase-negative staphylococci (CNS). Gram-negative ba-
cilli were biochemically divided into Enterobacteriaceae,
P. aeruginosa and glucose non-fermentative Gram-nega-
tive bacilli (NFB).
Growth was semiquantitated as follows: <50 colonies,
<50 colonies in the first inoculation zone; 100 colonies,
50-100 colonies in the first zone; 1+, >100 colonies in
the first zone; 2+, >10 colonies in the second zone.
2.4. Adenosine 5’-Triphosphate ( ATP )
Bioluminescence Method
ATP was purchased from Oriental Yeast Co., LTD.
Japan. The ATP solution at the concentration of 2.0 ×
10-6 M with 1% of the starch was prepared for the ex-
periments. The entire spout was cleaned by brushing
with soap and water. One mL of ATP solution was poured
to the faucet from the side of up-stream after removal of
the faucet. After reset of forcet, water was running at
various water volume for 15 and 30 seconds, respec-
tively. Water flow Volume performed 40, 80 mL/ss. Then,
samples were collected by wiping the entire surface of
spout with the attached tape for the experiments. The
experiments were done 10 times and the results were
shown as the average (+/–SD). Samples were measured
in relative light units (RLU) by using a luminometer
(ATP Luminometer PD-20 Kikkoman Co., Japan)
2.5. Statistical Assessment
When statistically analyzing bacteria detection rates in
relation to flow volume adjustment, a χ2 independence
test was used with the level of significance set at p < 0.05.
2.6. Detection Rate of P. Aeruginosa in
Inpatients and Drug Usage for
P. Aeruginosa
Detection rate of P. aeruginosa in inpatients was cal-
culated before and after adjustment for the entire hospi-
tal and each floor at which P. aeruginosa was detected a
3-month period before and after adjustment.
Drug usages for P. aeruginosa were also studied for
the entire hospital and each floor at which P. aeruginosa
was detected a 3-month period before and after adjust-
ment. Usage of the following antibiotics injected for
treatment was determined: Ceftazidime, cefepime dihy-
drochloride hydrate, cefozopran hydrochloride, imipenem
hydrate, meropenem hydrate, panipenem, doripenem
hydrate, biapenem, pazufloxacin mesilate, and cipro-
floxacin. When comparing usage among drugs, defined
daily dose (DDD) as recommended by the World Health
Organization (WHO) was used to correct for non-uni-
formity in specifications and dose (Ta b le 1) (www.wh-
occ.no/atcddd/). DDD for drugs not listed by WHO was
defined by modifying with the recommendation of WHO.
The study period before adjustment was from August to
October 2007 and after adjustment from January to
March 2008.
3. Results
3.1. Water Flow Volume Before and After
Adjustment
Average flow volume before and after adjustment was
87.6 mL/s and 149.4 mL/s, respectively (Table 2). Before
Table 1. Drug list and defined daily dose (DDD).
Drugs DDD (g)
Ceftazidime 4
Cefepime Dihydrochloride Hydrate 2
Cefozopran Hydrochloride 2 *
Imipenem Hydrate 2
Meropenem Hydrate 2
Panipenem 2 *
Doripenem Hydrate 1 *
Biapenem 1.2 *
Pazufloxacin mesilate 1
Ciprofloxacin 0.5
*DDD for drugs not listed by WHO was defined by modifying with the
definition of WHO.

Y. Nakamura et al. / Health 3 (2011) 146-150
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148
Table 2. Water flow Volume before and after adjustment.
Water flow Volume （mL/s）
30 50 60 70 90110120130140150160170200
mean ± S.D
Before adjustment 1 1 4 4 1 2 2 1 1 85.3 ± 35.4
After adjustment 4 3 2 1 1 4 2 149.4 ± 27.0
adjustment, minimum flow volume was 30 mL/s, and
flow volume at 11 hand-washing stations was <120 mL/s.
Maximum flow volume after adjustment was 200 mL/s.
3.2. Detection of P. Aeruginosa and NFB
from Hand-Washing Stations
P. aeruginosa was detected from 4 hand-washing sta-
tions (A-D) before adjustment and 1 station (A) after
adjustment. Quantity of bacteria was “1+” for Station A,
“100 colonies” for Station D, and “<50 colonies” for
Stations B and C before adjustment. After adjustment, P.
aeruginosa was not detected from Stations B, C and D. P.
aeruginosa was detected from Station A, but quantity of
bacteria decreased from “1+” before adjustment to “<50
colonies” after adjustment. Also, at 1 station (E), P.
aeruginosa was not detected before adjustment, but was
detected after adjustment, although quantity of bacteria
was low at “<50 colonies” (Table 3).
Although no significant change was identified in the
detection rate of P. aeruginosa including newly isolated
1 station (p = 0.368), when combining P. aeruginosa and
NFB, the number of stations with P. aeruginosa and/or
NFB decreased significantly from 15 before adjustment
to 9 after adjustment (p = 0.023) (Ta b l e 4 ). Before ad-
justment, quantity of bacteria was “2+” for 3 stations
and “1+” for 7 stations, but was “1+” for 3 stations and
“2+” for no stations after adjustment (Figure 1). As for
the other bacterial species, GPB was detected before and
after adjustment at 12 and 8 stations, respectively, and
CNS was detected before and after adjustment at 1 sta-
tion each. Streptococcus species, S. aureus and Entero-
bacteriaceae were not detected.
3.3. ATP Bioluminescence
ATP method is recommended due to ATP being widely
found in microorganisms and there are good correlations
between ATP bioluminescence method and microbi-
ological swabbing method [6]. So cleanliness was ex-
amined using ATP bioluminescence method for the con-
firmation of microbiological swabbing method. Increase
of flow volume resulted the increase of cleanliness at
both 15 and 30 seconds of running water (Table 5).
3.4. Comparison of P. Aeruginosa Detection
and Drug Usage among Inpatients
Detection rate of P. aeruginosa in all inpatients was
compared before and after adjustment. Detection rate of
P. aeruginosa for all floors before adjustment was 4.5%
(patients with P. aeruginosa/total patient count = 159/
3,500) and that 3 months after adjustment was 3.6%
(128/3,523). On the floors with Stations A through D
where P. aeruginosa was detected before adjustment,
detection rate before adjustment ranged from 3.5% to
10.8% and that after adjustment ranged from 2.3% to
9.1%, revealing no significant differences (Table 6).
Total drug usage over the 3-month period for all floors
before adjustment was 3,917 units and that after adjust-
ment was mostly comparable at 4,083 units (102.8%).
Table 3. Water flow Volume and quantity of bacteria of hand-washing stations at which P. aeruginosa were detected.
Before adjustment After adjustment
Hand-washing
stations Type of sink
Quantity of bacteria Water flow Volume
(mL/s) Quantity of bacteria Water flow Volume (mL/s)
A Shell 1+ 90 ＜50 colonies 120
B Shell ＜50 colonies 110 No Detection 140
C Integrated ＜50 colonies 30 No Detection 200
D Shell 100 colonies 70 No Detection 130
E Shell No Detection 120 ＜50 colonies 170

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149
Table 4. Umber of stations at which P. aeruginosa and/or glu-
cose non-fermentative Gram-negative bacilli were detected or
not before and after adjustment.
Detection No Detection P
Before adjustment 15 2
After adjustment 9 8 0.023
(a)
(b)
Figure 1. Water flow Volume and quantity of bacteria for
hand-washing stations at which P. aeruginosa and/or NFB was
detected before (a) and after (b) adjustment.
Table 5. The results of ATP bioluminescence.
Time of
running
water (sec)
Water flow
Volume
(mL/s)
After running water
(RLU：mean ± S.D) P
84 498.1 ± 275.16
15
40 1434.0 ± 974.21
0.0091
84 445.7 ± 346.15
30
40 1343.8 ± 642.81
0.0017
Experiments were done 10 times and the results were shown as the average
of 10 experiments (+/–SD).
Although average of drug usage for P. aeruginosa
slightly decreased to 83.3% at 4 stations on which P.
aeruginosa was detected, no significant change existed
Drug usage for P. aeruginosa decreased to 52.7% and
74.7% at Stations A and B, respectively (Table 7).
4. DISCUSSION
Various microorganisms exist in hospitals, and com-
plete removal is not really plausible. Furthermore, stud-
ies have found no correlation between environmental mi-
crobes and hospital infection [5,7,8], and the guidelines
published by the Centers for Disease Control and Pre-
vention state that periodic surveillance for environmental
bacteria is unnecessary [9,10]. However, Rutala et al.
reported surfaces may potentially contribute to cross-
transmission by acquisition of transient hand carriage by
health care personnel due to contact with a contaminated
surface [11]. In addition, Endlhart et al. reported a P.
aeruginosa outbreak in a hematology-oncology unit asso-
ciated with contamination of the surface cleaning equip-
ment when non-germicidal cleaning solutions were used
instead of disinfectants [12].
Microorganisms that adhere to surfaces directly
touched by people can be spread not only by hospital
staff, but also by patients, family members and visitors
[13,14]. Issues of cross-contamination and outbreak thus
need to be addressed and appropriate measures must be
taken to prevent environmental infection.
Recently, the use of motion sensor faucets has gained
popularity in hospitals throughout the Japan. To the best
of our knowledge, no studies that investigated water
flow volume, and the present study is the first to show
that highly hydrophilic P. aeruginosa and NFB can be
reduced by adjusting flow volume. This result was also
supported by experiments for cleanliness using ATP
bioluminescence method.
However, the present study did not find that higher
water flow volume could decrease the number of P.
aeruginosa patients or drug usage (Ta ble 6 ). In the pre-
sent study, the design of sinks precluded sufficient in-

Y. Nakamura et al. / Health 3 (2011) 146-150
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150
Table 6. Detection rate of P. aeruginosa in inpatients on the floors of hand-washing stations at which P. aeruginosa was detected
before adjustment.
Before adjustment After adjustment
Hand-washing
stations Patients detected
P. aeruginosa
No. of all
inpatients
Detection rate of
P. aeruginosa(%) Patients detected P. aeruginosa
No. of all
inpatients
Detection rate of
P. aeruginosa(%)
A 8 130 6.2 8 122 6.6
B 12 111 10.8 12 132 9.1
C 9 255 3.5 6 262 2.3
D 11 158 7.0 14 155 9.0
Table 7. Total drug usage over a 3-month period for hand-
washing stations where P. aeruginosa was detected before and
after adjustment.
Total drug usage over a 3-month
period
Hand-washing
stations
Before adjustmentAfter adjustment
Rate (%)
A 193.0 100.5 52.1
B 218.8 163.5 74.7
C 128.0 124.0 96.9
D 192.5 222.0 115.3
Total 732.3 610.0 83.3
creases in flow volume due to splashing, so sink designs
need to be investigated in relation to flow volume.
The present results showed that isolation and quantity
of bacteria could be reduced from spouts by adjusting
flow volume. Further studies might be needed.
REFERENCES
[1] Aumeran, C., Paillard, C., Robin, F., Kanold, J., Baud, O.,
Bonnet, R., Souweine, B. and Traore, O. (2007) Pseu-
domonas aeruginosa and Pseudomonas putida outbreak
associated with contaminated water outlets in an onco-
haematology paediatric unit. Journal of Hospital Infec-
tion, 65, 47-53. doi:10.1016/j.jhin.2006.08.009
[2] Kolmos, H.J., Thuesen, B., Nielsen, S.V., Lohmann, M.,
Kristffersen, K. and Rosdahl, V.T. (1993) Outbreak of
infection in a burnsunit due to Pseudomonas aeruginosa
originating from contaminated tubing used for irrigation
of patients. Journal of Hospital Infection, 24, 11-21.
doi:10.1016/0195-6701(93)90085-E
[3] Ferroni, A., Nguyen, L., Pron, B., Quesne, G., Brusset,
M.C. and Berche, P. (1998) Outbreak of nosocomial uri-
nary tract infections due to Pseudomonas aeruginosa in a
paediatric surgical unit associated with tap-water con-
tamination. Journal of Hospital Infection, 39, 301-307.
[4] Bert, F., Maubec, E., Bruneau, B., Berry, P. and Lam-
bert-Zechovsky, N. (1998) Multi-resistant Pseudomonas
aeruginosa outbreak associated tap water in neurosurgery
intensive care unit. Journal of Hospital Infection, 39,
53-62. doi:10.1016/S0195-6701(98)90243-2
[5] CDC (1999) Guideline for the prevention of surgical site
infection 1999. Infect Control Hosp Epidemiol, 20, 247-
278.
[6] Hasan, A., Utku, O. and Koray, K. (2006) Comparison of
results of ATP bioluminescence and traditional hygiene
swabbing methods for the determination of surface
cleanliness at a hospital kitchen. International Journal of
Hygiene and Environmental Health, 209, 203-206.
doi:10.1016/j.ijheh.2005.09.007
[7] Eickhoff, T.C. (1970) Microbiological sampling. Hospi-
tals, 44, 86-87.
[8] American Hospital Association Committee on Infections
within the Hospitals (1974) Statement on microbiologic
sampling in the hospital. Hospitals, 48, 125-126.
[9] Garner, J.S. and Favero, M.S. (1986) CDC guideline for
handwashing and hospital environment control. Infection
Control, 7, 231-243.
[10] Centers for Disease Control and Prevention Healthcare
Infection Control Practices Advisory Committee (HIC-
PAC) (2001) Draft guideline for environmental infection
control in healthcare facilities, 78-87.
[11] Rutala, W.A. and Weber, D.J. (2001) Surface disinfec-
tion: should we do it? Journal of Hospital Infection, 48,
S64-S68. doi:10.1016/S0195-6701(01)90017-9
[12] Engelhart, S., Krizek, L., Glasmacher, A., Fischnaller, E.,
Marklein, G. and Exner, M. (2002) Pseudomonas aeru-
ginosa outbreak in a haematology-oncology unit associ-
ated with contaminated surface cleaning equipment.
Journal of Hospital Infection, 52, 93-98.
doi:10.1053/jhin.2002.1279
[13] Widmer, A.F., Wenzel, R.P., Trilla, A., Bale, M.J., Jones,
R.N. and Doebbeling, B.N. (1993) Outbreak of Pseudo-
monas aeruginosa infections in a surgical intensive care
unit: probable transmissionvia hands of a health care
worker. Clinical Infectious Disease, 16, 372-376.
[14] Kolmos, H.J., Thuesen, B., Nielsen, S.V., Lohmann, M.,
Kristoffersen, K. and Rosdahl, V.T. (1993) Outbreak of
infection in a burnsunit due to Pseudomonas aeruginosa
originating from contaminated tubing used for irrigation
of patients. Journal of Hospital Infection, 24, 11-21.
doi:10.1016/0195-6701(93)90085-E