Báo cáo y học: "Growth of Microorganisms in Total Parenteral Nutrition Solutions Containing Lipi" docx

Int. J. Med. Sci. 2010, 7



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2010; 7(3):101-109
© Ivyspring International Publisher. All rights reserved

Research Paper
Growth of Microorganisms in Total Parenteral Nutrition Solutions Con-
taining Lipid
Takashi Kuwahara
1

, Kazuyuki Shimono
1
, Shinya Kaneda
1
, Takumi Tamura
1
, Masao Ichihara
2
, Yoshifumi
Nakashima
1

1. Preclinical Assessment Department, Otsuka Pharmaceutical Factory, Inc., Tokushima, Japan.
2. Research and Development Center, Otsuka Pharmaceutical Factory, Inc., Tokushima, Japan.
 Corresponding author: Takashi Kuwahara, Ph.D., Preclinical Assessment Department, Otsuka Pharmaceutical Factory,
Inc., 115 Tateiwa, Naruto, Tokushima 772-8601, Japan. Telephone: +81 88 685 1151 (Ext. 678) Fax: +81 88 684 0553; E-mail:

Received: 2010.02.01; Accepted: 2010.05.17; Published: 2010.05.18
Abstract
Background: To identify the microorganisms that can grow rapidly in total parenteral nu-
trition (TPN) solutions, we investigated the growth of the major causes of catheter-related
blood stream infection (Staphylococcus aureus, Serratia marcescens, Bacillus cereus, and Candida
albicans) in TPN solutions containing lipid. Methods: The pH value of a TPN solution con-
taining lipid (pH 6.0, containing 20 ppm of NaHSO

3
) was adjusted by the addition of HCl to
5.7, 5.4, or 4.9. The pH value of another TPN solution (pH5.5, containing 400 ppm of
NaHSO
3
) was adjusted by the addition of NaOH to 5.9, 6.3, or 6.8. A specific number of each
microorganism was added to 10 mL of each test solution and incubated at room temperature.
The number of microorganisms was counted as colony forming units at 0, 24, and 48 hrs later.
Results: C albicans increased similarly at any pH values in the TPN solution. The bacterial
species also increased rapidly at pH6.0 in the solution containing 20 ppm of NaHSO
3
, but
growth was suppressed as the pH value was reduced, with growth halted at pH4.9. However,
these bacterial species did not increase, even at pH5.9, in the other solution containing 400
ppm of NaHSO
3
. Conclusions: These results suggest that Candida species can grow rapidly in
almost all TPN solutions regardless of the acidity, lipid, and NaHSO
3
; also, some bacterial
species may grow in TPN solutions containing lipid unless the pH value is 5.0 or less.
Therefore, each TPN solution should be examined whether or not the bacterial species can
proliferate.
Key words: CRBSI, microbial growth, TPN solution, lipid, pH, bisulfite
INTRODUCTION
Catheter-related blood stream infection (CRBSI)
is one of the most common complications of intra-
venous catheters.
1-3
To reduce or prevent CRBSI, fac-

tors that enhance or inhibit microbial growth in pa-
renteral solutions should be investigated and identi-
fied. Total parenteral nutrition (TPN) solutions are
considered to be relatively good growth media for
microorganisms,
1,4
whereas a number of investigators
have shown that TPN solutions are poor growth me-
dia for most microorganisms that cause CRBSI, with
the exception of Candida species.
5-9
Likewise, we have
previously confirmed that while bacterial species do
not grow in TPN solutions without lipid, Candida
species grow rapidly.
10
Our data have shown that
bacterial species cannot grow due to the acidity, but
Candida species can grow regardless of the acidity.
10
In
contrast, most microorganisms grow rapidly in com-
mercial lipid emulsions,
11-15
and sporadic CRBSI and
Int. J. Med. Sci. 2010, 7


102
outbreaks have been traced to contaminated lipid

emulsion.
16,17
Because lipid emulsions have been
shown to contribute to the rapid growth of most mi-
croorganisms that cause CRBSI, it can be assumed that
TPN solutions containing lipid promote the microbial
growth compared with TPN solutions without lipid.
18

Consequently, the Center for Disease Control and
Prevention (CDC) has recommended that when any
infusion solutions containing lipid are administered,
the entire delivery system such as the administration
set be replaced every 24 hours.
19

As the major causes of CRBSI, Staphylococcus
aureus, Staphylococcus epidermidis, Serratia mar-
cescens, Escherichia coli, Klebsiella pneumonia, Can-
dida albicans, etc. were shown.
2,3,6,11
Furthermore,
blood stream infection outbreaks of Bacillus cereus via
intravenous line were recently reported in Japan.
20
In
the present study, we investigated the growth in TPN
solutions containing lipid of the same microorganisms
studied previously:
10

ie, Staphylococcus aureus as a
delegate of gram positive cocci, Serratia marcescens as
a delegate of gram negative rods, Bacillus cereus as a
delegate of gram positive rods, and Candida albicans
as a delegate of fungi. To clarify whether the acidity of
TPN solutions suppresses microbial growth in the
presence of lipid, the growth of all strains employed
were investigated at various pH values in a commer-
cial TPN solution containing lipid in the first experi-
ment. To identify which factors enhance or inhibit the
growth of each microorganism, we supplemented a
TPN solution containing lipid with multivitamins,
supplemented a TPN solution that did not contain
lipid with lipid, and increased the bisulfite concentra-
tion in a TPN solution containing both lipid and mul-
tivitamins in the following experiments.
MATERIALS AND METHODS
Microorganisms employed
A standard American Type Culture Collection
(ATCC) strain and 1 clinical isolate were used for each
microorganism; the standard strain ATCC6538 and
the clinical isolate N3 of Staphylococcus aureus, the
standard strain ATCC13880 and the clinical isolate N4
of Serratia marcescens, the standard strain ATCC11778
and the clinical isolate H2 of Bacillus cereus, and the
standard strain ATCC10231 and the clinical isolate N7
of Candida albicans.
Test solutions
A commercial TPN solution containing lipid
(ML; MIXID-L, Otsuka Pharmaceutical Factory, Inc.,

Japan), a commercial TPN solution without lipid
(AT1; AMINOTORIPA-1, Otsuka Pharmaceutical
Factory, Inc.), multivitamins (MV; Otsuka MV Injec-
tion, Otsuka Pharmaceutical Factory, Inc.), a 20% lipid
emulsion (IL; Intralipos 20%, Otsuka Pharmaceutical
Factory, Inc.), and a physiological saline were used.
The compositions of ML and AT1 are shown in Table
1.

Table 1. The compositions of ML and AT1
Solution ML

AT1
(
volume
)
900 mL

850 mL
Amino acids 30.0
g

25.0
g

Glucose 110.0
g

79.8
g

Fructose -

40.2
g

X
y
litol -

19.8
g

Li
p
id 15.6
g

-
Na
+
35 mE
q

35 mE
q

K
+
27 mE

q

22 mE
q

M
g
2+
5 mE
q

4 mE
q

Ca
2+
8.5 mE
q

4 mE
q

Cl
－
44 mE
q

35 mE
q

SO
4
2
－
5 mE
q

4 mE
q

Acetate
－
25 mE
q

44 mE
q

Gluconate
－
8.5 mE
q

4 mE
q

Citrate
3
－
-

10 mE
q

P 150 m
g


154 m
g

Zn 10
μ
mol

8
μ
mol
NaHSO
3
17 m
g

412 m
g

p
H 6.0

5.5

Osmotic
p
ressure ratio to
p
h
y
siolo
g
ical saline A
pp
rox. 4

A
pp
rox. 5



Int. J. Med. S
c
Experi
m
The pH val
u
saline (OPR
,
molalit

y
of
p
NaHSO
3
of
ppm (about
lutions of
M
addition of
0
Experi
m
supplement
e
Experi
m
and used as

OPR, and co
n
approximat
e
spectively.
T
justed to 5.9
,
NaOH. Eac
h
1/10 volum

e
(S+AT1V).
Experi
m
and used as

solutions of
the addition

and MLV(
p
(MLV+100
p
ppm).
Addition o
f
sampling
A spec
i
was added
t
plastic tube
s
room tempe
r
tion was sa
m
dition of mi
c
Measurem

e
Each a
l
oculated in
a
in duplicate.
tion was dil
u
saline befor
e
at 37ºC, the
n
each microo
r
mean CFU
o
aliquot, and

was calculat
e
aliquot vol
u
shown as
v
graphs. As
o
growth,
5,12,13
,
not anal

y
ze
d
ance of the
s
sessable wit
h
c
i. 2010, 7
m
ent 1: ML
w
u
e, osmotic p
r
,
the osmolal
p
h
y
siolo
g
ical
ML were 6.
0
20 ppm), re
s
M
L were ad
j

u
s
0
.5 mol/L H
C
m
ent 2: ML(p
H
e
d with MV (
M
m
ent 3: AT1
w

the base sol
u
n
centration
o
e
l
y
5, and 41
2
T
he other pH

,
6.3, or 6.8

b
h
pH solutio
n
e
of IL (L+A
T
m
ent 4: ML
w

the base so
l
MLV were a

of 0.5 mol/
L
p
H5.4) wer
e
p
pm) or 200
p
f
microorga
n
i
fic number
t
o each 10

m
s
, and all tub
e
r
ature (23-26
º
m
pled at 0, 2
4
c
roor
g
anisms
.
e
nt of viable

l
iquot of tes
t
a
So
y
bean Ca
When neces
s
u
ted 10-fold t
o

e
inoculation
.
n
umber of c
o
rg
anism was

o
f duplicate
d

number of
e
e
d b
y
usin
g
t
h
u
me, and dil
u
v
alues of C
F
o
ther experi

m
,
21,22
the data
d
statisticall
y,
s
e kinds of
d
h
out statistic
a
w
as used as t
h
r
essure ratio
t
it
y
of each s
saline), and
c
0
, approxim
a
s
pectivel
y

. T
h
s
ted to 5.7, 5.
C
l.
H
6.0), ML(p
H
M
LV) were
u
w
as supple
m
u
tion (AT1V)
.
o
f NaHSO
3
of

2
ppm (abou

solutions of
by
the additi
o

n
of AT1V
w
T
1V) or ph
ys
w
as supplem
e
l
ution (MLV)
d
j
usted to 5.
7
L
HCl. Besid
e
e
added
w
p
pm of Na
H
n
ism, incub
a
of each test
m
L of test sol

u
e
s were allo
w
º
C). An aliq
u
4
, and 48 ho
u
.


microorga
n
t
solution s
a
sein Di
g
est (
S
s
ar
y
, the aliq
u
o
10
7

-fold wi
t
.
After a 24-
h
o
lon
y
formin
g

counted for
d
ata was cal
c
e
ach microor
g
h
e number o
f
u
tin
g
ratio.
T
F
U/mL in s
e
m

ental studi
e
obtained in
t
,
because bi
o
d
ata is consi
d
a
l anal
y
sis.
h
e base soluti
o
t
o ph
y
siolo
g
i
c
olution/the
o
c
oncentratio
n
a

tel
y
4, and
h
e other pH
s
4, or 4.9 b
y

t
H
4.9), and th
o
u
sed.
m
ented with
M
.
The pH val
u

AT1V were
5
t 400 ppm),
r
AT1V were
a
o
n of 0.5 mol

/
w
as added w
i
s
iolo
g
ical sal
i
e
nted with
M
. The other
p
7
, 5.4, or 5.0

e
s, MLV(pH
5
w
ith 100 p
p
H
SO
3
(MLV+
2
a
tion and

microor
g
ani
s
u
tions in ste
r
w
ed to stand

u
ot of test so
l
u
rs after the
a
n
isms
a
mpled was
i
S
CD) a
g
ar pl
a
u
ot of test so
l
t

h ph
y
siolo
g
i
c
h
our incubat
i
g
units (CFU)

each plate.
T
c
ulated for e
a
g
anism per
m
f
CFU per pl
a
T
he results
a
e
mi-lo
g
arith

m
e
s of micro
b
t
his stud
y
w
e
o
lo
g
ical si
g
ni
f
d
ered to be
a

o
n.
c
al
o
s-
n
of
17
s

o-
t
he
o
se
M
V
u
e,
5
.5,
r
e-
a
d-
/
L
i
th
i
ne
M
V
p
H
by
5
.7)
p
m

2
00
s
m
r
ile

at
l
u-
a
d-
i
n-
a
te
l
u-
c
al
i
on

of
T
he
a
ch
m
L

a
te,
a
re
m
ic
b
ial
e
re
f
ic-
a
s-
RES
U
Expe
r
S
6.0, b
u
reduc
e
marces
c
increa
s
not in
c
cereus

presse
pH of
cans i
n
(Fi
g
ur
e
Figur
e
aureus
adjuste
Figur
e
in ML (
p
by addi
U
LTS
r
iment 1
. aureus incr
e
u
t
g
rowth wa
s
e

d, comin
g
t
o
c
ens increase
d
s
ed but with
s
c
rease at pH
increased at
d as the pH
v
4.9 (Fi
g
ure 3
)
n
creased rapi
d
e
4).
e
1. Effect of
in ML (pH6.0;

d by addition
o

e
2. Effect of p
H
p
H6.0; NaHS
O
tion of 0.5 m
o
e
ased in ML
s
suppresse
d
o
a halt at a p
d
rapidly in
M
s
uppression
a
values of 5.4

a pH of 6.0.

v
alue was re
d
)
. However,

b
d
l
y
and simi
l
pH on the g
r

NaHSO
3
, 20
p
o
f 0.5 mol/L H

H
on the grow
t
O
3
, 20 ppm). T
h
o
l/L HCl.
http://www.
m
at the ori
g
in

d
as the pH v
a
H of 4.9 (Fi
gu
M
L at a pH o
f
a
t a pH of 5.7
,

and 4.9 (Fi
gu

Its
g
rowth
w
d
uced, decre
a
b
oth strains
o
l
arl
y
at an
y

p
r
owth of Stap
h
p
pm). The pH
Cl.
t
h of Serratia
m
h
e pH value wa
s

m
edsci.org
103
al pH of
a
lue was
u
re 1). S.
f
6.0, also
,
and did
u
re 2). B.
w

as sup-
a
sin
g
at a
o
f C. albi-
p
H value

h
ylococcus
value was

m
arcescens
s
adjusted
Int. J. Med. S
c
Figure 3. Eff
e
(pH6.0; NaH
S
addition of 0.
5
Figure 4. Eff
e
ML (pH6.0;
N

by addition o
f



Experimen
t
Supple
m
the
g
rowth
resume the
cerning S. m
a
not affect th
e
c
i. 2010, 7
e
ct of pH on th
S
O
3
, 20 ppm).

5
mol/L HCl.
e
ct of pH on t

h
N
aHSO
3
, 20 pp
f
0.5 mol/L H
C
t
2
m
entation wi
of S. aureus
g
rowth at a
a
rcescens, B. c
e
e
m both at p
H
e growth of B
a

The pH value

h
e growth of
C
m). The pH v
a
C
l.
th MV to M
L
at a pH of
6
pH of 4.9 (
F
e
reus and C.
a
H
6.0 and at p
H
a
cillus cereus in
M
was adjusted

C
andida albican
s
a

lue was adjus
t
L
enhanced o
n
6
.0 but did
n
F
i
g
ure 5). C
o
a
lbicans, MV
d
H
4.9 (Fi
g
ure


M
L

by

s
in
t

ed
n
l
y

n
ot
o
n-
d
id

5).
Figur
e
cescens
,
pH4.9
t
amins
)

Expe
r
T
L+AT
1
diluti
n
tion.

I
n
marces
c
well a
s
at pH

6-8), s
i
S
u
B. cere
u
5.9, d
e
result
s
6.3 an
d
volu
m
g
rowt
h
A
e
5. Growth
o
,

Bacillus cere
u
in ML and in
M
)
.
r
iment 3
T
he OPR of
1
V (or S+AT1
ng
effect fro
m
n
AT1V, the

c
ens and B. c
e
s
at the ori
g
i
n

6.3 and inc
r
i

milar to the
r
u
rprisin
g
l
y
,
n
u
s increased
i
e
spite the pr
e
s
conflicted
w
d
pH 6.8, ho
w
m
e of IL to AT
1
h
of these ba
c
A
ddition of 1
/

o
f Staphylococ
c
u
s, and Candid
a
M
LV (ML sup
p
AT1V was
4
V) was 4.3 (o
m
the additio
n

standard st
r
e
reus did not
n
al pH of 5.5
r
eased rapid
l
r
esults of our

n
one of S. au

r
i
n L+AT1V
a
e
sence of lipi
d
w
ith those of
w
ever, suppl
e
1
V (L+AT1V
)
c
terial specie
s
/
10 volume
o
http://www.
m
c
us aureus, Ser
a
albicans at
p
p
lemented wit

4
.6, and the

r 4.2) as a res
u
n
of the isoto
r
ains of S.
a
increase at
p
but increase
ly
at pH 6.8

previous stu
d
r
eus, S. marce
s
a
t either pH
5
d
(Fi
g
ures 6-
8
Experiment

1
e
mentation
w
)
enhanced
m
s
(Fi
g
ures 6-8
)
o
f ph
y
siolo
g
i
c

m
edsci.org
104

ratia mar-
p
H6.0 and
h multivi-

OPR of

u
lt of the
nic solu-
a
ureus, S.
p
H 5.9 as
d slowly
(Fi
g
ures
dy
.
10

s
cens and
5
.5 or pH
8
). These
1
. At pH
w
ith 1/10
m
ildl
y
the
)

.
c
al saline
Int. J. Med. S
c
to AT1V (S
+
OPR from
4
bacteria less

IL (Fi
g
ures 6
Experimen
t
The
g
r
o
halted only
a
ppm of Na
H
S. aureus. H
o
added, the
gr
pH 5.7 and
(Figure 9).

Figure 6. Eff
e
adjusted by a
d
saline (S+AT1
Figure 7. Ef
f
adjusted by a
d
saline (S+AT1
c
i. 2010, 7
+
AT1V) cont
r
4
.6 to 4.2, e
n

sli
g
htl
y
tha
n
-8).
t
4
o

wths of 2 str
a
a
t pH 5.0 (Fi
g
H
SO
3
was not
e
o
wever, whe
n
r
owth of the
s
the clinical i
s
e
ct of lipid on

d
dition of 0.5
m
V).
f
ect of lipid o
n
d
dition of 0.5

m
V).
r
ibuted to t
h
n
hancin
g
the

n
did supple
m
a
ins of S. aure
u
g
ure 9). The
e
nou
g
h to st
o
n
200 ppm
o
s
tandard stra
i
s

olate was h
a

the growth
o
m
ol/L NaOH.
T
n
the growth
o
m
ol/L NaOH.
T
h
e reduction
g
rowth of
t
m
entation w
i
u
s in MLV w
e
addition of
1
o
p the
g

rowt
h
o
f NaHSO
3

w
i
n was halte
d
a
lted at pH
5
o
f Staphylococc
u
T
o AT1V was a
o
f Serratia ma
r
T
o AT1V was a
of
t
he
i
th
e
re

1
00
h
of

w
as
d
at
5
.4
T
were
h
pondi
n
tion o
f
strain
s
T
MLV
w
g
rowt
h
(Fi
g
ur
e

halted

and t
h
g
rowt
h
u
s aureus in A
T
dded 1/10 vol
u
r
cescens in AT
dded 1/10 vol
u
T
he growth o
f
h
alted at pH
5
ng
with the
r
f
200 ppm of
N
s
of

S. marcesc
e
T
he growth o
f
w
as halted b
o
h
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a

the
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rowth
o
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o
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of the clini
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T
1V (pH5.5;
N
u
me of 20% lip

i
1V (pH5.5; N
a
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me of 20% lip
i
f
2 strains of
5
.0 and pH
5
r
esults of Ex
p
N
aHSO
3
halt
e
e
ns at pH 5.7
f
the standar
d
o
th at pH 5.
0
ical isolate
w
a

ddition of
2
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f both strain
s
o
f 100 ppm
o
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al isolate at
p
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, 400 p
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+
a
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, 400 p
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i
d emulsion (L
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http://www.
m
S. marcescen
s

5
.4 (Fi
g
ure 10
)
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T
e
d the
g
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g
ure 10).

d
strain of B.

0
and pH 5.4
,
w
as halted a
t
2
00 ppm of
s
of

B. cereus
a
o
f NaHSO
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h
a
p
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g
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pm). The pH
v
+
AT1V) or ph
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p
m). The pH
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m
edsci.org
105

s
in MLV
)
, corres-
T
he addi-
h
of both

cereus in
,
and the
t
pH 5.0
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a
t pH 5.7,
a
lted the
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11).
v
alue was
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v
alue was
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siological
Int. J. Med. S
c
Figure 8. Eff
e
addition of 0.
(S+AT1V).
Figure 9. Eff
e
tamins). The
p
(+100ppm or


c
i. 2010, 7
e
ct of lipid on
t
5 mol/L NaO
H
e
ct of bisulfite

p
H value was
a

+200ppm).
t

he growth of
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H
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w

concentratio
n
a
djusted by a
d

B
acillus cereus i
n
w
as added 1/1
0
n
on the grow
t
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dition of 0.5
m
n
AT1V (pH5.
5
0
volume of 2
t

h of Staphyloc
o
m
ol/L HCl. T
o
5
; NaHSO
3
, 4
0
0% lipid emul
s
o
ccus aureus in

o
MLV was ad
d
0
0 ppm). The p
s
ion (L+AT1V
)

MLV (ML sup
d
ed 100 ppm
o
http://www.
m

H value was a
d
)
or physiolog

plemented wi
t
o
r 200 ppm o
f

m
edsci.org
106
d
justed by
ical saline
t
h multivi-
f
NaHSO
3

Int. J. Med. S
c
Figure 11. E
f
The pH value
+200ppm).

c
i. 2010, 7
f
fect of bisulfit
e
was adjusted
b
e
concentratio
b
y addition of
0
n on the gro
w
0
.5 mol/L HCl.

Figure 10.
E
Serratia marc
e
The pH value

w
as added 1
+200ppm).

w
th of Bacillus c
e

To MLV was a
E
ffect of bisul
f
e
scens in MLV (

w
as adjusted
00 ppm or
2
e
reus in MLV (
M
dded 100 ppm

f
ite concentr
a
ML suppleme
n
by addition of
2
00 ppm of
N

M
L suppleme
n
or 200 ppm o
http://www.
m
a
tion on the
g
n
ted with multi
0.5 mol/L HC
l
N
aHSO
3
(+1
0

n
ted with multi
f NaHSO
3
(+1
0

m
edsci.org
107
g
rowth of
vitamins).
l
. To MLV
0
0ppm or
vitamins).
0
0ppm or
Int. J. Med. Sci. 2010, 7



108
DISCUSSION
To reduce or prevent catheter-related blood
stream infection (CRBSI), we have to understand the
growth properties of the microorganisms that cause

this condition. We have previously investigated the
growth of the microorganisms that are known as the
major causes of CRBSI (Staphylococcus aureus, Serratia
marcescen, Bacillus cereus and Candida albicans) in total
parenteral nutrition (TPN) solutions without lipid.
10

Therefore, we investigated the growth of the same
microorganisms in TPN solutions containing lipid in
the present study.
In a commercial TPN solution containing lipid
(ML), both standard strains and clinical isolates of all
microorganisms (S. aureus, S. marcescens, B. cereus and
C. albicans) increased rapidly at the original pH of 6.0,
even without multivitamins. Although only C. albicans
increased equally at any pH value, the growth of S.
aureus, S. marcescens and B. cereus was suppressed as
the pH value was reduced, with growth halted at
pH4.9 (Experiment 1). However, these 3 bacterial
species did not increase in another TPN solution con-
taining lipid (L+AT1V) even at pH5.5 and pH5.9
(Experiment 3), which is the same result as obtained
in the solution without lipid (AT1V or S+AT1V); this
finding conflicts with the results of Experiment 1. The
conflicting results from these 2 TPN solutions may be
attributable to the difference in the bisulfite concen-
trations (ML contains NaHSO
3
at a very low concen-
tration [20 ppm], but L+AT1V contains NaHSO

3
at a
relatively high concentration [400 ppm]) because the
bactericidal effect of bisulfite is enhanced in acidic
conditions.
21
Therefore, the additional experiment
(Experiment 4) was performed to investigate the effect
of bisulfite concentration in the TPN solution con-
taining both lipid and multivitamins (MLV). As a re-
sult, the growth of the 3 bacterial species was sup-
pressed or halted at the same pH (5.4 or 5.7) as the
concentration of NaHSO
3
increased (20 ppm, 100
ppm, and 200 ppm). These results suggest that the
concentration of bisulfite in TPN solutions is an im-
portant factor for suppressing bacterial growth, espe-
cially between pH5.0 and pH6.0: the bacterial species
cannot increase at pH5.9 with 400 ppm of NaHSO
3
, at
pH5.7 or pH5.4 with 200 ppm of NaHSO
3
, and at
pH5.0 with 20 ppm of NaHSO
3
.
Other findings in the present study are as fol-
lows: 1) even if lipid is contained, the acidity of TPN

solution is the critical factor suppressing the bacterial
growth; 2) the addition of lipid enhances mildly the
growth of the bacterial species in TPN solutions but
does not affect the growth substantially; 3) the addi-
tion of multivitamins further enhances the growth of
S. aureus but does not affect the growth of S. marces-
cens, B. cereus, and C. albicans in TPN solutions con-
taining lipid; 4) C. albicans can grow regardless of
acidity, bisulfite, and lipid.
Because C. albicans could grow at pH5.5 with 400
ppm of NaHSO
3
(AT1V) in our previous study,
10
the
effect of bisulfite concentration on the growth of C.
albicans was not investigated in the present study.
However, it has been reported that C. albicans could
not increase in a TPN solution at pH4.4 with 500 ppm
of NaHSO
3
, whereas C. albicans increased in the same
TPN solution at pH4.4 with 40 ppm of NaHSO
3
or at
pH5.0 with 500 ppm of NaHSO
3
.
23
Practically, Candida

species can grow rapidly in almost all TPN solutions.
The pH values of most of the recent TPN solu-
tions are within 5.0 and 6.0, similar to the old TPN
solutions. On the other hand, the old TPN solutions
contain bisulfite at relatively high concentrations, but
the recent TPN solutions contain very low concentra-
tions of bisulfite or are bisulfite-free. To investigate
bacterial growth in the recent TPN solutions, referring
to results from the studies that used the old TPN so-
lutions that contained high concentration of bisulfite
is not appropriate, even at the same pH range. In the
recent TPN solutions containing lipid, some bacterial
species may proliferate unless the pH value is 5.0 or
less. Although the TPN solutions containing lipid can
be theoretically improved to be bacteriostatic by re-
ducing the pH value and/or increasing the bisulfite
concentration, more studies seem needed to improve
the solution because lipid emulsions become unstable
as the pH value reduces or as the concentration of
bisulfite increases.
In conclusion, Candida species can grow rapidly
in almost all TPN solutions regardless of the acidity
and the presence of lipid; also, some bacterial species
may grow in TPN solutions containing lipid unless
the pH value is 5.0 or less. Therefore, each TPN solu-
tion should be investigated to determine whether or
not the bacterial species can proliferate.
ACKNOWLEDGEMENTS
We are very grateful to Dr. Yoshifumi Inoue,
Kawasaki Hospital, Kobe, Japan, for his helpful sug-

gestions.
Conflict of Interest
We declare that there are no conflicts of interest
for all of us.
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