Stability
H. Bornside,2
Recent
absence
alters
bacteria
per
I
flora1
Ph.D.
ABSTRACT
and
fecal
is halved C/in.
Nutr.
the gram
experimental
numbers
and
of feces
remains
in its absence. 31: S 141-S
Thus, 144,
studies major constant,
the total
Journal
of Clinical
Nutrition
of the
output
that
neither
fecal
daily
bacteria.
fecal
of fecal
mass
bacteria
increased
dietary
Although
the
doubles
with
is related
to dietary
fiber total
added
nor
number dietary
fiber.
its of fiber Am.
1978.
The remarkable stability or constancy of fecal flora has frequently been observed; however, Zubrzycki and Spaulding (1) in 1962 were the first to attach significance to this constancy. They reported bacteroides, enterococci, cohiforms, diphtheroids, and lactobacilli as the major groups of human fecal flora, and proposed that an equilibrium among major groups produced stability important in protecting the host against enteric infection by members of minor groups (proteus, pseudomonas, staphylococci, salmonellae, and shigellae). They labeled as erroneous the notion that fecal flora varied with diet and from day to day in the same person. Others have subsequently shown that these major groups in the fecal flora are stable in a given person although they may vary from person to person (2), and that there is little difference between the fecal flora of infants and adults (3). Similar constancy of fecal flora has been shown for beagles fed sterile food in a locked environment for 1 year (4). With improved anaerobic methodology, bacteriologists can now enumerate and characterize the normal intestinal flora with greater accuracy. Several assumptions regarding the fecal microflora are supported by the results of various studies in man and animals and are discussed in recent papers (5, 6). First, the normal fecal flora is assumed to represent the cohonic flora. Second, the fecal flora is assumed to represent only the luminal flora; that associated with mucosal epithelial surfaces may differ markedly. Third, the fecal flora is assumed to vary with different types of diet. Epidemiological evidence correlating diet with colon cancer and other diseases implicates differences in fecal The American
show
groups
31: OCTOBER
bacteria and their metabolic activities as being associated with different diets. Therefore, recent experimental studies of the effect of increased dietary fiber, as well as its absence, warrant review from the focus of the stability of human fecal flora. Dietary
fiber
The low level of fiber in our Western diet has received much attention because of the proposed relationship of this deficiency to colon cancer and other colonic diseases and to metabolic diseases (7). Rooted in epidemiological data, the dietary fiber hypothesis states that a low-fiber diet promotes fecal stasis that allows more time for bacterial prohiferation, allows greater conversion of bile salts to potential carcinogens, and permits longer contact between carcinogens and the intestinal mucosa. Conversely, dietary fiber decreases intestinal transit time and increases the weight and volume of the stool. International comparisons of fecal bacteria and fecal steroids reveal differences that correlate with the incidence of colon cancer (8). Diet is presumed to alter the composition or the metabolic activity of intestinal microflora. Fecal bile acid concentration was much lower in low-incidence countries, and bile acids from high-incidence countries were more degraded. Concomitantly, aerobic bacteria were proportionately more numerous in specimens from how-incidence areas, and bacteroides
‘From the Department of Surgery, University Medical Center, 1542 Tulane Orleans, Louisiana 70112. 2 Professor of Surgical Research and
1978,
pp.
5141-5
144. Printed
in U.S.A.
Louisiana Avenue,
State New
Microbiology.
S141
Downloaded from https://academic.oup.com/ajcn/article-abstract/31/10/S141/4656082 by University of Glasgow user on 19 February 2019
George
of human
Sl42
BORNSIDE
were more prominent in high-incidence areas. Clostridia able to dehydrogenate the steroid nucleus were isolated more frequently from feces of individuals from high-incidence areas. These clostridia and high concentrations of bile acids were found more often in
.
I -
-
I
1-
-
0
feces of cancer patients than of controls (8). However, these reports have not been confirmed in this country (6, 9), or in subsequent studies by the earlier authors (Moore’s reference44)
OOO
‘1-Ie’.I
‘
,
Io I
The first of four recent experimental studies of fiber on human fecal bacteria is that of Walters et al. (10) who reported no alteration
0
I I
of flora or of steroid degradation when either wheat bran or sugar cane bagasse were added to the diet of healthy volunteers for 12-week periods. In the remaining studies (Table 1),
,,
a
_3 .8
o
‘rs
‘is
-
0
o
C 2
#{228}
r-
r-
o
o
r
no
,
r-
no
.
either the normal daily diet of healthy adult volunteers was supplemented with dietary fiber, or a low-fiber diet was contrasted with one high in fiber. Drasar and Jenkins (11) reported that addition of bananas and plantains, which are rich in dietary fiber, did not affect fecal flora. When Drasar et al. (12) studied the addition of bran fiber to the diet, they again found no changes. The predominant bacteria in all subjects were nonsporing anaerobes, but the dominant species in each subject was different and not affected by the test diet. Fuchs et al. (13) thought that they recognized trends caused by bran fiber, such as increased streptococci and chostridia and decreased lactobacilli and eubacteria. However, none of these changes was statistically significant. Thus, all investigators found no change in the concentration of bacteria in the groups they counted.
a
r.
no
u-’
u-S
u-
O
u-s
-
r
r-
rt “
u-s
1
u-
c
ss
-
o
#{176}‘#{176}‘#{176}
r-..
2 a
u-, r r
u-
us
‘
as
no
1
r-
sO sO r- r-
O
so
no
r
u
t-
no
t
no
no
.
,aI
(1
‘8
.O
‘.0
.
“ :a’
so
(4
(‘4
‘8
()LL,
k Chemically-defined
40o4oL)
diets
(cr-.
--
Chemically-defined liquid diets (14) are at the other extreme, and they allow evaluation of the effect of diets devoid of dietary fiber. These foods contain no undigestible bulk or fibrous materials and are taken orally to provide complete nutrition. They are almost totally absorbed in the upper small intestine. In 1970, Winitz et a!. (15) reported that
#{176}
a
diets
caused
dramatic
decreases
in
.
#{176}‘
#{176}
‘
“
.
U
U
m V
.
.
0
.
k ‘
:
.
#{149}
.fl
..
a
-
-
chemical
2
#{176} ‘
a
‘.
-
-
-
,
V
.
“3
.
a
-
-
V
stool types have
excretion of fecal confirmed
and in the concentration bacteria. Subsequent the reduction of fecal
and studies volume
.
a
Si
a
.
m us
Downloaded from https://academic.oup.com/ajcn/article-abstract/31/10/S141/4656082 by University of Glasgow user on 19 February 2019
LI.
STABILITY
OF
HUMAN
FECAL
and decreased frequency of stools, but none has confirmed any profound reduction or simplification of fecal flora (Table 2). Attebery et al. (16) noted increased enterobacteria and clostridia and did not detect extremely oxygen-sensitive anaerobes. Crowther et al. (17) noted increased enterobacteria and decreased enterococci. Bounous and Devroede (18) reported no changes with the exception of a significant decline in enterococci. Bornside and Cohn (19) found no statistically significant differences although some bacterial groups were lower during the diet period. The cumulative data emphasize that the fecal flora was not greatly altered during chemicaihy defined diets.
0
no
6 U.
One way to disrupt the constancy of fecal microflora is by oral administration of certain antibiotics. Preoperative bowel preparation, used by surgeons to suppress the microflora of the colon before elective colonic surgery (20), reduces the flora temporarily. It involves mechanical reduction of the fecal mass by means of daily cathartics, enemas, and consumption of a how-residue diet for 3 days along with oral antibiotics. A nonabsorbable aminoglycoside antibiotic (neomycin, kanamycin, or gentamicin) is used to obtain a high concentration of antibiotic in the stool. This antibiotic may be combined with another, such as erythromycin, bacitracin, tetracychine, or sulfathalidine, for broad coverage of both aerobes and anaerobes. After 2 to 3 days only yeast may be recovered from the feces. The return of the fecal flora to its pretreatment level within a few days after cessation of antibiotics attests to the stability of the flora. In the absence of antibiotics, the dietary and cleansing procedure per se diminishes the fecal mass within the colon and consequently the total number of fecal bacteria, but the numbers of each organism and the bacterial content per gram of feces remain unchanged (21-23). Conclusions The major groups of bacteria and their numbers per gram of feces are not altered by diets either supplemented with dietary fiber
no
xc
e’s
antisepsis
‘.o
u-s
-I
r4
ono
r4
eu-s
.i.
r-
1u
000’.
u-s r r- no
rso
0-
r-o’.
cI
ru-s r.I-
-o
-r
-
‘.or-
r.lr
r-’.0
r-u-s
‘.0
0r4 r- no
no.0 ‘.0 ‘.0
0
u-s
‘.0 ‘.0
r-
norr-
t-
.8 8 C 8
0
Do 0
8
1
a 8 8 0. In
2
‘8..a. no
0’.
‘.CN
LU
0.6’
Zn 0 0
In
V “3 #{149}0
V 8,
3
aa
“3 0
H
“3
o
0
-r 1no
I I
a
#{149}0
-
>.
-r 1no
3
#{149}0
r’1
..‘3
,.r-
,-
a3
a
.
a
pa a
‘0
E .
0
.
“3 V
.
C
.
-
0
a
0
-
-
V
0
V
.
3
Si
.
a
a a
a
-
V
.
Si
a a
V
.
.
H. Bornside,2
Recent
absence
alters
bacteria
per
I
flora1
Ph.D.
ABSTRACT
and
fecal
is halved C/in.
Nutr.
the gram
experimental
numbers
and
of feces
remains
in its absence. 31: S 141-S
Thus, 144,
studies major constant,
the total
Journal
of Clinical
Nutrition
of the
output
that
neither
fecal
daily
bacteria.
fecal
of fecal
mass
bacteria
increased
dietary
Although
the
doubles
with
is related
to dietary
fiber total
added
nor
number dietary
fiber.
its of fiber Am.
1978.
The remarkable stability or constancy of fecal flora has frequently been observed; however, Zubrzycki and Spaulding (1) in 1962 were the first to attach significance to this constancy. They reported bacteroides, enterococci, cohiforms, diphtheroids, and lactobacilli as the major groups of human fecal flora, and proposed that an equilibrium among major groups produced stability important in protecting the host against enteric infection by members of minor groups (proteus, pseudomonas, staphylococci, salmonellae, and shigellae). They labeled as erroneous the notion that fecal flora varied with diet and from day to day in the same person. Others have subsequently shown that these major groups in the fecal flora are stable in a given person although they may vary from person to person (2), and that there is little difference between the fecal flora of infants and adults (3). Similar constancy of fecal flora has been shown for beagles fed sterile food in a locked environment for 1 year (4). With improved anaerobic methodology, bacteriologists can now enumerate and characterize the normal intestinal flora with greater accuracy. Several assumptions regarding the fecal microflora are supported by the results of various studies in man and animals and are discussed in recent papers (5, 6). First, the normal fecal flora is assumed to represent the cohonic flora. Second, the fecal flora is assumed to represent only the luminal flora; that associated with mucosal epithelial surfaces may differ markedly. Third, the fecal flora is assumed to vary with different types of diet. Epidemiological evidence correlating diet with colon cancer and other diseases implicates differences in fecal The American
show
groups
31: OCTOBER
bacteria and their metabolic activities as being associated with different diets. Therefore, recent experimental studies of the effect of increased dietary fiber, as well as its absence, warrant review from the focus of the stability of human fecal flora. Dietary
fiber
The low level of fiber in our Western diet has received much attention because of the proposed relationship of this deficiency to colon cancer and other colonic diseases and to metabolic diseases (7). Rooted in epidemiological data, the dietary fiber hypothesis states that a low-fiber diet promotes fecal stasis that allows more time for bacterial prohiferation, allows greater conversion of bile salts to potential carcinogens, and permits longer contact between carcinogens and the intestinal mucosa. Conversely, dietary fiber decreases intestinal transit time and increases the weight and volume of the stool. International comparisons of fecal bacteria and fecal steroids reveal differences that correlate with the incidence of colon cancer (8). Diet is presumed to alter the composition or the metabolic activity of intestinal microflora. Fecal bile acid concentration was much lower in low-incidence countries, and bile acids from high-incidence countries were more degraded. Concomitantly, aerobic bacteria were proportionately more numerous in specimens from how-incidence areas, and bacteroides
‘From the Department of Surgery, University Medical Center, 1542 Tulane Orleans, Louisiana 70112. 2 Professor of Surgical Research and
1978,
pp.
5141-5
144. Printed
in U.S.A.
Louisiana Avenue,
State New
Microbiology.
S141
Downloaded from https://academic.oup.com/ajcn/article-abstract/31/10/S141/4656082 by University of Glasgow user on 19 February 2019
George
of human
Sl42
BORNSIDE
were more prominent in high-incidence areas. Clostridia able to dehydrogenate the steroid nucleus were isolated more frequently from feces of individuals from high-incidence areas. These clostridia and high concentrations of bile acids were found more often in
.
I -
-
I
1-
-
0
feces of cancer patients than of controls (8). However, these reports have not been confirmed in this country (6, 9), or in subsequent studies by the earlier authors (Moore’s reference44)
OOO
‘1-Ie’.I
‘
,
Io I
The first of four recent experimental studies of fiber on human fecal bacteria is that of Walters et al. (10) who reported no alteration
0
I I
of flora or of steroid degradation when either wheat bran or sugar cane bagasse were added to the diet of healthy volunteers for 12-week periods. In the remaining studies (Table 1),
,,
a
_3 .8
o
‘rs
‘is
-
0
o
C 2
#{228}
r-
r-
o
o
r
no
,
r-
no
.
either the normal daily diet of healthy adult volunteers was supplemented with dietary fiber, or a low-fiber diet was contrasted with one high in fiber. Drasar and Jenkins (11) reported that addition of bananas and plantains, which are rich in dietary fiber, did not affect fecal flora. When Drasar et al. (12) studied the addition of bran fiber to the diet, they again found no changes. The predominant bacteria in all subjects were nonsporing anaerobes, but the dominant species in each subject was different and not affected by the test diet. Fuchs et al. (13) thought that they recognized trends caused by bran fiber, such as increased streptococci and chostridia and decreased lactobacilli and eubacteria. However, none of these changes was statistically significant. Thus, all investigators found no change in the concentration of bacteria in the groups they counted.
a
r.
no
u-’
u-S
u-
O
u-s
-
r
r-
rt “
u-s
1
u-
c
ss
-
o
#{176}‘#{176}‘#{176}
r-..
2 a
u-, r r
u-
us
‘
as
no
1
r-
sO sO r- r-
O
so
no
r
u
t-
no
t
no
no
.
,aI
(1
‘8
.O
‘.0
.
“ :a’
so
(4
(‘4
‘8
()LL,
k Chemically-defined
40o4oL)
diets
(cr-.
--
Chemically-defined liquid diets (14) are at the other extreme, and they allow evaluation of the effect of diets devoid of dietary fiber. These foods contain no undigestible bulk or fibrous materials and are taken orally to provide complete nutrition. They are almost totally absorbed in the upper small intestine. In 1970, Winitz et a!. (15) reported that
#{176}
a
diets
caused
dramatic
decreases
in
.
#{176}‘
#{176}
‘
“
.
U
U
m V
.
.
0
.
k ‘
:
.
#{149}
.fl
..
a
-
-
chemical
2
#{176} ‘
a
‘.
-
-
-
,
V
.
“3
.
a
-
-
V
stool types have
excretion of fecal confirmed
and in the concentration bacteria. Subsequent the reduction of fecal
and studies volume
.
a
Si
a
.
m us
Downloaded from https://academic.oup.com/ajcn/article-abstract/31/10/S141/4656082 by University of Glasgow user on 19 February 2019
LI.
STABILITY
OF
HUMAN
FECAL
and decreased frequency of stools, but none has confirmed any profound reduction or simplification of fecal flora (Table 2). Attebery et al. (16) noted increased enterobacteria and clostridia and did not detect extremely oxygen-sensitive anaerobes. Crowther et al. (17) noted increased enterobacteria and decreased enterococci. Bounous and Devroede (18) reported no changes with the exception of a significant decline in enterococci. Bornside and Cohn (19) found no statistically significant differences although some bacterial groups were lower during the diet period. The cumulative data emphasize that the fecal flora was not greatly altered during chemicaihy defined diets.
0
no
6 U.
One way to disrupt the constancy of fecal microflora is by oral administration of certain antibiotics. Preoperative bowel preparation, used by surgeons to suppress the microflora of the colon before elective colonic surgery (20), reduces the flora temporarily. It involves mechanical reduction of the fecal mass by means of daily cathartics, enemas, and consumption of a how-residue diet for 3 days along with oral antibiotics. A nonabsorbable aminoglycoside antibiotic (neomycin, kanamycin, or gentamicin) is used to obtain a high concentration of antibiotic in the stool. This antibiotic may be combined with another, such as erythromycin, bacitracin, tetracychine, or sulfathalidine, for broad coverage of both aerobes and anaerobes. After 2 to 3 days only yeast may be recovered from the feces. The return of the fecal flora to its pretreatment level within a few days after cessation of antibiotics attests to the stability of the flora. In the absence of antibiotics, the dietary and cleansing procedure per se diminishes the fecal mass within the colon and consequently the total number of fecal bacteria, but the numbers of each organism and the bacterial content per gram of feces remain unchanged (21-23). Conclusions The major groups of bacteria and their numbers per gram of feces are not altered by diets either supplemented with dietary fiber
no
xc
e’s
antisepsis
‘.o
u-s
-I
r4
ono
r4
eu-s
.i.
r-
1u
000’.
u-s r r- no
rso
0-
r-o’.
cI
ru-s r.I-
-o
-r
-
‘.or-
r.lr
r-’.0
r-u-s
‘.0
0r4 r- no
no.0 ‘.0 ‘.0
0
u-s
‘.0 ‘.0
r-
norr-
t-
.8 8 C 8
0
Do 0
8
1
a 8 8 0. In
2
‘8..a. no
0’.
‘.CN
LU
0.6’
Zn 0 0
In
V “3 #{149}0
V 8,
3
aa
“3 0
H
“3
o
0
-r 1no
I I
a
#{149}0
-
>.
-r 1no
3
#{149}0
r’1
..‘3
,.r-
,-
a3
a
.
a
pa a
‘0
E .
0
.
“3 V
.
C
.
-
0
a
0
-
-
V
0
V
.
3
Si
.
a
a a
a
-
V
.
Si
a a
V
.
.
