296
J. C. KAKAVAS
TABLE 5
Effect of p-acetylaminobenzoic acid on sulfanilamide activity for Streptococcus agalactiae in tryptose broth
%
Sulfanilamide-mg. = .
P- acetylaminobouzoic
acid-gm.
F - 12a - 4 Culture -
1 : 100,000.
Growth in Original
Tubes.
Tube number
1
1,000
0.0001
0.1cc.
—
2
1,000
0.001
0.1
–
3
1,000
0.005
0.1
—
4
1,000
0.008
0.1
—
5
1,000
0.01
0.1
—
6
1,000
0.015
0.1
—
7
1,000
0.02
0.1
—
8
1,000
0.025
0.1
—
9
1,000
0
0.1
—
10
0
0.025
0.1
+
11
0
0
0.1
+
Results of subcultures made from above tubes into tryptose broth
Hours incubated
before
subculturing
11 . . .
24 . . .
48 . . .
72 . . .
96 . . .
123 . . .
Tube number
1
—
—
—
—
—
—
2
—
—
—
—
—
—
3
+
—
—
—
—
—
4
—
—
—
—
—
—
5
+
—
—
—
—
—
6
—
—
—
—
—
—
7
—
+
—
—
—
—
8
+
+
+
—
—
—
9
—
—
—
—
—
—
10
+
+
+
+
+
+
11
+
+
+
+
+
+
DISCUSSION
Although it is not possible at present to formulate
a concise explanation for the mode of action of sul-
fonamide drugs on microorganisms, certain facts
have been revealed which have an important bearing
on the use of these drugs in chemotherapy. In the
light of the results presented in this study, at least
three factors must be taken into consideration in
the treatment of Str. agalactiae infection of the
bovine udder. In the first place, at normal body
temperature the teat duct, and the clinical result of
those studies have been reported in a previous
publication.
In addition to the temperature and the drug
concentration, a third factor has been discovered
which influences the activity of sulfanilamide.
Among the many bacterial (37° C) sulfanilamide
temperature (37° C.) sulfanilamide in the concentra-
tion of 20 mg. per cent is not germicidal against Str.
agalactiae. A rise of three to four degrees above the
normal temperature is required to destroy these
organisms with 20 mg. per cent sulfanilamide. Since
streptococci mastitis is usually a nonfebrile infection,
and since it is not possible to raise the sulfanilamide
level in the body of the cow much above 20 mg. per
cent without producing serious damage to the animal,
the oral administration of sulfanilamide is of little
or no therapeutic value in the treatment of
streptococci mastitis.
In the second place, evidence is presented to show
that sulfanilamide is germicidal for Str. agalactiae
at 37° C. in concentrations above 100 mg. per cent.*
By analogy it may be assumed that since a high level
of sulfanilamide concentration is undoubtedly es-
tablished in the mucosa of the stomach and small
intestine when the drug is given orally, similar levels
may be attained in the mammary tissue if the drug
is given via the teat duct, and the clinical results of
those studies have been reported in a previous
publication.
In addition to the temperature and the drug
concentration, a third factor has been discovered
which influences the activity of sulfanilamide.
Among the many bacterial metabolites, p-aminoben-
zoic acid, which is claimed to be an essential growth-
substance for bacteria and which Ansbacher9 claims
to be a vitamin of the B complex group, has been
found to be a sulfanilamide inhibiting substance.
From the experimental data presented in this report,
Str. agalactiae produces metabolites which counteract
the bactericidal effect of sulfanilamide. No attempt
was made to identify the nature of this inhibiting
substance. However, p-aminobenzoic acid was found
to nullify sulfanilamide activity against organisms
of the Lancefield group B in the same manner as that
manifested for the other bacterial species that have
been reported.
SUMMARY
(1) The results of these in vitro tests reveal that
at body temperature (37° C.), sulfanilamide in a
concentration of 20 mg. per cent has no bactericidal
effect against Lancefield group B streptococci.
However, a concentration of 20 mg. per cent of
sulfanilamide will destroy these streptococci at a
temperature of 40.5° C.
(2) In order for sulfanilamide to be bactericidal
against group B streptococci at 37.5° C., it is
necessary to have a concentration of the drug of over
100 mg. per cent and this high drug level must be
attained during the early bacterial growth phase.
* In vitro experiments conducted in this laboratory have
shown that considerable variation exists in susceptibility to
sulfanilamide by these organisms ; some strains were killed
with 100 mg. per cent ; others required 800 mg. per cent.