43
sick and will not be subjected to certain dangers associated with primary
vaccination with calf lymph virus, but will obtain a solid and lasting im-

| munity to smallpox. Furthermore, it is possible that a cultured virus may
be developed which will be suitable for intradermal use and will not require
J Lis prompt dermal revaccination with a potent calf lymph vaccine to produce an
enduring immunity. These matters are for future investigation,

Although the final objective desired has not been attained, much
progress toward it has been made. During this progression the first cul-
tured virus for use in human beings was prepared and many observations on
the cultivation of viruses have been made. These are valuable to colleagues
working in similar fields, notably those striving to perfect vaccines for

the prevention of yellow fever and influenza.

PNEUMONIA
Dr. Avery and Associates.

Serun therapy in lobar pneumonia has been fostered in our Hospi-
tal for many years. This type of treatment had reached a high state of per-
fection when eighteen months ago chemotherapy of the disease suddenly ap-
peared upon the scens, The ease with which the latter form of therapy can
be administered and its relative inexpensivoness necessitated a study of
its merits by us,: particularly in view of the fact that our figures on serum
therapy are the.best in existence. During the past year such a study has
ea: been conducted and will be continued during the coming year. In addition,
the work of Dr. Dubos has disclosed a very interesting and potent substance
obtained from a soil bacillus, which may act as a key to further studies on
chemotherapy.

The production of antibacterial substances by soil microorganisms.

Organic matter does not accumulate in nature; the dead bodies of plants and

 
 

44

animals that fall upon the earth and all the waste materials which find
their way into sewage water, eventually become the prey of countless species
of microorganisms that break them down to the most simple forms of matter
found in the mineral world. The complex process which changes a decaying
block of wood, or a dead animal, into carbon dioxide, water, ammonia and
simple mineral salts cannot be performed by any one single microbial spe-
cies. Countless different kinds of molds and bacteria in turn attack the
many different organic molecules of which living tissues are composed. Fur-
thermore, each one of these microbes performs only a limited, well-defined
task, It is, therefore, assumed that - given enough time, patience and
skill —- bacteriologists will eventually discover in nature microorganisns
selectively adapted to the decomposition of almost any type of organic sub-
stance.

During the past few years this principle has found its application
in the isolation from soil of bacteria that carry out reactions of interest
to the biochemist and the bacteriologist. Two examples will serve to il-

lustrate the method and its possibilities.

 

I, The decomposition of the capsular polysaccharides of‘ pneumo-
coccus by bacterial enzymes. Virulent pneumococci are surrounded by a cap-
sule consisting of complex carbohydrates which protects these bacteria
against the normal defense mechanisms of the animal tissues. The capsular
substances, although fairly simple in etructure, cannot be decomposed by
any of the cells or fluids of the animal tissues. When the same capsular
substances are added to soil, howover, they are attacked by certain soil
bacteria which use them as a source of food; the same bacteria isolated in

pure culture and removed from the soil can also decompose the capsular sub-

stances in the test tube.

Beet eee

 

   
45

It has been possible to obtain in solution the enzymes - the di-
gestive juices - by means of which the soil bacteria dissolve the capsular
substances. The same enzymes, separated from the bodies of the bacteria
that produce them, are capable, both in the test tube and in the animal, of
destroying the pneumococcus capsules, and as a matter of fact can be used
to protect animals against infection with virulent pneumococci,

This example illustrates the different steps by which one can ob-
tain from the soil selective microbial agents capable of attacking given
substances. The substance to be decomposed is added to soil in order to
stimlate the miltiplication of soil microorganisms capable of using it as
a source of food. The active microbes are then separated from the soil and
isolated in pure culture. Finally the agent by means of which they perform
the reaction - a soluble enzyme for instance ~ is separated from the micro-
bial bodies, purified, and its activity is tested.

II, Preparation and properties of a bacterial agent which kills
Gram-positive microorganisms. The soil bacteria which have just been men-
tioned do not kill the pneumococcus cell; they do not affect its essential
life functions, but only dissolve its capsular substance. It appeared pos-
sible that there might exist in nature microorganisms capable of attacking,

not only well defined chemical substances, but also the living cells of

«

other, unrelated microbial species. In the first place attempts were made

to discover soil microorganisms antagonistic to the disease-producing Gram-
positive coce’. (pneumococci, streptococci, staphylococci), a group of bac-
teria in which workers in our Hospital have been interested for a long time.
Pneumococei, streptococci, staphylococci, although they differ
with respect to their pathogenicity and cultural characteristics, have in

common a number of propertios that place them in one natural group. Their

 

 
 

ie

46

similarity in structure is reflected in the fact that they can be stained
by the Gram technique — a differential staining method widely used in bac-
teriology. In fact, all the microbial cells which take the Gram stain - the
"Gram-positive bacteria" ~ can be clearly set apart from the Gram-negative
organisms by a number of morphological, cultural and biochemical properties.

In order to find out whether there exist in soil any microorgan-
isms capable of attacking the living cells of Gram-positive bacteria, sus-
pensions of living pneumococci, streptococci, and staphylococci were re-
peatedly added to a sample of earth, in the hope that the continued pres-
ence of these foreign cells would stimulate the development of a soil popu-
lation capable of living at their expense. This in fact did happen, and it
was possible to isolate from the sample of soil, a sporulating bacillus ca-
pable of killing and destroying the living cells of Gram-positive bacteria.

It was soon observed, however, that the soil bacillus does not ac-
tually feed on the living Gram-positive cells. It first kills them by means
of a powerful bacterial poison (a "bactericidal" substance) and then uti-
lizes their dead bodies. The present report deals with the isolation and
properties of the chemical substance, secreted by the soil bacillus, which
causes the death of the pathogenic cocci. The antibacterial ("bacterici~
dai") substance is abundantly produced when the soil bacillus is grown in
a peptone solution. It can be separated from the peptone culture by extrac-
tion with alcohol, in which the substance is very soluble, followed by pre-
cipitation in aqueous salt solution, in which it is practically insoluble.
The material which precipitates out of the salt solution is thus obtained
free of the bacterial cells and carries all the bactericidal activity of
the original culture. Minute amounts of this material are sufficient to

kill in the test tube enormous numbers of Gram-positive bacteria, and to

 
"

4?
protect mice against infection with virulent pneumococci and streptococci.

The material obtained by extraction with alcohol and precipitation
in salt solution is not, however, a single substance. One can separate from
it, by differential solubilities in alcohol-ether mixtures, two fractions
which are very closely related in chemical structure, but which differ in
some of their biological activities, One of these fractions has been ob-
tained in crystalline form and will be referrod to as the "crystalline"
fraction. The other has not yet been crystallized, although it has been ob-
tained in a state of purity. For reasons that will become obvious later it
has been called the "protective" fraction.

Much is already known of the chemical composition of these two
fractions. Suffice it to say that they possess the same essential molecular
structure and that the protective fraction differs from the crystalline prod-
uct by the possession of a simple chemical grouping, which makes up only a
small fraction of the total molecule.

Both fractions exhibit in the test tube a remarkable bactericidal :
activity against Gram—positive microorganisms, e.g., 0.01 - 0.02 mg. of
either substance is enough to kill 1,000,000,000 pneumococci or streptococci
within 2 hours at 37°C, Staphylococci, Gram-positive bacilli, and even
yeast cells are also killed by the same substances in the test tube, al-""-
though the susceptibility varies’ from one microbial species to another. ° -

' -§td2l- smaller amounts of either fraction inhibit the growth of

 

Gram-positive bacteria in nutrient broth. This is particularly striking in
the case of pneumococcus which fails to grow in nutrient broth containing a
dilution of 1/500,000,000 of the active substance.

It is not yet clear how the bactericidal substance exerts its

killing action upon the susceptible cells; it is only known that, although
we

 

48
the affected cells retain unimpaired many of their biochemical activities,
they lose the ability to oxidize certain essential foodstuffs and conse~
quently die of starvation. In any case, it is important to emphasize that,
whatever the nature of the mechanism or its action, the active substance has
been found effective only against Gram-positive organisms, whereas the Gram-
negative bacilli, for example, those of the colon-typhoid group, remain un-
affected.

As stated above, both the crystalline and the protective fraction
are effective in the test tube. The crystalline fraction, however, appears
to be ineffective in the animal body and fails to protect mice against in-
fection with virulent pneumococci and streptococci. On the contrary, one
gingle dose of the protective substance injected into the abdominal cavity
is sufficient to protect mice against 10,000 fatal doses of pneumococci or
streptococci administored by the samo route. The material has proven equal-
ly effective against infection with the five different types of pneumococci
and the fourteen different types of hemolytic streptococci (group A and C)
which have been tested so far. It is permissible to hope, therefore, that
it will also prove effective against all virulent strains of these bacterial
species,. irrespective of type specificity.

When slightly larger doses, 0.002 ~ 0.005 mg., of the bactericidal
agent are used and when the treatment is repeated on three consecutive days,
it is possible to protect mice against 1,000,000 fatal doses of Type I or
Type II pneumococcus. Furthermore, it is also possible to cure mice of a
well established infection when treatment is delayed for several hours after
injection of the infective organisms. Many mice treated two to six, or even
seventeen, hours after infection with Type I or Type III pneumococcus were

saved, although all the control untreated animals died between 30 and 44

 

en ae

a a ea ee a

 

 
a te on ee

e %

49

hours after infection.

~

It must be pointed out that in all these experiments, both the in-
fecting organisms and the bactericidal substance were injected by the intra-
abdominal route. To date less success in treating animals by any other
route has been attained; only a few of the infected animals wero saved when
the bactericidal substance was injected intravenously, subcutaneously or in-
tramuscularly. Several possibilities may be invoked to account for this
failure: a) The active substance when introduced in the general circulation
may be eliminated so fast that it never reaches an effective concentration;
b) it may be inactivated in some tissues, for instance by hydrolysis or con-
Jugation; c) the active substance is known to be very insoluble in aqueous
media and may, therefore, fail to diffuse and reach the different foci of in-
fection,

Little is known as yet of the toxicity of the material; 0.1 to
0.2 mg. of the protective fraction injected by the intra-abdominal route
will often kill mice within 48 hours. Smaller amounts, although they do not
kill the animals, cause some loss of weight and degenerative changes of the
different organs. Rabbits are also susceptible and are killed within 24
hours following the injection of 5~10 ng. of the material. It is evident,
therefore, that the protective substance ig a very potent toxin for mamma-
lian specios; it is also true, however, that so far no toxic effect has
been recognized with the small amounts of substance which are sufficient
to protect animals against infection. Finally it must be pointed out that
the crystalline fraction which, although very bactericidal in the test tube,
is inactive in the animal, also fails to cause any obvious toxic reaction in
rabbits and mice.

The findings just reported have revealed the existence and to some

extent the chemical nature of a new type of bactericidal agent which, al-
50
though extremely active against Gram-positive microorganisms, fails to at-
tack Gram-negative bacilli. This selective affinity for a certain type of
microbial cell may be of importance in deciding the value of a substance as
a therapeutic agent. Any bactericidal agent to be effective in the body
must attack selectively the microbial parasite, without injuring the colls
of the host to be treated. It is encouraging to note, therefore, that the
bactericidal agent described in the present report is not equally toxic for
all types of cells, but on the contrary exhibits a selective affinity for a
well defined group of microorganisms. In this respect it will become im-
portant to study the reasons that determine the specific affinity of the
bactericidal substance for the Gram-positive cells. An understanding of
this affinity may serve as a guide further to enhance the specificity of the
agent and decrease at the same time its affinity for the tissue cells of the
infected host; sharper specificity would probably decrease the toxicity for
the mammalian tissue cells and increase its effectiveness against the micro-
bial cells in the animal body.

It has already been pointed out that the toxicity and the insolu-
bility of the material limit its effectiveness in the animal body; it is
worth while considering, therefore, whether means can be found to overcome
these limitations. It will be recalled that the crystalline fraction, al-
though very active in the test tube, is neither active in the animal body,
nor toxic for the mammalian organisms. On the other hand, the toxicity of |
the protective fraction, as well as its ability to protect animals against
pneumococcus and streptococcus infections, is associated with the presence
in the molecule of a minor chemical grouping not present in the crystalline
fraction. It appears possible that, by replacing this differentiating chem-

ical grouping by some other group properly selected, one may decrease the
 

bye

an

51

toxicity of the natural bacterial product, while maintaining its protective
value. It is also possible that by adding to the molecule a chemical group
with strong affinity for water one may render the material more soluble in
tissue fluids, and at the same time allow it to diffuse more rapidly through
the organs.

So far, the experimental work has been concerned only with pneumo-
coccus and streptococcus infections. It must be remembered, however, that
the bactericidal agent is very effective against other types of Gram—posi-
tive organisms. It has been shown for instance that it kills very rapidly
the cells of a Gram-positive spore-bearing aerobic bacillus. The anthrax
bacillus belongs to this group, and it will be important to determine the
effect of the bactericidal agant on this discase~producing microbe both in
the test tube and in the animal body.

It has been suggested earlier in the report that there will prob-
ably be found in nature, in soil for instance, microorganisms capable of at-~
tacking the living cells of other, unrelated microbial species. From cul-
tures of these soil organisms it should be possible to release free of the
bacterial cells the agent by means of which they attack the susceptible spe-
cies. In the present report there have been described the preparation and
properties of such an agent which is active against Gram-positive microorgan-
isms. It is permissible to hope that one will eventually discover soil ore
ganisms which attack other types of disease-producing microbes ~ the Gran-
negative bacilli, the acid fast bacteria, etc. - and that the active sub- .
stance by means of which they exert their antagonistic effect will be iso-
lated. These agents may not themselves be effective in the animal body. An
understanding of their chemical nature and of the mechanism of their action

will undoubtedly, however, give the bacteriologist and the chemist new conm-

 

SPR MI nares +

 

 
52
pounds and new techniques for the development of chemotherapy on a rational

basis.

CARDIOVASCULAR DISEASES
Dr. Cohn and Associates.

These workers are investigating diseases of the heart and blood
vessels. In this group of maladies is the disorder called "essential hy-
pertension", i.e., unexplained high blood pressure. From the work already
conducted the investigators have been led to believe that in many cases of
unexplained high blood pressure a reason for the disorder may be found. For
example, quite a high percentage of their cases shows renal abnormalities,
such as constricted renal blood vessels, constricted outlets of the kidney,
or kidney stones. Having found in some of the patients a possible reason
for the high blood pressure, they hope that by intensive examination of the
remaining members of the group to uncover, in some of them at least, the
cause of their trouble. In othor words, these workers are of the opinion
that the high blood pressure in patients with essential hypertension may be

explained, and that the reason for it will not always be the same.

DISEASES OF THE BLOOD
Dr. Rhoads and Associates.

For a number of years Dr. Rhoads and his group have conducted
clinical and experimental investigations on sprue, pernicious anemia, re-
fractory anemias, leukemia, and a number of other diseases. During the
course of their work, Dr. Rhoads came to believe that many of the maladies,
although presenting entirely different clinical pictures, had nevertheless
something in common, namely a conditioned deficiency. Indeed, he brought a

certain amount of evidence that this idea deserves consideration, for many

   

we Rage ct