John Weinzirl.

The action of sunlight upon bacteria with special reference to B. tuberculosis online

. (page 3 of 3)
Online LibraryJohn WeinzirlThe action of sunlight upon bacteria with special reference to B. tuberculosis → online text (page 3 of 3)
Font size
QR-code for this ebook


duction was not diminished, although the number of colonics was greatly reduced.

B. pyocyaneus.
Kedzior worked with this organism and found it was killed in agar [)lates in
between 2} and 3 J hours. By the method of direct exposure, the writer found it was
dest roved as follows:

TABLE 14.



Date


Method of Exposuee


Results of Exposuee (Mm.)


Growth


No Growth


April 7


On glass, uncovered

" paper, "
glass.


a


a. 5. «>. ao
5, 10, ao, 30
a, 5, 10. 15, ao
4. 10


^ ,i


May


June 30





Two other chromogens were tried, with the following results:

TABLE IS.



Date



Organism



Method of Exposure



Results of Exposure (Mtk.)



Growth



I



No Growth



Afril a.
May IS-
19.

a8.
xs.
10 .
a8.



Sar. aurantica



A pink air-micrococcus



On glass, direct



under glass
direct

under glass
direct



3, 6, 10, IS, as

a, s« 10, ao

10, ao, 30, 40, 60

60

a, s, xo, ao

10, ao, 30. 40, 60

60, 90



These two organisms show a higher order of resistance to the influence of sunlight
than those heretofore considered. (See PI. 3. B.) Indeed, they constitute a group
by themselves, to which, presumably, many of the bacteria found in the air belong.
Whether the resistance they exhibit is due to a failure to break up the groups, or to a
sporeKke condition (so-called arthrospore) of the bacterium, remains uncertain. But,
from the nature of the suspensions used, and from the character of the growth in the
plates, the writer is inclined to hold the latter view.

* Arh, a. d. kais. CsndhtsanU., i8o4, 9% P« 40S>



Digitized by



Google



Action of Sunught upon Bacteria



147



It is fortunate that the pathogenic organisms show no such powers of resistance,
or the problem of coping with them would be materially more difficult.

B. tuberculosis.

Coming now to the bacillus of tuberculosis, which is the chief factor
in the present investigation, one finds practically no previous tests
that are satisfactory, with which to compare the results. Koch's
remarks are seemingly based upon casual observation, which, how-
ever, indicated that the organism was highly sensitive to light, pre-
sumably more so than other bacteria. Strauss came close to the
truth in his trial by exposing a film on glass plates, which he found
was killed in 30 minutes. Other workers have used sputum with
variable results, ranging from 24 to 30 hours, up to days or weeks.

The earlier results when the bacillus was exposed on egg medium
have been given; they are relatively high, varying between two and
five hours in time necessary to kill; in aqueous suspensions it was
killed in i to I hour. The later results, when no culture medium
was used in the exposure, are as follows :



TABLE x6.



Date



No. OF
Okgan-

ISM



September

41

October
Noveinber

December



A^



Method of Exposure



Results of Exfosubb



Growth



No Growth



8, 1905.

8, 1905.

8. 190$.
a8, 190$.
II. 1905.
30, 1905.
34. 190$.
36. 1905.
36, 1905.
36, X905.
36, 1905.
36. 1905.

4. 1906.
II, 1906.



lOI

no
xoi

lOX
lOI
lOI
lOI
lOI
XOI
I03

1x0

113

lOI
X03



On paper, under gla«

+ moisture, on paper, under gla«

On paper, under glass

+ moisture, on paper, under glass
On paper, under gU»



direct



*. I, li



i I. li
xo, ao



a. 3. 4. S. 6 (hrs.)

X, If, 3, a}, % (hrs.)

i. I. xi, a, 3i. 3 (hrs.)

2, a*. 3. 4 P»r8.)

30, 45, 60 (min.)

10. 30, ^o, ^5, 60 (min.)

I, a, 3 Oar6.)

xo, ao, 30, ^5, 60 (min.)

ao, 30, 45, 60 (min.)

10, ao, 30, AS, 60 (min.)

ao, 30. 45. 00 (min.)

ao (min.)

5. xo, IS, ao (min.)



In the work prior to December, the data showing greatest lon-
gevity were obtained, as previously noted, by rubbing the pure culture
upon the paper and then making the exposure; the December data
were secured from aqueous suspensions inoculated upon paper,
while those in April and later were films from suspensions, dried on
paper and exposed to the sun directly, i. e., without glass or other
intervening medium.



Digitized by



Google



148 John Weinzirl

Leaving out of account the earlier results, as not being satisfactory,
it appears that the method of direct exposure gives as consistent and
similar results with tubercle as with other non-spore-bearing bacteria;
it is more sensitive than some, but less so than B. colt, for example*
Too close comparisons are not admissible here, for the time is so
short that shght but imavoidable variations may place the result on
one side or the other. Apparently tubercle is not especially sensitive
to light. This may be only apparently so, for, as was mentioned
earlier, homogeneous suspensions are not so readily obtained mth
tubercle as with other bacteria, and, as a result, clumping, with
consequent protection, takes place.

In this connection, another experiment wiU be of interest. A
sample of sputum, containing numerous tubercle bacilli and also
cocci, etc., was spread in thin films on papers and exposed under
glass in the usual way. In the cultures where development took
place, M. pyogenes aureus and albus were present; but in those that
remained free from contamination, tubercle failed to develop. The
periods of exposure were 10, 20, 30, 45, and 90 minutes. A repetition
of this experiment gave the same results. This would seem to indi-
cate that the tubercle bacillus is not more resistant to the action of
light than were the other bacteria that chanced to be present in the
sputa.

The details of an experiment made on April 4 wiU be interesting
and instructive, especially in helping to explain the variable results
obtained with tubercle, and also its apparent endurance. A watery
suspension of a culture of tubercle No. loi was employed. This
suspension was filtered through a layer of glass wool, and subse-
quently inoculated upon paper strips. These strips were sealed at
one end to the bottom of a petri dish by means of hot parafiFin. After
inoculation, they were exposed, uncovered, to direct bright simlight
between 12:28 and 12:54 p. m. The results are given in Table 17.

It is seen that none of the five- minute exposures was kiUed ; that
two out of four of the lo-minute exposures grew, one showing only
a single colony; also two from the 15-minute lot showed each a single
colony; and that none of the 20- minute cultures grew. Two con-
trols gave excellent growth. Although the suspension from which
these inoculations were made was filtered, and a macroscopic exami-



Digitized by



Google



Action of Sunlight upon Bacteria



149



TABLE 17.

RXSXTLTS WITH TOBESCLB, BY DiKBCT EXPOSURE



Result



Good growth

Four colonies

Fair growth

Slight growth

No growth

One small colony

No growth

Good growth

Contaminated

One colony
*• •«

No growth




Good growth



nation showed decided improvement in homogeneity as compared
with the original, yet a microscopic examination still revealed occa-
sional clumps of bacilli aggregating 10-50 in number. Undoubt-
edly it is due to this tendency to clump that tubercle gives such varying
results, and a false impression is obtained in regard to its true resist-
ance to sunlight, which is probably not greater than that of the common
pus coed.

An experiment was made with Holler's grass bacillus, which is
acid-fast and simulates tubercle very closely, except that it grows at
room temperature on common media. In this case it was not killed
in 15 minutes, on May 11, at midday. Here clumping was marked,
and was accompanied by a corresponding longer period of resistance
to simlight.

It was stated by Koch that cultures of tubercle are killed in five
to seven days in diflFuse light. This point was also tested, cultures
on paper slips being exposed for comparison. The exposures were
made directly in front of a north window in the laboratory next to the
window-sill, all the cultures being under glass.

In this series the pure culture was rubbed onto the paper slips.
The simlight afforded by a number of days was necessary for these
long exposures. While the results are too few for drawing any positive
conclusions, they do not indicate any extraordinary sensitiveness to
diffuse light on the part of tubercle, for the culture of October 21
required six days of exposure and then was not killed. The cultures



Digitized by



Google



ISO



John Weinzikl



TABLE 18.



Date


CULTUKK


MXTHODOr
EXPOSUSE


Results of Exposure (Houss)


Growth


No Growth


September 7. «9os

'* 7, 1905


No. 101
** 101
*' 101

" lOI

" 101
" no


On egg medium
On paper + moisture
On egg medium
On paper

On paper


a. 5. 9j. 15. aaj. 30
2, 5, 9*. IS. aa*, 3©
aS> 30. 35. 40, 45. 5©






October ai, 1905

a I, 1905

ai. iQos

ai, iQos




as. 30, 35. 40. 45. So
30, 35. 40, 45. 50
30, 35. 40, 45. 50


as
as



on paper slips show that diflFuse light does have an effect; this is not
due to desiccation, for when moisture was added the result was similar.

Taking the results for tubercle as a whole, there is no good reason
to ascribe to this organism any special powers in the way of resistance
or lack of resistance to sunlight; in fact, it possesses about the same
order of reistance as the other nonsporogenous pathogenic bacteria.

A number of experiments were carried out to determine which
rays acted bactericidally upon B, tuberculosis. The method adopted
was to employ the paper slip cultures under a single pane of red,
green, or blue glass. These glass panes were found, however, not to
give pure monochromatic light, for the red filtered through the blue,
and the blue through the red, while both filtered through the green.
Under these circumstances. Tubercle No. loi gave the following
results:

TABLE 19.



Trial


Date


Method of Exposure


Result of Exposure (Min.)


Growth


No Growth


(a)


May 3

" 17
" 17
*• 17
" 17


Under cobrleaB glass
" red **

" colorless "
" red




5, 10, IS, ao, 30, 45

30,45

45

10, IS, ao, 30, 4S

10, ao, 30

30


c)

\e)

'4=


S, 10, IS, ao

S, 10, 15, ao, 30

5

5

5. 10

S, 10, ao, 30

5. 10


ao, 30



These experiments indicate that it is the violet end of the spectrum
that is fatal for tubercle, just as for other forms.

Since the data which have been recorded in the foregoing tables
are distributed throughout the paper, it appears wise to collect them
in a single table for convenience of reference and comparison. The
table is as follows:



Digitized by



Google



Action of Sunught upon Bacteria



151



TABLE ao.
Summary op Results op Exfosino Bacteru to Direct Sunlight



Date
March 30. . . .

;; as

aj

April 7

11

May IX

** II

** 11

April 37

May 10

** 15

April aa

"^^ .?:::::

April II

'* a?

May 19

Biarch 31....

April a?

May 10

April a

aa

May IS

April 7

II

aa

May 10

Apnl 87

May II

April 7

" II

May 9

June 30

April a

May IS

•• I?:::::
;• IS

«• It:.::

** la

December 94
a6
a6

April 4

December a6

April II

December a6
a6

April a3



Organism



B. coli


" (No. 711)

B. tyfju>sus

««
B. dysttUtriae

S. ckoUrat-nsiaHcae

B. difjuherice

M. Pyog. aurtus

•* tt

M. tetragemu

B. prodigiosus
B. pyocyaneus

Sar. auratUica

Pink air-coccus



MttUer*s grass badllus
Tubercle loi (human)



lOI

loa (human )
loa (human)
no (bovine)
113 (avian)
113



Method of
Exposure



Direct



Under glass
Direct

Under glass
Direct

Under glass



Direct
Under glass

Direct
Under glass

Direct



Limits of Life
(Min.)



o and



TO
60
60

ao
60
00
IS

o
30

o
IS



6
10
a
S

IS
10
xo
S
5
S



10
60
10



PRACTICAL BEARINGS OF THE RESULTS.

In reading the publications of the workers in this field, especially
those of the earlier investigators, one notices that they exp)ected
rather more disinfectant action from the sunlight than was found;
and so there seems to be something of a tone of disappointment.
However this may be, it is certain that the results they obtained fell
far short of doing justice to the disinfecting action of the sun*s ra)rs.
While this action has been considered important from a sanitary view-



Digitized by



Google



152 ' John Weinzirl

point, it is certain that it is much more powerftil than previous results
have indicated. Were it not for this powerful repressive agent,
coupled especially with the repressive action of desiccation, it seems,
indeed, that our chances for waging a successful war against disease
and other objectionable bacteria would be slight; but when we
realize that 2 to 10 minutes of active sunlight are sufficient to kill
them when directly exposed, we can readily understand how the vast
majority of all such bacteria are effectively destroyed, and only an
infinitesimal number remains. This gives sanitary science new hopes
and fresh courage with prospects of the highest success.

These results explain, in a measure, the advantages of a dry
climate, such as the western and southwestern portions of the United
States possess, where, due to the dryness and the sup)erab\mdant sun-
shine, most bacteria, and esp)edally the non-spore-bearing disease
germs are quickly destroyed. Above all, they emphasize the im-
portance of well-lighted and ventilated houses. The sunlight is a
friend and protector of our welfare and should not be barred from
our homes by shutters and heavy shades; for there is truth in the
Italian sajdng: "Where sunlight enters not, there the physician
goes."

CONCLUSIONS.

The conclusions arrived at may then be summarized as follows:
The methods heretofore employed in testing the bactericidal action of
sunlight do not seem to be well suited for this determination, since
the results do not indicate the full power of this agent.

The light is absorbed by the medium in which the bacteria are
planted, and the glass cover both absorbs and reflects a considerable
portion of the effective rays. A more suitable method consists in
planting the bacteria upon glass or paper and exposing directly, i. e.,
without glass or other cover, to the sun's rays. By this method most
of the non-spore-bearing bacteria, including B. luberctUosis^ B, diph-
theriae, B. typhosus^ S. cholerae-asiaticae^ B. coli, B, prodigiosus,
and others, are killed in a remarkably short period of time, varying
from 2 to 10 minutes. This time is considerably lengthened if the
suspension used is not homogeneous and the bacteria consequently
become clumped or bunched in the film. Certain saprophytic bac- 1



Digitized by



Google



PLATE 2.



Digitized by



Google



Digitized by



Google



PLATE 3.



Fig. 2.



Digitized by



Google



Digitized by



Google



Action of Sunlight upon Bacteria 153

teria, such as the micrococci foiind in the air, require a much longer
period of exposure to kill them, the time being upward of an hour.

By the method employed in the foregoing work, practically all
the disturbing and complicating factors of the older methods are elimi-
nated: the time required for exposure is so short that desiccation
becomes a negligible factor, or practically so; the formation of bac-
tericidal by-products in the medium, such as hydrogen peroxide,
phenol, organic peroxides, etc., is entirely removed, and consequently
the action must be ascribed wholly to the sunlight.

So far as B. tuberculosis is concerned, it is the more refrangible
rays, or the violet end of the spectrum, which are bactericidal for this
organism.

Finally, the results by direct exposure of the bacteria indicate that
sunlight is a much more powerful germicidal agent, and consequently
a more important hygienic factor, than it has heretofore been con-
sidered; that the bacteria, when freely exposed, are killed in one-
fifth to one-twentieth of the time formerly considered necessary.

ACKNOWLEDGMENTS.

In closing I wish to express my deepest gratitude to Professor H.
L. Russell for suggesting and directing the present investigation;
I have also to acknowledge with thanks the kindly assistance of Pro-
fessors W. D. Frost and E. G. Hastings, and Dr. C. A. Fuller, all of
whom have been ever ready to promote and encourage the work.

EXPLANATION OF PLATES.

Plate 2,

Tubercle cultiires grown on egg medium after exposing to direct sunlight
as follows: A — § hr.; B — i hr.; C — 1| hrs.; D — 2 hrs. no growth). Note the area
of the infected paper in each tube.

Plate 3.

Fig. I. — ^Showing petri plates exposed uncovered to direct sunlight. A is
M. tetragenus exposed 2 minutes; B is a pink micrococcus from the air, and was
exposed 60 minutes. The crosi and circle are made up of the bacterial colonies; they
serve as mechanical devices for distinguishing the culture inoculated from the foreign
or contaminating bacteria.

Fig. 2. — B, coli in agar plates exposed to sunlight. A —control; B — io min;
C«v^Q xnin. D — 30 min.; E— 45 min.



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



r



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



'Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



Digitized by



Google



''^'



Digitized by



Google



f-



Digitized by



Google



Digitized by



Google



' ,



Digitized by



gle



Digitized, by



Google



AlOSMlBSIbM




* b890541329i4a



III [



Digitized by



M^-l^Hl-^j



Google



Digitized by



Google



Digitized by



Google





1 3

Online LibraryJohn WeinzirlThe action of sunlight upon bacteria with special reference to B. tuberculosis → online text (page 3 of 3)