274
Effect of Penicillin Injections on Staphylococci
[XVII
same treatment and also the three that received 4 injections at intervals of 12 hours were appa-
rently free of the injection when samples 5 were taken six and 12 hours after the last injec-
tion, but samples 6 or 7, taken on the third and sixth day following the last injection and samples
taken subsequently were found to be infected. Since one of the quarters receiving 8 injections was
apparently cleared of the infection and another was probably cleared, while the infection disappeared
only temporarily from the quarters receiving 4 injections, it would appear that a more prolonged
antibacterial action was produced by 8 injections than by 4, although given within the same period
of time. However, since no growth of staphylococci occurred on any of the plates inoculated with
samples 2 to 5, inclusive, it is possible that they contained sufficient penicillin to inhibit growth of
the organism and that growth occurred on the plates inoculated with samples taken subsequently
because all of the penicillin injected had been absorbed or eliminated.
Referring to Table IV, it will be noted that sample 6 from the right front quarter of cow 10 was
infected with coagulase positive nonhemolytic staphylococci but that the staphylococci found in
samples 7 and 9 were hemolytic. A similar variation was observed in milk samples examined before
the injections were made. Coagulase positive nonhemolytic staphylococci were present in a sample
taken from this quarter 12 days before sample 1.
The first ¼ to ½ of the milk obtained from three of the quarters receiving injections at six-hour
intervals contained slugs or strings of mucus and was watery after the first injection and the milk
of the other quarter receiving the same treatment was similarly affected after the second injection.
Later, this portion of the milking was of a greenish or yellowish color. This condition continued up
to the time of taking samples 5, six hours after the last injection.
Similar changes occurred in the milk of the quarters receiving 4 injections at eight-hour intervals
but to a lesser degree. The milk of one quarter in this group was altered in appearance after the first
injection and of the other two after the second injection. The milk of one of the latter was of normal
appearance at all other succeeding examinations.
When samples 6 were taken on the third day following the last injection, the milk of all quarters
was of normal appearance.
The average daily milk production for one week before and for the first, second, and third weeks
after treatment are shown in the following Table:—
Cow
91.
.
.
.
.
10.
.
.
.
.
1.
.
.
.
.
27
.
.
.
.
.
216.
.
.
.
.
Before
treatment
lb.
17.15
23.12
31.94
32.94
41.62
1st Week
after
lb.
16.60
21.41
29.10
35.02
38.41
2nd Week
after
lb.
16.80
20.03
29.90
28.80
28.80
3rd Week
after
lb.
16.10
19.70
29.90
32.30
32.00
Stage of lactation
when treated
50th week
38th „
15th „
11th „
14th „
Cow 10 had three quarters injected, two with 8 doses and one with 4 doses. One quarter was
treated in each of the others. Cows 91 and 1 received 8 doses and 27 and 216, 4 doses.
As to the effect of the injections on the udder tissues, only 1 cow, 91, showed any symptoms of
irritation. The lower portion of the quarter treated in this cow was swollen and hardened three
hours after the first injection but the swelling was not hot or painful to pressure. In a few hours,
the entire quarter was involved and after the second injection the swelling increased slightly. No
further change occurred until after the fourth injection. The swelling had begun to decrease and
had disappeared entirely on the third day following the last dose.
The temperature of the cows was taken at the time of each injection and was within the normal
range in all instances except at the time of the second injection, when it was 103.2 F. in cow 91,
103.2 F. in cow 10, and 103.6 F. in cow 27, and at the time of the third injection 102 F. in cow 216.