38 SHELLFISH CONTAMINATION FROM SEWAGE-POLLUTED WATERS. 
in an Erlenmeyer flask was used for each of the tests on shucked 
oysters, while about 3 dozen medium-sized oysters and hard 
clams in the shell were laid on the shelves of the sterilizer for the 
other experiments. The steamer was full of live steam when the 
samples were introduced. Tables Nos. 12 to 15, inclusive, show the 
results of these tests. 
TaBLe 12.—The destruction, by steaming, of bacteria in shucked oysters artificially infected 
with B. coli. 
t | ce Per cent gas in dex tnese emer tion tubes (four days, 
Sample. | Timeof | centimeter | ater £ Per cent 
: Be: cooking. | (plait. agar | Se = ee ee 
| ey’ | O-Lee | 0.01 ce | 0.001 ce) 0.0001 ce | 0.00001 ce | 0.000001 ce 
| Minutes. 
5 Cae et | Uncooked.| 80,000,000 |.......- 35 35 30 40 40 | 0.00 
Bosse. 5 725, 000 45 40 45 45 0 0 | 99.09 
eee | 10, ~—-20, 500 45 40 45 35 40 0 | 99.90 
Diane: | 15 | 170 0 0 0 0 0 0 | 99.99-+ 
Bo | 20 100|- 0 0 0 0 0 0 | 99.99+ 
] a ee | 25 65 0 0 0 O|~* 0 0 | 99. 99+ 
Gsses 30 | 07 0 0 0 0 0 0 |100. 00 
These results show that all B. coli were destroyed during from 10 to 
15 minutes’ exposure to live steam. In the following experiment on 
steaming shucked oysters, naturally infected, all B. cola types failed 
to develop when exposed to live steam for from 5 to 10 minutes. 
TaBLE 13.—Bacteriological results showing effect of steaming shucked oysters naturally 
infected. 
| Bacteria | Per cent gas in dextrose 
cont Sune three days, at 37° C. 
Sample Time of | : Per cent ae 
: (plain agar : Remarks. 
No. cooking. at 25°C. | | killed. — 
for three | 0.5 cc | 0.1 ce | 0.01 ce 
days). 
| Minutes. 
eee Uncooked.| 716,000 35 20 0 | 0.00 Variety of colonies on plates. 
ee 5 13, 000 50 0 0 98.10+ | Less variety of colonies on 
plates. 
SAeeee ee _ 10 2 0 0 0 99.99+ | Both colonies spore bearing. 
L eee | 15 10 0 0 ) 99.99+ | Spore-bearing colonies on plates. 
Sseaeese 20 10 0 0 0 99. 99-+- Do. | 
beteaeeilo | 25 9 | 0 0 0 | 99.99+ Do. 
(isecease | 30 a | 0 0 0 99. 99-++ Do. 
TaBLeE 14.—Bacteriological results showing the effect of steaming oysters in the shell. 
[ : | 
| Bacteria Per cent gas in dextrose | 
| be eae four days at 37°C. | 
Ss |. Ti d | Per cent | : 
Sample | Fue | oe oeat | eeaied Remarks. 
| | 42) te | | 
forfour | 0.1ee | 0.01 ce | 0.001 ce | | 
| | days). | | us| 
| Minutes. | 
1 See Uncooked. | 15,000 20 5 O- | 0.00 | Variety of colonies on plates. 
ee aie Yes) 6, 700 1 0 O-| 55.33 | Less variety of colonies on 
| plates. 
Be aie 10 270 0 0 0 | 98.20 | Colonies largely spore bearing. 
Ae one 15 250 0 0 0 98.33 | Colonies all spore bearing. 
Ree ace 20 40 0 0 0 | * 99.73 Do. 
(TERS See 25 20 0 0 0 | 99.80 Do. 
baaaes 30 20 0 0 0 99. 80 Do. 
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