BACTERIOLOGICAL STUDY OF RETAIL ICE CREAM. 



19 



Table .12. — Bacteria of the colon group found in ice cream as determined on litmus- 



lactose-asparagin agar. 



Sample 



Manu- 

 fac- 

 turer. 



B. coli 



per cubic 



Sample 



Manu- 

 fac- 

 turer. 



B. coli 

 per cubic 



Sample 



Manu- 

 fac- 

 turer. 



B. coli 

 per cubic 



No. 



centi- 

 meter. 



No. 



centi- 

 meter. 



No. 



centi- 

 meter. 



32 



A 



120 



160 



C 



10 



49 



K 



120, 000 



33 



A 



86,000 



161 



C 



30 



50 



K 



75,000 



37 



A 



100 



186 



c 



140 



51 



K 



300, 000 



3S 



A 



100 



187 



c 



700 



79 



Ki 



150 



39 



A 



8,000 



188 



c 



50 



80 



Ki 



40 



40 



A 



900 



44 



D 



2,400 



81 



Ki 



30 



83 



A 



420 



45 



D 



7,700 



82 



Ki 



40 



124 



A 



80 



89 



D 



4,600 



134 



Ki 



10 



125 



A 



10 



52 



E 



600,000 



135 



Ki 



20 



138 



A 



10 



53 



E 



47,000 



136 



Ki 



10 



139 



A 



10 



54 



E 



5,600 



137 



Ki 



'0 



143 



A 



10 



140 



E 



30 



70 



M 



1,730 



151 



A 



10 



141 



E 



10 



71 



M 



550 



152 



A 



40 



142 



E 



400 



72 



M 



2,530 



153 



A 



10 



67 



F 



3,900 



73 



M 



2,350 



168 



A 



50 



68 



F 



3,900 



84 







7,600 



169 



A 



30 



69 



F 



5,000 



87 







12, 200 



31 



B 



15,400 



146 



F 



100 



62 



L 



11,900 



41 



B 



2,500 



147 



F 



■0 



63 



L 



3,000 



42 



B 



17,100 



74 



G 



20 



64 



L 



3,000 



43 



B 



2,800 



75 



G 



10 



65 



L 



123,000 



126 



B 



300 



76 



G 



100 



66 



P 



3,000 



127 



B 



100 



77 



G 



230 



144 



Q 



20 



128 



B 



200 



78 



G 



820 



145 



Q 



20 



133 



B 



1,000 



148 



G 



120 



132 



R 



10 



158 



B 



2,900 



149 



G 



50 



175 



S 



300 



162 



B 



10 



150 



G 



200 



176 



S 



800 



163 



B 



400 



59 



H 



6,500 



177 



s 



600 



164 



B 



700 



60 



H 



1,200 



171 



T 



90 



165 



B 



10 



61 



H 



15,000 



172 



T 



800 



166 



B 



1,400 



157 



H 



10 



173 



T 



1,200 



167 



B 



1,800 



55 



I 



5,600 



174 



T 



100 



170 



B 



14,000 



56 



I 



7,200 



178 



U 



1,400 



46 



C 



700 



57 



I 



400 



179 



u 



4,000 



47 



C 



2,400 



58 



I 



12,000 



180 



w 



2,700 



85 



C 



13,300 



154 



I 



10 



181 



w 



300 



86 



C 



13,500 



155 



I 



900 



182 



w 



700 



90 



C 



6,000 



156 



I 



300 



183 



X 



4,100 



91 



C 



8,300 



88 



J 



3,100 



184 



X 



30 



159 



C 



40 



48 



K 



108,000 



185 



X 



300 



1 In xV dilution. 



During this series of examinations the suspected colon colonies 

 on the asparagin-agar plates from 19 samples were picked off and 

 inoculated into lactose-broth fermentation tubes. After incuba- 

 tion for 48 hours at 37° C. (97.5° F.) the tubes were examined for 

 the presence of gas. The number of cultures picked off and the num- 

 ber showing gas, together with the percentage of the cultures suspected 

 of being gas formers from the examination of the plate, are shown in 

 Table 11. An examination of the results shows that in 10 of the 19 

 plates studied all the colonies considered gas formers developed gas 

 in fermentation tubes. In other words, 100 per cent were gas formers. 

 Among the other 9 samples the percentage ranged from 87.17 to 100 

 per cent. This shows that it is possible to detect quite accurately 

 any colonics of gas-forming bacteria on litmus-lactose-asparagin 

 agar. 



One 1 1 M in lied and twenty samples of ice cream were examined 

 during the summer and winter seasons by the use of the above-men- 

 tioned medium. The results are tabulated in Table 12. Gas-forming 



