Abstract
A study has been made of 57 specimens of feces from normal humans, from which by direct plating, 1454 strains of bacteria have been isolated. Eight of the 57 were stored at 37°C. and plated 60 times during the period of their viability, 2 to 3 months, yielding 592 strains. Duplicates of these 8 and 4 others of the 57 were kept in the ice box and on, 162 platings have yielded 1086 strains. The period of viability for cold stored suspensions varies but may exceed 15 months. The feces were suspended in sterile saline to a heavy turbidity and platings have been made from these suspensions. The procedure diagrammed has been adopted. It provides for adequate purification of strains isolated, permits a comparison of the reactions of purified and original strains, and utilizes the tests now considered most significant for the group. Recognition of lactose-deficient organisms in normal feces 1 has led to the inclusion in the series of all organisms typical of the group which ferment dextrose. Strains failing to ultimately dissimulate lactose are dropped. Adequate sampling has been the rule, 11.2 organisms on average being picked from each of the 279 platings. The strains have been tested for their fermentation of dextrose, lactose, saccharose, dulcite, salicin, alpha-methyl-d-glucoside and cellose; for their methyl-red, Voges-Proskauer, citrate utilization, milk and gelatin reactions; and for the production of indol and hydrogen sulphide. Data pertinent to the topic of this paper are presented in Table I.∗
The only group member found in several fresh fecal specimens was some form of Coli (Escherichia). Of the 1262 strains in the corrected summary only 2 were Intermediate (Citrobacter). On storage the 2–3% of Aerogenes (Aerobacter) originally present in fresh feces greatly increase and the Coli disappear—a process more marked for specimens ice box stored and in such specimens complete in about 5 weeks. Almost coincident with the disappearance of typical coli intermediates types appear and they increase and persist with cold storage. They occur also but are not prominent at any
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