Boric Acid Lactose Broth as a Medium for the Detection of Fecal Coliform Bacteria1

Possible Explanations for the Inhibitory Action of Boric Acid Lactose Broth at 43 C on Fecal Coliform Bacteria1

“…Possible explanations for inhibitory effect of BALB at 43 C. All the above experiments point to one of two explanations. It may be that E. coli growing at lower favorable temperatures in favorable media always have some cells capable and some incapable of initiating growth in BALB at 43 C. If this is the case, it will explain the results of our present and previous work (Njoku-Obi and Skinner, 1957). The methods used in the studies would not demonstrate strains, all cells are completely incapable of initiating growth in the unfavorable medium.…”

“…It would therefore be assumed that the explanation for the lower counts of Escherichia in feces by the boric acid lactose broth is the existence, in feces, of nontolerant strains. That this is not the true explanation for the results of Njoku-Obi and Skinner (1957) will be shown by the following experiments.…”

“…It has been shown (Njoku-Obi and Skinner, 1957) that the most probable number of coliforms and of Escherichia species in human feces is consistently higher when counts are made by dilution extinction methods in standard lactose broth at 35 C than when boric acid lactose broth (Vaughn et al, 1951) at 43 C is used. This is an example of a general phenomenon repeatedly noted in the literature.…”