Incubation at 44°C. as a test for faecalcoli

Abstract

1. The use ofEsch. colialone as an index of faecal pollution for shellfish, and the correlation between the 44° C. MacConkey test and citrate tests are discussed.2. The mercury-toluene thermo-regulator used in these experiments, which gives a maximum variation of ± 0.1° C., is discussed briefly and illustrated.3. Experiments are described in which 522 colonies from polluted shellfish were isolated, inoculated into MacConkey's broth and incubated at temperatures of 37° C. and at successive 1° intervals from 41 to 46° C., in accurately controlled water-baths. An almost perfect negative correlation was found to exist between 44° C. incubation and the citrate test.4. It appeared that temperatures above 44° C. are detrimental to the growth ofEsch. coli.5. Certain cultures of citrate-negative lactose fermenters at 37° C., which were inhibited at 44° C., were found on further investigation to be mostly intermediate types.