Microbiological methods. Methodology for enteropathogenic Escherichia coli

Abstract

Pathogenic biotypes of Escherichia coli grow poorly at temperatures greatly different from that of the host. Percentages quantitatively recovered at 42.0, 44.0, 44.5, and 45.5 degrees C in lauryl tryptose broth were 100, 76, 76, and 42, respectively. Corresponding values for 175 strains of varied origin were 98, 89, 82, and 65%. Maximal growth temperature is dependent upon medium. Lauryl tryptose and elevated coliform broths were equivalent in the recovery of small inocula (100 cells/ml) at 41.5-44.5 degrees. MacConkey, enteric enrichment, and Gram-negative broths were inhibitory at corresponding values. Growth at elevated temperature in nutrient broth is enhanced by carbohydrate. Standard lactose enrichment media fail to recover slow lactose fermenters. An acidified glutamic acid medium was unsuitable for recovery of E. coli. The data suggest modification of standard temperatures for the recovery of pathogenic biotypes. Previously recommended analytical methods have been simplified and supplemented. The enhancement of motility in indole-nitrite broth at 35 degrees C is recommended. A 4-tube semiquantitative test is offered for tentative identification of somatic and capsular antigens. Inclusion of Alkalescens-Dispar strains is warranted by their pathogenic behavior. Examination in Shigella and Alkalescens-Dispar sera is required to cover the dysentery-like biotypes. Pathogenic potential cannot be inferred from serotype.