A Rapid and Direct Plate Method for Enumerating Escherichia coli biotype I in Food

Abstract

Direct enumeration of Escherichia coli biotype 1 in foods within 24 h has been achieved by a development of the method of Delaney, McCarthy & Grasso (1962) which is based on the production of indole at 44°. Indole positive E. coli growing at this temperature on a cellulose acetate membrane overlaying tryptone bile agar can be demonstrated. Characterization of 555 indole positive colonies from 843 samples of food showed that 95% were E. coli biotype 1 and a further 3·4% were ‘faecal coliforms’. Anaerogenic and non‐lactose fermenting E. coli are detected and the significance of these strains is discussed.

The response of fecal coliforms and antibiotic‐resistantEscherichia colito incremental doses of ozone during disinfection of activated sludge effluent

“…An Índole spot-test (17) was used to confirm Índole production. Lactose fermentation and indole production at 44.5°C were presumed to indicate E. coli (18,19). This method was confirmed in an earlier study (2) using the API 20E identification system.…”

A rapid and simple method for the detection and enumeration ofEscherichia coliin cleansed shellfish

“…The ability to do the former, however, is easily lost Bueschkens & Stiles, 1984) or may go undetected because of the presence of food particles in the medium (Varga & Doucet, 1984). For these reasons indole production is considered to be a more reliable indicator of the organism's presence (Anderson & Baird-Parker, 1975;Holbrook, Anderson & Baird-Parker, 1980) and Delany, McCarthey & Grasso (1962) proposed a rapid test for the detection of E. coli in water based on this test only. Indole detection alone has not been used for the enumeration of E. coli in foods, although the plate technique of Anderson & Baird-Parker (1975) used this attribute in combination with bile tolerance.…”

“…For these reasons indole production is considered to be a more reliable indicator of the organism's presence (Anderson & Baird-Parker, 1975;Holbrook, Anderson & Baird-Parker, 1980) and Delany, McCarthey & Grasso (1962) proposed a rapid test for the detection of E. coli in water based on this test only. Indole detection alone has not been used for the enumeration of E. coli in foods, although the plate technique of Anderson & Baird-Parker (1975) used this attribute in combination with bile tolerance. However, this method has been shown to be less sensitive than MPN methods (Motes, McPherson & De Paola, 1984).…”

Validation of a Novel Rinse and Filtration Method for Efficient Processing of Fresh Produce Samples for Microbiological Indicator Enumeration

“…Another advantage of the membrane fdtration method is ihat the membrane can be placed directly on selective or nonselective agars, or in enrichment broths for pathogen detection. Membrane filtration has been adapted to a variety of applications (3,(30)(31)(32)40), including recovery and enumeration of injured bacterial cells (12). Overall, the membrane filtration method has the advantage of improving the analytical sensitivity of an assay by increasing the sample volume that can be assayed in a single test (40).…”