Timed-release capsule method for coliform enumeration

Abstract

Wax-coated capsules containing selective ingredients (brilliant green and oxgall) were added at the time of inoculation of most-probable-number media (modified lactose broths). The inhibitory ingredients gradually diffused from the capsules into the nonselective media, imparting selectivity to the media. Concentrations of brilliant green did not reach inhibitory levels until 2 or more h had elapsed, which permitted repair of some injured cells. Resuscitation of heatinjured Escherichia coli B cells occurred in the capsule-containing media, but not in conventional brilliant green bile 2% broth or violet red bile agar. No statistically significant differences were noted between coliform counts obtained on two groups of water samples by using the capsule, most-probable-number, membrane filtration, and pour plate methods. The capsule method could be used, however, as a combined presumptive and confirmed test for the examination of water. Improvements are needed to adapt the capsule method to the analysis of some categories of foods.

Timed-Release Capsule Method for the Detection of Salmonellae in Foods and Feeds

“…The feasibility of combined procedures for use in microbial assays has been demonstrated here and by Lanz and Hartman (11). We hope that others will be stimulated to substantiate the present results, improve upon the combined procedures, and possibly devise other applications of the same principle.…”

The isolation of salmonellas and campylobacters

“…Alford & Knight (1969) delayed the addition of selenite to selenite cystine broth until 4 h after incubation had commenced. They found that the efficiency of isolation of salmonellas was similar to that achieved by using an overnight pre-enrichment followed by 24 h enrichment procedure with the bonus that the time taken to complete the examination of samples was reduced by 1 d. Similar procedures utilizing wax-coated capsules containing selective agents have been utilized in the examination of water and foods for coliforms and salmonellas (Lanz & Hartman 1976).…”

“…typhi (Harvey & Price 1964). The performance of some of these media has been investigated but with no overall agreement (Wells et al 1958;Montford & Thatcher 1961;Guinee et al 1965;Kumar et al 1971Kumar et al , 1972Carlson & Snoeyenbos 1974;Fagerberg & Avens 1974, 1976.…”

Effect of a Repair Step on the Recovery of Coliforms From Frozen Blanched Vegetables

“…Trypticase soy broth (TSB) or agar (TSA) have been used as the repair media prior to culturing in lauryl sulfate tryptose broth (LST) or on violet red bile agar (VRBA) (Warseck et al 1973;Speck et al 1975). Another procedure has been to add time-release capsules containing inhibitors (brilliant green and oxgall) to lactose broth to impart selectivity to the medium following repair (Lanz and Hartman 1976).…”