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

Abstract

A new method was developed for the detection of injured and uninjured salmonellae in foods and feeds. The steps of pre-enrichment in a nonselective broth and selective enrichment in a selective medium were combined into a single procedure. This was achieved by the gradual release of selective agents from wax-coated gelatin capsules added at the time of inoculation of nonselective basal broths. Pre-enrichment in lactose broth was combined with selective enrichment in tetrathionate or selenite-cystine broth by using timed-release capsules containing iodine or selenite. Five different categories of foods and feeds, naturally contaminated with salmonellae, were examined to compare the efficiencies of the capsule methods with conventional procedures. Combination of the separate steps of pre-enrichment and selective enrichment into a single procedure was feasible and resulted in substantial savings of labor and materials.

Improvement in Salmonella detection in milk and dairy products: comparison between the ISO method and the Oxoid SPRINT Salmonella test

“…The analysis is complete within 48 h, including Salmonella detection on selective solid media. Important constituents of the procedure are the Oxyrase enzyme system producing anaerobic conditions in the enrichment medium (Adler and Crow 1981; Yu and Fung 1991) and the SPRINT Salmonella Timed Release Capsules (Sveum and Hartman 1977) releasing a selective agent formulation, after 6 h pre‐enrichment, that turns the non‐selective enrichment broth into a selective broth on the basis of Rappaport–Vassiliadis medium (Vassiliadis 1983) (Fig. 1).…”

Combined enrichment procedure for the detection of salmonellae in foods

“…Tetrathionate was formed in combined tetrathionate ( This principle was also adopted for use in the isolation of solmonellae from foods by Sveum and Hartman (1977). Iodine or selenite was gradually released from timed-release capsules added at the time of inoculation and the medio progressively became selective.…”

“…Three different selenite combined enrichment medio were used in this study. SEL 1, introduced by Sveum and Hartman (1977) consisted of (per liter); lactose broth, 13 g; discdium phosphate, 10 g; and L-cystine, 0.01 g. The components of SEL 2 were (per liter): lactose, 5 g; peptone, 5 g; disodium phosphate, 10 g; and L-cystine, 0.01 g. SEL 3 ingredients were (per liter): lactose, 4 g; tryptone, 5 g; disodium phosphate, 10 g; and L-cystine, 0.01 g. Table 2 lists the constituents of the combined selenite broths and conventional SC broth. The selenite basais were adjusted to pH 6.8, and 225 ml quantities were added to 500 ml flasks and sterilized (121 C, 15 min).…”

Combined enrichment procedure for the detection of salmonellae in foods

“…This principle was also adopted for use in the isolation of solmonellae from foods by Sveum and Hartman (1977). Iodine or selenite was gradually released from timed-release capsules added at the time of inoculation and the medio progressively became selective.…”

“…Three different selenite combined enrichment medio were used in this study. SEL 1, introduced by Sveum and Hartman (1977) consisted of (per liter); lactose broth, 13 g; discdium phosphate, 10 g; and L-cystine, 0.01 g. The components of SEL 2 were (per liter): lactose, 5 g; peptone, 5 g; disodium phosphate, 10 g; and L-cystine, 0.01 g. SEL 3 ingredients were (per liter):…”