Isolation of Salmonellae from Sewage with a New Procedure of Enrichment

Abstract

Forty samples of sewage on Moore's swabs were examined for the presence of salmonellae. They were first pre‐enriched in buffered peptone water. From each pre‐enrichment, three enrichments were made: (1) in a new, considerably modified, formula of Rappaport medium (R 10) incubated at 43 °C (R 10/43 °C), (2) in the usual formula (R25) of the same medium at 37 °C (R25/37 °C) and (3) in Muller‐Kauffmann's tetrathionate broth at 43 °C (MK/43 °C). Practically the same numbers of swabs were found positive by the first two enrichment procedures, 38 and 39 respectively, while only 17 were found positive by the MK procedure. The R10/43 °C method was superior to the two other procedures; it yielded 103 strains of salmonellae as against 82 with the second Rappaport procedure, and only 25 with the MK/43 °C technique. A similar observation was made concerning the frequency of isolation of different serotypes by the three procedures; the number of the isolated serotypes was 24, 19 and 11, respectively. The new R 10/43 °C method of enrichment had also a much stronger inhibitory effect on the competing bacteria than the two other procedures of enrichment used.

A comparison of enrichment media for the isolation of salmonellae from seagull cloacal swabs

“…Tetrathionate broth was superior to selenite. Previous reports on the isolation of salmonellae from a number of sources, including pork sausages, minced meat, sewage, pig faeces (Vassiliadis et al 1977(Vassiliadis et al , 1978a, sewage-polluted water (Harvey et al 1979) and chicken giblets have all recommended the use of Rappaport's broth. In support of these findings this study has shown that when used to recover salmonellae from seagull cloacal swabs, Rappaport's broth is significantly superior to either selenite F or Muller-Kauffmann tetrathionate broth, both in terms of the number of salmonella isolates and in the variety of serotypes obtained.…”

“…This modification has been used to good effect in the isolation of salmonellae from a wide range of samples (Vassiliadis et al 1977(Vassiliadis et al , 1978a(Vassiliadis et al , b, 1979.…”

Isolation of Salmonella with the use of 100 ml of the R10 modification of Rappaport's enrichment medium

“…(b) The modified Rappaport's medium formula R 10 (Vassiliadis et al , 1978b, was prepared from solutions A, B and C described by Rappaport, Konforti & Navon (1956), using malachite green oxalate p.a. in the preparation of solution C ).…”

“…We have recently reported that a modification of Rappaport's enrichment medium (R 10 medium), inoculated from pre-enrichments in buffered peptone water (P medium) and incubated at 43 'C, was more efficient in the detection of salmonellas from samples of pork sausages, minced meat, sewage, and faeces of healthy pigs (Vassiliadis et al 1977(Vassiliadis et al , 1978a(Vassiliadis et al , b, 1979a than the Muller-Kauffmann tetrathionate broth prepared in accordance with the International Standards Organization document ISO 3565 (MK broth) (Edel & Kampelmacher, 1969Anon. 1975).…”

“…They observed that the R 25 broth was the most efficient medium in salmonella isolations from polluted river water. In our recent investigations we have found that the R 10 medium was at least as efficient as the R 25 medium in the isolation of salmonellas and that the R 10 medium compared to the R25 broth has the advantage of inhibiting more considerably the competing organisms, especially those which are lactose-and sucrose-negative on brilliant green deoxycholate agar (Vassiliadis et al 1977(Vassiliadis et al , 1978a(Vassiliadis et al ,b, 1979a.…”