Elevated temperature technique for the isolation of salmonellas from sewage and human faeces

Abstract

SUMMARYModified Moore's swabs, placed in sewers for 5 days, were used to concentrate salmonellas from sewage. Duplicate cultures of swab strips in selenite broth were incubated at 41 and 370 C. respectively. Salmonella organisms were recovered consistently from the swabs when the enrichment broths were incubated at 410 C. However, when equal portions of the same swabs were incubated at 370 C., only 22 % of them yielded Salmonella organisms. These results indicate an advantage in incubating the selenite broths at 410 C. rather than 370 C. in attempting to isolate salmonellas from sewage.One hundred and fifty faecal samples were examined for salmonellas by culture in selenite broths incubated at 41 and 370 C. Twelve (8 %) samples were positive at 410 C. compared to only 10 (6.7 %) positive samples at 370 C. This difference is not statistically significant to indicate an advantage of the elevated-temperature of incubation over the conventional temperature in attempting to isolate salmonellas from human faeces. Moreover, results of the recovery rates ofS. paratyphi B, S. typhi, and S. typhimurium indicate that an incubation temperature of 370 C. is more appropriate for recovering salmonellas from artificially infected faecal samples than an incubation temperature of 410 C. This stresses the inability of laboratory studies to mimic conditions in nature.

Modified enrichment-serology procedure for detection of salmonellae in soy products

“…Various preenrichment media have been recommended (1, 2, 4, 10, 13, 16, 17, 19) for the repair of stressed cells. In addition, elevated temperatures of 41 and 43°C have been used to resuscitate sublethally injured cells (7,10,15). Because of the high heat application during the soy processing procedure and the dryness of the product, salmonellae, if present, would be present in small numbers and would be stressed.…”

Application of the rapid lysine decarboxylase test for early isolation and detection of salmonellae in sewage and other wastewaters

“…Each colony must be subjected to an array of various biochemical reactions before it is serologically confirmed, requiring 2 to 3 days. Development of an elevated-temperature technique (13)(14)(15) has, no doubt, improved the salmonella recovery rate from polluted waters; however, the time required to complete the test must be shortened. Since, there is little chance of reducing the time necessary for enrichment and streaking on selective media, the solution would be to identify the Salmonella colonies more rapidly.…”