Rapid, Direct Fluorescent-Antibody Method for the Detection of Salmonellae in Food and Feeds

Abstract

An improved immunofluorescent-antibody (FA) method for the detection of salmonellae in foods and feeds was developed. This FA method combines a rapid cultural phase and a serological phase that allow for propagation of salmonellae in a minimum time, employing the industrial 8-hr work day as a guide. Two hundred fifty naturally contaminated human food and animal feed samples, representing 647 trials, were tested by the FA method. A total of 18 different food and feed samples was used. The method used by the Association of Official Analytical Chemists (AOAC) for the detection of salmonellae was the control method. The percent agreement when comparing the FA slide method to the AOAC method ranged from 87.1 to 95.3%, depending upon the conjugated antisera used in comparative studies.

Control of nonspecific staining in the fluorescent antibody technique for the detection of salmonellae in foods

“…Cross-reactions did not occur when H antibodies were used in the indirect FA technique (18). A conjugate prepared from Salmonella polyvalent H antiserum gave a higher degree of agreement (95.7%) with the cultural technique than did two commercially purchased FA conjugates prepared from globulin fractions of OH antiserum (25). The H conjugate recorded fewer false positives and detected salmonellae in all of the culturally positive samples.…”

A Comparison of the Fluorescent Antibody Method and a Standardized Cultural Method for the Detection of Salmonellas

“…The results reported here show that the proposed draft standard I S 0 technique for the isolation of salmonellas from foods and feedingstuffs may also be used for the FA technique at the pre-enrichment stage. No modifications, such as culture in a nonselective broth after selective enrichment ('post-enrichment')-which appears to be desirable to eliminate quenching of fluorescence by selenite or tetrathionate (Thomason & Wells 1971;Insalata et al 1972;Smyser & Snoeyenbos 1976)-are necessary although Fantasia et al (1975) recommend selenite-cystine broth for successive enrichment cultures before FA slide preparation. Application of the FA technique at an early stage in the culture method for isolation of salmonellas gave a number of false positive FA results, although these may have been false negative cultural results.…”

Direct Fluorescent-Antibody Technique for the Microbiological Examination of Food and Environmental Swab Samples for Salmonellae

“…The procedure used for FA slide preparation, FA staining, and microscope examination were identical to those described by Insalata et al (7).…”