Multiplex PCR method for detection of three Aeromonas enterotoxin genes.

A novel multiplex PCR method using three sets of specific primers was developed for the detection of the cytotoxic (act), heat-labile (alt), and heat-stable (ast) enterotoxin genes in Aeromonas spp. This assay was used to characterize 35 reference strains as well as 537 food-borne isolates. A total of seven gene pattern combinations were encountered, including act, alt, act/alt, act/alt/ast, act/alt/148-bp amplicon, alt/ast, and alt/148-bp amplicon.

Antibiotic Resistance of Agricultural and Foodborne Salmonella Isolates in Canada: 1986-1989.

A total of 689 Salmonella cultures isolated during 1986-1989 from Canadian agricultural products and from imported fish, shellfish, and reptiles were examined for resistance to a test panel of 11 antibiotics. The incidence of antibiotic resistance in strains from all sources seemingly increased during the study period, whereas the occurrence of resistance within individual sample categories fluctuated annually. Although poultry figured as a major reservoir of resistant salmonellae (53.

Enzyme Immunoassay - Membrane Filter Method for Detection of Salmonellae in Foods.

An enzyme-linked immunosorbent assay (ELISA) technique using a horseradish peroxidase-protein A-Spicer Edwards antiserum complex was developed for the detection of Salmonella colonies on membrane filters. In pure culture, 64 Salmonella species tested gave a positive reaction (purple stain). Of 22 naturally contaminated food samples, there was an exact correlation between the AOAC hydrophobic grid-membrane filter procedure and the ELISA technique (40.

Effective Enrichment-Plating Conditions for Detection of Salmonella in Foods.

The performance of tetrathionate brilliant green (TBG) and selenite cystine (SC) enrichments, and bismuth sulfite (BSA) and brilliant green sulfa (BGS) plating media was assessed on the basis of data on 2085 Salmonella -contaminated low and high moisture foods that were collected during a 6-year (1977 to 1983) study involving 22 laboratories. None of the eight enrichment- plating combinations considered identified all positive samples. TBG was markedly more sensitive than SC for detection of salmonellae in high moisture foods, where enrichment in TBG and plating on both BSA and BGS identified 92% of contaminated samples.

Salmonella Detection in Foods: Present Status and Research Needs for the Future.

Standard cultural procedures generally require 4 to 5 d for presumptive evidence of Salmonella in foods. Attempts at greater method brevity have resulted in the use of selective enrichment cultures as test material for short immunological tests including fluorescent antibody (FA), enrichment serology (ES), enzyme-linked immunosorbent assay (ELISA), direct immunoenzyme (DI) and membrane filter-disc-immunoimmobilization (MFDI) assays. Nonimmunological tests such as the lysine-iron-cystine-neutral red (LICNR) broth and a C-dulcitol radiometric technique have also been applied to enrichment broth cultures.

Update on Preenrichment and Selective Enrichment Conditions for Detection of Salmonella in Foods.

The search for short and sensitive cultural methods for detection of Salmonella in foods has met with limited success. Short (3-8 h) incubation of non-selective enrichment media do not provide conditions for effective resuscitation of stressed or injured salmonellae and result in unacceptably high numbers of false-negative results. Isolation of Salmonella is not dependent on the nutritional value of preenrichment media; simple media such as lactose and nutrient broths are equally reliable as highly nutritive sterility testing media.