Comparison of two newly developed forms of an enzyme-linked immunosorbent assay for the detection of staphylococcal toxic shock syndrome toxin-1 (TSST-1).

Two modifications of an enzyme-linked immunosorbent assay (ELISA) were applied to the quantitative determination of TSST-1 in culture supernatants of S. aureus strains. In both techniques, biotinylated antibodies (anti-TSST-1), obtained by means of either glutaraldehyde or N,N-dimethyl formamide were used. IgG and biotin were conjugated in various ratios and the different conjugates thus obtained were examined for their reactivity in the ELISA tests. The application of the glutaraldehyde-method resulted in more active, sensitive and stable conjugates. Furthermore, acceptable TSST-1 standard curves under fixed conditions were only obtained when the appropriate ratio of biotin to IgG had been determined before the biotinylated antibodies were employed.

Correlation between enterotoxigenicity, tested by different ELISA-techniques, antibiotic resistance patterns and phage groups of Staphylococcus aureus strains.

A group of 596 Staphylococcus aureus strains isolated from various clinical sources or implicated in food poisoning was investigated for enterotoxins A and B (SEA and SEB) production. The conventional ELISA techniques (competitive and sandwich ELISA) were compared with a newly developed avidin-biotin ELISA in their ability to detect the enterotoxins. The avidin-biotin system was not remarkably influenced by SPA up to 10 micrograms/ml. A semi-quantitative competitive ELISA for the detection of staphylococcal protein A (SPA) in culture supernatants was carried out in parallel. The strains isolated in cases of food poisoning showed different antibiotic resistance patterns, whereas the strains from clinical sources were selected for either methicillin or penicillin resistance only. The strains isolated in food poisoning outbreaks (FP strains) were enterotoxin A positive in 22%, enterotoxin B positive in 11%, and SEA + SEB positive in 9% of cases. The strains with resistance to penicillin only (PER strains) produced SEB in 26%, SEA in 14%, and both toxins in 7% of the cases. The methicillin-resistant strains (MCR strains) produced SEA in 59% of cases, whereas SEB was produced in 6% only (SEA + SEB: 20%). 37% of the SEA producers belonged to phage group III (SEB: 30%; SEA + SEB: 25%) and 12% (SEB: 11%; SEA + SEB: 9%) to phage group I. 26% of the SEA-producing and 37% of the SEB-producing strains (SEA + SEB: 23%) were non-typable.

An avidin-biotin ELISA for the detection of staphylococcal enterotoxins A and B.

The avidin-biotin system was incorporated into the enzyme-linked immunosorbent assay (ELISA) to establish a new detection method for staphylococcal enterotoxins A and B in culture supernatants. Staphylococcal protein A (SPA) does not interfere significantly with the procedure. The test shows good sensitivity for the toxins and the ease and rapidity with which the assay can be performed make it a valuable tool for the routine detection of enterotoxins.

[Demonstration of enterotoxin in Staphylococcus aureus cultures by the ELISA test and the microslide test]. / Nachweis von Enterotoxin in Kulturüberständen von Staphylococcus aureus mit dem ELISA-Test und dem Microslide-Test.

340 S. aureus strains, isolated either from routine food test samples, or from food leftovers, from healthy or sick persons in cases of suspected food poisoning in various places of the Federal Republic of Germany, were tested for enterotoxin production. The enterotoxin types A, B and C (SEA, SEB and SEC) were determined both by the ELISA and the microslide test (MS-test), the enterotoxin types D and E by the MS-test only. Comparison of the two test methods clearly shows that the ELISA technique is superior to the MS method: The sensitivity of the ELISA was at 2.5 ng, whereas that of the MS-test was limited to approximately 1 microgram. The ELISA revealed 6.2% more of the strains as enterotoxin producers, and reproducibility of the test results was also better with the ELISA than with the MS-test. Furthermore, the ELISA is far more efficient, consuming less test reagents, and with a capacity for testing more strains in a shorter time procedure. The incidence rate of the various enterotoxin types, referred to one representative strain each per outbreak of food poisoning or group of persons investigated, is as follows: 45.3% SEA, 17.2% SEB, 23.4% SEC. The incidence rate of SED, SEE or SE-type combinations was less than 5%. In sick persons, SEA- and SEC-producing strains occurred within the same range, i.e. 34.8% and 30.4% respectively. SEA-producing S. aureus strains had the highest frequency in food samples (61.5%) and in healthy individuals (53.6%).