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.