Screening of clinical S. aureus-isolates for the production of exfoliative toxin. A methodological study.

Screening S. aureus-isolates for the production of exfoliative toxin (ET) and discrimination between its two known variants (ETA, ETB) by immunodiffusion (ID), isoelectric focusing (IEF) and animal experiment were assessed methodologically using isolates from a patient with bullous impetigo and a patient with Ritter von Rittershain's disease. Only by animal assay one of the isolates could be identified as ET-producer. ID was used for the discrimination between ETA and ETB. It is concluded that the in-vivo assay for ET-production using live staphylococci can not yet be replaced by ID and IFE and that in patients with staphylococcal scalded skin syndrome swabs should be taken from multiple lesions und all S. aureus isolates obtained should be screened for ET-production to prevent false-negative results. Lysotyping alone gives no proof of ET-production since types II 55/71 and II 3A/3C do not produce ET in all cases and toxinogenic S. aureus strains of phage groups I and III have been described.