Identification of a chromosomal determinant of enterotoxin A production in Staphylococcus aureus

Chromosomal mapping of the determinants for enterotoxin A and enterotoxin B production in three strains of Staphylococcus aureus was attempted by using conventional transformation procedures and a series of multiply marked derivatives of NCTC 8325 as recipients. A gene governing enterotixin A production (entA+) in strain S-6 was located on the chromosome between the pur-110 and ilv-129 markers, very close to a determinant of alpha-hemolysin production, hla+. The entA+ gene of strain FRI-196E was shown not to be located at the same position; its location could not be determined. The entB+ genes of strains S-6 and C243 were not located within the known linkage groups examined. Recombinants were screened for enterotoxin production by a new procedure that combined characteristics of immune serum plate and optimal sensitivity plate procedures. The strains and methods used in this study of enterotoxin determinants should prove useful in genetic studies to locate other chromosomal determinants of S. aureus whose phenotypes are difficult to score or select for.