Relation of enterotoxin production and lipolytic activity in Staphylococcus aureus strains isolated from acute diarrhoeal diseases to clinical course of illness.

Two sets of cases of acute diarrhoeal disease caused by plasma-coagulase-positive Staphylococcus aureus strains were studied. Testing the isolates for staphylococcal enterotoxin (SE) production and for lipolytic activity on egg-yolk agar in relation to the clinical course of the illness showed that only part of the cases could be attributed to the effect of SE and that lipolytic activity apparently also played some pathogenetic role. In one of the sets (205 cases) SE production was found in only 29% of the strains isolated; the clinical course in the corresponding patients was typical of staphylococcal enterotoxicosis. Pronounced lipolytic activity without SE production was demonstrated in 30% of strains; here the clinical course was much milder and protracted. Where both factors were produced (21% of cases), the clinical pattern of enterotoxicosis predominated but was somewhat modified. Two outbreaks in one of which SE production and in the other only clear-cut lipolytic activity were found also differed mutually in the clinical respect. The first displayed a picture of typical staphylococcal enterotoxicosis, the second comprised mild diarrhoeal cases with an incubation period of 6-9 hours, diffuse abdominal pain and no fever. Accordingly, the above observations showed a certain positive correlation between the presence of some staphylococcal exoproducts (SE, lipolytic-activity factor) and the clinical course of the disease. This was particularly striking in infants up to 2 years of age. Lipolytic activity seemed to be associated with mild diarrhoeal staphylococcal disease, although the co-participation of (an)other, so far undetermined factor(s), could not be precluded.