Toxic shock syndrome toxin-1 (TSST-1): influence of its production by subinhibitory antibiotic concentrations.

Using seven different toxic shock syndrome toxin-1 (TSST-1) producing Staphylococcus aureus strains, we examined the influence on growth and toxin production of subinhibitory concentrations of clindamycin, erythromycin, lincomycin, kanamycin, tetracycline and tunicamycin. The behaviour of six S. aureus (= W/MT-strains) was identical, the one of S. aureus MN8 was different in part. Using the different subinhibitory antibiotic concentrations, bacterial growth was inhibited by tunicamycin only. Toxin production was influenced by clindamycin, erythromycin, lincomycin, kanamycin and tetracycline without simultaneous changes in the number of cells; MN8 was more sensitive to clindamycin and lincomycin than W/MT strains. Very small differences or no differences at all were found between the two bacterial groups in experiments using erythromycin, kanamycin and tetracycline. Tunicamycin caused elevated TSST-1 concentrations of 100% (MN8) or 65% (W/MT) above the control level if used at concentrations of 4 mg/l or 16 mg/l respectively; this result is interpreted as a higher output of TSST-1 caused by the damage to the bacterial cell wall. From these results it is not possible to conclude that different mechanisms of regulation of TSST-1 expression exist between S. aureus MN8 and the other TSST-1 positive S. aureus strains.