FIG. 1.

Influence of subinhibitory concentrations (one-fourth the MIC) of penicillins (A) and other β-lactam antibiotics (B) on β-galactosidase (LacZ) production of the fusion strain S. aureus Wood 46-3. Wood 46-3 cultures grown without and with antibiotics were monitored with regard to LacZ production until the early stationary phase. Maximal LacZ values are given as relative light units (RLU). Means ± standard deviations for five experiments are given. The values obtained with each antibiotic were compared to those obtained for the control without antibiotic by an unpaired t test: ∗, P ≤ 0.01; the other differences were not statistically significant (P > 0.05). The abbreviations are listed in Table 2.