FIG 4.
Inhibition zone produced by LTV17 and meropenem with and without L1 β-lactamase. A lawn of S. maltophilia K279a (left) or the ampR frameshift mutant (ampRFS) (right) was spread as if for CLSI disc susceptibility testing (using a 108 CFU/ml suspension of bacteria). In all cases, 2 μl of reaction mixture (50 mM Tris [pH 7.5]) with meropenem (MER, 12 mM) or LTV17 (0.4 mM) mixed (+L1) or not mixed (−L1) with purified L1 β-lactamase (1 μM final) was immediately spotted onto the lawn (t = 0 h) (top panels) or was spotted following 1 h of preincubation at 37°C (t = 1 h) (bottom panels). The plate was then incubated for 18 h at 37°C. This figure is representative of the results determined for three biological replicates.