Fig 5. Pre-incubation with subinhibitory concentrations of the beta-lactam antibiotic 6-APA increases the beta-lactamase activity and LL-37 susceptibility of S. aureus Newman.

Bacteria were incubated for 60 min at 37°C in the absence or presence of 6-APA. For an aliquot of each sample the beta-lactamase activity was subsequently determined with nitrocefin as test reagent (A). The residual bacteria were incubated with or without LL-37 for another 60 min and the surviving CFUs were quantified (B). Samples were run in triplicate and one representative experiment of three performed is shown. ***, p<0.001.