Detection of the cell wall-affecting antibiotics at sublethal concentrations using a reporter Staphylococcus aureus harboring drp35 promoter - lacZ transcriptional fusion.

Previously, various inhibitors of cell wall synthesis induced the 435 gene of Staphylococcus aureus efficiently. To determine whether 435 could be exploited in antistaphylococcal drug discovery, we cloned the promoter of 435 (P-d) and developed different biological assay systems using an engineered S. aureus strain that harbors a chromosomally-integrated P-d - lacZ transcriptional fusion. An agarose-based assay showed that Pd is induced not only by the cell wall-affecting antibiotics but also by rifampicin and ciprofloxacin. In contrast, a liquid medium-based assay revealed the induction of P-d specifically by the cell wall-affecting antibiotics. Induction of P-d by sublethal concentrations of cell wall-affecting antibiotics was even assessable in a microtiter plate assay format, indicating that this assay system could be potentially used for high-throughput screening of new cell wall-inhibiting compounds. [BMB reports 2010; 43(7): 468-473]