“…The indole–2‐pyridone hybrids 80a,b (MIC: 0.78–6.3 μg/ml) possessed an excellent broad‐spectrum activity against a panel of wild‐type and drug‐resistant Gram‐negative strains, including permeable E. coli BAS849 ( E. coli p ), wild‐type E. coli ATCC 25922 ( E. coli WT ), highly fluoroquinolone‐resistant E. coli strains SKM18 ( E. coli R1 ) bearing four mutations (two in gyrA and two in parC ) in the quinolone resistance‐determining region (QRDR), and clinical isolate ELZ4251 ( E. coli R2 ), wide‐type strains of A. baumannii ATCC BAA‐747 ( A. bau WT ) and K. pneumoniae ATCC 35657 ( K. pneu WT ), as well as fluoroquinolone‐resistant clinical isolate A. baumannii MMX2240 ( A. bau R ), whereas the reference ciprofloxacin (MIC: >250 μg/ml) was devoid of activity against E. coli R1 , E. coli R2 , and A. bau R . [ 158,159 ] In a murine septicemia model, hybrids 80a,b (20 mg/kg, intravenous administration) showed obvious inhibition in mice infected with a lethal dose of E. coli . The mechanistic study revealed that these two hybrids could target both bacterial DNA gyrase and topoisomerase IV, and they could serve as dual‐action antibacterial candidates.…”