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Table 2 Effect of conessine and steroidal alkaloids in combination with levofloxacin on the viability of P. aeruginosa PAM1020, PAM1032 and PAM1034

From: Steroidal alkaloids and conessine from the medicinal plant Holarrhena antidysenterica restore antibiotic efficacy in a Galleria mellonella model of multidrug-resistant Pseudomonas aeruginosa infection

  Strain Agent (s) Concentration (mg/L) Log CFU/ml
Inoculum Untreated control Treatment (±SD) Log reduction
Single treatment at MIC0.5a PAM1020 Conessine 32    9.47 ± 0.03 0.27
  Alkaloids 1024 5.16 ± 0.06 9.74 ± 0.06 8.76 ± 0.01 0.98
  LVX 0.125    8.91 ± 0.02 0.83
PAM1032 Conessine 32    9.42 ± 0.01 0.45
  Alkaloids 1024 5.44 ± 0.08 9.87 ± 0.14 8.82 ± 0.06 1.05
  LVX 1    8.19 ± 0.68 1.68
PAM1034 Conessine 32    9.54 ± 0.09 0.13
  Alkaloids 1024 5.64 ± 0.21 9.67 ± 0.02 8.88 ± 0.23 0.79
  LVX 2    8.18 ± 0.10 1.49
Combinations at MIC0.5 PAM1020 Conessine + LVX 32 + 0.125 5.16 ± 0.06 9.74 ± 0.06 9.25 ± 0.03 0.49
  Alkaloids + LVX 1024 + 0.125    8.12 ± 0.16 1.62
PAM1032 Conessine + LVX 32 + 1 5.44 ± 0.08 9.87 ± 0.14 5.35 ± 0.43 4.52
  Alkaloids + LVX 1024 + 1    7.70 ± 0.13 2.17
PAM1034 Conessine + LVX 32 + 2 5.64 ± 0.21 9.67 ± 0.02 5.54 ± 0.09 4.13
  Alkaloids + LVX 1024 + 2    6.85 ± 0.67 2.82
  1. aA MIC was not detectable for the steroidal alkaloids so the highest concentration tested was used in this assay
  2. Viability was determined in 96-well microplates after 24 h exposure to the antibiotics in MHB at 37 °C. Data shown is the mean and standard deviation from quadruple experiments. Highlighted treatments are those that resulted in ≥2 log10 reduction compared to untreated controls