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Table 3 Evaluation of synergistic interaction between some natural beta lactamase inhibitors in association with selected permeabilizers with no antibacterial activity on susceptibility of beta lactamase producer isolates to different beta lactam antibiotics

From: Natural outer membrane permeabilizers boost antibiotic action against irradiated resistant bacteria

Mean inhibition zone (mm) / Susceptibility break points
Permeabilizers Ab- alone ECG ECG + GA ECG + T Quercetin Q + GA Q + T Permeabilizers Ab-alone Gallic acid Thymol
aAntibiotics (Ab) bAntibiotics (Ab)
Escherichia coli 2
 PRL ≥21 6/R 6/R 20/M 23/S 15/R 19/M 24/S TZP ≥21 14/R 20/M 26/S
 CFP ≥21 6/R 6/R 16/M 21/S 16/M 21/S 25/S SCF ≥22 14/R 19/M 20/M
Acinetobacter baumannii 4
 PRL 6/R 6/R 19/M 21/S 16/R 24/S 21/S TZP 15/R 20/M 21/S
 CFP 6/R 6/R 23/S 20/M 16/M 20/M 22/S SCF 14/R 22/S 23/S
Pseudomonas aeruginosa 8
 PRL 12/R 12/R 16/R 25/S 18/S 22/S 20/S TZP 17/R 23/S 26/S
 CFP 10/R 10/R 15/R 21/S 17/M 20/M 22/S SCF 15/R 25/S 21/M
Pseudomonas aeruginosa 9
 PRL 6/R 6/R 18/S 19/S 12/R 19/S 21/S TZP 11/R 22/S 22/S
 CFP 6/R 6/R 22/S 25/S 15/R 22/S 24/S SCF 12/R 22/S 25/S
Enterobacter cloacae 13
 PRL 6/R 6/R 20/M 23/S 15/R 20/M 24/S TZP 20/M 30/S 27/S
 CFP 6/R 6/R 18/M 21/S 18/M 20/M 23/S SCF 18/M 25/S 23/S
  1. ECG Epigallocatechin gallate, Q Quercetin, GA Gallic acid, T Thymol
  2. aStandard discs of single β-lactam antibiotics PRL (100 μg) = Piperacillin CFP (75 μg) = Cefoperazone
  3. b Standard discs of antibiotics combined with β-lactamase inhibitors
  4. TZP (100/10 μg) = Piperacillin/ tazobactam SCF (75/30 μg) = Cefoperazone/ sulbactam