Although phase 1 clinical trials have found that high doses (12 g/day) of systemic CCM are safe [19], the use of polyphenols as antimicrobials is likely to

be limited to use as topical agents. The toxicity of EGCG was limited to minor skin irritation in mammalian models [20] at high concentrations and no adverse effects were seen with preparations containing up to 500 mg/Kg/day. phosphatase inhibitor In this study we present data on the activity of CCM alone and in combination with EGCG against a well characterised collection of MDR A. baumannii clinical isolates. Methods Chemicals reagents and media Curcumin powder (≥90% purity) extracted from Curcuma longa was purchased from the Cayman Chemical Company

(Michigan, USA). Epigallocatechin gallate (≥95% purity) was donated by Unilever PLC (Bedford, UK). All growth media (Iso-Sensitest broth) was purchased from Thermo Scientific (Basingstoke, UK), sterilised and made up locally according to the manufacturer’s instructions. Bacterial strains Nine Acinetobacter Ro-3306 clinical trial baumannii isolates were studied. These included the antibiotic susceptible type strain ATCC 19606 and 8 MDR clinical isolates. These have been extensively characterised previously and were chosen to be representative of UK epidemic clones (OXA-23 clones 1, 2, ‘Burn’) and/or exhibit resistance to colistin, tigecycline or produce metallo-β-lactamases (NDM enzymes) [21] Properties of the strains are detailed in Table 1. All isolates were stored at -70°C in microbank vials (Tucidinostat Thermofisher, UK) and thawed prior to their use. Table 1 Resistant determinants and sources of multidrug-resistant clinical isolates of Acinetobacter baumannii Isolate Properties Isolate source AB 19606 Antibiotic Susceptible type Strain. National Collection of type cultures AB 14 MDR PFGE defined UK OXA-23 clone 1 OXA-23-like carbapenemase producer. Dr J Turton, Public Health Tangeritin England, Colindale, UK AB 16 MDR PFGE defined

UK OXA-23 clone 2 OXA-23 carbapenemase producer. Dr J Turton, Public Health England, Colindale, UK AB 186 MDR PFEG defined UK ‘burn’ strain, OXA-23 producer. Dr J Turton, Public Health England, Colindale, UK AB 202 Tigecycline-resistant strain UK OXA-23 clone 1 isolate. Barts Health NHS Trust, London, UK AB 205 Colistin resistant UK OXA-23 clone 1 isolate. Barts Health NHS Trust, London, UK AB 292 MDR PFGE-defined OXA-23-like carbapenemase producer. Barts Health NHS Trust, London, UK AB 306 MDR NDM-1 carbapenemase producer. Barts Health NHS Trust, London, UK AB 308 MDR NDM-2 carbapenemase producer. S. Gottig, Goethe Universistat, Frankfurt, Germany Determination of minimum inhibitory concentrations Minimum inhibitory concentrations (MICs) were determined in corning 96-well microtitre plates (Corning, Amsterdam, The Netherlands).