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. GSK2126458 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 see more 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 (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 Loperamide 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).