Antibacterial activity of epigallocatechin-3-gallate (EGCG) and its synergism with β-lactam antibiotics sensitizing carbapenem-associated multidrug resistant clinical isolates of Acinetobacter baumannii.
BACKGROUND
Infections caused by Acinetobacter baumannii were responsive to conventional antibiotic therapy. However, recently, carbapenem-associated multidrug resistant isolates have been reported worldwide and present a major therapeutic challenge. Epigallocatechin-3-Gallate (EGCG) extracted from green tea exhibits antibacterial activity.


OBJECTIVE
We evaluated the antibacterial activity of EGCG and possible synergism with antibiotics in carbapenem-associated multidrug resistant A. baumannii. A potential mechanism for synergism was also explored.


METHODS
Seventy clinical isolates of A. baumannii collected from geographically different areas were analyzed by minimal inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of EGCG. Checkerboard and time-killing assays were performed to exam the synergism between EGCG and antibiotics. The effects of EGCG on a multidrug efflux pump inhibitor (1-[1-naphthylmethyl] piperazine; NMP) and β-lactamase production were also examined in A. baumannii.


RESULTS
Sixty-three of 70 clinical isolates of A. baumannii carried carbapenemase-encoding genes with carbapenem-associated multidrug resistance. Levels of MIC and MBC of EGCG ranged from 64 to 512µg/ml and from 128 to ≥1024µg/ml, respectively among the clinical isolates. MIC90and MBC86levels were 256µg/ml and 512µg/ml of EGCG, respectively. Subinhibitory concentration of EGCG in combination with all antibiotics tested, including carbapenem, sensitized (MICs fall≤1.0µg/ml) all carbapenem-associated multidrug resistant isolates. Checkerboard and time-killing assays showed synergism between EGCG and meropenem (or carbenicillin) counted as fractional inhibitory concentration of < 0.5 and cell numbers' decrease per ml of >2log10 within 12h, respectively. EGCG significantly increased the effect of NMP but was unrelated to β-lactamase production in A. baumannii, suggesting EGCG may be associated with inhibition of efflux pumps.


CONCLUSIONS
Overall we suggest that EGCG-antibiotic combinations might provide an alternative approach to treat infections with A. baumannii regardless of antibiotic resistance.
Jericho Senior High School, Jericho, New York 11753, United States.
Spencer
S
Lee
Department of Biology, Long Island University, Brooklyn, New York, 11201, United States.
Ghaida Saleh Al
GS
Razqan
Department of Biology, Long Island University, Brooklyn, New York, 11201, United States ; Department of Medicine, Michael E. DeBakey VA Medical Center, Baylor College of Medicine, Houston, Texas, 77030, United States. Electronic address: dong.kwon@liu.edu.
Dong H
DH
Kwon
D000151:Acinetobacter Infections / Q000188:drug therapy*; D040981:Acinetobacter baumannii / Q000187:drug effects*; D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use*; D015780:Carbapenems / Q000494:pharmacology / Q000627:therapeutic use*; D002392:Catechin / Q000494:pharmacology / Q000627:therapeutic use*; D018432:Drug Resistance, Multiple / Q000187:drug effects; D006801:Humans; D008826:Microbial Sensitivity Tests; D008517:Phytotherapy; D010936:Plant Extracts / Q000494:pharmacology / Q000627:therapeutic use*; D047090:beta-Lactams / Q000494:pharmacology / Q000627:therapeutic use*
D000900:Anti-Bacterial Agents; D015780:Carbapenems; D010936:Plant Extracts; D047090:beta-Lactams; D002392:Catechin
Acinetobacter baumannii; Antibacterial activity; EGCG