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Antimicrobial activity of essential oils against multidrug-resistant clinical isolates of the Burkholderia cepacia complex.

ABSTRACT: Members of the Burkholderia cepacia complex (Bcc) are an important cause of opportunistic or nosocomial infections that may be hard to treat due to a high incidence of multidrug resistance. We characterised a collection of 51 clinical isolates from this complex, assigning them to 18 sequence types using multi-locus sequence type analysis. Resistance to eight commonly used antibiotics was assessed using by using agar-dilution assays to calculate MICs and widespread and heterogeneous multidrug resistance was confirmed, with eight strains proving resistant to all antibiotics tested. Disc diffusion screening of antimicrobial activity of a range of plant essential oils against these Bcc isolates identified six oils with significant activity (lavender, lemongrass, marjoram, peppermint, tea tree and rosewood) and broth microdilution assays indicated that of these lemongrass and rosewood oils had the highest activity, with MIC50 values of 0.5% and MIC90 values of 1%. Comparison of MIC and MBC values showed that four of these six oils, including lemongrass and rosewood, were bacteriocidal rather than bacteriostatic in their effects. Qualitative analysis of the four bacteriocidal essential oils via GC/MS indicated the presence of 55 different component compounds, mostly monoterpenes. We assessed selected essential oil components as anti-Bcc agents and demonstrated that terpinen-4-ol and geraniol were effective with MICs of 0.125-0.5% (v/v) and 0.125-1% (v/v), respectively. Time-kill studies indicate that these two alcohols are effective against non-growing cells in an efflux-dependent manner. Analysis of bacterial leakage of potassium ions and 260 nm UV-absorbing material on treatment with terpinen-4-ol and geraniol suggested that the observed anti-Bcc activity was a consequence of membrane disruption. This finding was supported by a gas chromatography analysis of bacterial fatty acid methyl esters, which indicated changes in membrane fatty acid composition caused by terpinen-4-ol and geraniol. These essential oils or oil components may ultimately prove useful as therapeutic drugs, for example to treat Bcc infections in CF patients.

SUBMITTER: Vasireddy L

PROVIDER: S-EPMC6072103 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Project description:In persons with cystic fibrosis (CF), airway infection with Burkholderia cepacia complex (Bcc) species or Burkholderia gladioli presents a significant challenge due to inherent resistance to multiple antibiotics. Two chromosomally encoded inducible β-lactamases, a Pen-like class A and AmpC are produced in Bcc and B. gladioli Previously, ceftazidime-avibactam demonstrated significant potency against Bcc and B. gladioli isolated from the sputum of individuals with CF; however, 10% of the isolates tested resistant to ceftazidime-avibactam. Here, we describe an alternative antibiotic combination to overcome ceftazidime-avibactam resistance. Antimicrobial susceptibility testing was performed on Bcc and B. gladioli clinical and control isolates. Biochemical analysis was conducted on purified PenA1 and AmpC1 β-lactamases from Burkholderia multivorans ATCC 17616. Analytic isoelectric focusing and immunoblotting were conducted on cellular extracts of B. multivorans induced by various β-lactams or β-lactam-β-lactamase inhibitor combinations. Combinations of piperacillin-avibactam, as well as piperacillin-tazobactam plus ceftazidime-avibactam (the clinically available counterpart), were tested against a panel of ceftazidime-avibactam nonsusceptible Bcc and B. gladioli The piperacillin-avibactam and piperacillin-tazobactam-ceftazidime-avibactam combinations restored susceptibility to 99% of the isolates tested. Avibactam is a potent inhibitor of PenA1 (apparent inhibitory constant [Ki app] = 0.5 μM), while piperacillin was found to inhibit AmpC1 (Ki app = 2.6 μM). Moreover, piperacillin, tazobactam, ceftazidime, and avibactam, as well as combinations thereof, did not induce expression of bla penA1 and bla ampC1 in the B. multivorans ATCC 17616 background. When ceftazidime-avibactam is combined with piperacillin-tazobactam, the susceptibility of Bcc and B. gladioli to ceftazidime and piperacillin is restored in vitro Both the lack of bla penA1 induction and potent inactivation of PenA1 by avibactam likely provide the major contributions toward susceptibility. With in vivo validation, piperacillin-tazobactam-ceftazidime-avibactam may represent salvage therapy for individuals with CF and highly drug-resistant Bcc and B. gladioli infections.

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Antimicrobial activity of essential oils against multidrug-resistant clinical isolates of the Burkholderia cepacia complex.

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