Antimicrobial activity of antibiotics in combination with natural flavonoids against clinical extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae

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Extended-spectrum β-lactamases (ESBLs) are plasmid-mediated class A enzymes commonly found in the family Enterobacteriaceae, mainly in Klebsiella pneumoniae. Flavonoids have also been reported to possess antimicrobial activity. In this study, the in vitro activities of 18 antibiotics and 12 flavonoids against 20 ESBL-producing K. pneumoniae isolates were evaluated. All of these isolates were susceptible to imipenem and cefinetazole, but were resistant to ampicillin, ampicillin/sulbactam, aztreonam, cefazolin, cefoperazone, cefotaxime, ceftazidime, ceftriaxone, cefuroxime, piperacillin and ticarcillin. Susceptibilities to amikacin, amoxicillin/clavulanate, cefoxitin, ciprofloxacin and gentamicin were variable. Myricetin, a flavonol, inhibited ESBL-producing K. pneumoniae isolates at a high minimum inhibitory concentration (MIC) (MIC90 value 256 mg/mL), but exhibited significant synergic activity against ESBL-producing K. pneumoniae in separate combination with amoxicillin/clavulanate, ampicillin/sulbactam and cefoxitin. Because of the low-toxic nature of flavonoids, the combination of antibiotics and flavonoids is a potential new strategy for developing therapies for infections caused by ESBL-producing bacteria in the future.

Original languageEnglish
Pages (from-to)612-617
Number of pages6
JournalPhytotherapy Research
Issue number7
Publication statusPublished - Jul 2005



  • Amoxicillin/clavulanate
  • Ampicillin/sulbactam
  • Cefoxitin
  • Myricetin
  • Time-kill curves

ASJC Scopus subject areas

  • Drug Discovery
  • Organic Chemistry
  • Pharmacology

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