Original Research Article

Antimicrobial Activity of Flavonoids against Extended-Spectrum β-Lactamase (ESβL)-Producing Klebsiella pneumoniae

B Özçelik^1*, D Deliorman Orhan², S Özgen¹, F Ergun²

¹Department of Pharmaceutical Microbiology, Faculty of Pharmacy, Gazi University, 06330, Ankara, Turkey, ²Department of Pharmacognosy, Faculty of Pharmacy, Gazi University, 06330 Ankara, Turkey

*Corresponding author: E-mail: berrin@gazi.edu.tr , microberr@yahoo.com
 

Received: 10 July 2008                                                                          Revised accepted: 22 August 2008          

Purpose: In the present study, six flavonoids (5,7-dimethoxyflavanone-4’-O-β-D-glucopyranoside, 5,7-dimethoxyflavanone-4’-O-[2’’-O-(5’’’-O-trans-cinnamoyl)-β-D-apiofuranosyl]-β-D-glucopyranoside, naringenin-7-O-β-D-glucopyranoside, 5,7,3’-trihydroxy-flavanone-4’-O-β-D-glucopyranoside, rutin, and nicotiflorin) isolated from Galium fissurense, Viscum album ssp. album and Cirsium hypoleucum were screened against extended-spectrum β-lactamase producing multidrug-resistant (trimetoprime-sulphametoxazole, sulbactam-ampicillin, clavulonate-amoxicilin, ceftriaxon,  cefepime, imipenem, ceftazidime, tobramicin, gentamicin, ofloxacin, ciprofloxacin) bacteria Klebsiella pneumoniae (ESβLs).

Methods: We performed susceptibility testing according to the Clinical and Laboratory Standards Institute (CLSI, formerly NCCLS) and used an inhibition endpoint for determination of the minimum inhibition concentrations (MICs).

Results: All the flavonoids showed in vitro antimicrobial activity against all the isolated strains of K. pneumoniae similar to the control antibacterial (ofloxacin) at the concentrations of 32 - 64 µg ml^-l; another control, ampicillin, had no activity. Since, ESβL-producing strains are known to be resistant to all b-lactam antibiotics, our results fall notably within the concentration range for antimicrobial activity.

Conclusion: To the best of our knowledge, this is the first report of the study of the activity of these flavonoids against (ESβL)-producing K. pneumoniae and may throw light to the low-toxicity of flavonoids, and their potentials for developing therapies for infections caused by ESβL-producing bacteria in the future. Further work is under investigation to identify their precise antibacterial mechanism.