Purpose:
In the present study, six flavonoids (5,7-dimethoxyflavanone-4'-O-β-D-glucopyranoside, 5,7dimethoxyflavanone-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 (trimetoprimesulphametoxazole, 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 β-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.
