Antibacterial Effects of Zataria multiflora, Ziziphus, Chamomile and Myrtus communis Methanolic Extracts on IMP-Type Metallo-Beta-Lactamase-Producing Pseudomonas aeruginosa

Carbapenem resistance due to acquired metallo-beta-lactamases (MBLs) is considered to be more serious than other resistance mechanisms. The aim of this study was to examine the effects of the methanolic extracts of Zataria multiflora, Ziziphus, Chamomile and Myrtus communis leaves on IMP-type MBL- producing Pseudomonas aeruginosa strains. This cross-sectional descriptive study was conducted on burn patients hospitalized in Shahid Motahari Hospital, Tehran, Iran, during 2012 - 2013. Antibiotics and extracts susceptibility tests were performed using the disc diffusion and broth micro dilution methods. The metallo-beta-lactamase detection was performed by combination disk diffusion test. The bla (VIM) and bla (IMP) genes were detected by polymerase chain reaction (PCR) and sequencing methods. Eighty-three out of 96 samples were imipenem-resistant P. aeruginosa strains. Among 83 imipenem-resistant P. aeruginosa strains, 48 (57.9%) were MBL producers. Polymerase chain reaction and sequencing methods proved that these isolates were positive for blaIMP-1 genes, whereas none were positive for bla (VIM) genes. The minimum inhibitory concentration (MIC) for imipenem was 128 (µg/mL) for all strains. The MIC and minimum bactericidal concentration (MBC) of M. communis were 6.25 and 12.5 (mg/mL) for all isolates, respectively; the MIC and MBC of Z. multiflora were somehow the same. Methanolic extract of Chamomile showed to have a beneficial effect on this strain, while the Ziziphus leaves methanolic extract showed no significant effect on these isolates. The results of this study reveal that the M. communis extract and methanolic extract of Chamomile have a high antibacterial effect on regular and IMP-producing P. aeruginosa strains; so, these extracts can be suitable alternatives for less-effective antibiotics, which are commonly used.