Background: Carbapenem resistance due to acquired metallo-beta-lactamases (MBLs) is considered to be more serious than other resistance mechanisms. Objectives: 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. Materials and Methods: 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. Results: 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. Conclusions: 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.

Background: The aim of the present study was to investigate biofilm formation among Methicillin-resistant Staphylococcus aureus (MRSA) isolated from children referring to a pediatric hospital in Tehran.

Introduction: Staphylococcus aureus is known to be a major cause of skin and soft tissue infections, pneumonia and invasive diseases. In this study, attempts were made to examine the prevalence of tsst-1, eta, etb, and luk-PV genes among methicillin-resistant S. aureus (MRSA) isolated from children in Tehran. Methodology: In the present cross-sectional study, a total of 100 MRSA were isolated from children who were referred to a pediatric hospital during 11-month period of September 2014 to August 2015. Isolates were identified using biochemical tests and then, using PCR, the isolates were tested for the presence of mecA, tsst-1, eta, etb, and luk-PV genes. Susceptibility of isolates to cefoxitin, penicillin, erythromycin, clindamycin, gentamicin, rifampin, minocycline, co-trimoxazole, linezolid, and vancomycin were evaluated using standard methods. Results: It was found that the MRSA isolates had the greatest resistance to clindamycin (72%) and erythromycin (59%), while the lowest rates of resistance were observed to be related to minocycline (6%) and rifampin (12%). All of isolates were sensitive to vancomycin and linezolid. The mecA gene was detected in all the isolates. Moreover, luk-PV and tsst-1 were detected in 18% and 17% of the isolates, respectively. None of the isolates harbored eta and etb genes. Conclusions: Our data provide specifications about the toxin production status of S. aureus isolates from pediatric children. The current study showed increased resistance to different antibiotics in S. aureus isolates. Therefore, to prevent multi-resistance to other antibiotic classes, it is essential to withhold prescriptions and stop unessential use of available antibiotics.