title: Enhancing the Anti-Enterococci Activity of Different Antibiotics by Combining With Metal Oxide Nanoparticles.
abstract: BACKGROUND
  Enterococci have emerged as more virulent and multidrug-resistant in community and hospital settings. The emergence of vancomycin resistant enterococci (VRE) in hospitals has posed a serious threat to public health. The widespread use of antibiotics to treat VRE infections has resulted in the development of resistant forms of these organisms.
  
  
  OBJECTIVE
  Present study deals with the efficacy of antibiotic-nanoparticle combination against clinical isolates of VRE. This study has effectively evaluated the anti-enterococcal activity of metallic nanoparticles and their combination with antibiotics with the aim to search for new biocidal combinations.
  
  
  METHODS
  Initially, the isolates were identified by various biochemical tests and also by PCR, targeting ddl, vanA and vanB genes. Antibiotic susceptibility testing was carried out by disc diffusion method. Minimum inhibitory concentration (MIC) of both antibiotics and metal nanoparticles against VRE was done using broth dilution method. On the basis of MICs, a combination of both antibiotics and nanoparticles was used by physical mixing of antibiotics and different concentrations of nanoparticles.
  
  
  RESULTS
  The MIC of metal nanoparticles were found in the range of 0.31 - 30 mM. The combination of both antibiotics and nanoparticles has effectively reduced the MICs of ciprofloxacin from 16 - 256 μg/mL to 2 - 16 μg/mL, erythromycin 1024 - 2048 μg/mL to 128 - 512 μg/mL, methicillin 32 - 256 μg/mL to 8 - 64 μg/mL and vancomycin 2 - 512 μg/mL to 0.5 - 64 μg/mL.
  
  
  CONCLUSIONS
  Among the nanoparticles, ZnO was found as a potent metallic nanoparticle which effectively reduced the MIC upon combination with the antibiotics. The combination exhibited enhanced bactericidal activity against multidrug resistant clinical strains of VRE with dose dependency. Further extensive study on this aspect can prove their beneficial clinical use against resistant pathogens to combat increasing resistance to antibiotics.
authors.affiliation: Department of Microbiology, Quaid-i-Azam University, Islamabad, Pakistan; Department of Microbiology and Immunology, College of Medicine, University of Illinois, Chicago, USA.
authors.forename: Saira
authors.initials: S
authors.lastname: Iram
authors.affiliation: Department of Pharmacy, COMSATS Institute of Information Technology, Abbottabad, Pakistan.
authors.forename: Jawad
authors.initials: J
authors.lastname: Akbar Khan
authors.affiliation: Department of Pharmacy, COMSATS Institute of Information Technology, Abbottabad, Pakistan.
authors.forename: Nargis
authors.initials: N
authors.lastname: Aman
authors.affiliation: Department of Biotechnology, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, Pakistan.
authors.forename: Akhtar
authors.initials: A
authors.lastname: Nadhman
authors.affiliation: Riphah Institute of Pharmaceutical Sciences G-7/4, Islamabad, Pakistan.
authors.forename: Zikra
authors.initials: Z
authors.lastname: Zulfiqar
authors.affiliation: Department of Pharmacy, COMSATS Institute of Information Technology, Abbottabad, Pakistan.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Arfat Yameen
keywords: Antimicrobial Susceptibility; Enterococci; Metallic Nanoparticles; VRE; ZnO