title: Role of duty cycle on Pseudomonas aeruginosa growth inhibition mechanisms by positive electric pulses.
abstract: BACKGROUND
  P. aeruginosa considered as a notoriously difficult organism to be controlled by antibiotics or disinfectants. The potential use of alternative means as an aid to avoid the wide use of antibiotics against bacteria pathogen has been recently arisen remarkably.
  
  
  OBJECTIVE
  Effect of extremely low frequency positive electric pulse with different duty cycles on Pseudomonas aeruginosa (ATCC: 27853) growth by constructed and implemented exposure device was investigated in this study.
  
  
  METHODS
  The exposure device was applied to give extremely low frequency in the range of 0.1 up to 20 Hz with the capability to control the duty cycle of each pulse with variation from 10% up to 100%. Growth curves of Pseudomonas aeruginosa were investigated before and after exposure to different frequencies (0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 Hz) through measuring the optical density and cell count. Exposures to selected frequencies in the whole ranges of duty cycles were done. These studies were followed by DNA fragmentation, transmission electron microscope (TEM), antibiotic susceptibility tests, and dielectric measurements.
  
  
  RESULTS
  Findings revealed inhibition effect by 48.56% and 47.4% together with change in the DNA structural properties for samples exposed to 0.5 Hz and 0.7 Hz respectively. Moreover the data indicated important role of duty cycle on the inhibition mechanism.
  
  
  CONCLUSIONS
  It is concluded that there are two different mechanisms of interaction between positive electric pulse and microorganism occurred; 0.5 Hz caused rupture in cell wall while 0.7 Hz caused denaturation of the inner consistent of the cell.
authors: Biophysics Department, Faculty of Science, Cairo University, Giza, Egypt.
authors: Fadel M
authors: FM
authors: Ali
authors: Biophysics Department, Faculty of Science, Cairo University, Giza, Egypt.
authors: Reem H
authors: RH
authors: Elgebaly
authors: Department of Biomedical Equipments & Systems, Faculty of Applied Medical Sciences, October 6 University, Giza, Egypt.
authors: Mona S
authors: MS
authors: Elneklawi
authors: Medical Laboratory Department, Faculty of Applied Medical Sciences, October 6 University, Giza, Egypt.
authors: Amal S
authors: AS
authors: Othman
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D053938:DNA Fragmentation / Q000187:drug effects; D004269:DNA, Bacterial / Q000235:genetics; D004560:Electricity; D006801:Humans; D011552:Pseudomonas Infections / Q000188:drug therapy / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics / Q000254:growth & development*
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial
keywords: DNA; Extremely low frequency; Pseudomonas aeruginosa; TEM; duty cycle; positive electric pulse