title: Cellular effects of monohydrochloride of L-arginine, N-lauroyl ethylester (LAE) on exposure to Salmonella typhimurium and Staphylococcus aureus.
abstract: OBJECTIVE
  Here we study the effect of monohydrochloride of L-arginine, N(alpha)-lauroyl ethylester (LAE), a cationic preservative derived from lauric acid and arginine, on the cell envelopes of Salmonella typhimurium and Staphylococcus aureus at sub-lethal concentration such as their respective minimal inhibitory concentrations, 32 and 8 microg ml(-1), respectively.
  
  
  RESULTS
  Bacterial populations were studied by using transmission electron and fluorescence microscopy (TEM and FM), flow cytometry (FC) and ion-flux across the cellular membrane. Cell integrity was altered mainly in the outer membrane of S. typhimurium, but there was no significant change in the cytoplasm. However, in Staph. aureus, clear zones, abnormal septation and mesosome-like structures were observed in the cytoplasm. Bacterial populations were double-stained with propidium iodide (PI) and SYTO-13 for FC analysis. In S. typhimurium the proportion of damaged cells after 24 h was 97% and in Staph. aureus 56.3%. LAE induced transmembrane ion flux, the increase of potassium leakage after 30 min of contact was 7.7 and 3.34 microg ml(-1) for Staph. aureus and S. typhimurium, respectively. Membrane disruption was detected by measuring the proton flow across the membrane.
  
  
  CONCLUSIONS
  Disturbance in membrane potential and structural changes was caused by LAE, although cells were not disrupted.
  
  
  CONCLUSIONS
  This is the first time the cellular effects of LAE on bacterial cells were studied.
authors.affiliation: Laboratori de Microbiologia, Facultat de Farmacia, Universitat de Barcelona, Barcelona, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Rodríguez
authors.forename: J
authors.initials: J
authors.lastname: Seguer
authors.forename: X
authors.initials: X
authors.lastname: Rocabayera
authors.forename: A
authors.initials: A
authors.lastname: Manresa
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology*; D002462:Cell Membrane / Q000378:metabolism; D015169:Colony Count, Microbial; D005434:Flow Cytometry / Q000379:methods; D008826:Microbial Sensitivity Tests / Q000379:methods; D008854:Microscopy, Electron / Q000379:methods; D008856:Microscopy, Fluorescence / Q000379:methods; D011188:Potassium / Q000378:metabolism; D012486:Salmonella typhimurium / Q000187:drug effects* / Q000648:ultrastructure; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000648:ultrastructure
chemical_list: D000890:Anti-Infective Agents; C031371:N(alpha)-lauroylarginine ethyl ester; D001120:Arginine; D011188:Potassium