title: Activity of Norspermidine on Bacterial Biofilms of Multidrug-Resistant Clinical Isolates Associated with Persistent Extremity Wound Infections.
abstract: Biofilm formation is a major virulence factor for numerous pathogenic bacteria and is cited as a central event in the pathogenesis of chronic human infections, which is in large part due to excessive extracellular matrix secretion and metabolic changes that occur within the biofilm rendering them highly tolerant to antimicrobial treatments. Polyamines, including norspermidine, play central roles in bacterial biofilm development, but have also recently been shown to inhibit biofilm formation in select strains of various pathogenic bacteria. The aim of this study was to evaluate in vitro the biofilm dispersive and inhibitory activities of norspermidine against multidrug-resistant clinical isolates of Acinetobacter baumannii(n = 4), Klebsiella pneumoniae (n = 3), Pseudomonas aeruginosa (n = 5) and Staphylococcus aureus (n = 4) associated with chronic extremity wound infections using the semi-quantitative 96-well plate method and confocal laser microscopy. In addition to the antibiofilm activity, biocompatibility of norspermidine was also evaluated by measuring toxicity in vitro to human cell lines and whole porcine tissue explants using MTT viability assay and histological analysis. Norspermidine (5-20 mM) had variable dispersive and inhibitory activity on biofilms which was dependent on both the strain and species. Of the clinical bacterial species evaluated herein, A. baumannii isolates were the most sensitive to the effect of norspermidine, which was in part due to the inhibitory effects of norspermidine on bacterial motility and expression of genes involved in the production of homoserine lactones and quorum sensing molecules both essential for biofilm formation. Importantly, exposure of cell lines and whole tissues to norspermidine for prolonged periods of time (≥24 h) was observed to reduce viability and alter tissue histology in a time and concentration dependent manner, with 20 mM exposure having the greatest negative effects on both tissues and individual cell lines. Collectively our findings demonstrate that, similar to other polyamines, norspermidine displays both inhibitory and dispersive activities on biofilms of clinical multidrug-resistant bacterial isolates, in particular for strains of A. baumannii. Additionally our findings suggest that direct application may be considered on tissues, albeit for limited exposure times.
authors.affiliation: Infectious Disease Service, Department of Medicine, San Antonio Military Medical Center, JBSA Fort Sam Houston, San Antonio, TX, USA.
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Cardile
authors.affiliation: Extremity Trauma and Regenerative Medicine Task Area, United States Army Institute of Surgical Research, JBSA Fort Sam Houston, San Antonio, TX, USA.
authors.forename: Ronald L
authors.initials: RL
authors.lastname: Woodbury
authors.affiliation: Extremity Trauma and Regenerative Medicine Task Area, United States Army Institute of Surgical Research, JBSA Fort Sam Houston, San Antonio, TX, USA.
authors.forename: Carlos J
authors.initials: CJ
authors.lastname: Sanchez
authors.affiliation: Extremity Trauma and Regenerative Medicine Task Area, United States Army Institute of Surgical Research, JBSA Fort Sam Houston, San Antonio, TX, USA.
authors.forename: Sandra C
authors.initials: SC
authors.lastname: Becerra
authors.affiliation: Extremity Trauma and Regenerative Medicine Task Area, United States Army Institute of Surgical Research, JBSA Fort Sam Houston, San Antonio, TX, USA.
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Garcia
authors.affiliation: Infectious Disease Service, Department of Medicine, San Antonio Military Medical Center, JBSA Fort Sam Houston, San Antonio, TX, USA.|Infectious Disease Clinical Research Program, Department of Preventive Medicine and Biostatistics, Uniformed Services University of the Health Sciences, Bethesda, MD, USA.
authors.forename: Katrin
authors.initials: K
authors.lastname: Mende
authors.affiliation: Extremity Trauma and Regenerative Medicine Task Area, United States Army Institute of Surgical Research, JBSA Fort Sam Houston, San Antonio, TX, USA.
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Wenke
authors.affiliation: Infectious Disease Service, Department of Medicine, San Antonio Military Medical Center, JBSA Fort Sam Houston, San Antonio, TX, USA. kevin.s.akers.mil@mail.mil.|Extremity Trauma and Regenerative Medicine Task Area, United States Army Institute of Surgical Research, JBSA Fort Sam Houston, San Antonio, TX, USA. kevin.s.akers.mil@mail.mil.
authors.forename: Kevin S
authors.initials: KS
authors.lastname: Akers
mesh_terms: D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000502:physiology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects*; D024901:Drug Resistance, Multiple, Bacterial; D006801:Humans; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000502:physiology; D053038:Quorum Sensing / Q000187:drug effects; D013095:Spermidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000502:physiology; D014946:Wound Infection / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; C006760:norspermidine; D013095:Spermidine
keywords: Biofilm dispersal; Biofilm inhibition; Norspermidine; Polyamine; Wound infection