title: Antimicrobial/anti-biofilm activity of expired blood platelets and their released products.
abstract: BACKGROUND
  Although platelets are not part of the classical immune system, they have many features that indicate their role in the anti-infective host defense. They come into interactions with microorganisms, which results in co-aggregation and co-adhesion or destruction of the microbes due to the action of antimicrobial peptides released from platelets.The aim of this study was to evaluate the killing effect of platelets against planktonic and biofilm cultures of Staphylococcus aureus and to test their synergy with antibiotics.
  
  
  METHODS
  S. aureus ATCC 29213; platelet rich plasma (1-3 days post shelf life). Evaluation of bactericidal activity of platelets or their lysates against planktonic cultures of S. aureus--CFU calculation after 4- and 24-hour co-incubation. Assessment of S. aureus biofilm viability under the influence of platelets--Live/Dead® BacLight™ Bacterial Viability Kit. Determination of minimum inhibitory concentrations (MICs) (oxacillin, vancomycin, linezolid) and estimation of the synergistic action of antibiotics and platelet lysates--a gradient-diffusion test strip.
  
  
  RESULTS
  Microbicidal activity of "expired" platelets and their lysates has been shown as a significant reduction in the population of staphylococci in their planktonic cultures by 56-87% and a decrease in metabolic activity of biofilm formation by 7-38%. These activities were enhanced after activation with ADP. Platelet lysates showed a synergistic effect with β-lactam antibiotic (oxacillin) and glycopeptide (vancomycin) but not with oxazolidinone (linezolid).
  
  
  CONCLUSIONS
  In summary, platelets even after the medical expiry date are still a good source of antimicrobial low molecular weight proteins (PMPs). Testing of bacterial resistance to PMPs may be advisable as a predictive indicator of susceptibility to treatment of infections such as infective endocarditis and other local infections of biofilm nature.
authors.affiliation: Department of Haemostatic Disorders, Medical University of Łódź, Łódź, Poland.
authors.forename: Marcin I
authors.initials: MI
authors.lastname: Różalski
authors.forename: Bartłomiej
authors.initials: B
authors.lastname: Micota
authors.forename: Beata
authors.initials: B
authors.lastname: Sadowska
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Paszkiewicz
authors.forename: Marzena
authors.initials: M
authors.lastname: Więckowska-Szakiel
authors.forename: Barbara
authors.initials: B
authors.lastname: Różalska
mesh_terms: D000081:Acetamides / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000890:Anti-Infective Agents / Q000494:pharmacology; D018441:Biofilms; D001792:Blood Platelets / Q000276:immunology*; D004697:Endocarditis, Bacterial / Q000188:drug therapy / Q000276:immunology / Q000382:microbiology; D006801:Humans; D000069349:Linezolid; D008826:Microbial Sensitivity Tests; D010068:Oxacillin / Q000494:pharmacology; D023303:Oxazolidinones / Q000494:pharmacology; D013203:Staphylococcal Infections / Q000188:drug therapy* / Q000276:immunology* / Q000382:microbiology; D013210:Staphylococcus / Q000187:drug effects; D013211:Staphylococcus aureus / Q000187:drug effects; D014640:Vancomycin / Q000494:pharmacology; D001620:beta-Thromboglobulin / Q000276:immunology*
chemical_list: D000081:Acetamides; D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D023303:Oxazolidinones; C061615:PPBP protein, human; D001620:beta-Thromboglobulin; D014640:Vancomycin; D000069349:Linezolid; D010068:Oxacillin