Linezolid

Gentamicin sulfate (Fisiopharma, Salerno, Italy), Linezolid (Fresenius Kabi, Bad Homburg, Germany), and Vancomycin (Pharmatex, Milan, Italy) were used at a dose commonly used in clinical practice: 1 mg/mL, 2 mg/mL, and 5 mg/mL, respectively. Before the tubes' centrifugation, antibiotics were added to the fresh blood at increasing concentrations as described in the Table 1.Table 1

Information concerning antibiotic addition before PRF preparation

	Added volume (mL)	Total antibiotic amount (mg)
Control	–	–
Gentamicin 1 mg/mL
G1	0.25	0.25
G2	0.5	0.5
G3	0.75	0.75
G4	1	1
Linezolid 2 mg/mL
L1	0.25	0.5
L2	0.5	1
L3	0.75	1.5
L4	1	2
Vancomycin 5 mg/mL
V1	0.25	1.25
V2	0.5	2.5
V3	0.75	3.75
V4	1	5

Amoxicillin, ciprofloxacin, ofloxacin, clindamycin, cefotaxime, and piperacillin were purchased from Sigma (St. Gallen, Louis, MO, USA). Monohydrate cefepime dichlorhydrate was supplied from Gerda (Paris, France). Trihydrate meropenem and sodium cefoxitin were supplied from Panpharma (Fougères, France). Pentahydrate ceftazidime and sodium cefazolin were supplied from Mylan (Saint Priest, France). Ertapenem was supplied from MSD (Puteaux, France). Daptomycin was supplied from Medac SAS (Lyon, France). Aztreonam was supplied from Sanofi Aventis (Gentilly, France). Linezolid was supplied from Fresenius Kabi (Sevres, France). Internal standards (Amoxicillin-D₄, cefazolin-¹³C₂¹⁵N, meropenem-D₆, ofloxacin-D₈, ciprofloxacin-D₈, piperacillin-D₅, cefotaxime-D₃, and Linezolid-D₃) were purchased from TRC (Toronto, ON, Canada). Acetonitrile, methanol, formic acid, and water, all LC-MS hypergrade for mobile phase, were obtained from Biosolve (Dieuze, France). Plasma was purchased from the French Blood Bank (“Etablissement Français du Sang”, EFS, Reims, France).