Platelet rich fibrin (PRF) is a new therapy option for chronic wounds with yet unproven therapeutic efficacy. This randomised controlled trial aims to provide evidence of the efficacy of PRF as monotherapy as well as a growth promoting carrier matrix for antimicrobial compounds. The investigators therefore designed a four armed trial with three PRF arms which are compared to each other as well as to an active comparator. The treatment arms are as follows: Study arm 1: PRF with amikacin and teicoplanin Study arm 2: PRF with placebo (0.9% sodium chloride) Study arm 3: PRF with PHMB (polyhexanid) plus Macrogolol (Lavasorb®) Study arm 4: Acticoat 7® wound dressing as active control Patients with infected chronic wounds may be included in this trial. Infection shall be diagnosed by an experienced senior infectious diseases specialist. Patients with untreated peripheral vascular occlusive disease as defined by an ABI (ancle brachial index) of \< 0,7 are excluded from the trial as are patients with an uncontrolled diabetes mellitus or patients who have not received sufficient treatment for a diabetic foot syndrome. Any underlying illness will be treated following standard of care. In case of chronic venous insufficiency four-layered compression bandages will be applied each visit if tolerated by the patient. Alternatively compression stockings (Class III) are permitted. This is mentioned as Disease specific treatment in the protocol. Patients will receive treatment for 56 days. After 28 and 56 days the wound surface will be compared to the baseline. Infection parameters (c-reactive protein and leucocyte count) will be measured weekly. Evaluation of systemic antimicrobial therapy will be performed at each visit. Systemic antimicrobial therapy is started at the discretion of a senior infectious diseases specialist.