<div><p>Heptane (Hep), diethyl ether (Et<sub>2</sub>O), acetone (Me<sub>2</sub>CO) and methanolic (MeOH) extracts, as well as ( − )-usnic acid and squamatic acid, were obtained from thallus of <i>Cladonia uncialis</i> (Cladoniaceae). The antimicrobial activities of these extracts, ( − )-usnic acid and squamatic acid, were tested against reference strains: <i>Staphylococcus aureus</i>, <i>Escherichia coli</i> and <i>Candida albicans</i>. In addition, Me<sub>2</sub>CO extract was analysed against 10 strains of Methicillin-resistant <i>S. aureus</i> (MRSA) isolated from patients. All extracts exerted antibacterial activity against the reference strain <i>S. aureus</i>, comparably to chloramphenicol [minimum inhibitory concentration (MIC) = 5.0 μg/mL]. The Me<sub>2</sub>CO extract exhibited the strongest activity against <i>S. aureus</i> (MIC = 0.5 μg/mL), higher than ( − )-usnic acid, whereas squamatic acid proved inactive. The Me<sub>2</sub>CO extract showed potent antimicrobial activity against MRSA (MIC 2.5–7.5 μg/mL). Also no activity of <i>C. uncialis</i> extracts against <i>E. coli</i> and <i>C. albicans</i> was observed.</p></div
