The present invention relates to specific beta-lactone compounds and compositions thereof for the treatment of infections, such as, e.g., infections with bacteria or infections with protozoa, in particular infections with Gram-positive and/or Gram-negative bacteria and of infectious diseases caused by or related to Gram-positive and/or Gram-negative bacteria, and to the modulation of virulence of Gram-positive and/or Gram-negative bacteria or of protozoa by specific beta-lactone compounds. The invention further relates to the use of the compounds or compositions for preventing or eliminating biofilms.