Antibiotic resistance acquired by various bacterial fungal and viral pathogens poses therapeutic
problems of increasing severity. Among the infections that are very difficult to treat, biofilm-associated
cases are one of the most hazardous. Complex structure of a biofilm and unique physiology of the biofilm
cells contribute to their extremely high resistance to environmental conditions, antimicrobial agents and
the mechanisms of host immune response. Therefore, the biofilm formation, especially by multidrugresistant
pathogens, is a serious medical problem, playing a pivotal role in the development of chronic and
recurrent infections. These factors create a limitation for using traditional chemiotherapeutics and contribute
to a request for development of new approaches for treatment of infectious diseases. Therefore, early
reports on antimicrobial activity of several complexes of metal ions, bearing thiosemicarbazide or
thiosemicarbazones as the ligands, gave a boost to worldwide search for new, more efficient compounds
of this class, to be used as alternatives to commonly known drugs. In general, depending on the presence
of other heteroatoms, these ligands may function in a di-, tri- or tetradentate forms (e.g., of N,S,-, N,N,S-,
N,N,N,S-, N,N,S,S-, or N,S,O-type), which impose different coordination geometries to the resultant complexes.
In the first part of this review, we describe the ways of synthesis and the structures of the ligands
based on the thiosemicarbazone motif, while the second part deals with the antimicrobial activity of their
complexes with selected metal ions.