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Forty-five derivatives of thiosemicarbazide were synthesized, and their antibacterial activity against Gram-positive and Gram-negative bacteria was evaluated. Some of the described compounds exhibited interesting activity against reference strains of Gram-positive bacteria, whereas only two derivatives had the ability to inhibit the growth of Gram-negative species (Escherichia coli ATCC 25922, Klebsiella pneumoniae ATCC 13883, Proteus mirabilis ATCC 12453). The most potent antimicrobial activity was observed in the cases of salicylic acid hydrazide derivatives. The differences in activity inspired us to conduct conformational analysis using molecular mechanics level. The obtained results suggest that the molecule geometry, especially at the N4-terminus of thiosemicarbazide skeleton, determines the antibacterial activity. Unfortunately, in opposition to what we expected, only one of the tested compounds inhibited the activity of the topoIV enzyme, and none of them was active against DNA gyrase.

In the present article, we describe the inhibitory potency of nine thiosemicarbazide derivatives against bacterial type IIA topoisomerases, their antibacterial profile and molecular modelling evaluation. We found that one of the tested compounds, compound 7, significantly inhibits activity of Staphylococcus aureus DNA gyrase with an IC50 below 15 μM. Besides, this compound displays antibacterial activity on reference Staphylococuss spp. and Enterococcus faecalis strains as well as clinical S. aureus isolates at non-cytotoxic concentrations in mammalian cells with MIC values ranging from 16 to 32 μg/mL thereby indicating, in some cases, equipotent or even more effective action than standard drugs such as vancomycin, ampicillin and nitrofurantoin. The computational studies showed that both molecular geometry and the electron density distribution have a great impact on antibacterial activity of thiosemicarbazide derivatives.

A series of 1,2,4-triazole-based compounds was designed as potential antibacterial agents using molecular hybridization approach. The target compounds (23-44) were synthesized by Mannich reaction of 1,2,4-triazole-3-thione derivatives with ciprofloxacin (CPX) and formaldehyde. Their potent antibacterial effect on Gram-positive bacteria was accompanied by similarly strong activity against Gram-negative strains. The toxicity of the CPX-triazole hybrids for bacterial cells was even up to 18930 times higher than the toxicity for human cells. The results of enzymatic studies showed that the antibacterial activity of the CPX-triazole hybrids is not dependent solely on the degree of their affinity to DNA gyrase and topoisomerase IV.

Urinary tract infections (UTI) are one of the common chronic and recurrent bacterial infections. Uropathogens which are able to form biofilm constitute a major etiological factor in UTI, especially among elder patients who are subject to long-term catheterization. It is caused by the capacity of the microorganisms for efficient and permanent colonization of tissues and also adhesion to diverse polymers used for urological catheter production such as propylene, polystyrene, silicone, polyvinyl chloride or silicone coated latex. Antibiotic therapy is the most common treatment for UTI. Fluoroquinolones, nitrofurans, beta-lactams, aminoglycosides, trimethoprim and sulfonamides are used predominantly. However, the biofilm due to its complex structure constitutes an effective barrier to the antibiotics used in the treatment of urinary tract infections. In addition, the growing number of multidrug resistant strains limits the usage of many of the currently available chemotherapeutic agents. Therefore, it seems important to search for new methods of treatment such as coating of catheters with non-pathogenic E. coli strains, the design of vaccines against fimbrial adhesive proteins of the bacterial cells or the use of bacteriophages.

In this work we reported the synthesis and evaluation of in vitro antimicrobial activities of hydrazones 6 obtained from 3-oxido-1H-imidazole-4-carbohydrazides 4. All new compounds were characterized by spectroscopic methods. Hydrazones 6 were tested for their in vitro antimicrobial activity against four Gram-positive and four Gram-negative strains of bacteria as well as one fungal species. Three of the tested compounds appeared to be promising agents against reference strains of Escherichia coli, Staphylococcus aureus and Staphylococcus epidermidis. They were also tested against twelve clinical isolates of S. aureus and their cytotoxic effect on murine fibroblasts and HeLa human tumor cell line was determined.

A series of 1,3,4-thiadiazoles and s-triazoles were subjected to Molinspiration, ALOGPS 2.1, and Osiris programs to predict their molecular properties that are important for drug candidates. Subsequently, all of them were docked into the active sites of enzymes namely glucosamine-6-phosphate synthase (GlcN-6-P), VIM-2 metallo-β- lactamase (VIM-2), chitinase A1 (ChiA1), and sterol 14 alpha-demethylase (CYP51) that were considered in antimicrobial studies of thiadiazole and s-triazole derivatives. Since all compounds fulfilled the criteria for good membrane permeability, oral bioavailability, low toxicity and the potential inhibitory activities towards VIM-2, ChiA1, and CYP51, most of them were synthesized and their antimicrobial activity has been tested.