## 3 Results
### Microbiology  
The results of the performed tests, as indicated in Table 1, show the potential antimicrobial activity of some of the obtained compounds, namely, **2**, **3**, **5**, **6**, **8**, **9**, and **14**-**16**, against tested microorganisms. In contrast, for compounds **4**, **7**, **10**, **11**, **12**, and **13**, no antimicrobial activity was found.  
Among the microorganisms that were taken into account in the evaluation of the activity of these substances, Gram-positive bacteria turned out to be the most sensitive. The tested compounds showed a similar effect to them, with the exception of hydrazide-hydrazone **15**. This compound had particular effectiveness. The minimum inhibitory concentration (MIC) of substance **15** which inhibited bacterial growth ranged from 1.95 ug/mL (for some _Staphylococcus_ spp.) to 15.62 ug/mL (for _Enterococcus faecalis_ ATCC 29212). This proves the strong or very strong activity of this substance against these microorganisms. The minimum bactericidal concentration (MBC) values of hydrazide-hydrazone **15**, which showed a lethal effect against Gram-positive bacteria, were in the range of 3.91-62.5 ug/mL. The MBC/MIC values for this hydrazide-hydrazone were within the range of 1-4, which indicates the lethal effect of this compound. The activity of compound **15** against the _Staphylococcus aureus_ strains ATCC 25923 and ATCC 43300 was twofold greater than the reference compound--nitrofurantoin. On the other hand, against the _S. aureus_ ATCC 6538 strain, the activity of this substance was seven times higher than for nitrofurantoin. Compound **15** also showed good activity in comparison to nitrofurantoin against strains of _S. epidermidis_ ATCC 12228 and _Microococcus luteus_ ATCC 10240--two and eight times greater, respectively.  
The remaining substances (**2**, **3**, **5**, **8**, and **16**) inhibited the growth of the bacterial strains at the concentrations of 250-1000 ug/mL. The minimum bactericidal concentrations that killed tested microbes were >1000 ug/mL. Compounds **6**, **9**, and **14** displayed similar ranges of activity against some Gram-positive bacteria (_Staphylococcus_ spp., _Bacillus subtilis_ ATCC 6633, and _M. luteus_ ATCC 10240), or not at all.  
Among Gram-negative bacteria, the antimicrobial effect was only demonstrated by compound **15** (MIC = 125-1000 ug/mL, MBC > 1000 ug/mL). _Escherichia coli_ ATCC 25922 was the most sensitive strain against this substance (MIC = 125 ug/mL). In contrast, _Pseudomonas aeruginosa_ ATCC 9027 did not have any sensitivity. Compound **2** was also found to have a weak effect against _Bordetella bronchiseptica_ ATCC 4617. No antibacterial effect was observed for the remaining Gram-negative rods. In relation to yeast-like fungi of the genus _Candidia_, a slight antifungal effect of compounds **2**, **3**, **5**, **8**, **15**, and **16** was demonstrated (weak or moderate antimycotic effect). The minimum fungicidal concentration (MFC) values of the tested substances exceeded 1000 \(\mathrm{\SIUnitSymbolMicro g}\)/mL. The _Candidia parapsilosis_ ATCC 22019 strain was the most sensitive to the tested substances (**2**, **3**, **5**, **8**, **15**, and **16**). The remaining compounds (**4**, **6**, **7**, and **9**-**14**) did not show an inhibitory effect on the growth of the fungi in the tested concentration ranges.