## 1 Introduction  
Antibiotics have been one of the most dynamically developing groups of medicines of the last decade [1]. The first use of an antibiotic (penicillin) in the early 20 th century became a landmark in treating infections. Thanks to this, it was possible to reduce the mortality and the risk of postinfectious complications [2]. Unfortunately, as a result of the common use of penicillin, a strain of _Staphylococcus aureus_ bacterium appeared, which produced the penicillin enzyme, giving it resistance to penicillin [3]. In response to this fact, newer antibiotics were introduced as treatments. Additionally, strains of bacteria resistant to these new antibacterial agents were also isolated [4]. This was an important signal that the golden age antibiotics would not last forever. This century has seen that the problem of antibiotic resistance poses a real threat to patients and global public health [5]. Alarm pathogens are particularly dangerous due to therapeutic limitations. These include multidrug-resistant pathogens (MDR), extended resistance pathogens (XDR), as well as pathogens resistant to all available antibacterial drugs (PDR) [6, 7]. This group includes extremely virulent strains of methicillin-resistant _S. aureus_ (MRSA) [3, 8, 9]. This etiological agent is thought to be one of the most common causes of life-threatening infections in palliative care facilities and during inpatient treatment [10]. This problem has been noticed by key institutions and global and European public health organizations [1]. The EAAD (European Antibiotic Awareness Day) and the WAAW (World Antibiotic Awareness Week) information campaigns, organized by the European Centre for Disease Prevention and Control (ECDC) and the World Health Organization (WHO), aim to raise awareness of global antimicrobialresistance and encourage general public healthcare professionals to follow best practices to avoid the further emergence and spread of drug-resistant infections [11].  
Among chemotherapeutic, we can find compounds which contain the hydrazide-hydrazone moiety in their chemical structure (i.e., nitrofurazone, furazolidone, and nitrofurantoin) [12] (Figure 1). As can be seen from the literature review, the compounds with an azomethine group (-NH-N=CH-) show a significant and broad spectrum of bioactivity, mainly antibacterial [13; 14; 15; 16; 17; 18; 19; 20], antifungal [21], antitubercular [22], antimycobacterial [23], anticancer [24; 25; 26; 27], anti-inflammatory [28], anticonvulsant [29], and antiviral activity [30]. Several previously published articles by our research team proved that hydrazide-hydrazones can exhibit significant antimicrobial and anticancer activity [12; 31; 32; 33; 34; 35]. The method of synthesis that allowed us to obtain hydrazide-hydrazones with good yields was described in our previous articles: the condensation of hydrazide with an appropriate aldehyde in an ethyl alcohol environment [32; 34; 35].  
The 1,2,3-thiadiazole moiety also has great potential for designing new molecules with potential antimicrobial activity [36; 37]. In the work of [PERSON] et al., the biological activities of a series of new 1\(\beta\)-methylcarbapenems were compared. Among the tested compounds, the 1,2,3-thiadiazole derivative showed the strongest antibacterial activity and advanced pharmacokinetics in rats compared with other five-membered and six-membered derivatives [37].  
We assumed that the combination of these two pharmacophores--the hydrazide-hydrazone and 1,2,3-thiadiazole moieties--could have a beneficial biological effect.  
Based on the results obtained so far and on literature reports on the biological potential of hydrazide-hydrazones, in this study, we synthesized novel compounds in order to obtain substances with significant antimicrobial activity.