## 3 Results and Discussion
### Antimicrobial Activity  
Previous studies showed that silver(I) metal complexes-based different \(N\)-heterocycles such as imidazole, 1,2,4-triazole and tetrazole were active against two strains including _Ps. aeruginosa_ and _S. aureus_ and more potent (ca. 4-8 folds) better than the silver nitrate (AgNO\({}_{3}\)) as positive control [58]. Also, silver(I)-imidazole and silver(I)-L-histidine polymer complexes were shown to have an equal potency of the studied microbial strains _S. aureus_ and _Ps. aeruginosa_ (MIC 15.7 and 12.5 \(\mu\)g/mL), on the other hands, silver(I)-1,2,3-triazole polymer complex had no effect on the bacteria [59]. Several examples of the silver metal complexes based on nicotine compounds have been explored by our research group previously [60], where [Ag(isonicotinamide)\({}_{2}\)-\(\mu\)-O,O'(NO\({}_{3}\))]\({}_{2}\) and [Ag2-\(\mu\)-O,O'(2-aminonicotinium)\({}_{2}\)-(NO\({}_{3}\))\({}_{2}\)]\({}_{n}\) exhibited a remarkable effect towards _Ps. aeruginosa_ with MIC ranged 2-8 \(\mu\)g/mL, another example for the silver metal complex such as [Ag(ethylnicotinate)\({}_{2}\)](NO\({}_{3}\)) showed against two strains including _S. aureus_ and _S. pyogenes_ (MIC = 4-16 and 2-4 \(\mu\)g/mL, respectively). [Ag(ethylisonicotinate)\({}_{2}\)(NO\({}_{3}\))], [Ag(methylisonicotinate)\({}_{2}\)(H\({}_{2}\)O)](NO\({}_{3}\)), and[Ag(ethylnicotinate)\({}_{2}\)](NO\({}_{3}\)) possessed high efficacy towards _P. mirabilis_ (MIC 1-16 \(\mu\)g/mL). Also, we have explored silver(I)-based pyridine complexes and the anti-microbial activity against _S. lutea_ and _M. lutea_, which provided interesting and promising results with the MIC = 2 and 4 \(\mu\)g/mL, respectively [44]. In this paper we introduced another group of silver(I) pyridine complexes with relatively high biological activity against a broad spectrum of MDR (multi drug resistance) and ATCC standard bacteria as well as the fungus _C. albicans_. The Minimum Inhibition Concentrations (MIC) of the tested compounds were tested and 17 antibiotics were used for the activity comparison. The detailed results are given in Table 2 and presented graphically in Figure 11. One of the advantages of this set of silver complexes is its broad-spectrum activity against MDR (multi drug resistance) bacteria isolated from diabetic foot ulcers as well as the ATCC standard bacteria with different action ranging from MIC = 4 \(\mu\)g/mL for compound **2** against _Ps. Aeruginosa_ to MIC = 64 \(\mu\)g/mL for compound **1** against _K. pneumoniae_ and _E. Coli_. An additional advantage of silver compounds is that they, in contrast with antibiotics in general, are active against fungi. Thus complexes **1**-**3** were active against the yeast _C. albicans_ (See Table 2). When looking to these data, we also need to consider the different silver contents of the three compounds. These being by weight 28% for **1**, 41% for **2** and 30% for **3**. The best action is for **2** against _Ps. Aeruginosa_ with MIC value of 4 \(\mu\)g/mL. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Metal/Ligand** & **1** & **2** & **3** \\ \hline
**Ag** & 0.6222 & 0.7284 & 0.6852 \\
**Py-ligand** & 0.1071 & 0.0762 & 0.1395 \\
**NO\({}_{3}\)** & \(-0.8365\) & \(-0.8046\) & \(-0.9642\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The net natural charges at ligand groups and Ag. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Antibiotic**} & \multicolumn{4}{c}{**Gram-Positive Bacteria**} & \multicolumn{4}{c}{**Gram-Negative Bacteria**} & \multicolumn{4}{c}{**Fungj**} \\ \cline{2-11}  & \multicolumn{4}{c}{**MIC**(gal)-**(gal)**} & \multicolumn{2}{c}{**Gram-**(gal)**} & \multicolumn{2}{c}{**Gram-**(gal)**} & \multicolumn{2}{c}{**Fungj**} \\ \cline{2-11}  & \multicolumn{4}{c}{**S. [PERSON]**} & \multicolumn{2}{c}{**M. Infors2**} & \multicolumn{2}{c}{**S. aurrows2**} & \multicolumn{2}{c}{**E. coli2**} & \multicolumn{2}{c}{**K. pneumoniae2**} & \multicolumn{2}{c}{**PJs. **} & \multicolumn{2}{c}{**_s. argmings2_**} & \multicolumn{2}{c}{**PJs.