# Selected Useful Properties of Polylactide Films Containing Nisaplin and Natamax
## 3 Results and Discussion
### Antibacterial Properties  
When analyzing polymer materials with altered properties, it is important to distinguish between two concepts, namely effectiveness and antibacterial activity. Antibacterial activity is a difference in the logarithm of the number of cells found on an antibacterial-treated product and an untreated product after inoculation and incubation of bacteria. Antibacterial effectiveness is the ability of an antibacterial agent to inhibit the growth of bacteria on the surface of materials treated with an antibacterial agent, as determined by the value of the antibacterial activity [32]. The biocidal properties of PLA films containing nisaplin and natamax are presented in Table 4.  
Bacteria are divided into two groups: Gram-negative and Gram-positive. This division is caused by differences in the structure of the cell wall; therefore, these bacteria have different effects, e.g., antibiotics, but also bacteriocins or other bactericidal substances. Gram (+)-bacteria do not have an outer cell membrane, and their wall is thicker and composed of a layer of peptidoglycans, which is murein. In Gram (\(-\))-bacteria, an outer cell membrane is present, and their cell wall is thinner because it contains fewer layers of murein. Both _Escherichia coli_ and _Pseudomonas aeruginosa_ are Gram-negative bacteria, while _Staphylococcus aureus_ is a Gram-positive bacterium. All bacterial strains used in the tests have recommendations from international standards that set the limits of the bactericidal \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample Description** & **Sample Description** & **R** & **\% Reduction** & **Antimicrobial Efficacy** \\ \hline \multirow{6}{*}{_E. coli_ (ATCC 8739P)_} & L & - & - & - \\  & LN0.2 & 1.2 & \textgreater{}90.0 & satisfactory \\  & LN0.6 & 1.4 & \textgreater{}90.0 & satisfactory \\  & LN1.0 & 1.9 & \textgreater{}90.0 & very good \\  & LN0.2 & 1.5 & \textgreater{}90.0 & satisfactory \\  & LX0.6 & 1.6 & \textgreater{}90.0 & satisfactory \\  & LX1.0 & 1.9 & \textgreater{}99.0 & very good \\ \hline \multirow{6}{*}{_S. aureus_ (ATCC 65388)} & L & - & - & - \\  & LN0.2 & 1.9 & \textgreater{}99.9 & very good \\  & LN0.6 & 2.0 & \textgreater{}99.9 & very good \\  & LN1.0 & 2.4 & \textgreater{}99.9 & very good \\  & LX0.2 & 2.1 & \textgreater{}99.9 & very good \\  & LX0.6 & 2.5 & \textgreater{}99.9 & very good \\  & LX1.0 & 2.7 & \textgreater{}99.9 & very good \\ \hline \multirow{6}{*}{_P. aeruginosa_ (ATCC 8739)} & L & - & - & - \\  & LN0.2 & 1.6 & \textgreater{}90.0 & satisfactory \\ \cline{1-1}  & LN0.6 & 1.6 & \textgreater{}90.0 & satisfactory \\ \cline{1-1}  & LN1.0 & 1.9 & \textgreater{}90.0 & very good \\ \cline{1-1}  & LX0.2 & 1.8 & \textgreater{}90.0 & satisfactory \\ \cline{1-1}  & LX0.6 & 2.1 & \textgreater{}99.9 & very good \\ \cline{1-1}  & LX1.0 & 2.3 & \textgreater{}99.9 & very good \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Antimicrobial activity of samples with nisaplin (LN0.2, LN0.6, LN1.0) and natamax (LX0.2, LX0.6, LX1.0) against pathogenic strains in relation to the control (L) [33]. properties of materials. Each strain is a human pathogen, and the most common strains occur in nosocomial infections. The differences obtained in the results of the antibacterial properties of the film may depend on the strain's membership in a given group, but also on the type of a given microorganism, as well as on the difference in the mechanism of action of bacteriocins, which may consist in attacking the bacterial cell wall or the membrane surrounding the bacteria, interfering with bacterial reproduction or blocking protein production by bacteria. The best antibacterial effect against _E. coli_, _S. aureus_, and _P. aeruginosa_ was observed for PLA films containing the highest concentration of nisaplin, i.e., for samples (LN1.0) and natamax (LX1.0). Interestingly, biocidal properties against _S. aureus_ were recorded for all samples with nisaplin (LN0.2, LN0.6, LN1.0) and for all samples with natamax (LX0.2, LX0.6, LX1.0).