## 3 Results and Discussion
### Virulence of P. aeruginosa Isolated from Pre-Columbian Textiles  
Of the virulence-related parameters of _P. aeruginosa_, eight were examined for two _P. aeruginosa_ strains isolated from the pre-Columbian textiles: biofilm formation on glass and polypropylene; pyocyanin production; proteolytic activity toward albumin, mucin, fibrinogen, and casein, and hemolysis. The antibiogram test was also performed to ascertain their susceptibility to seven different antimicrobial agents. The environmental strains KP842564 and KP842565 showed a strong ability to form biofilms on glass and polypropylene (\(2.8\times 10^{8}\)-\(5.3\times 10^{8}\) CFU/cm\({}^{2}\)). Polypropylene was colonized by _P. aeruginosa_ KP842565 and the clinical strain more intensively than glass, while biofilm formation by KP842564 was the same on both surfaces (\(4.1\times 10^{8}\) CFU/cm\({}^{2}\)). Although the strains isolated from the textiles showed good ability to inhabit both tested abiotic surfaces, the formation of biofilms was only statistically comparable to that of the clinical isolate on glass (Table 2). The ability to form biofilm on both abiotic (e.g., polystyrene, polypropylene, silicone, glass) and biotic (e.g., tissue) surfaces is one of the virulence factors known to be directly related to the pathogenicity of _P. aeruginosa_[5]. Biofilm formation confers significant resistance to antimicrobials and \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Feature**} & \multicolumn{3}{c}{**Environmental Strains**} & \multirow{2}{*}{**Clinical Strain**} \\ \cline{2-2} \cline{4-5}  & & **KP842564** & & **KP842565** \\ \hline Virulence-related & & & & \\ parameters & & & & \\ \hline Biofilm formation (log & polypropylene & \(8.6\pm 0.4\)a & \(8.7\pm 0.3\)a & \(9.2\pm 0.4\) \\ (CFU/cm\({}^{2}\))) \(\pm\) SD & glass & \(8.6\pm 0.5\)b & \(8.4\pm 0.6\)b & \(8.9\pm 0.4\) \\ \hline Pyocyanin production (\(\upmu\)g/mL) \(\pm\) SD & \(1.09\pm 0.3\)a & \(0.39\pm 0.2\)a & \(8.48\pm 0.8\) \\ \hline Proteolytic & bovine serum albumin & \(16.4\pm 1.1\)a & \(0\)a & \(20.8\pm 0.4\) \\ activity—decreased & mucin & \(22.0\pm 0.7\)a & \(0\)a & \(25.6\pm 0.5\) \\ wettability zone (mm) \(\pm\) SD & fibrinogen & \(12.6\pm 1.7\)a & \(0\)a & \(17.6\pm 1.1\) \\ casein & \(14.4\pm 0.5\)a & \(0\)a & \(19.6\pm 1.1\) \\ \hline Hemolytic index \(\pm\) SD & & \(1.50\pm 0.07\)b & \(1.46\pm 0.05\)b & \(1.41\pm 0.09\) \\ \hline  & amikacin & 23/S & 28/S & 22/S \\ Susceptibility to & imipenem & 33/S & 32/S & 27/S \\ anticribals—inhibition & cefepime & 34/S & 31/S & 11/R \\ zone (mm)/category * & ciprofloxacin & 37/S & 33/S & 33/S \\ zone (mm)/category * & azrenam & 27/S & 25/S & 0/R \\ polymorph B & 12/S & 16/S & 0/R \\ piperacillin—tazobactam & 22/S & 21/S & 20/I \\ \hline Additional features & & & & \\ \hline Biofilm on archeological & after 3 days & \(5.8\pm 0.5\) & \(8.7\pm 0.8\) & nd \\ textile (log (CFU/cm\({}^{2}\))) & after 5 days & \(6.8\pm 0.6\) & \(8.6\pm 0.7\) & nd \\ \hline Sequence homology of 16S rRNA to the clinical strain (\%) & 99.7 & 99.5 & – \\ \hline SD—standard deviation;a statistically significant difference in comparison to clinical _P. aeruginosa_ (\(p<0.05\));b no statistically significant difference in comparison to clinical _P. aeruginosa_;c category: S—susceptible, I—intermediate, R—resistant; nd—not determined. & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Characteristics of the clinical strain of _P. aeruginosa_ and the environmental strains isolated from archeological textiles. components of the host immune system, making biofilm-based infections a significant clinical problem. Furthermore, there is increasing evidence that biofilm-mediated infection facilitates the development of chronic and recurring infectious diseases [1,2] ([PERSON], 2009; [PERSON] et al., 2009). In this context, the ability of _P. aeruginosa_ strains originating from textiles to colonize glass and polypropylene is of major importance. Among the arsenal of virulence factors produced by _P.