Biofilm Pyocyanin And Siderophore Production Of Commensal Pseudomonas Aeruginosa Isolates

Abstract

Pseudomonas aeruginosa (P. aeruginosa) has been one of the most concerned pathogens recently due to its high multidrug resistance rate. This bacterium can colonize humans and be a part of human normal flora, but it can take opportunity to cause infection when the host immune system weakens. The potential of those colonizing strains to cause disease in humans depends on their virulence factors. Therefore, this study aimed to analyze the virulence of colonizing/commensal P. aeruginosa isolates via accessing their ability to produce biofilm, pyocyanin, and siderophores. Simultaneously, algD-specific PCR was also tested to confirm the ability of algD target gene for quick commensal P. aeruginosa identification. To do this, twenty-nine P. aeruginosa-like isolates from healthy people were subjected to algDspecific PCR and confirmed by 16S rRNA sequencing. The confirmed P. aeruginosa isolates were then used for biofilm formation testing using crystal violet staining method, pyocyanin production testing using chloroform assay and siderophore testing using blue agar CAS method. Among twenty-nine P. aeruginosa–like isolates, 16 isolates were confirmed to be P. aeruginosa by using 16S rRNA sequencing. Interestingly, the algD-specific PCR was shown to be highly specific when all algD positive isolates are P. aeruginosa and its sensitivity was 93.75% (15/16). Regarding virulence testing results, 100% (16/16) of the isolates could generate biofilm, pyocyanin, and siderophores. Among sixteen commensal isolates, there were 25% (4/16) of weak, 56.25% (9/16) of moderate and 18.75% (3/16) of strong biofilm producers. The pyocyanin concentration ranged from 0.05 g/mL to 1.28 g/mL. In the siderophore testing, the average of the halo zone sizes was 1.31 ± 0.34 mm and 93.75% (15/16) of samples were weak siderophore producers. Furthermore, the virulence factor production (biofilm, pyocyanin, and siderophores) of the commensal P. aeruginosa isolates was significant lower than the clinical isolates from a previous study (p<0.05, Mann-Whitney U test). In conclusion, algD-specific PCR was confirmed as a useful tool to identify commensal P. aeruginosa isolates and even though the commensal isolates had the ability to produce biofilm, pyocyanin, and siderophores, their ability was lower than the clinical isolates.