A potential role of extracellular DNA in biofilm and ciprofloxacin resistance

Objectives: This study aims to broaden our knowledge of the role of eDNA in bacterial biofilms and antibiotic-resistance gene transfer among isolates. Methods: Staphylococcus aureus, E. coli, and Pseudomonas aeruginosa were isolated from different non-repeated 170 specimens. The bacterial isolates were identified using morphological and molecular methods. Different concentrations of genomic DNA were tested for their potential role in biofilms formed by study isolates employing microtiter plate assay. Ciprofloxacin resistance was identified by detecting a mutation in gyrA and parC. Results: The biofilm intensity significantly decreased (P < 0.05) concerning S. aureus isolates and insignificantly (P > 0.05) concerning E. coli isolates. Yet, one E. coli isolate's biofilm was significantly decreased (P < 0.05) linearly with increasing eDNA. Of considerable interest, the addition of eDNA led to a significant increase (P < 0.05) in the biofilm of the two-tested P. aeruginosa isolates. Moreover, eDNA participated in transferring Ciprofloxacin resistance to the sensitive isolate when it presents in its biofilm. Conclusion: eDNA has a dual effect on bacterial biofilms either supportive or suppressive following bacterial species per se. Also, it seems to play an important role in antibiotic resistance within the biofilm.