What Are the Optimal Irrigating Wound Vacuum Parameters When Using Bacteriophage Therapeutics?

<b><i>Objective:</i></b> Bacteriophages are promising adjuvant anti-biofilm agents. Yet novel ways to repeatedly administer bacteriophages in vivo are needed. One technique utilizes irrigating wound vacuum systems. However, the proper parameters to use with bacteriophages are poorly defined. Therefore, the objective of this study was to elucidate proper bacteriophage irrigating vacuum parameters. <b><i>Methods:</i></b> Individual <i>Pseudomonas aeruginosa</i> and <i>Staphylococcus aureus</i> clinical isolates were allowed to form biofilms in microwell plates and then exposed to repeated irrigations with saline or with bacteriophages over 8 hours. The repeated irrigations corresponded to theoretical different dwell times of the irrigating vacuum system. Residual biofilm mass was compared among groups by staining with crystal violet and measuring optical density. <b><i>Results:</i></b> As the number of saline irrigations increased, there was less biofilm burden, and this was substantially less than growth controls (p < 0.05). When compared with saline, bacteriophages substantially reduced biofilms except for the <i>P. aeruginosa</i> bacteriophage at dwell times of 20 minutes. Furthermore, bacteriophages caused no observable colony forming units per milliliter for all dwell times except 20-minute dwell times, and this was statistically significant (p < 0.05) when compared with saline infusions. <b><i>Conclusions:</i></b> Frequent irrigation with shorter dwell times facilitates biofilm disruption and reduces bacterial burden. However, if dwell times are too short, bacteriophages may not have sufficient time to hydrolyze biofilm and to infect and kill bacteria. On the basis of our model, we propose a minimum of 1 hour dwell time but appreciate that more translational research is needed to refine these approaches.