(WHS-K1.04) PSEUDOMONAS AERUGINOSA ACTIVATES LASI/R QUORUM SENSING, SELECTIVE ANTIOXIDANT ENZYMES, AND TYPE VI SECRECTION SYSTEM DURING BIOFILM FORMATION AND CHRONIC WOUND INITIATION
Thursday, May 16, 2024
9:15 AM – 10:15 AM East Coast USA Time
Pseudomonas aeruginosa (PA) is an opportunistic pathogen frequently isolated from cutaneous chronic wounds. Some PA strains are highly virulent, establish strong biofilm and are antibiotic resistant. How PA colonizes chronic wounds with biofilm formation in response to oxidative stress (OS), is still unknown. The purpose of this study is to investigate the changes in gene expression when PA is challenged with high levels of OS, and how it increases virulence, decreases OS and becomes biofilm-forming in chronic wounds. We used a biofilm-forming PA strain isolated from the chronic wounds of our murine model and performed qPCR to obtain gene expression patterns as PA developed biofilm in vitro in the presence of high levels of OS and then verified the findings in vivo. We found that the planktonic bacteria while forming biofilm under OS conditions, overexpressed the Quorum Sensing genes lasI and lasR, rhlI, and rhlR, which are important for the bacteria to communicate with each other to form biofilm. We also found that the antioxidant stress genes sodA, sodB, katA, katB and oxyR important in reducing the OS in the microenvironment for survival, were also overexpressed. In addition, expression of biofilm formation genes such as pelA and pelB and pslA and pslB and virulent genes phzA and phzM for phenyzine production were increased. In vivo, we found that the levels of gene expression for quorum sensing, biofilm formation, and virulence were all upregulated during biofilm development. However, of the antioxidant genes, only oryR, katA and sodB were upregulated. To identify unique genes, we performed a broader transcriptomic analysis of PA using the RNAseq in vivo and identified the activation of novel genes/pathways of the Type VI Secretion Systems involved in PA pathogenicity. Several genes of the core secretion structure, including tssB and tssC, and phospholipase effector proteins, such as tli5, are significantly upregulated. PA is known to activate the Type VI Secretion System to compete with other bacteria in its microenvironment and target mammalian cells for infection. In conclusion, PA survives the harsh, high OS microenvironment present in chronic wounds and colonizes these wounds with biofilm by turning on virulent, biofilm-forming and survival genes. Therefore, effective biofilm removal and or return after debridement may be accomplished by disrupting the lasR system and/or sodA, katA and katB expression and potentially also the Type VI Secretion System. Because it is well known that biofilm in human chronic wounds readily returns after debridement, these findings could have implications for treatment of human chronic wounds to eliminate PA containing biofilm immediately after debridement.