CeBiTec Colloquium
Monday, July 29th 2009, 17 c.t.
G2-104, CeBiTec building
Dr. Michael Hogardt
Max von Pettenkofer-Institut für Hygiene und Medizinische Mikrobiologie, Ludwig-Maximilians-Universität München
Phenotypic and genotypic characterization of Pseudomonas aeruginosa recovered from chronically infected wounds
P. aeruginosa is a common pathogen of chronic wound infections (WI) that are often associated with comorbid diseases such as diabetes mellitus and other vascular diseases. To expand our knowledge about the dynamics of P. aeruginosa wound infections, we systematically characterized 217 P. aeruginosa isolates from 74 patients suffering from chronically infected wounds with respect to pathogenicity, antimicrobial resistance patterns and their adaptation process during ongoing wound infection.
Interestingly, the majority of P. aeruginosa isolates were tested positive for virulence-associated traits (VATs), such as siderophores, pyocyanin, swimming motility, twitching motility, elastase and protease activity. Second the prevalence of exoU- and exoS gene was 36% and 64%, respectively. However, the expression of VATs was highly variable and while several outstanding high and low producers of VATs were found. These results correlated with a high variation in the cytotoxicity of P. aeruginosa wound isolates against J774 macrophages. Exceptional phenotypes were noted in the case of exoS-negative/exoU-positive isolates (typically highly cytotoxic) that exhibited only very low cytotoxicity and in case of exoS-positive /exoU-negative isolates that exhibited unusual high cytotoxicity. Moreover, among sequential and isogenic P. aeruginosa isolates, variants with decreased elastase production and loss-of-function mutations in the lasR gene occurred. Finally, the genotypic characterization of P. aeriginosa wound isolates using SNP-based P. aeruginosa genechips revealed that no dominant genotype occurred.
In summary, the characterization of P. aeruginosa isolates from chronically infected wounds (i) revealed a broad phenotypic and genotypic heterogeneity (ii) indicated that in particular the core genome determines the virulence potential of P. aeruginosa, and (iii) showed that during infection of chronic wounds virulence-attenuated and thus adapted variants of P. aeruginosa were selected.