Paraoxonase and acylated homoserine lactones in urine from patients with urinary tract infections--relationship to microbial diversity by 16S rRNA gene sequencing

Paraoxonase (PON) comprises a trio of mammalian enzymes that have been reported to have a number of roles including the inhibition of bacterial virulence and biofilm formation by microorganisms that quorum sense with acylated homoserine lactones (AHLs). PON have previously been reported to inhibit P. aeruginosa biofilm formation in mammalian airways and skin. An innate immune role for PON in urinary tract infection has not previously been reported. We performed western blots for PON1 in urine from patients with urinary tract infection (UTI), and also tested UTI urine for the presence of AHLs using a cellular reporter system. Urine sample microbiota was assessed through sequencing of the 16S rRNA marker gene. We report here that PON1 was not found in the urine of control subjects, however, in patients with UTI, PON1 was associated with the presence of E. coli in urine. AHLs, but not PON, were found in the bulk urine of those with P. aeruginosa UTI. Microbial consortia of PON positive UTI urine was found to be distinct from PON negative UTI urine; differentially over-represented bacteria in PON positive samples included a number of environmental opportunists. We hypothesize that PON may inhibit the quorum sensing activity of AHLs in UTI, as has previously described in skin and airways.

Efficacy of Synthetic Furanones on Listeria monocytogenes Biofilm Formation

Furanones are analogues of acylated homoserine lactones with proven antifouling activity in both Gram-positive and Gram-negative bacteria though the interference of various quorum sensing pathways. In an attempt to find new strategies to prevent and control Listeria monocytogenes biofilm formation on stainless steel (SS) surfaces, different concentrations of six synthetic furanones were applied on biofilms formed by strains isolated from food, environmental, and clinical sources grown onto AISI 316 SS coupons. Among the furanones tested, (Z-)-4-Bromo-5-(bromomethylene)-2(5H)-furanone and 3,4-Dichloro-2(5H)-furanone significantly (p < 0.05) reduced the adhesion capacity (>1 log CFU cm−2) in 24 h treated biofilms. Moreover, individually conducted experiments demonstrated that (Z-)-4-Bromo-5-(bromomethylene)-2(5H)-furanone was able to not only significantly (p < 0.05) prevent L. monocytogenes adhesion but also to reduce the growth rate of planktonic cells up to 48 h in a dose-dependent manner. LIVE/DEAD staining followed by epifluorescence microscopy visualisation confirmed these results show an alteration of the structure of the biofilm in furanone-treated samples. Additionally, it was demonstrated that 20 µmol L−1 of 3,4-Dichloro-2(5H)-furanone dosed at 0, 24 and 96 h was able to maintain a lower level of adhered cells (>1 log CFU cm−2; p < 0.05). Since furanones do not pose a selective pressure on bacteria, these results represent an appealing novel strategy for the prevention of L. monocytogenes biofilm grown onto SS.

Paraoxonase and acylated homoserine lactones in urine from patients with urinary tract infections

Paraoxonases are mammalian enzymes that have a number of roles including the inhibition of bacterial virulence and biofilm formation by microorganisms that quorum sense with acylated homoserine lactones. Paraoxonases have previously been reported to inhibit P. aeruginosa biofilm formation in mammalian airways and skin. An innate immune role for paraoxonases in urinary tract infection has not previously been reported. We performed western blots for paraoxonase1 in urine from patients with urinary tract infection; we also tested urinary tract infection urine for the presence of acylated homoserine lactones using a cellular reporter system. We report here that paraoxonase1 was not found with our western blot assay in the urine of normal control patients; in those with urinary tract infection, paraoxonase1 was associated with E. coli UTI. Acylated homoserine lactones, but not paraoxonases, were found in the bulk urine of those with P. aeruginosa urinary tract infection. We hypothesize that paraoxonase may play a similar innate immune role in infected urine as has previously described in skin and airways.

Petunidin as a competitive inhibitor of acylated homoserine lactones in Klebsiella pneumoniae

Most of the bacterial species communicate with each other through a mechanism called Quorum Sensing (QS) to regulate their phenotypic characteristics.