Antimicrobial Adaptation in Uropathogenic Escherichia coli

Catheter-associated urinary tract infections (CAUTIs) make up the largest proportion of hospital acquired infections. Uropathogenic Escherichia coli (UPEC) are a major causative agent of CAUTI partially due to the bacteria’s ability to form biofilms on the catheter surface in addition to their extensive array of virulence factors that facilitate infection. Anti-infective coatings for urinary catheters are a promising strategy to prevent bacterial attachment and subsequent biofilm formation on the catheter thus helping to prevent CAUTI. Concerns have been raised that exposure to biocides may select for biocide resistant populations of bacteria in addition to promoting cross-resistance with third part agents such as antibiotics. This, in addition to further concerns over biocide cytotoxicity, has led to the search for alternative anti-infective coating agents that exhibit long-term antimicrobial activity and low-level cytotoxicity. Quorum sensing inhibitors (QSIs) have emerged as potential candidates to prevent such biofilm associated infections, however the long-term effects of QSIs and biocides in uropathogens is poorly understood. In this investigation, the impact of repeated exposure of eight UPEC strains to four biocides (PHMB, triclosan, BAC, silver nitrate) and three QSIs (cinnamaldehyde, furanone C30 and F-DPD) were evaluated. Antimicrobial susceptibility in planktonic (MIC and MBC) and biofilm (MBEC) states were determined before and after repeated exposure to each antimicrobial. Changes in pathogenicity were assessed in a Galleria mellonella waxworm model and through the use of cell invasion assays (SMC and HUEPC cell lines). Antimicrobial activity and cytotoxicity of antimicrobial impregnated polymers was assessed via inhibition assays and through agar overlay tests. After the initial assessment, the sol gel coating was determined to have the highest biocompatibility, and was assessed for antimicrobial activity in a continuous culture drip-flow biofilm reactor. In an attempt to understand the mechanisms that govern antimicrobial adaptation in UPEC, strain EC958 was subjected to full genome and RNA-sequencing and differential expression gene analysis. The results of these experiments show the multiple and varied effects that occur after exposure to broad-spectrum antimicrobials must be taken into consideration when developing a new antimicrobial coating as these effects have impacts on resistance, virulence, biofilm formation, and antibiotic resistance.