Determination of antibiotic susceptibility of the bacteria causing urinary tract infections using a novel lab-on-a-chip design

Crane, Benjamin (2023) Determination of antibiotic susceptibility of the bacteria causing urinary tract infections using a novel lab-on-a-chip design. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Urinary tract infections (UTIs) are one of the most common types of bacterial infection in the UK, and also are expensive to treat costing the National Health Service ~£54 million between 2016 and 2017. Culture-based antibiotic susceptibility testing (AST) is used to identify an antibiotic to treat drug-resistant urinary tract infections and takes 48 hours to complete. Faster prescription of effective antibiotics should reduce the risk of sepsis and poor clinical outcomes. To address this need, we developed a Lab-on-a-Chip (LOC) based method to conduct electrochemical AST using screen-printed macroelectrodes (SPEs) and antibiotic-loaded hydrogels. SPEs were fabricated using carbon-graphite based inks, with resazurin bulk modified SPEs (R-SPEs) being fabricated through modification of the SPEs WE. Polyvinyl alcohol (PVA) based hydrogels were loaded with the following antibiotics were used; cephalexin, ceftriaxone, colistin, gentamicin, piperacillin, trimethoprim and vancomycin as well as an antibiotic-free control. LOC devices were then designed to encapsulate both the R-SPEs and the antibiotic hydrogels to enable multiplexed electrochemical AST to occur on a single device. In the initial testing of the R-SPEs and the antibiotic hydrogels independently of a LOC device, antibiotic susceptibility could be determined in 90 minutes for E. coli. After the preliminary work, eight chambered LOC devices were spiked with simulated UTI samples. Each chamber contained an R-SPE and an antibiotic hydrogel. After an incubation step, susceptibility of Escherichia coli and Klebsiella pneumoniae could be established in 85 minutes of testing which is significantly faster than the 48 hours required for conventional culture-based AST. The sensitive detection of resazurin afforded by using the electrochemical detection methodology incorporated onto a LOC device described here offers an inexpensive and simple method for the determination of antibiotic susceptibility that is faster than using a culture-based approach.