Moving microcapillary antibiotic susceptibility testing (mcAST) towards the clinic: unravelling kinetics of detection of uropathogenic E. coli, mass-manufacturing and usability for detection of urinary tract infections in human urine.

Sarah H. Needs, Jeremy Pivetal, Jessica Hayward, Stephen P. Kidd, Ho Yin Lam, Tai Diep, Kiran Gill, Martin Woodward, Nuno M. Reis, Alexander D. Edwards

Research output: Contribution to journalArticlepeer-review

3 Citations (SciVal)

Abstract

Innovation in infection based point-of-care (PoC) diagnostics is vital to avoid unnecessary use of antibiotics and the development of antimicrobial resistance. Several groups including our research team have in recent years successfully miniaturised phenotypic antibiotic susceptibility tests (AST) of isolated bacterial strains, providing validation that miniaturised AST can match conventional microbiological methods. Some studies have also shown the feasibility of direct testing (without isolation or purification), specifically for urinary tract infections, paving the way for direct microfluidic AST systems at PoC. As rate of bacteria growth is intrinsically linked to the temperature of incubation, transferring miniaturised AST nearer the patient requires building new capabilities in terms of temperature control at PoC, furthermore widespread clinical use will require mass-manufacturing of microfluidic test strips and direct testing of urine samples. This study shows for the first-time application of microcapillary antibiotic susceptibility testing (mcAST) directly from clinical samples, using minimal equipment and simple liquid handling, and with kinetics of growth recorded using a smartphone camera. A complete PoC-mcAST system was presented and tested using 12 clinical samples sent to a clinical laboratory for microbiological analysis. The test showed 100% accuracy for determining bacteria in urine above the clinical threshold (5 out of 12 positive) and achieved 95% categorical agreement for 5 positive urines tested with 4 antibiotics (nitrofurantoin, ciprofloxacin, trimethoprim and cephalexin) within 6 h compared to the reference standard overnight AST method. A kinetic model is presented for metabolization of resazurin, demonstrating kinetics of degradation of resazurin in microcapillaries follow those observed for a microtiter plate, with time for AST dependent on the initial CFU ml -1 of uropathogenic bacteria in the urine sample. In addition, we show for the first time that use of air-drying for mass-manufacturing and deposition of AST reagents within the inner surface of mcAST strips matches results obtained with standard AST methods. These results take mcAST a step closer to clinical application, for example as PoC support for antibiotic prescription decisions within a day.

Original languageEnglish
Pages (from-to)736-750
Number of pages15
JournalSensors & Diagnostics
Volume2
Issue number3
DOIs
Publication statusPublished - 3 May 2023

Bibliographical note

Funding Information:
This research was supported by the EPSRC (EP/L013983/1 and EP/R022410/1) and by the National Institute for Health and Care Research (NIHR) under its Invention for Innovation (i4i) Programme (Grant Reference Number NIHR203362). The views expressed are those of the authors and not necessarily those of the NIHR or the Department of Health and Social Care. We thank Simon Andrews, Wajiha Imtiaz and Zara Rafaque for the UPEC isolates which was supported by Higher Education Commission, Pakistan (Pin Number: 2BM2-093) and Commonwealth Scholarship Commission (CSC Ref# PKCN-2017-215).

Publisher Copyright:
© 2023 The Author(s).

ASJC Scopus subject areas

  • Chemistry (miscellaneous)
  • Analytical Chemistry

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