Use of the CTX-M and CTX-M Multi NG Biotech Tests in the development of new technologies to detect antibiotic resistance

Dr Lisa M Miller, Postdoctoral Research Associate, University of York

Written: 21.06.21

Our work is focused on the development of new technologies to detect antibiotic resistance. We work closely with clinicians at York Teaching Hospital NHS Trust with the goal of improving the diagnosis and treatment of complicated urinary tract infections (UTIs). Our research has covered a range of different testing platforms and more recently, we have been working on a rapid point-of-care test that can detect indicators of the more difficult-to-treat infections. By developing a lateral flow assay that can detect the extended spectrum β-lactamases (ESBLs) in a urine sample from a UTI patient, it would be possible to identify the more severe infections earlier and improve the treatment of these patients. By ensuring the prescription of an effective antibiotic, it would not only improve patient outcomes but also contribute towards preventing the rise in antibiotic resistance.

These ESBLs often present in multi-drug resistant infections, making them an excellent indicator of the more serious bacterial infections. As CTX-M-15 is one of the most common ESBLs, it was selected as part of our panel of enzymes for screening our new test. As part of a comparison with commercial products, we were interested in the CTX-M and CTX-M M NG Biotech tests available from UNA Health, which are able to detect this specific ESBL. The two tests are simple to use and provide clear readouts, as expected of a lateral flow assay. We tested both CTX-M and CTX-M M across a range of concentrations using pure, recombinant CTX-M-15 in the buffer provided with the test kits (Fig. 1 and 2). The detection of these tests was impressive, with positive test results observed even at the lowest concentration tested (1.2 fM). The coloured test lines were easier to observe by eye than shown in the photos.
These lateral flow assays were easy to use and provided clear readouts. In our experience, the use of these tests for confirming the presence of β-lactamase was preferable over the commonly used colourimetric test for β-lactamase activity (nitrocefin).

Fig. 1: CTX-M test results with CTX-M-15 across a concentration range of 1.2 μM – 1.2 fM, incremental serial dilutions of 10-fold shown left to right.

Fig. 2: CTX-M M test results with CTX-M-15 across a concentration range of 1.2 μM – 1.2 fM, incremental serial dilutions of 10-fold shown left to right.