- Pseudomonas aeruginosa bacteria are common pathogens that are difficult to treat and are therefore critical to diagnose early when involved in infections.
- The commonly used method for confirming a P. aeruginosa infection is cultural inoculation, which takes 2-3 days to yield results.
- 2-Aminoacetophenone (2-AA) is a volatile substance produced by P. aeruginosa bacteria in high concentrations. Detection of 2-AA using mass spectrometry has proven successful, but the expensive equipment and highly trained personnel involved make this method impractical in the clinic.
- We determined through experiments and in silico docking analysis that there is a binding site between 2-AA and a native LuxR receptor from Vibrio fischeri. Based on this knowledge, we set out to create a biosensor using E. coli harbouring a plasmid encoding LuxR and a reporter luciferase for bioluminescence.
- Through mutagenesis we found a LuxR variant with three amino acids mutated (termed m22). It shows improved binding with 2-AA, yielding a higher specificity (preventing false positives) and a lower detection limit.
- We have designed a prototype device for detecting P. aeruginosa in pus samples using this novel biosensor. It is made of three primary components: a simple plastic tube containing the sample, a cap containing the E. coli-based biosensor, and a bioluminescence detector above the cap. These components are enclosed in a light-sealed aluminium capsule.
- Our device allows inexpensive detection of P. aeruginosa infection in a matter of hours.
- Initial tests with pus from otitis externa (outer ear infections) yielded correct diagnosis in 25/26 cases (7 positive, 17 negative). Only one false negative was reported, which can likely be attributed either to contamination (in the culture used for comparison) or to a rare P. aeruginosa variant that produces less 2-AA.
- Other infections of head and neck origin were correctly detected in 16/20 cases (4 positive, 12 negative) with 4 false negatives. Due to this poorer performance we plan to focus primarily on otitis externa in the short term.
- Seeking funding for research to improve efficiency and expand to other applications
- Seeking industrial collaboration to advance to clinical trials
- Between 1 million and 3 million cases of otitis externa in the US annually, 20%-60% of which are caused by P. aeruginosa
- At least 90% of malignant otitis externa cases, common in diabetic and immunocompromised individuals, are caused by P. aeruginosa
- Potential applications in cystic fibrosis, otitis media, infected burns, infected catheters, diabetes complications and more