Ondine Biomedical Inc. (AIM: OBI), a Canadian life sciences company specialising in light-activated antimicrobial therapies, has announced laboratory findings showing no development of resistance to its methylene blue photodisinfection technology (MB-aPDT) across six multidrug-resistant Staphylococcus aureus strains, including MRSA, VISA and LRSA. The in vitro study, conducted at Ondine Research Laboratories in Bothell, Washington, subjected each strain to 20 serial sub-lethal exposure cycles without detecting any reduction in susceptibility to MB-aPDT. The findings were presented as an oral presentation at the 6th International Photodynamic Therapy and Photodiagnosis Symposium (PDT 2026) in Nancy, France, and are to be submitted for publication in a peer-reviewed journal.

Key Points

  • Ondine Biomedical Inc. (AIM: OBI) is a Canadian life sciences company developing photodisinfection therapies for hospital infection prevention
  • Laboratory testing showed no observed resistance to MB-aPDT across six multidrug-resistant S. aureus strains after 20 consecutive sub-lethal exposure cycles
  • No consistent cross-resistance was detected across 13 antibiotics spanning 11 classes; a ciprofloxacin control developed resistance under identical conditions, validating the test methodology
  • Investors may watch for peer-reviewed publication of the full study and progress updates on Ondine's ongoing Phase 3 trial of Steriwave in the United States

No Resistance Detected Across Six Multidrug-Resistant S. aureus Strains in Bothell Laboratory Study

The study evaluated six well-characterised S. aureus strains encompassing MRSA, VISA, LRSA, and strains harbouring multidrug efflux-pump (norA) and biocide-tolerance (qacA) genes. Researchers applied 20 serial sub-lethal exposures at 0.5 times the minimum inhibitory concentration, recovering and re-culturing surviving bacteria between each cycle. Susceptibility was assessed using MIC assays benchmarked against epidemiological cut-off values, alongside cross-resistance testing against 13 clinical antibiotics. Crucially, ciprofloxacin used as a parallel control rapidly developed resistance under the same conditions, confirming the assay's ability to detect resistance when it arises.

MB-aPDT's Multi-Target Oxidative Mechanism Hypothesised to Explain High Genetic Barrier to Resistance

Ondine's announcement states that conventional antibiotics typically act on single molecular targets, enabling bacteria to evolve resistance relatively rapidly. MB-aPDT instead generates reactive oxygen species upon light activation, simultaneously disrupting multiple bacterial cell structures. The company's Director of Research and Development, Dr. Caetano P. Sabino, stated in the announcement that the genetic barrier to resistance "appears remarkably high" given that no susceptibility reduction was detected after 20 MB-aPDT exposure cycles, contrasting directly with the ciprofloxacin comparator. The findings are described as building on earlier Ondine research published in 2009 by Pedigo et al.

Steriwave Commercially Authorised in Canada, UK, EU, Mexico and Australia as Phase 3 US Trial Enrolment Completes

Ondine's nasal photodisinfection product, Steriwave, is a single five-minute procedure administered by healthcare professionals at the point of care and is commercially available outside the United States in Canada, the UK, the EU under CE mark, Mexico, and Australia. The announcement notes that Steriwave is used in perioperative infection-prevention programmes at hospitals in those markets. In the United States, the technology holds Qualified Infectious Disease Product designation and Fast Track status from the FDA and has recently completed enrolment in its Phase 3 clinical trial, though Steriwave is not approved or commercially available there.

Antimicrobial Resistance Burden and Mupirocin Compliance Challenges Underpin Commercial Opportunity for Photodisinfection

The announcement references a 2024 Lancet GRAM Project evaluation estimating that drug-resistant bacterial infections were directly responsible for 1.14 million deaths globally in 2021. It also cites published data indicating full patient adherence to standard multi-day mupirocin home decolonisation regimens at approximately 40%, and mupirocin resistance identified in up to 34.4% of evaluated MRSA clinical isolates. These figures, drawn from cited third-party sources in the announcement, highlight the clinical context in which Ondine positions its single-application Steriwave procedure, though investors should note that laboratory findings do not constitute clinical or regulatory approval for any indication.