Use of Antimicrobial Photodynamic Therapy to Inactivate Multidrug-Resistant Enterobacter spp.: Scoping Review

Background/Objectives: Multidrug-resistant (MDR) Enterobacter spp. are critical pathogens within the ESKAPE group, frequently exhibiting resistance to carbapenems. Antimicrobial photodynamic therapy (aPDT) represents a promising non-antibiotic strategy to circumvent these resistance mechanisms. This scoping review aims to map the current evidence regarding the efficacy of aPDT in inactivating Enterobacter spp., identifying the most effective photosensitizers (PS), light parameters, and existing research gaps. Methods: A systematic search was performed across PubMed, Scopus, and Google Scholar (2013–2025) following PRISMA-ScR guidelines and registered on OSF. Studies were included if they evaluated aPDT against Enterobacter spp. (in vitro or in vivo) and provided quantitative data on microbial reduction. Data was extracted using a standardized charting form covering bacterial strains, PS type, light source, and viability reduction. The results from the eligible sources of evidence were synthesized narratively to address the review objectives. Results: Despite the clinical priority of Enterobacter, only seven studies met the eligibility criteria. Methylene Blue remains the most frequently studied PS, achieving reductions of 3–8 log10. Emerging evidence highlights the synergistic efficacy of monocationic chlorins and graphene-based nanomaterials in enhancing the bactericidal effect of light-based treatments. Notably, aPDT demonstrated the ability to inactivate carbapenemases, the bacterial enzymes responsible for carbapenem resistance. However, only two studies evaluated in vivo applications, primarily within dental settings. Conclusions: aPDT is a promising method against MDR Enterobacter spp. and bypasses traditional resistance mechanisms. However, the limited number of studies indicates a significant knowledge gap. Future research should focus on standardized in vivo protocols and the synergy between aPDT and conventional antibiotics to support clinical translation.