Pierre Fechter

Antibiotic resistance is becoming increasingly widespread, underlining the importance of rapid, accurate identification of bacterial infections for effective diagnostic, clinical, and environmental management. While next-generation sequencing excels at genetic characterization, it falls short in real-time, in situ detection, a critical gap where nucleic acid aptamers emerge as a compelling alternative. These synthetic oligonucleotides enable direct, low-cost, and versatile detection of bacterial targets without requiring DNA extraction or amplification. Their portability supports point-of-care diagnostics, while their molecular precision enables integration into advanced bioimaging platforms for non-invasive, real-time, spatial, and functional monitoring of pathogens in biological environments. This perspective explores the potential of aptamers for bacterial bioimaging, assessing the landscape of bacterial-targeting aptamers, zooming in on aptamer-based bioimaging approaches for bacterial detection, addressing key challenges, and outlining future opportunities, such as real-time dynamic infection imaging and theranostics, polyclonal/multivalent aptamers, multiplex imaging, aptamer-based biosensors, and AI-driven detection.

Background: Combination therapy is increasingly explored as an alternative approach to manage bacterial infections and limit the emergence of antibiotic resistance. Building on traditional medicinal knowledge, this study aimed to investigate the potential synergistic antibacterial effects between Krameria lappacea (Dombey) Burdet & B.B.Simpson root extracts and conventional antibiotics. Methods: Root extracts were prepared using supercritical fluid extraction with different proportions of ethanol as a co-solvent. Their in vitro antibacterial activity was evaluated against Gram-positive bacteria and their interactions with gentamicin and vancomycin were assessed using an agar dilution-based combination assay. The chemical composition of the extracts was characterized using HRMS/MS-based dereplication and molecular networking. To further investigate the compounds contributing to the observed activity, an MS-guided isolation strategy was applied to an independent K. lappacea extract, resulting in the purification of a major neolignan previously detected in the active KL5 extract, which was subsequently evaluated using broth microdilution assays. Results: The less polar extract KL5, enriched in neolignans, exhibited the strongest antibacterial activity, with MIC values ranging from 3 to 12 µg/mL against Gram-positive strains. In combination assays, KL5 exhibited synergistic or additive interactions with gentamicin depending on the bacterial strain, whereas no synergistic effect was observed with vancomycin. The isolated neolignan displayed antibacterial activity and showed an additive interaction with gentamicin against Staphylococcus spp. Conclusions: These findings support the potential of K. lappacea neolignan-rich extracts as antibiotic adjuvants. The activity of the isolated neolignan supports the contribution of this chemical class to the antibacterial properties of KL5, while the absence of synergy for the isolated compound suggests that additional constituents and/or multicomponent interactions may contribute to the effect observed for the whole extract.

Antimicrobial resistance (AMR) remains a major threat to modern medicine, fueled by the excessive use of antibiotics and the spread of multidrug-resistant pathogens such as methicillin-resistant Staphylococcus aureus (MRSA). In this study, we designed and synthesized a series of 2-aryl-4-aminoquinazoline derivatives bearing an aminoalkylimidazole linker, combining two pharmacophoric motifs associated with antimicrobial activity. Starting from anthranilamide, the compounds were prepared in three straightforward steps, affording good yields and high purity. Their structures were confirmed by FT-IR spectroscopy, ¹H and ¹³C nuclear magnetic resonance (NMR), and high-resolution mass spectrometry (HRMS). Biological evaluation showed that series 5 exhibited strong selectivity toward S. aureus, with compounds 5c and 5d displaying minimum inhibitory concentrations (MICs) between 2.2 and 4.4 µM. No significant activity was observed against other tested strains. Cytotoxicity assays in HepG2 cells revealed moderate to low inhibition. Molecular docking indicated preferential binding to dihydrofolate reductase (DHFR) and relevant interactions with topoisomerase IV, resembling reference inhibitors. ADME analysis predicted favourable absorption, blood–brain barrier permeability, and compliance with Lipinski’s rules.

Aptamers, short nucleic acid sequences with high specificity and affinity for their targets, are promising candidates for diagnostic applications due to their ability to detect a wide range of pathogens. We present a fluorescent bioimaging approach for detecting Pseudomonas aeruginosa , based on aptamer F23. Conjugated with fluorescent dye, its detection efficacy was evaluated on 15 Gram‐negative and ‐positive bacteria, including fixed and live cells, as homogeneous and heterogeneous populations. We developed an automated, open‐access software for quantifying microscopy images. Its high sensitivity enables accurate quantification of bacteria labeled with aptamers. For example, it successfully detected 1122 P. aeruginosa cells labeled with aptamer F23 out of a total of 1123 P. aeruginosa cells in a single image. With 200,000 analyzed bacteria, we demonstrated that the aptamer effectively detects various reference and clinical strains of P. aeruginosa , while failing to detect Gram‐positive Staphylococcus aureus , Staphylococcus haemolyticus , Staphylococcus epidermidis , and Corynebacterium striatum , as well as Gram‐negative Klebsiella pneumoniae , Acinetobacter baumannii , and Escherichia coli . This aptamer is therefore a promising tool to distinguish P. aeruginosa from different strains of the skin microbiota. However, our quantitative method also revealed partial labeling to other bacterial cells, highlighting the issue of refining aptamer selection to improve selectivity.

The rising prevalence of bacterial infections, antibiotic resistance, and emerging pathogens underscores the urgent need for innovative diagnostic approaches. Aptamers, short nucleic acid sequences with high specificity and affinity for their targets, are promising candidates for diagnostic applications due to their ability to detect a wide range of pathogens. In this study, we present a fluorescent aptamer-based bioimaging approach for detecting Pseudomonas aeruginosa , a multidrug-resistant pathogen of significant clinical concern. Conjugated with fluorescent dye, the detection efficacy of the F23 aptamer was evaluated on 15 different Gram-negative and Gram-positive bacteria, including fixed and lived cells, as well as homogeneous and heterogeneous population. To quantify microscopy images, we developed an automated, open-access identification software using ImageJ. Its high sensitivity provides a robust platform for accurately quantifying bacteria labeled with aptamers and potentially other fluorescent ligands. For instance, it successfully detected 1122 P. aeruginosa cells labeled with aptamer F23 out of a total of 1123 P. aeruginosa cells in a single image. With almost 200,000 analyzed bacteria and an exceptionally clear signal-to-noise ratio, we demonstrated that the F23 aptamer effectively detects various reference and clinical strains of Pseudomonas aeruginosa , while failing to detect Gram-positive Staphylococcus aureus, Staphylococcus haemolyticus, Staphylococcus epidermidis and Corynebacterium striatum , as well as Gram-negative Klebsiella pneumonia, Acinetobacter baumannii , and Escherichia coli . The F23 aptamer is therefore a promising tool to distinguish Pseudomonas aeruginosa from different strains of the skin microbiota. However, our quantitative method also revealed partial labeling to other bacterial cells, highlighting the issue of refining aptamer selection to improve selectivity.

Biomedical and Pharmacology Journal (BPJ) is an international, open access, peer reviewed, quarterly research journal.