Detection of Klebsiella. Pneumoniae Infection with an Antisense Oligomer Against its Ribosomal RNA

Oligonucleotide probes for imaging and diagnosis of bacterial infections

The rise of infectious diseases as a public health concern has necessitated the development of rapid and precise diagnostic methods. Imaging techniques like nuclear and optical imaging provide the ability to diagnose infectious diseases within the body, eliminating delays caused by sampling and pre-enrichments of clinical samples and offering spatial information that can aid in a more informed diagnosis. Traditional molecular probes are typically created to image infected tissue without accurately identifying the pathogen. In contrast, oligonucleotides can be tailored to target specific RNA sequences, allowing for the identification of pathogens, and even generating antibiotic susceptibility profiles by focusing on drug resistance genes. Despite the benefits that nucleic acid mimics (NAMs) have provided in terms of stabilizing oligonucleotides, the inadequate delivery of these relatively large molecules into the cytoplasm of bacteria remains a challenge for widespread use of this technology. This review summarizes the key advancements in the field of oligonucleotide probes for in vivo imaging, highlighting the most promising delivery systems described in the literature for developing optical imaging through in vivo hybridization.

The role of Nucleic Acid Mimics (NAMs) on FISH-based techniques and applications for microbial detection

Fluorescent in situ hybridization (FISH) is a powerful tool that for more than 30 years has allowed to detect and quantify microorganisms as well as to study their spatial distribution in three-dimensional structured environments such as biofilms. Throughout these years, FISH has been improved in order to face some of its earlier limitations and to adapt to new research objectives. One of these improvements is related to the emergence of Nucleic Acid Mimics (NAMs), which are now employed as alternatives to the DNA and RNA probes that have been classically used in FISH. NAMs such as peptide and locked nucleic acids (PNA and LNA) have provided enhanced sensitivity and specificity to the FISH technique, as well as higher flexibility in terms of applications. In this review, we aim to cover the state-of-the-art of the different NAMs and explore their possible applications in FISH, providing a general overview of the technique advancement in the last decades.

Peptide-Conjugated Phosphorodiamidate Morpholino Oligomers for In Situ Live-Cell Molecular Imaging of Dengue Virus Replication

Current methods to detect and monitor pathogens in biological systems are largely limited by the tradeoffs between spatial context and temporal detail. A new generation of molecular tracking that provides both information simultaneously involves in situ detection coupled with non-invasive imaging. An example is antisense imaging that uses antisense oligonucleotide probes complementary to a target nucleotide sequence. In this study, we explored the potential of repurposing antisense oligonucleotides initially developed as antiviral therapeutics as molecular probes for imaging of viral infections in vitro and in vivo. We employed nuclease-resistant phosphorodiamidate synthetic oligonucleotides conjugated with cell-penetrating peptides (i.e., PPMOs) previously established as antivirals for dengue virus serotype-2 (DENV2). As proof of concept, and before further development for preclinical testing, we evaluated its validity as in situ molecular imaging probe for tracking cellular DENV2 infection using live-cell fluorescence imaging. Although the PPMO was designed to specifically target the DENV2 genome, it was unsuitable as in situ molecular imaging probe. This study details our evaluation of the PPMOs to assess specific and sensitive molecular imaging of DENV2 infection and tells a cautionary tale for those exploring antisense oligonucleotides as probes for non-invasive imaging and monitoring of pathogen infections in experimental animal models.

The Promise of Molecular Imaging in the Study and Treatment of Infectious Diseases

Infectious diseases are a major threat to humanity, and it is imperative that we develop imaging tools that aid in their study, facilitate diagnosis, and guide treatment. The alarming rise of highly virulent and multi-drug-resistant pathogens, their rapid spread leading to frequent global pandemics, fears of bioterrorism, and continued life-threatening nosocomial infections in hospitals remain as major challenges to health care in the USA and worldwide. Early diagnosis and rapid monitoring are essential for appropriate management and control of infections. Tomographic molecular imaging enables rapid, noninvasive visualization, localization, and monitoring of molecular processes deep within the body and offers several advantages over traditional tools used for the study of infectious diseases. Noninvasive, longitudinal assessments could streamline animal studies, allow unique insights into disease pathogenesis, and expedite clinical translation of new therapeutics. Since molecular imaging is already in common use in the clinic, it could also become a valuable tool for clinical studies, for patient care, for public health, and for enabling precision medicine for infectious diseases.