Radiolabelled Bacterial Metallophores as Targeted PET Imaging Contrast Agents for Accurate Identification of Bacteria and Outer Membrane Vesiclesin vivo

Abstract

Modern technologies such as 16s DNA sequencing capable of identifying microbes and provide taxonomic resolution at species and strain-specific levels is destined to be transformative1. Likewise, there is an emerging need to accurately identify both infectious and non-infectious microbes non-invasively in the body at the genus and species level to guide diagnosis and treatment strategies. Here, we report development of radiometal-labelled bacterial chelators, knowns as metallophores that allow non-invasive and selective imaging of bacteria and bacterial products in vivo. We show that these novel contrast agents are able to identify E. coli with strain level specificity and other bacteria, such as K. pneumoniae, based on expression of distinct cognate transporters on the bacterial surface. The probe is also capable of tracking probiotic, engineered bacteria and bacterial products, outer membrane vesicles (OMVs), in unique niches such as tumours. Moreover, we report that this novel targeted imaging approach has impactful applicability in monitoring antibiotic treatment outcomes in patients with pulmonary infections, thereby providing the ability to optimize individualized therapeutic approaches. Compared to traditional techniques used to manufacture probes, this strategy simplifies the process considerably by combining the function of metal attachment and cell recognition into a single molecule. Thus, we anticipate that these probes will be widely used in both clinical and investigative settings in living systems for non-invasive imaging of infectious and non-infectious organisms.

Escherichiacoli Nissle 1917 as a Novel Microrobot for Tumor-Targeted Imaging and Therapy

“…A strategy of engineered EcN with exogenous reporter genes hSSTR2 has been reported for in vivo tumor visualization [ 49 ]. The outer membrane protein receptor FyuA of EcN can selectively recognize the 64 Cu and 89 Zr labeled metallophore yersiniabactin (YbT), which has a high affinity for transition metals [ 50 ]. A substantially higher PET signal was also observed in the EcN colonized tumor than that without the bacterial injection.…”

Molecular imaging of bacterial outer membrane vesicles based on bacterial surface display

“…Pastor et al presented a radiolabeling method 16 based on the classic stannous-chloride reduction of technetium. Siddiqui et al 17 describe a method for the radiolabeling of bacteria and OMVs for positron emission tomography (PET) based on the bacterial expression of FyuA, an outer membrane receptor for the metallophore yersiniabactin (YbT). They demonstrated that 64 Cu-labeled YbT can be incorporated into FyuA-expressing bacteria and their OMVs selectively.…”

In Situ Measurements of Dynamic Bacteria Transport and Attachment in Heterogeneous Sand-Packed Columns

“…Utilization of PET imaging for quantification of bacterial transport and attachment in column experiments first requires radiolabeling the bacteria with a positron-emitting radioisotope. Bacteria have been radiolabeled using two different approachessiderophore-derived chelators − and a glucose analogue uptake . While these approaches are being developed for in vivo bacteria imaging in medicine, they have not yet been leveraged to study bacterial transport dynamics in environmental or geologic systems.…”