Imaging of Pseudomonas aeruginosa infection with Ga-68 labelled pyoverdine for positron emission tomography

Dalibor Dolezal,Hubertus Haas,Eva Umlaufova,Clemens Decristoforo,Andrea Palyzova,Milos Petrik,Marian Hajduch,Zbynek Novy,Vladislav Raclavsky,Vladimir Havlicek

doi:10.1038/s41598-018-33895-w

Abstract

Pseudomonas aeruginosa is an increasingly prevalent opportunistic pathogen that causes a variety of life-threatening nosocomial infections. Novel strategies for the development of new antibacterial treatments as well as diagnostic tools are needed. One of the novel diagnostic strategies for the detection of infection could be the utilization of siderophores. Siderophores are low-molecular-weight chelators produced by microbes to scavenge essential iron. Replacing iron in siderophores by suitable radiometals, such as Ga-68 for positron emission tomography (PET) imaging, opens approaches for targeted imaging of infection. Here we report on pyoverdine PAO1 (PVD-PAO1), a siderophore produced by P. aeruginosa, labelled with Ga-68 for specific imaging of Pseudomonas infections. PVD-PAO1 was labelled with Ga-68 with high radiochemical purity. The resulting complex showed hydrophilic properties, low protein binding and high stability in human serum. In vitro uptake of 68Ga-PVD-PAO1 was highly dependent on the type of microbial culture. In normal mice 68Ga-PVD-PAO1 showed rapid pharmacokinetics with urinary excretion. PET imaging in infected animals displayed specific accumulation of 68Ga-PVD-PAO1 in infected tissues and better distribution than clinically used 18F-fluorodeoxyglucose (18F-FDG) and 68Ga-citrate. Ga-68 labelled pyoverdine PAO1 seems to be a promising agent for imaging of P. aeruginosa infections by means of PET.

Highlights

Invasive microbial infections are one of the leading causes of morbidity and mortality especially in immunocompromised hosts[1,2]
Uptake of 68Ga-PVD-PAO1 by P. aeruginosa was highly dependent on the bacterial culture conditions
Uptake study of different siderophores not produced by P. aeruginosa radiolabelled with Ga-68 in iron-deficient P. aeruginosa cultures showed negligible uptake of these compounds compared to 68Ga-PVD-PAO1 (Fig. 3A)

Summary

Introduction

Invasive microbial infections are one of the leading causes of morbidity and mortality especially in immunocompromised hosts[1,2]. Current diagnostic methods including culture, serology, molecular and radiology techniques used for pathogen identification are often slow, invasive, lack sensitivity and/or specificity, and are unable to localize infection in the body. Standard methods for assessing respiratory infections with P. aeruginosa are suboptimal and new diagnostic tools to identify the causative pathogen are needed[3,6]. One of the new diagnostic strategies for the specific detection of manifested infection could be the utilization of labelled siderophores. P. aeruginosa can use different strategies to acquire iron including production of siderophores, uptake of exogenous siderophores (xenosiderophores) produced by other microorganisms, uptake of heme molecules from the host or the use of Feo system[11]. P. aeruginosa produces different types of siderophores including pyoverdine (PVD) and uses highly efficient FpvA transporters specific for ferripyoverdine uptake[12,13]. A similar Trojan horse strategy utilizing different Ga-68 labelled siderophores was successfully established for imaging of fungal pathogen Aspergillus fumigatus in the past[16,17]

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Discussion

Conclusion