Acute endocarditis, an infection of the heart valve, is most deadly when the causative agent is the bacterium Staphylococcus aureus. S.aureus establishes a localized infection in the heart through secretion of staphylocoagulase, a protein that recruits and tethers to the infection site a host protein called prothrombin. This protein complex then triggers the formation of blood clots that help shield the bacterium from the immune system. Blood cultures are used for clinical diagnosis.
Conceivably, methods to identify the culprit pathogen directly in the heart could provide information about the precise site and extent of infection, which in turn could optimize treatment. Panizzi et al. have designed a noninvasive imaging strategy for detecting S. aureus endocarditis that exploits the pathogen’s dependence on prothrombin to establish infection. Systemic injection of prothrombin analogs tagged with fluorescent or PET (positron emission tomography) imaging probes enabled the authors to visualize S.aureus endocarditis in mice and monitor the response to antibiotic therapy.
Whether this strategy can be applied safely and effectively in a clinical setting is not yet known.
The article was published in Nat. Med. 17, 1142–1146 (2011); doi: 10.1038/nm.2423 (2011).