Bacterial Uptake of Radiotracer F-PABA

Example 3

The ability of different bacterial species to take up [¹⁸F]F-PABA was studied. The radiotracer accumulated in both methicillin sensitive S. aureus (MSSA, Newman) and methicillin-resistant S. aureus (MRSA), as well as the Gram negative bacteria E. coli and Klebsiela pneumoniae.

In the case of MSSA we also demonstrated that heat-killed cells were unable to take up [¹⁸F]F-PABA (FIG. 1). In contrast, [¹⁸F]F-PABA was not taken up by Enterococcus faecalis. E. faecalis has a folate salvage pathway and can take up folate from the environment. Thus, folic acid biosynthesis is dispensable in this organism, which also explains why sulfonamides are not used to treat infection by E. faecalis. These studies suggest that F-PABA uptake depends on on the de novo biosynthesis of folate.