Tropheryma whipplei infection (Whipple's disease) in a patient after liver transplantation.

Whipple's disease (WD) is a rare infection caused by the bacterium Tropheryma whipplei that can affect multiple organs and most commonly occurs in the immunocompetent host. Only 3 cases of WD have been reported in the setting of immunosuppression for organ transplantation. Here, we report the first case of WD, to our knowledge, in a patient after liver transplantation with comorbid graft-versus-host-disease. We discuss the diagnostic challenges in this setting and the value of electron microscopy and in situ hybridization methods for confirming the infection. WD may be under-diagnosed in immunosuppressed transplant patients because the disease can present with atypical clinical and histological features that suggest other conditions.

Characterization of Borrelia burgdorferi BlyA and BlyB proteins: a prophage-encoded holin-like system.

The conserved cp32 plasmid family of Borrelia burgdorferi was recently shown to be packaged into a bacteriophage particle (C. H. Eggers and D. S. Samuels, J. Bacteriol. 181:7308-7313, 1999). This plasmid encodes BlyA, a 7.4-kDa membrane-interactive protein, and BlyB, an accessory protein, which were previously proposed to comprise a hemolysis system. Our genetic and biochemical evidence suggests that this hypothesis is incorrect and that BlyA and BlyB function instead as a prophage-encoded holin or holin-like system for this newly described bacteriophage. An Escherichia coli mutant containing the blyAB locus that was defective for the normally cryptic host hemolysin SheA was found to be nonhemolytic, suggesting that induction of sheA by blyAB expression was responsible for the hemolytic activity observed previously. Analysis of the structural features of BlyA indicated greater structural similarity to bacteriophage-encoded holins than to hemolysins. Consistent with holin characteristics, subcellular localization studies with E. coli and B. burgdorferi indicated that BlyA is solely membrane associated and that BlyB is a soluble protein. Furthermore, BlyA exhibited a holin-like function by promoting the endolysin-dependent lysis of an induced lambda lysogen that was defective in the holin gene. Finally, induction of the cp32 prophage in B. burgdorferi dramatically stimulated blyAB expression. Our results provide the first evidence of a prophage-encoded holin within Borrelia.

Bacteriophages of spirochetes.

Historically, a number of bacteriophage-like particles have been observed in association with members of the bacterial order Spirochetales, the spirochetes. In the last decade, several spirochete bacteriophages have been isolated and characterized at the molecular level. We have recently characterized a bacteriophage of the Lyme disease agent, Borrelia burgdorferi, which we have designated phiBB-1. Here we review the history of the association between the spirochetes and their bacteriophages, with a particular emphasis on phiBB-1 and its prophage, the 32-kb circular plasmid family of B. burgdorferi.