Laboratory Diagnosis of 37 Cases of Bartonella Endocarditis Based on Enzyme Immunoassay and Real-Time PCR.

Bartonella spp., mostly Bartonella quintana and B. henselae, are a common cause of culture-negative endocarditis. Serology using immunofluorescence assay (IFA) and PCR performed on cardiac tissues are the mainstays of diagnosis. We developed an enzyme immunoassay (EIA) and a novel multiplex real-time PCR assay, utilizing Bartonella genus-specific, B. henselae-specific, and B. quintana-specific SimpleProbe probes, for diagnosis of Bartonella endocarditis. We aimed to evaluate the performance of these assays. Thirty-seven patients with definite endocarditis, 18 with B. henselae, 18 with B. quintana, and 1 with B. koehlerae, were studied. Diagnosis was confirmed by conventional PCR and DNA sequencing of surgical cardiac specimens. Similar to the case with IFA, anti-Bartonella IgG titers of ≥1:800 were found in 94% of patients by EIA; cross-reactivity between B. henselae and B. quintana precluded species-specific serodiagnosis, and frequent (41%) but low-titer cross-reactivity between Coxiella burnetii antibodies and B. henselae antigen was found in patients with Q fever endocarditis. Low-titer (1:100) cross-reactivity was uncommonly found also in patients with brucellosis and culture-positive endocarditis, particularly Enterococcus faecalis endocarditis. Real-time PCR performed on explanted heart valves/vegetations was in complete agreement with results of sequence-based diagnosis with characteristic melting curves. The genus-specific probe identified five additional endocarditis-associated Bartonella spp. at the genus level. In conclusion, EIA coupled with a novel real-time PCR assay can play an important role in Bartonella endocarditis diagnosis and expand the diagnostic arsenal at the disposal of the clinical microbiologist. Since serology remains a major diagnostic tool, recognizing its pitfalls is essential to avoid incorrect diagnosis.

The cytokine midkine and its receptor RPTPζ regulate B cell survival in a pathway induced by CD74.

Lasting B cell persistence depends on survival signals that are transduced by cell surface receptors. In this study, we describe a novel biological mechanism essential for survival and homeostasis of normal peripheral mature B cells and chronic lymphocytic leukemia cells, regulated by the heparin-binding cytokine, midkine (MK), and its proteoglycan receptor, the receptor-type tyrosine phosphatase ζ (RPTPζ). We demonstrate that MK initiates a signaling cascade leading to B cell survival by binding to RPTPζ. In mice lacking PTPRZ, the proportion and number of the mature B cell population are reduced. Our results emphasize a unique and critical function for MK signaling in the previously described MIF/CD74-induced survival pathway. Stimulation of CD74 with MIF leads to c-Met activation, resulting in elevation of MK expression in both normal mouse splenic B and chronic lymphocytic leukemia cells. Our results indicate that MK and RPTPζ are important regulators of the B cell repertoire. These findings could pave the way toward understanding the mechanisms shaping B cell survival and suggest novel therapeutic strategies based on the blockade of the MK/RPTPζ-dependent survival pathway.

Molecular Diagnosis of Cat Scratch Disease: a 25-Year Retrospective Comparative Analysis of Various Clinical Specimens and Different PCR Assays.

Cat-scratch disease (CSD), caused primarily by Bartonella henselae, is a common etiology of infectious regional lymphadenopathy. Lymphadenopathy is preceded by a primary inoculation lesion and may progress to suppuration. Laboratory diagnosis of CSD is hampered by the limitations of available confirmatory tests. PCR, in general, is highly sensitive and specific; however, clinical sensitivity in CSD varies greatly between studies. We aimed to identify clinical specimens and PCR assays best suited for CSD diagnosis using a national CSD registry and a uniform case definition. Different clinical specimens and PCR assays, including conventional and real-time PCR, were evaluated. PCR was positive in 335/390 (86%) CSD patients and 425/482 (88%) PCR tests. The highest PCR sensitivity was achieved in lymph node pus aspirates (96%; n = 278 tests) followed by primary lesions (88%; n = 50), lymph node fine needle aspirations (85%; n = 46), lymph node biopsy specimens (73%; n = 91) and paraffin-embedded lymph nodes (59%; n = 17), (P < 0.001). Sensitivity was similar in all types of PCR assays studied. PCR negative predictive value of pus aspirate and lymph node biopsy specimen patient groups was 82% and 72%, respectively. Specificity was 100% based on 125 non-CSD patients with negative PCR. In conclusion, the specimen type rather than the PCR assay type has a major impact on CSD molecular diagnosis. We assume that the inadequate sensitivity of the biopsy specimens was due to sampling errors or the presence of inhibitory factors. Primary lesions should be sampled more frequently for CSD diagnosis. Physicians should be aware of the low PCR negative predictive value of lymph node biopsy specimens. IMPORTANCE Polymerase chain reaction (PCR) for the detection of Bartonella henselae is an important tool for the diagnosis of cat scratch disease (CSD); however, clinical sensitivity varies greatly between studies. The current study shows that the specimen type, with pus aspiration, fine needle aspiration, and primary inoculation lesion having significantly higher sensitivity than fresh or formalin-fixed paraffin-embedded lymph node biopsy specimen, rather than the type of the PCR assay, whether a conventional or a real-time assay, has a major impact on the performance of diagnostic PCR for CSD. The new data provide new tools for the clinical microbiologist when interpreting the results of the PCR assays. Primary inoculation lesions, although easily accessible, are often neglected and should be sampled more frequently for molecular diagnosis of CSD. Physicians should be aware that negative PCR, particularly if performed on fresh or paraffin-embedded lymph node biopsy specimens, does not exclude CSD.