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Members of the genus Bartonella are fastidious Gram-negative facultative intracellular bacteria that are typically transmitted by arthropod vectors. Several Bartonella spp. have been found to cause culture-negative endocarditis in humans. Here, we report the case of a 75-year old German woman with prosthetic valve endocarditis due to Bartonella washoensis. The infecting agent was characterized by sequencing of six housekeeping genes (16S rRNA, ftsZ, gltA, groEL, ribC, rpoB) applying a multilocus sequence typing (MLST) approach. The 5097 bp of the concatenated housekeeping gene sequence from the patient were 99.0% identical to a B. washoensis strain from a red squirrel (Sciurus vulgaris orientis) from China. 39% (24/62) of red squirrel (S. vulgaris) samples from the Netherlands were positive for the B. washoensis gltA gene variant detected in the patient. This suggests that the red squirrel is the reservoir host for human infection in Europe.

Members of the genus Bartonella are fastidious Gram-negative facultative intracellular bacteria that are typically transmitted by arthropod vectors. Several Bartonella spp. have been found to cause culture-negative endocarditis in humans. Here, we report the case of a 75-year-old German woman with prosthetic valve endocarditis due to Bartonella washoensis. The infecting agent was characterized by sequencing of six housekeeping genes (16S rRNA, ftsZ, gltA, groEL, ribC, and rpoB), applying a multilocus sequence typing (MLST) approach. The 5,097 bp of the concatenated housekeeping gene sequence from the patient were 99.0% identical to a sequence from a B. washoensis strain isolated from a red squirrel (Sciurus vulgaris orientis) from China. A total of 39% (24/62) of red squirrel (S. vulgaris) samples from the Netherlands were positive for the B. washoensis gltA gene variant detected in the patient. This suggests that the red squirrel is the reservoir host for human infection in Europe.

Acanthamoeba can cause severe ocular and cerebral diseases in healthy and immunocompromised individuals, respectively. Activation of complement appears to play an important role in host defence against infection. The exact mechanism, however, is still unclear. The aim of the present study was to investigate the effect of normal human serum (NHS) and normal mouse serum (NMS) on Acanthamoeba trophozoites, the binding of different complement factors to Acanthamoeba and the activation of the complement system. Moreover, we aimed to work out any possible differences between different strains of Acanthamoeba. A virulent T4 strain, a non-virulent T4 strain and a virulent T6 strain were included in the study. It was shown that NHS, but not NMS clearly has amoebicidal properties. After 5min of incubation with NHS, amoebae showed plasma membrane disruption and extrusion of intracellular components. Cells were completely destroyed within 60min of incubation in NHS but stayed intact after incubation in heat-inactivated serum. The binding of human C3 and C9 to amoebae was established by immunoblotting. Although incubation with mouse serum did not result in lysis of Acanthamoeba trophozoites an immunofluorescence assay (IFA) demonstrated a strong deposition of mouse complement factor C3 activation products, moderate binding of C1q, but no binding of MBL-A and MBL-C. EDTA inhibited the binding of C3 to acanthamoebae. Binding of amoebae to C3b was observed with sera from C1qa-/- and MBL-A/C-/- mice, but not with serum from Bf/C2-/- mice demonstrating an activation of complement via the alternative pathway. There were no significant differences between the three Acanthamoeba strains investigated. Altogether, our results prove that NHS is amoebolytic and that Acanthamoeba binds to C3 and C9 and activates the complement system via the alternative pathway.

We investigated the possibility of transfer immunity from Cryptosporidium parvum-infected interferon-gamma (GKO) and interleukin-12p40 (IL-12KO) deficient C57BL/6 mice to naive mice by transfer of intraepithelial lymphocytes (IELs) and CD4(+) T cells from spleen and mesenteric lymph nodes (MLNs). Three days after the transfer recipients were infected with C. parvum. IELs isolated from GKO donor mice after resolution of infection (day 15) but not at the peak of infection (day 8) significantly reduced the parasite load in recipient mice. In IL-12KO mice, IELs and also CD4(+) T cells isolated from the spleen and MLNs of donor mice at the peak of infection (day 5) and after resolution (day 15) significantly reduced the parasite excretion, emphasizing the role of interferon-gamma in the host-parasite interaction. However, after resolution of infection, interferon-gamma-independent mechanisms have evolved that render GKO IELs capable of protecting mice from severe infection.