Septicemia and Candidatus Neoehrlichia mikurensis | CDC EID

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Volume 16, Number 7–July 2010
Dispatch
Septicemia Caused by Tick-borne Bacterial Pathogen Candidatus Neoehrlichia mikurensis
Jan S. Fehr,1 Guido V. Bloemberg,1 Claudia Ritter, Michael Hombach, Thomas F. Lüscher, Rainer Weber, and Peter M. Keller
Author affiliations: University Hospital, Zurich, Switzerland (J.S. Fehr, T.F. Lüscher, R. Weber); and University of Zurich, Zurich (G.V. Bloemberg, C. Ritter, M. Hornbach, P.M. Keller)

Suggested citation for this article

Abstract
We have repeatedly detected Candidatus Neoehrlichia mikurensis, a bacterium first described in Rattus norvegicus rats and Ixodes ovatus ticks in Japan in 2004 in the blood of a 61-year-old man with signs of septicemia by 16S rRNA and groEL gene PCR. After 6 weeks of therapy with doxycycline and rifampin, the patient recovered.
Since the novel bacterial genus Neoehrlichia wass first described in 2004, its pathogenic role in humans has remained unexplained (1). Related bacteria such as Ehrlichia chaffeensis and Anaplasma phagocytophilum are emerging tick-borne human pathogens that cause monocytic and granulocytic ehrlichiosis, respectively. These tick-borne diseases manifest themselves as febrile illness, mild transient hepatitis, transient thrombocytopenia, and occasionally as a rash. The family Anaplasmataceae compromises the genera Ehrlichia, Anaplasma, Neorickettsia, and Aegyptianella, and the proposed genus Neoehrlichia. These are all obligate intracellular bacteria, which currently are difficult or impossible to isolate and culture (2). Infections caused by agents of this bacterial family have been recognized as an emerging problem in the past 2 decades, possibly due to ecologic changes and the resulting expansion of tick populations (3).

Case Report
In August 2009, a 61-year-old Caucasian man who lived in Switzerland sought treatment at the emergency department of University Hospital in Zurich, reporting a 10-day history of malaise, temperature as high as 39.5°C, chills, and moderate dyspnea. Six weeks previously, he had undergone coronary artery bypass graft surgery and mitral valve reconstruction for which prosthetic material was used. The patient had not noticed tick bites or a skin rash; neither did he recall a rodent bite. A pet dog and cat lived in his household.

Physical examination showed a reduced general health condition and a temperature of 38.5°C. Blood pressure was 109/68 mm Hg, heart rate was 86 beats/min, and oxygen saturation was 95% with 2 L nasal oxygen. No murmur was detected on cardiac auscultation. No skin or joint abnormalities were found. Laboratory tests showed elevated leukocytes (12.9 × 103 cells/μL), with a high fraction of neutrophils (10.1 × 103 cells/μL) and thrombocyte count within reference range (277 × 103 cells/μL); aminotransferase levels within reference ranges (aspartate aminotransferase 18 U/L, alanine aminotransferase 20 U/L); and an elevated C-reactive protein (CRP) of 68 mg/L (reference range <5 mg/L). Chest radiograph showed no signs of cardiac decompensation or of pulmonary infiltrates. Transthoracic echocardiograph showed only minor insufficiency of the aortic and tricuspid valves. In addition, degenerative alterations of aortic valve, but no vegetations, were noted with comparable findings in the follow-up echocardiograph 1 week later.

At the follow-up visit, no hints of infectious foci were found. Five sets of blood cultures were drawn with >12 h difference between the first and the last set. Antimicrobial drug treatment for endocarditis with prosthetic material, consisting of vancomycin, gentamicin, and rifampin, was initiated.

Blood cultures remained negative for microbial growth, even after extended incubation. Serologic tests for agents of culture-negative endocarditis and tick-borne diseases were performed. Enzyme immunoassays (EIAs) were positive for immunoglobulin (Ig) G antibodies reactive to Bartonella henselae (512) and B. quintana (1,024), Coxiella burnetii (phase II IgG titer 160), Rickettsia rickettsii/conorii (IgG 256), and Rickettsia typhi (IgG 128), Mycoplasma pneumoniae (index 2.7). IgM was positive only for A. phagocytophilum (512, atypical fluorescence pattern), presenting a low titer of IgG at this stage. Serologic test results for Brucella spp., Chlamydia trachomatis, Chlamydia pneumoniae, and Borrelia burgdorferi were negative. Species-specific PCRs for A. phagocytophilum, Tropheryma whipplei, B. henselae, B. quintana, Legionella spp., and L. pneumophila were negative.

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Septicemia and Candidatus Neoehrlichia mikurensis | CDC EID

Suggested Citation for this Article
Fehr JS, Bloemberg GV, Ritter C, Hombach M, Lüscher TF, Weber R, et al. Septicemia caused by tick-borne bacterial pathogen Candidatus Neoehrlichia mikurensis. Emerg Infect Dis [serial on the Internet]. 2010 Jul [date cited]. Available from http://www.cdc.gov/EID/content/16/7/1127.htm
DOI: 10.3201/eid1607.091907