Serologic testing for <i>Bartonella</i> in Manitoba, Canada, 2010–2020: a retrospective case series

Abstract

<h3>Background:</h3> <i>Bartonella</i> are gram-negative bacilli not identified by routine bacterial culture. The objectives of this study were to review the results of all serologic testing for <i>Bartonella</i> ordered in Manitoba, Canada, and to review cases with positive test results among adults to assess species identification, risk factors, clinical manifestations and outcomes. <h3>Methods:</h3> This retrospective study included all <i>Bartonella</i> serologic tests ordered in Manitoba and performed at the National Microbiology Laboratory, Winnipeg, from Jan. 1, 2010, until Dec. 31, 2020. We analyzed the aggregate data for all serologic tests for <i>Bartonella</i> for patients of all ages. We reviewed the charts of adult (age ≥ 18 yr) patients with serologic positivity for <i>Bartonella</i> who had a medical chart at 1 of Winnipeg’s 2 largest hospitals (Health Sciences Centre and St. Boniface Hospital) to extract clinical and demographic data and create a case series. Descriptive statistics were performed. <h3>Results:</h3> During the study period, 1014 <i>Bartonella</i> serologic tests were ordered in adult and pediatric patients, of which 24 (2.4%) gave a positive result. Sixteen adults (12 men and 4 women; mean age 48 yr) seen at a participating hospital had a positive result. Molecular species-level identification occurred on explanted cardiac valves in 5 (31%) of the 16 cases; <i>B. quintana</i> was identified in all 5. Six patients (38%) were diagnosed with probable <i>B. quintana</i> infection, for a total of 11 <i>B. quintana</i> cases (69%); 8 (73%) of the 11 had endocarditis. Four cases of <i>B. quintana</i> infection (36%) were associated with rural residence. Four cases (25%) of probable <i>B. henselae</i> were identified; 2 patients had fever and lymphadenopathy, and 2 had endocarditis. The remaining patient was deemed to have a false-positive result as his <i>B. henselae</i> titre was at the threshold for positivity, his <i>B. quintana</i> serologic test gave a negative result, and his clinical syndrome was not suggestive of <i>Bartonella</i> infection. Two patients died; both had multivalvular <i>B. quintana</i> endocarditis with ruptured intracranial mycotic aneurysms. <h3>Interpretation:</h3> <i>Bartonella quintana</i> was a common cause of <i>Bartonella</i> serologic positivity among adults in Manitoba in 2010–2020 and was associated with endocarditis and systemic embolization. As <i>B. quintana</i> is transmitted by body lice, active case finding for people who lack suitable housing, both in urban and rural settings, should prioritize those with elevated <i>Bartonella</i> titres to receive echocardiography and detect endocarditis before systemic embolization occurs.

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