Histoplasma capsulatum (HC) comprises eight phylogenetically distinct clades as defined by multilocus sequence typing (MLST). Limited animal data suggest that virulence of North American and Latin American strains of HC may differ, hypothetically accounting for unique clinical features observed in cohorts from different locations. Differential clinical disease has never been studied in patients with genotype-defined histoplasmosis.
We conducted a retrospective cohort study including all culture-proven histoplasmosis cases from four university-affiliated hospitals in Quebec (Canada), between 1988-2013. HC isolates were genotyped using MLST. Demographic and clinical data were independently collected by chart review.
A total of 63 patients were included in this preliminary analysis. The median age was 42 (range 21-81) and a majority of patients were male (n=49, 77.8%). Forty-six (73.0%) patients were immunocompromised as a result of HIV infection (n=28), solid organ transplantation (n=8), rheumatologic disease (n=6) or others (n=4). Disseminated progressive histoplasmosis (DPH) was observed in 39 (61.9%) patients, while 16 (25.4%) and 5 (7.9%) patients presented with acute and chronic pulmonary forms, respectively. HC isolates were identified as North American 2 (NAm2), Latin American A (LAmA) and other clades in 31 (49.2%), 26 (41.3%) and 6 (9.5%) patients, respectively. Ten patients were born in South America, while 12 had reportedly traveled to this area. Patients infected with LAmA were younger (mean 40.2 vs 49.4 year-old; p=0.02) and were more likely to be infected with HIV (17/26 vs 6/31; p=0.005). There was a tendency towards an association between DPH and LAmA infection (p=0.10). No significant differences were observed between NAm2 and LAmA infections with regards to clinical manifestations and outcomes (mortality, admission to intensive care unit and use of amphotericin B).
We did not confirm distinct clinical features between NAm2 and LAmA histoplasmosis, although the study was under-powered to detect small differences. In our endemic region, a significant proportion of culture-proven histoplasmosis was not indigenous (travel- or immigration-associated).
J. D. Talbot,
S. S. Moonjely, None
D. C. Vinh, None
R. Pelletier, None
C. Lavallée, None
C. Tremblay, None
S. F. Dufresne, None
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