Patients in the Intensive Care Unit are Exposed to Amoeba-Associated Pathogens

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Abstract
Objective: : To study the role of amoeba-associated alpha Proteobacteria as infecting agents in intensive care units (ICUs).Design: : Amoeba-associated alpha Proteobacteria were isolated from water samples taken from ICU taps and general hospital reservoir tanks using an amoebal co-culture procedure. Isolates were identified by 16S rDNA gene sequence comparison, and one isolate of each species was used as an antigen in a microimmunofluorescence assay to test the sera of the patients in the ICUs and compare them with those of control subjects.Setting: : The four university hospitals in Marseilles, France.Patients: : The sera of 85 patients in the ICUs with nosocomial pneumonia were tested.Results: : We isolated 64 bacterial strains that were identified asAfipiaspecies or close relatives within the Rhizobiaceae subgroup of alpha Proteobacteria. These bacteria were assigned to 8 different species. Eleven patients were found to have an elevated antibody titer to eitherAfipiagenospecies 1, or 3 still unnamed bacteria. No specific antibodies were detected in 100 control subjects (P<.01).Conclusion: : These preliminary results support the hypothesis that ICU patients are exposed to amoeba-associated alpha Proteobacteria.