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 as Afipia species 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 either Afipia genospecies 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.