Isolation of new fastidious alpha Proteobacteria and Afipia felis from hospital water supplies by direct plating and amoebal co-culture procedures.

As water is a source of nosocomial infections in hospitals, the presence of fastidious Gram-negative bacteria in water samples taken in a university hospital was investigated. Water samples were inoculated onto agar plates and into amoebal microplates for co-culture. Sixty-eight alpha proteobacteria isolates were obtained and characterized using phenotypic methods and 16S rRNA gene sequence comparison. The latter approach divided the strains into seven clusters. Of these, one corresponded to previously recognized Afipia felis and it is likely that six were closely related new species. As these bacteria are fastidious and can not be cultivated on standard microbiological media, their possible role in hospital-acquired human infections should be investigated.