Pulmonary granuloma caused by Pseudomonas andersonii sp nov

Pulmonary granuloma is a common lesion for which gram-negative bacteria are rarely implicated as a cause. Hence, most physicians are unaware of this e tiology. We isolated a gram-negative bacterium from a surgically resected p ulmonary granuloma in a 42-year-old, nonimmunocompromised woman. Within the necrotizing granuloma, numerous organisms also were demonstrated by Gram s tain, suggesting a cause-disease relationship. Characterization of the bact erium by sequence analysis of the 16S ribosomal gene, cellular fatty acid p rofiling, and microbiologic studies revealed a novel bacterium with a close relationship to Pseudomonas. We propose a new species for the bacterium, P seudomonas andersonii. These results suggest that the differential diagnosi s of a lung granuloma also should include this gram-negative bacterium as a potential causative agent, in addition to the more common infections cause d by acid-fast bacilli and fungi. This bacterium was shown to be susceptibl e to most antibiotics that are active against gramnegative bacteria.