1. Lanzhou Center for Tuberculosis Research, Lanzhou University; 2. Lanzhou Pulmonary Hospital; 3. Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University，Baltimore 21205, USA
Abstract：In the process of screening for L-form mycobacteria, 340 sputum specimens during the period from September 2008 to September 2009 in Lanzhou Pulmonary Hospital were cultured on LJ medium, Middlebrook MGIT-960， 92-3 TB liquid medium with or without sodium chloride and Middlebrook 7H9 semi-solid medium with or without sucrose, then the growth condition and the morphology of colony were observed. One bacterial strain numbered 866 had embedded growth on 7H9-L semi-solid as fried egg colonies, which was acid fast negative and round under optical microscope. After subculture, the colony showed pinkish and reddish color, the bacteria appeared as rod in optical and scanning electron microscopes (SEM)，and there were a few positive rod bacteria by acid fast staining. 16S rRNA DNA sequence analysis revealed that the strain belonged to Gordonia bronchialis series of Gordona genus in Actinomycosis order. The patient，78-year-old, had coughed and expectorated sputum intermittently for four years with some sigh of deterioration of immunity. In conclusion, the elder patient might be infected with L-form of Gordonia bronchialis, which may suggest that Gordonia bronchialis L-form infection could underlie persistent lung infection in elderly patients.