Bacteriological characterization of a Mycobacterium parascrofulaceum strain isolated from a Chinese pneumonia patient

Background: A Mycobacterium parascrofulaceum strain was isolated from a pneumonia patient-the first such reported case from China. The bacteriological characteristics of the strain were determined. Methods: Species identification was performed by homologue gene sequence comparison, then a series of biochemical tests was conducted to elucidate the bacteriological characteristics. Drug susceptibility and pathogenicity to mice of the strain were tested. Results: The clinical M. parascrofulaceum strain presented a very similar phenotypic profile to that of Mycobacterium scrofulaceum. The M. parascrofulaceum strain was sensitive to rifabutin, rifapentine, clarithromycin, azithromycin, cefoxitin, and moxifloxacin in vitro. At week 2 post-infection, the lung tissues of mice demonstrated a local inflammatory response denoted by peri-bronchiolar inflammatory infiltrates. At weeks 4 and 8, the lung tissues showed peri-bronchiolar inflammatory infiltrates with large aggregates of lymphocytes and part of the tissue showed granulomatous lesions; there was no appreciable necrosis. The colony-forming units (CFU) count of infected lung and spleen increased gradually during the 8 weeks of the experiment. Conclusions: The M. parascrofulaceum strain isolated in China was sensitive to rifabutin, rifapentine, clarithromycin, azithromycin, cefoxitin, and moxifloxacin. The mycobacteria were capable of proliferating in mice and could lead to pathological changes in the lungs of the mice.