Clinical and microbiological features of definite Mycobacterium gordonae pulmonary disease: the establishment of diagnostic criteria for low-virulence mycobacteria

Background: Although Mycobacterium gordonae isolation from respiratory samples is usually regarded as contamination, M. gordonae can cause definite pulmonary disease. The establishment of a standard diagnostic criteria of pulmonary disease that is caused by this low virulence mycobacterium is obviously necessary.

Methods: We performed clinical research on over 200 cases in which M. gordonae was isolated over an 8-year period, focusing on the M. gordonae subtype. Sequence analysis of rpoB was performed to identify the genotypes.

Results: A total of 287 respiratory samples (209 cases) were positive for M. gordonae. Twenty-seven cases (12.9%) had a positive culture more than twice and 11 of these cases (5.3%) had more than three positive cultures. Ultimately, three cases (1.4%) were newly diagnosed as M. gordonae pulmonary disease using our own diagnostic criteria. In all of the identified M. gordonae cases, the cultures tested positive with a Mycobacteria Growth Indicator Tube test at 24 days; however, in patients with definitive pulmonary disease, the cultures were positive at 9 days. A subtype analysis revealed that all of the definitive disease cases had subtype C.

Conclusion: The time taken to detect a positive culture and subtype of the isolates could be used as the diagnostic criteria for definite M. gordonae pulmonary disease.