A High Proportion of Novel Mycobacteria Species Identified by 16S rDNA Analysis Among Slowly Growing AccuProbe-Negative Strains in a Clinical Setting

Abstract

Sequencing of the 16S ribosomal DNA (rDNA )for identification of nontuberculous mycobacteria (NTM) has contributed to the establishment of more than 35 new species during the last decade. Increasingly, NTM are accepted as potential or proven pathogens. We identified, by 16S rDNA sequence analysis, slowly growing NTM isolates negative by AccuProbe (GenProbe, San Diego, CA) that previously were identified by using conventional biochemical techniques, to determine the accuracy of reporting AccuProbenegative NTM prior to sequence-based identification. Of 82 strains, 30 were deemed novel. An attempt was made to determine the clinical importance of previously misidentified novel species. Clinical cases are described for a number of strains previously identified as Mycobacterium terrae complex, Mycobacterium scrofulaceum, and Mycobacterium avium complex. As sequence-based identification methods become more commonplace in clinical microbiology laboratories, there is a need to understand the significance of previously undescribed species, which often mimic and subsequently are identified as well-established species. Many nontuberculous mycobacteria (NTM) are ubiquitous in the environment and may colonize and occasionally cause infection in humans. Mycobacterium avium complex, Mycobacterium kansasii, and members of the Mycobacterium fortuitum complex are causative agents for most NTM infections and currently have a well-understood environmental epidemiology. 1 Other NTM species rarely cause infection,