Project description:Accurate and timely mycobacterial species identification is imperative for successful diagnosis, treatment, and management of disease caused by nontuberculous mycobacteria (NTM). The current most widely utilized method for NTM species identification is Sanger sequencing of one or more genomic loci, followed by BLAST sequence analysis. MALDI-TOF MS offers a less expensive and increasingly accurate alternative to sequencing, but the commercially available assays used in clinical mycobacteriology cannot differentiate between Mycobacterium intracellulare and Mycobacterium chimaera, two closely related potentially pathogenic species of NTM that are members of the Mycobacterium avium complex (MAC). Because this differentiation of MAC species is challenging in a diagnostic setting, Bruker has developed an improved spectral interpretation algorithm to differentiate M. chimaera and M. intracellulare based on differential spectral peak signatures. Here, we utilize a set of 185 MAC isolates that have been characterized using rpoB locus sequencing followed by whole genome sequencing in some cases, to test the accuracy of the Bruker subtyper software to identify M. chimaera (n = 49) and M. intracellulare (n = 55). 100% of the M. intracellulare and 82% of the M. chimaera isolates were accurately identified using the MALDI Biotyper algorithm. This subtyper module is available with the MALDI Biotyper Compass software and offers a promising mechanism for rapid and inexpensive species determination for M. chimaera and M. intracellulare.
Project description:Recent studies have shown that respiratory isolates from pulmonary disease patients and household water/biofilm isolates of Mycobacterium avium could be matched by DNA fingerprinting. To determine if this is true for Mycobacterium intracellulare, household water sources for 36 patients with Mycobacterium avium complex (MAC) lung disease were evaluated. MAC household water isolates from three published studies that included 37 additional MAC respiratory disease patients were also evaluated. Species identification was done initially using nonsequencing methods with confirmation by internal transcribed spacer (ITS) and/or partial 16S rRNA gene sequencing. M. intracellulare was identified by nonsequencing methods in 54 respiratory cultures and 41 household water/biofilm samples. By ITS sequencing, 49 (90.7%) respiratory isolates were M. intracellulare and 4 (7.4%) were Mycobacterium chimaera. In contrast, 30 (73%) household water samples were M. chimaera, 8 (20%) were other MAC X species (i.e., isolates positive with a MAC probe but negative with species-specific M. avium and M. intracellulare probes), and 3 (7%) were M. avium; none were M. intracellulare. In comparison, M. avium was recovered from 141 water/biofilm samples. These results indicate that M. intracellulare lung disease in the United States is acquired from environmental sources other than household water. Nonsequencing methods for identification of nontuberculous mycobacteria (including those of the MAC) might fail to distinguish closely related species (such as M. intracellulare and M. chimaera). This is the first report of M. chimaera recovery from household water. The study underscores the importance of taxonomy and distinguishing the many species and subspecies of the MAC.
Project description:Mycobacterium chimaera is a nontuberculous mycobacterial species that causes cardiovascular, pulmonary, and postsurgical infections. Here, we report the first complete genome sequence of M. chimaera This genome is 6.33 Mbp, with a G+C content of 67.56%, and encodes 4,926 protein-coding genes, as well as 74 tRNAs, one ncRNA, and three rRNA genes.
Project description:A global outbreak of infections due to Mycobacterium chimaera has been linked to the LivaNova (formerly Sorin) 3 T heater-cooler units (HCUs). We performed a study to investigate M. chimaera from HCUs in China. Water samples were collected from all 3 T HCUs (n = 5) at our hospital in May 2017. Mycobacteria isolates were subjected to genome sequencing using the HiSeq X10 Sequencer. Species were identified based on average nucleotide identity with M. chimaera type strain DSM 44623T. Paired-end reads of all M. chimaera genomes were retrieved from the SRA database and, together with our isolates, were mapped against the chromosome of M. chimaera reference strain ZUERICH-1 to call SNPs. Mycobacteria grew from three HCUs manufactured in 2009 but not from the two in 2016. The three isolates were identified as M. chimaera and differed from each other by 4 to 6 SNPs, and from ZUERICH-1 by 7 to 10 SNPs. The three isolates belonged to the subgroup 1.1 and were most closely related to strains of the subgroup 1.1 from HCUs or patients in Europe, Australia/New Zealand and USA, suggesting the same common source. This is the first report of M. chimaera from HCUs in China.