![]() Bayesian analysis of population structure (BAPS) using these same data confirmed this clustering ( Fig. chimaera forms a monophyletic lineage within the M. A robust phylogeny inferred from the alignments strongly suggested that M. These comparisons identified 448,878 variable nucleotide positions in a 2,340,885-bp core genome. chimaera genomes included 49 HCU-associated and 14 previously described patient isolates, not all of which were associated with Stöckert 3T HCU contamination ( 8, 12). chimaera MC_ANZ045 complete reference chromosome. intracellulare complex, we conducted whole-genome pairwise comparisons of the 96 taxa to the M. chimaera genomes from North America, Australia, and New Zealand and 33 other related, publicly available mycobacterial genomes from the M. Using 96 mycobacterial genome sequences comprising 63 M. chimaera genomes, we first assessed the phylogenetic coherence of M. To identify DNA segments present only in M. chimaera in both clinical and environmental samples.Īssessment of M. We describe the initial development and validation of a sensitive, specific, and quantitative PCR (qPCR) assay for identification of M. ![]() chimaera and absent from other mycobacteria. Here we addressed this issue by using comparative genomics to identify DNA sequences present in M. A rapid and reliable diagnostic tool is urgently needed to support clinical management of patients and to establish the efficacy of heater-cooler unit decontamination procedures. This delay carries significant clinical, health provision, and medicolegal implications, as patients may be exposed to contaminated machines during this turnaround time of up to 6 to 8 weeks. chimaera is slow growing therefore, current culture-based laboratory methods, followed by Sanger sequencing of amplicons for one or more combinations of conserved sequence regions, or line-probe hybridization assays are not amenable to timely and specific detection of this pathogen. chimaera ANZ045 revealed a single circular 6,078,672-bp chromosome and five circular plasmids ranging in size from 21,123 to 324,321 bp ( 8). The complete 6,593,403-bp genome sequence of M. intracellulare complex ( 6), and two recent population genomic analyses have confirmed this relationship ( 8, 13). chimaera is a distinct entity within the M. ![]() Phylogenetic comparisons of 16S-23S rRNA internal transcribed spacer (ITS) sequences, and/or partial rpoB or hsp65 sequences ( 2, 5, – 7, 17, 18), suggest that M. The most plausible hypothesis for this widespread contamination is a point source outbreak, although the underlying causative factors are not currently known ( 9, – 16). chimaera has heightened with global reports of invasive infections (including endocarditis and vascular graft infections associated with the use of LivaNova PLC Stöckert 3T heater-cooler units during cardiac surgery). Mycobacterium chimaera is an environmental mycobacterium and infrequent pathogen, most commonly linked with pulmonary disease ( 1, – 8). We have thus developed a robust molecular assay that can be readily and rapidly deployed to screen clinical and environmental specimens for M. Screening 33 water samples from heater-cooler units with this assay highlighted the increased sensitivity of PCR compared to culture, with 15 of 23 culture-negative samples positive by M. In vitro screening against DNA extracted from 40 other mycobacterial species and 22 bacterial species from 21 diverse genera confirmed the in silico-predicted specificity for M. chimaera with a detection limit of 100 CFU/ml in whole blood spiked with bacteria. We targeted one of these regions and developed a TaqMan quantitative PCR (qPCR) assay for M. In silico comparisons indicated six DNA regions present only in M. chimaera is a phylogenetically coherent group. Here, we assessed 354 mycobacterial genome sequences and confirmed that M. Given the global dissemination of this clone, its potential to cause invasive disease, and the laboriousness of current culture-based diagnostic methods, there is a pressing need to develop rapid and accurate diagnostic assays specific for M. ![]() ![]() chimaera clone, associated with contaminated hospital heater-cooler units used during the surgery. Investigations suggest worldwide spread of a specific M. chimaera infections following cardiac surgery. Although most commonly associated with pulmonary disease, there has been growing awareness of invasive M. Mycobacterium chimaera is an opportunistic environmental mycobacterium belonging to the Mycobacterium avium- M. ![]()
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