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Genetic diversity of Mycobacterium avium isolates recovered from clinical samples and from the environment: molecular characterization for diagnostic purposes.

ABSTRACT: Isolation of Mycobacterium avium complex (MAC) organisms from clinical samples may occur in patients without clinical disease, making the interpretation of results difficult. The clinical relevance of MAC isolates from different types of clinical samples (n = 47) from 39 patients in different sections of a hospital was assessed by comparison with environmental isolates (n = 17) from the hospital. Various methods for identification and typing (commercial probes, phenotypic characteristics, PCR for detection of IS1245 and IS901, sequencing of the hsp65 gene, and pulsed-field gel electrophoresis) were evaluated. The same strain was found in all the environmental isolates, 21 out of 23 (91.3%) of the isolates cultured from urine samples, and 5 out of 19 (26.3%) isolates from respiratory specimens. This strain did not cause disease in the patients. Testing best characterized the strain as M. avium subsp. hominissuis, with the unusual feature that 81.4% of these isolates lacked the IS1245 element. Contamination of certain clinical samples with an environmental strain was the most likely event; therefore, characterization of the environmental mycobacteria present in health care facilities should be performed to discard false-positive isolations in nonsterile samples, mainly urine samples. Molecular techniques applied in this study demonstrated their usefulness for this purpose.

SUBMITTER: Alvarez J

PROVIDER: S-EPMC2292972 | biostudies-literature | 2008 Apr

REPOSITORIES: biostudies-literature

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Genetic diversity of Mycobacterium avium isolates recovered from clinical samples and from the environment: molecular characterization for diagnostic purposes.

Alvarez Julio J García Ignacio Gómez IG Aranaz Alicia A Bezos Javier J Romero Beatriz B de Juan Lucía L Mateos Ana A Gómez-Mampaso Enrique E Domínguez Lucas L

Journal of clinical microbiology 20080213 4

Isolation of Mycobacterium avium complex (MAC) organisms from clinical samples may occur in patients without clinical disease, making the interpretation of results difficult. The clinical relevance of MAC isolates from different types of clinical samples (n = 47) from 39 patients in different sections of a hospital was assessed by comparison with environmental isolates (n = 17) from the hospital. Various methods for identification and typing (commercial probes, phenotypic characteristics, PCR fo ...[more]

PMID: 18272714

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Project description:The genetic similarity between Mycobacterium avium subsp. paratuberculosis and other mycobacterial species has confounded the development of M. avium subsp. paratuberculosis-specific diagnostic reagents. Random shotgun sequencing of the M. avium subsp. paratuberculosis genome in our laboratories has shown >98% sequence identity with Mycobacterium avium subsp. avium in some regions. However, an in silico comparison of the largest annotated M. avium subsp. paratuberculosis contigs, totaling 2,658,271 bp, with the unfinished M. avium subsp. avium genome has revealed 27 predicted M. avium subsp. paratuberculosis coding sequences that do not align with M. avium subsp. avium sequences. BLASTP analysis of the 27 predicted coding sequences (genes) shows that 24 do not match sequences in public sequence databases, such as GenBank. These novel sequences were examined by PCR amplification with genomic DNA from eight mycobacterial species and ten independent isolates of M. avium subsp. paratuberculosis. From these analyses, 21 genes were found to be present in all M. avium subsp. paratuberculosis isolates and absent from all other mycobacterial species tested. One region of the M. avium subsp. paratuberculosis genome contains a cluster of eight genes, arranged in tandem, that is absent in other mycobacterial species. This region spans 4.4 kb and is separated from other predicted coding regions by 1,408 bp upstream and 1,092 bp downstream. The gene upstream of this eight-gene cluster has strong similarity to mycobacteriophage integrase sequences. The GC content of this 4.4-kb region is 66%, which is similar to the rest of the genome, indicating that this region was not horizontally acquired recently. Southern hybridization analysis confirmed that this gene cluster is present only in M. avium subsp. paratuberculosis. Collectively, these studies suggest that a genomics approach will help in identifying novel M. avium subsp. paratuberculosis genes as candidate diagnostic sequences.

Project description:We studied a cohort of 221 high-risk pediatric B-progenitor ALL patients that excluded known high risk ALL subtypes (BCR-ABL1 and infant ALL), using Affymetrix single nucleotide polymorphism microarrays, gene expression profiling and candidate gene resequencing. A CNA poor outcome predictor was identified using a semi-supervised principal components approach, and tested in an independent validation cohort of 258 pediatric B-progenitor ALL cases. Over 50 regions of recurring somatically acquired CNA, with the most frequently targeted genes encoding regulators of B-lymphoid development (66.8% of cases; with PAX5 targeted in 31.7% and IKZF1 in 28.6%). A CNA classifier identified a very poor outcome subgroup in the high-risk cohort (P=4.2x10-5) and was strongly associated with the presence of deletions involving IKZF1, which encodes the early lymphoid transcription factor IKAROS. This classifier, and IKZF1 deletions, also predicted poor outcome and elevated minimal residual disease at the end of induction therapy in the validation cohort. The gene expression signature of the poor outcome group was characterized by reduced expression of B lineage specific genes, and was highly related to the expressing signature of BCR-ABL1 ALL, a known high-risk ALL subtype also characterized by a high frequency of IKZF1 deletion.Somatically acquired deletions involving IKZF1 identify a very poor outcome subgroup of pediatric ALL patients. Incorporation of molecular tests to identify IKZF1 deletion in diagnostic leukemic blasts should improve the ability to accurately risk stratify patients for appropriate therapy. Affymetrix U133A arrays were performed according to the maufacturers directions on RNA extracted from cryopreserved diagnostic bone marrow or peripheral blood samples. Samples with less than 80% blasts were flow sorted prior to RNA extraction Experiment Overall Design: One hundred seventy five pediatric B-progenitor ALL samples were studied using either Affymetrix U133A

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Genetic diversity of Mycobacterium avium isolates recovered from clinical samples and from the environment: molecular characterization for diagnostic purposes.

Publications

Genetic diversity of Mycobacterium avium isolates recovered from clinical samples and from the environment: molecular characterization for diagnostic purposes.

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