Background The application of whole-exome sequencing for the diagnosis of genetic disease has paved the way for systems-based approaches in the clinical laboratory. Here, we describe a clinical metabolomics method for the screening of metabolic diseases through the analysis of a multi-pronged mass spectrometry platform. By simultaneously measuring hundreds of metabolites in a single sample, clinical metabolomics offers a comprehensive approach to identify metabolic perturbations across multiple biochemical pathways. Methods We conducted a single- and multi-day precision study on hundreds of metabolites in human plasma on 4, multi-arm, high-throughput metabolomics platforms. Results The average laboratory coefficient of variation (CV) on the 4 platforms was between 9.3 and 11.5% (median, 6.5–8.4%), average inter-assay CV on the 4 platforms ranged from 9.9 to 12.6% (median, 7.0–8.3%) and average intra-assay CV on the 4 platforms ranged from 5.7 to 6.9% (median, 3.5–4.4%). In relation to patient sample testing, the precision of multiple biomarkers associated with IEM disorders showed CVs that ranged from 0.2 to 11.0% across 4 analytical batches. Conclusions This evaluation describes single and multi-day precision across 4 identical metabolomics platforms, comprised each of 4 independent method arms, and reproducibility of the method for the measurement of key IEM metabolites in patient samples across multiple analytical batches, providing evidence that the method is robust and reproducible for the screening of patients with inborn errors of metabolism.

The esg locus of Myxococcus xanthus appears to control the production of a signal that must be transmitted between cells for the completion of multicellular development. DNA sequence analysis suggested that the esg locus encodes the E1 decarboxylase (composed of E1 alpha and E1 beta subunits) of a branched-chain keto acid dehydrogenase (BCKAD) that is involved in branched-chain amino acid (BCAA) metabolism. The properties of an esg::Tn5 insertion mutant supported this conclusion. These properties include: (i) the growth yield of the mutant was reduced with increasing concentrations of the BCAAs in the medium while the growth yield of wild-type cells increased, (ii) mutant extracts were deficient in BCKAD activity, and (iii) growth of the mutant in media with short branched-chain fatty acids related to the expected products of the BCKAD helped to correct the mutant defects in growth, pigmentation and development. The esg BCKAD appears to be involved in the synthesis of long branched-chain fatty acids since the mutant contained reduced levels of this class of compounds. Our results are consistent with a model in which the esg-encoded enzyme is involved in the synthesis of branched-chain fatty acids during vegetative growth, and these compounds are used later in cell-cell signalling during development.

Leclercia adecarboxylata has been rarely isolated from environmental and clinical specimens. On review of the world literature, we found two reports of L. adecarboxylata infection: one report described a patient with hepatic cirrhosis, and the other described a child dependent on total parenteral nutrition. L. adecarboxylata was isolated from five infected patients who were evaluated at our institution. Three patients had lower-extremity wound infections in which L. adecarboxylata was part of a mixed microbial growth. One patient had pneumonia due to multiple bacteria, including L. adecarboxylata, which were isolated from sputum. L. adecarboxylata was isolated from the blood of one patient with neutropenia and from the blood of the two patients reported in the literature. All patients except one had fever and leukocytosis. L. adecarboxylata isolates were susceptible to all the antimicrobials tested. L. adecarboxylata is most frequently isolated as part of a mixed microbial growth. Its role in these infections is not clear. However, the organism caused bacteremia in three patients.

The esg locus is required for the formation of multicellular fruiting bodies and spores by the developmental bacterium Myxococcus xanthus. Studies have suggested that esg mutants are defective in the production of an essential signal (E-signal) used in cell-cell communication and that E-signalling is required for the expression of many developmental genes. Recently we have determined that the esg locus encodes components of a branched-chain keto acid dehydrogenase, a multienzyme complex involved in branched-chain amino acid metabolism in many bacteria and higher organisms. During vegetative growth in M. xanthus, this enzyme complex appears to participate in the production of the branched-chain fatty acids found in this organism. M. xanthus fatty acids (including the branched-chain fatty acids) have been observed to have a variety of effects on developing cells. These effects include: (i) the lysis of M. xanthus cells (autocide activity), (ii) acceleration of the rate of sporulation and (iii) rescue of sporulation by certain development-defective mutants. These and other results suggest a model in which the branched-chain fatty acids, synthesized during growth, are released from cellular phospholipid by a developmentally regulated phospholipase during fruiting-body formation. This model proposes that one or more of the branched-chain fatty acids that are released constitutes the E-signal which must be transmitted between cells to complete M. xanthus development.