Challenges of Francisella classification exemplified by an atypical clinical isolate.

The accumulation of sequenced Francisella strains has made it increasingly apparent that the 16S rRNA gene alone is not enough to stratify the Francisella genus into precise and clinically useful classifications. Continued whole-genome sequencing of isolates will provide a larger base of knowledge for targeted approaches with broad applicability. Additionally, examination of genomic information on a case-by-case basis will help resolve outstanding questions regarding strain stratification. We report the complete genome sequence of a clinical isolate, designated here as F. novicida-like strain TCH2015, acquired from the lymph node of a 6-year-old male. Two features were atypical for F. novicida: exhibition of functional oxidase activity and additional gene content, including proposed virulence determinants. These differences, which could potentially impact virulence and clinical diagnosis, emphasize the need for more comprehensive methods to profile Francisella isolates. This study highlights the value of whole-genome sequencing, which will lead to a more robust database of environmental and clinical genomes and inform strategies to improve detection and classification of Francisella strains.

Electrospray ionization with ambient pressure ion mobility separation and mass analysis by orthogonal time-of-flight mass spectrometry.

Rapid screening and identification of drug and other mixtures are possible using a novel ambient pressure high-resolution ion mobility (APIMS) orthogonal reflector time-of-flight mass spectrometer (TOFMS). Departing ions from the APIMS drift tube traversed a pressure interface between the APIMS and TOFMS where they were subjected to numerous gas collisions that could produce selective fragmentation. By increasing the accelerating field in the pressure interface region, the ions generated using water-cooled electrospray ionization (ESI) underwent collision-induced dissociation (CID). Mixtures of ESI ions were separated by APIMS based on their respective size-to-charge (s/z) ratios while CID and analysis of mass-to-charge (m/z) ratios occurred in the pressure interface and TOFMS. Product ions that were formed in this pressure interface region could be readily assigned to precursor ions by matching the mobility drift times. This process was demonstrated by the examination of a mixture of amphetamines and the resulting fragmentation patterns of the mobility-separated precursor ion species [M + H](+).

Evaluation of opiate separation by high-resolution electrospray ionization-ion mobility spectrometry/mass spectrometry.

The separation of opiates and the primary metabolites was evaluated with ESI-IMS/MS. Seven opiate molecules were analyzed, and spectra were shown for each compound. The IMS separation of two isomers (morphine and norcodeine) was shown with baseline separation. Differences in the mobilities were found for the nonacetylated, monoacetylated, and biacetylated compounds. In this study, two primary findings are reported. First, IMS can easily separate metabolic isomers, and second, the two-dimensional separation capability of IMS/MS can be employed to confidently identify and separate both the opiates and metabolites. Although previous IMS studies have shown the separation of isomers, this is the first example to show the capability of IMS to separate metabolic isomers (within 70 s), a significant advantage in high-throughput screening for pharmacokinetic studies. Second, the monoacetylated and biacetylated compounds were found to form more compact ions for the sodium adducts in comparison to the protonated molecular ions. On the basis of the mobilities, information on structures and conformation can be deduced when sodium and protonated ions are compared.

Evaluation of suspected interferents for TNT detection by ion mobility spectrometry.

The use of ion mobility spectrometry systems to detect explosives in high security situations creates a need to determine compounds that interfere and may compromise accurate detection. This is the first study to identify possible interfering air contaminants common in airport settings by IMS. Seventeen suspected contaminants from four major sources were investigated. Due to the ionization selectivity gained by employing chloride reactant ion chemistry, only 7 of the 17 compounds showed an IMS response. Of those seven compounds, only 4,6-dinitro-o-cresol (4,6DNOC) was found to have a similar mobility to 2,4,6-trinitrotoluene (TNT) with K(o) values of 1.55 and 1.50 cm(2) V(-1) s(-1), respectively. Although baseline resolution between TNT and 4,6DNOC was not achieved, the drift time for TNT was still easily identified. Alkyl-nitrated phenols, due to acidic fog, responded the strongest in the IMS. The effect of contamination on TNT sensitivity was investigated. Charge competition between TNT and 2,4-dinitrophenol (2,4DNP) was found to occur and to effect TNT sensitivity.