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Fast atom bombardment (FAB) of the lysed cells and crudellpld extracts of bacterla results In the selective desorption of phorphoupkk that are characteristic of bacterlal specks. I n thk paper, constant neutral loss (CNL) llnked scarmlng of the magnetk and electrlc sector flekls of a double focuslng mass spectrometer Is evaluated as an approach to the analysls of bacterla cells that can provlde greater selectlvlty for polar llplds and speclflclty for partlcular phosphollpld classes. I n the metastable t h e frame, neutral losses of phosphorylethanolamlne, phosphorylglycerol, and other polar head groups are be8t obtalned from protonated molecular Ions analyzed In the posltlve Ion mode. SelectlvHy Is Improved (relathre to normal magnetk fleld scans) for phosphollplds of a partlcular class In the presence of more abundant phosphollpMs and the background Ion dgnal characteristk of FAB m a s spectra. I n addklon, CNL scans penntl the observation of momnnethy@hoaphattklylethanolamhre, a mhror pbsphoUpkl prewnt In a few bacterla, such as P. vu&8f/s, but lndlstlngulshabk In mass from fatty acld homologues of PE contalnIng addltlonal methylene groups. Slnce fatty acld content In bacterial lipids (and therefore the masses appearlng In a particular spectrum) reflects growth condltlons as well as specks, the ldenttflcatlon of specllc phosphollpld classes by CNL scans provlcks a promlskrg approach to the klentllicatlon and cladlcatlon of bacterla.Membrane lipids are important biomarkers that can be used to differentiate bacteria from one another (1-3). We have found that desorption mass spectrometry techniques selectively ionize polar membrane lipids directly from lysed bacteria to provide mass spectra that are characteristic of Gram stain and species (4, 5). Both phospholipids and glycolipids are selectively desorbed by these techniques. The most common phospholipids contain two fatty acids, a glycerolphosphate core, and a polar head group which determines the phospholipid class (Scheme I). The variable portions of phospholipids (the head group and the fatty acids) are both found in distribution patterns that are chemotaxonomically significant.Thus, one approach to characterizing bacteria involves the chromatographic analysis of fatty acids extracted from bacteria cultured and harvested under standard conditions (6). Fatty acids are identified by retention times and their distribution is determined from the relative peak areas. While there are limits to the range of fatty acids that a given species will produce, the fatty acid distribution itself can vary significantly in the same species grown on different media, at different Scheme I -CO-O-CH, I CO-0-CH CH, I L/ 0-t-0 R J J R -CHiCH

BackgroundTo investigate the possible effects of different levels of attributes of a point-of-care test (POCT) on sexually transmitted infection (STI) professionals' decisions regarding an ideal POCT for STI(s).MethodsAn online survey was designed based on a large-scale in-depth focus discussion study among STI experts and professionals. The last section of the survey “build your own POCT” was designed by employing the discrete choice experiment approach. Practicing clinicians from two venues, STI-related international conference attendees and U.S. STD clinic clinicians were invited to participate in the survey. Conditional logistical regression modeling was used for data analysis.ResultsOverall, 256 subjects took the online survey with 218 (85%) completing it. Most of the participants were STD clinic clinicians who already used some POCTs in their practice. “The time frame required” was identified as a major barrier that currently made it difficult to use STI POCTs. Chlamydia trachomatis was the organism chosen as the top priority for a new POCT, followed by a test that would diagnose early seroconversion for HIV, and a syphilis POCT. Without regard to organism type selected, sensitivity of 90–99% was always the most important attribute to be considered, followed by a cost of $20. However, when the test platform was prioritized for early HIV seroconversion or syphilis, sensitivity was still ranked as most important, but specificity was rated second most important.ConclusionsSTI professionals preferred C. trachomatis as the top priority for a new POCT with sensitivity over 90%, low cost, and a very short completion time.

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