The National Institute of Standards and Technology (NIST) and the Pacific Northwest National Laboratory (PNNL) are each creating quantitative databases containing the vapor-phase infrared spectra of pure chemicals. The digital databases have been created with both laboratory and remote-sensing applications in mind. A spectral resolution of approximate, equals 0.1 cm(-1) was selected to avoid degrading sharp spectral features, while also realizing that atmospheric broadening typically limits line widths to 0.1 cm(-1). Calculated positional (wave- number, cm(-1)) uncertainty is /=9) path length-concentration burdens and fitting a weighted Beer's law plot to each wavenumber channel. The two databases include different classes of compounds and were compared using 12 samples. Though these 12 samples span a range of polarities, absorption strengths, and vapor pressures, the data agree to within experimental uncertainties with only one exception.

To identify traits that predict avian pathogenic Escherichia coli (APEC) virulence, 124 avian E. coli isolates of known pathogenicity and serogroup were subjected to virulence genotyping and phylogenetic typing. The results were analyzed by multiple-correspondence analysis. From this analysis, five genes carried by plasmids were identified as being the most significantly associated with highly pathogenic APEC strains: iutA, hlyF, iss, iroN, and ompT. A multiplex PCR panel targeting these five genes was used to screen a collection of 994 avian E. coli isolates. APEC isolates were clearly distinguished from the avian fecal E. coli isolates by their possession of these genes, suggesting that this pentaplex panel has diagnostic applications and underscoring the close association between avian E. coli virulence and the possession of ColV plasmids. Also, the sharp demarcation between APEC isolates and avian fecal E. coli isolates in their plasmid-associated virulence gene content suggests that APEC isolates are well equipped for a pathogenic lifestyle, which is contrary to the widely held belief that most APEC isolates are opportunistic pathogens. Regardless, APEC isolates remain an important problem for poultry producers and a potential concern for public health professionals, as growing evidence suggests a possible role for APEC in human disease. Thus, the pentaplex panel described here may be useful in detecting APEC-like strains occurring in poultry production, along the food chain, and in human disease. This panel may be helpful toward clarifying potential roles of APEC in human disease, ascertaining the source of APEC in animal outbreaks, and identifying effective targets of avian colibacillosis control.

ColV plasmids have long been associated with the virulence of Escherichia coli, despite the fact that their namesake trait, ColV production, does not appear to contribute to virulence. Such plasmids or their associated sequences appear to be quite common among avian pathogenic E. coli (APEC) and are strongly linked to the virulence of these organisms. In the present study, a 180-kb ColV plasmid was sequenced and analyzed. This plasmid, pAPEC-O2-ColV, possesses a 93-kb region containing several putative virulence traits, including iss, tsh, and four putative iron acquisition and transport systems. The iron acquisition and transport systems include those encoding aerobactin and salmochelin, the sit ABC iron transport system, and a putative iron transport system novel to APEC, eit. In order to determine the prevalence of the virulence-associated genes within this region among avian E. coli strains, 595 APEC and 199 avian commensal E. coli isolates were examined for genes of this region using PCR. Results indicate that genes contained within a portion of this putative virulence region are highly conserved among APEC and that the genes of this region occur significantly more often in APEC than in avian commensal E. coli. The region of pAPEC-O2-ColV containing genes that are highly prevalent among APEC appears to be a distinguishing trait of APEC strains.Avian pathogenic Escherichia coli (APEC) strains are the etiologic agents of colibacillosis in birds, an important problem in the poultry industry (7). Along with uropathogenic E. coli (UPEC) and the E. coli strain causing neonatal meningitis or septicemias, APEC strains fall under the category of extraintestinal pathogenic E. coli (ExPEC) (39). ExPEC strains are characterized by the possession of virulence factors that enable their extraintestinal lifestyle and make them distinct from commensal and diarrheagenic E. coli strains (39). Among APEC strains, the iroBCDEN locus (11), shown to encode the siderophore salmochelin in Salmonella enterica (16), the aerobactin operon (51), and the yersiniabactin operon (21) are iron acquisition systems thought to contribute to virulence. Other putative APEC virulence factors include those contributing to complement resistance, such as the increased serum survival gene (iss) (31,33,37); tsh, the temperature-sensitive hemagglutinin gene (34); and the presence of ColV plasmids (37). In fact, it appears that large virulence plasmids, including ColV plasmids, are a defining feature of the APEC pathotype (37, 44).ColV and ColV plasmids have interested scientists for many years, with Gratia first describing ColV as "principle V" in 1925 (53). ColV plasmids, which encode ColV production, typically range in size from 80 to 180 kb (53) and encode traits such as aerobactin production (51) and complement resistance (31). Unlike other colicins, ColV itself is a small protein that is exported from the cell and behaves more like a microcin, disrupting the formation of cell membrane potential required for energy production (53). The ColV operon ...

A preformed T-microchannel imprinted in polycarbonate was postmodified with a pulsed UV excimer laser (KrF, 248 nm) to create a series of slanted wells at the junction. The presence of the wells leads to a high degree of lateral transport within the channel and rapid mixing of two confluent streams undergoing electroosmotic flow. Several mixer designs were fabricated and investigated. All designs were relatively successful at low flow rates (0.06 cm/s, > or = 75% mixing), but had varying degrees of success at high flow rates (0.81 cm/s, 45-80% mixing). For example, one design operating at high flow rates was able to split an incoming fluorescent stream into two streams of varying concentrations depending on the number of slanted wells present. The final mixer design was able to overcome stream splitting at high flow rates, and it was shown that the two incoming streams were 80% mixed within 443 microm of the T-junction for a flow rate of 0.81 cm/s. Without the presence of the mixer and at the same high flow rate, a channel length of 2.3 cm would be required to achieve the same extent of mixing when relying upon molecular diffusion entirely, while 6.9 cm would be required for 99% mixing.