The high-affinity phosphate transporter Pst in Proteus mirabilis HI4320 and its importance in biofilm formation.

Proteus mirabilis causes urinary tract infections (UTIs) in individuals requiring long-term indwelling catheterization. The pathogenesis of this uropathogen is mediated by a number of virulence factors and the formation of crystalline biofilms. In addition, micro-organisms have evolved complex systems for the acquisition of nutrients, including the phosphate-specific transport system, which has been shown to be important in biofilm formation and pathogenesis. A functional Pst system is important during UTIs caused by P. mirabilis HI4320, since transposon mutants in the PstS periplasmic binding protein and the PstA permease protein were attenuated in the CBA mouse model of UTI. These mutants displayed a defect in biofilm formation when grown in human urine. This study focuses on a comparison of the proteomes during biofilm and planktonic growth in phosphate-rich medium and human urine, and microscopic investigations of biofilms formed by the pst mutants. Our data suggest that (i) the Deltapst mutants, and particularly the DeltapstS mutant, are defective in biofilm formation, and (ii) the proteomes of these mutants differ significantly from that of the wild-type. Therefore, since the Pst system of P. mirabilis HI4320 negatively regulates biofilm formation, this system is important for the pathogenesis of these organisms during complicated UTIs.

Complicated catheter-associated urinary tract infections due to Escherichia coli and Proteus mirabilis.

Catheter-associated urinary tract infections (CAUTIs) represent the most common type of nosocomial infection and are a major health concern due to the complications and frequent recurrence. These infections are often caused by Escherichia coli and Proteus mirabilis. Gram-negative bacterial species that cause CAUTIs express a number of virulence factors associated with adhesion, motility, biofilm formation, immunoavoidance, and nutrient acquisition as well as factors that cause damage to the host. These infections can be reduced by limiting catheter usage and ensuring that health care professionals correctly use closed-system Foley catheters. A number of novel approaches such as condom and suprapubic catheters, intermittent catheterization, new surfaces, catheters with antimicrobial agents, and probiotics have thus far met with limited success. While the diagnosis of symptomatic versus asymptomatic CAUTIs may be a contentious issue, it is generally agreed that once a catheterized patient is believed to have a symptomatic urinary tract infection, the catheter is removed if possible due to the high rate of relapse. Research focusing on the pathogenesis of CAUTIs will lead to a better understanding of the disease process and will subsequently lead to the development of new diagnosis, prevention, and treatment options.

The influence of roughness, angle, range, and transducer type on the echo signal from planar interfaces.

The received electrical echo signal from a pulse-echo system insonifying a planar interface was measured for varying degrees of rms roughness [0 to 0.29 mm (0 to 1.7 lambda)], angles of incidence, theta, (-7 degrees to 7 degrees), and ranges to a planar or focused transducer. The effect of varying theta is quantified in terms of the energy of the received signal, E(theta), and the normalized spectrum of the received signal. E(theta) is approximately Gaussian when using a planar transducer or a focused transducer with the reflecting interface located at or beyond the focal point. For focused transducers with the interface located closer than the geometrical point of focus, two maxima can sometimes be observed when varying the incident angle. As is generally known, the width of E(theta) is strongly dependent on transducer type, e.g., for a smooth interface, the -3 dB width for a 25.4 mm diameter 5-MHz planar and focused transducer was approximately 0.5 degree and 4 degrees (at the focal point), respectively. E(0 degree) as a function of surface roughness, Rq, was nearly linear on a decibel scale, with a slope of -109 dB/(Rq/lambda) and -61 dB/(Rq/lambda) for planar and focused transducers, respectively. The characteristic nulls present in the normalized spectra of the echo signal at non-normal incidence tend to vanish with increasing Rq when using planar transducers. For focused transducers, the normalized spectra change from relatively flat to monotonically decreasing as Rq increases, and they exhibit reduced amplitude with increased incident angle.

Spectroscopic properties of Cr(4+):Lu(3)Al(5)O(12).

We report on the near-infrared absorption, emission, and lifetime data of Cr(4+):Lu(3)Al(5)O(12) (Cr:LAG) and compare the results with the known laser material Cr(4+)-doped Y(3)Al(5)O(12) (Cr:YAG). Lu(3)Al(5)O(12) has a smaller unit cell than Y(3)Al(5)O(12), and this feature is reflected in its spectroscopic properties. The low-temperature luminescence spectrum is shifted by 85 cm(-1) to higher energy compared with Cr:YAG. The luminescence lifetime of Cr:LAG at 10 K is 28.7 micros (Cr:YAG, 30.6 micros) and at 300 K is 4.3 micros (Cr:YAG, 3.5 micros). From these lifetimes we postulate that the quantum efficiency in Cr:LAG is higher than in Cr:YAG. We discuss the potential of Cr:LAG as a tunable near-infrared laser.