Failure of an Automated Blood Culture System To Detect Nonfermentative Gram-Negative Bacteria

During a 1-year study we observed that both aerobic and anaerobic blood culture bottles from patients were negative by the BacT/Alert system during a 7-day incubation period. However, upon subcultivation of negative bottles, growth of Pseudomonas aeruginosa was detectable. In an attempt to explain this observation, aerobic BacT/Alert Fan bottles were seeded with a defined inoculum (0.5 McFarland standard; 1 ml) of Escherichia coli, Klebsiella pneumoniae, Serratia marcescens, P. aeruginosa, Stenotrophomonas maltophilia, or Acinetobacter baumannii. Half of the inoculated bottles were loaded into the BacT/Alert system immediately, and the remainder were preincubated for 4, 8, 16, and 24 h at 36°C. With preincubation all bottles seeded with the Enterobacteriaceae signaled positive during the next 1.5 h. Organisms in bottles seeded with the nonfermentative species P. aeruginosa and A. baumannii remained undetected by the BacT/Alert system for 7 days. S. maltophilia was detected if the preincubation time was equal or less than 8 h. Without preincubation all bottles seeded with the Enterobacteriaceae or nonfermentative species signaled positive. Since nonfermentative species seem to enter a state of bacteriostasis within the preincubation period, we reasoned that an unknown factor is consumed. Accordingly, a smaller inoculum should allow the detection of nonfermentative species, even after preincubation, and serial dilutions of P. aeruginosa were detected in preincubated bottles. In this case preincubated bottles signaled positive faster than bottles without preincubation. We conclude that all bottles from clinical settings should be subcultured prior to loading to avoid false negatives. An alternative may be preincubation at room temperature

Poly(fluorenevinylene) derivative by Gilch polymerization for light-emitting diode applications

The synthesis of poly(9,9-di-n-octylfluorene-2,7-vinylene) (PFV) via Gilch polymerization together with its characterization and purification using membrane technology was reported. The purity and structure of the monomer were confirmed by 1H NMR , 13C NMR, and elemental analyses. The key factor for obtaining the high molecular weight of the PFV was the introduction of a chloromethyl group into the 9,9-di-n-octylfluorene unit. The optical absorption (Abs) and photoluminescence (PL) spectra of the thin PFV film were obtained.close1039

Synthesis of Polyfluorenes with Pendant Silylcarboranes

The synthesis of a novel silylcarborane-containing fluorene monomer is reported in the present paper. Homo- and copolymerization via microwave-assisted Ni(0)-medialed coupling are described, and the influence of sterically crowded silylcarboranes on the polymerization outcome is assessed. The fluorescence spectra and thermal characteristics of the resulting polymers are analyzed and compared to determine the impact of carborane cages. Pendant carboranes are shown to improve the stability of annealed thin films. and potential implications in sensing devices and neutron detection are discussed