Strain- and host species-specific inflammasome activation, IL-1ß release, and cell death in macrophages infected with uropathogenic Escherichia coli.

Uropathogenic Escherichia coli (UPEC) is the main etiological agent of urinary tract infections (UTIs). Little is known about interactions between UPEC and the inflammasome, a key innate immune pathway. Here we show that UPEC strains CFT073 and UTI89 trigger inflammasome activation and lytic cell death in human macrophages. Several other UPEC strains, including two multidrug-resistant ST131 isolates, did not kill macrophages. In mouse macrophages, UTI89 triggered cell death only at a high multiplicity of infection, and CFT073-mediated inflammasome responses were completely NLRP3-dependent. Surprisingly, CFT073- and UTI89-mediated responses only partially depended on NLRP3 in human macrophages. In these cells, NLRP3 was required for interleukin-1ß (IL-1ß) maturation, but contributed only marginally to cell death. Similarly, caspase-1 inhibition did not block cell death in human macrophages. In keeping with such differences, the pore-forming toxin α-hemolysin mediated a substantial proportion of CFT073-triggered IL-1ß secretion in mouse but not human macrophages. There was also a more substantial α-hemolysin-independent cell death response in human vs. mouse macrophages. Thus, in mouse macrophages, CFT073-triggered inflammasome responses are completely NLRP3-dependent, and largely α-hemolysin-dependent. In contrast, UPEC activates an NLRP3-independent cell death pathway and an α-hemolysin-independent IL-1ß secretion pathway in human macrophages. This has important implications for understanding UTI in humans.

Multielemental characterisation of cobalt by glow discharge quadrupole mass spectrometry.

Multielemental determination and the assessment of purity of cobalt metal used in the preparation of Ni-based super-alloys have been carried out by glow discharge quadrupole mass spectrometry (GD-QMS). Relative sensitivity factors (RSF) generated from certified iron matrix reference samples (NIST 663 and 664 low alloy steel pin standards) could be used for the determination of different trace element constituents of the sample. Different wet chemical procedures were also carried out for the determination of the trace constituents in the sample. The GD-QMS results are in reasonably good agreement with those obtained from wet chemical procedures, validating the use of the RSF values generated on low alloy steel standards for the computation of trace element concentrations in cobalt metal. A variety of molecular ions formed through the reaction of cobalt (matrix) with the discharge gas (argon) were also detected.

Neonatal gastrointestinal perforations.

Fourteen neonates presented with clinical and radiological evidence of gastrointestinal perforation, of which 13 were treated by operative intervention. No infant was formula fed, had rectal bleeding or radiological evidence of pneumatosis intestinalis. Operative findings revealed localized perforation in ten of which three were gastric, two distal ileal, three cecal and two in sigmoid colon. Gangrene with extensive perforation of jejunum, ascending colon and transverse colon were seen in one each. Blood cultures were positive in four, one grew E. coli and three Klebsiella while peritoneal cultures were positive in six, one grew E. coli and five Klebsiella. Ten neonates survived and are being followed up. Three of the four cases who died had white blood cell count greater than 25 x 109/L and grew Klebsiella on peritoneal culture. Factors predisposing to gastrointestinal perforations in neonates are discussed, emphasis is made on the cautious use of umbilical, gastric and rectal catheters, and the need for early surgical intervention.