PCR assays have proved useful for detecting and characterizing Shiga toxin-producing Escherichia coli (STEC). Recent advances in PCR technology have facilitated the development of real-time fluorescence PCR assays with greatly reduced amplification times and improved methods for the detection of amplified target sequences. We developed and evaluated two such assays for the LightCycler instrument: one that simultaneously detects the genes for Shiga toxins 1 and 2 (stx 1 and stx 2 ) and another that simultaneously detects the genes for intimin (eae) and enterohemolysin (E-hly). Amplification and sequence-specific detection of the two target genes were completed within 60 min. Findings from the testing of 431 STEC isolates of human and animal origin, 73 isolates of E. coli negative for stx genes, and 118 isolates of other bacterial species with the LightCycler PCR (LC-PCR) assays were compared with those obtained by conventional block cycler PCR analysis. The sensitivities and specificities of the LC-PCR assays were each 100% for the stx 1 , eae, and E-hly genes and 96 and 100%, respectively, for the stx 2 gene. No stx 2 genes were detected from 10 stx 2f -positive isolates because of significant nucleotide differences in their primer annealing regions. Melting curve analyses of the amplified Shiga toxin genes revealed sequence variation within each of the tested genes that correlated with described and novel gene variants. The performance characteristics of the LC-PCR assays, such as their speed, detection method, and the potential subtyping information available from melting curve analyses, make them attractive alternatives to block cycler PCR assays for detecting and characterizing STEC strains.
We tested the effectiveness of ampicillin bound to nanoparticles of polyisohexylcyanoacrylate (PIHCA) in treating C57BL/6 mice experimentally infected with Salmonella typhimurium C5. The diameter of the nanoparticles was 187 13 nm, and the ampicillin/PIJICA ratio was 0.2/1. The proportion of ampicillin bound was 90 3%. All control mice and all those treated with nonloaded nanoparticles died within 10 days of infection. By contrast, all mice treated with a single i 'ection of 0.8 mg of nanoparticle-bound ampicillin survived. With free ampicillin, a similar curative effect required three doses of 32 mg each. Lower doses delayed but did not reduce mortality. The sharp increase in the therapeutic index of ampicillin after linkage to
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