Oxacillinases and antimicrobial susceptibility of Ralstonia pickettii from pharmaceutical water systems in Croatia.

This study evaluated antibiotic susceptibility and presence of blaOXA22 and blaOXA60 genes in 81 isolates of Ralstonia pickettii obtained from different purified and ultra-pure water systems in two different geographical areas of Croatia. E-test and disc diffusion test were performed to determine antibiotic susceptibility. Polymerase chain reaction was applied to detect genes encoding OXA-22 and OXA-60 oxacillinases previously identified in R. pickettii. The isolates were genotyped by pulsed-field gel electrophoresis. The results revealed variable susceptibility/resistance profiles. Our isolates exhibited high susceptibility rates to ceftriaxone, cefotaxime, piperacillin-tazobactam, ciprofloxacin, imipenem, cefepime and in lesser extent to ceftazidime. High rates of susceptibility were also observed for sulphamethoxazole-trimethoprim and piperacillin. High resistance rates were noticed for ticarcillin-clavulanate, aztreonam and meropenem, as well as for all aminoglycosides tested. Modified Hodge test was positive in 51·9% strains, indicating production of carbapenemases. blaOXA22 and blaOXA60 genes were detected in 37·0 and 80·3% strains, respectively. Pulsed-field gel electrophoresis identified three major clusters containing subclusters. R. pickettii should be taken seriously as a possible cause of nosocomial infections to ensure adequate therapy, to prevent the development of resistant strains and to try to reduce the possibility of R. pickettii surviving in clean and ultra clean water systems.

Electron ionisation induced fragmentation of fused norbornene analogues containing SiMe2 or GeMe2 and oxygen bridges. Migration of SiMe2 and GeMe2 groups.

The main electron ionisation induced fragmentation processes of fused norbornene analogues containing SiMe2 or GeMe2 and oxygen bridges, as well as their dependence on substitution, were investigated using mass (MS) and tandem mass (MS/MS) spectrometric analysis. Formation of the rearrangement ions of m/z 176 in the mass spectra of fused norbornene analogues containing SiMe2 and m/z 222 in the mass spectrum of norbornene analogues containing GeMe2 provides firm evidence for the migration of a SiMe2 and GeMe2 bridge, respectively.

Gas phase reaction rate measurements in Fourier transform mass spectrometry.

Determination of the concentration of neutral polycyclic aromatic hydrocarbon molecules in the mass spectrometer for reaction rate measurement is investigated. Copyright 1999 John Wiley & Sons, Ltd.