Universal transition state scaling relations for (de)hydrogenation over transition metals.

We analyse the transition state energies for 249 hydrogenation/dehydrogenation reactions of atoms and simple molecules over close-packed and stepped surfaces and nanoparticles of transition metals using Density Functional Theory. Linear energy scaling relations are observed for the transition state structures leading to transition state scaling relations for all the investigated reactions. With a suitable choice of reference systems the transition state scaling relations form a universality class that can be approximated with one single linear relation describing the entire range of reactions over all types of surfaces and nanoclusters.

[Stenotrophomonas maltophilia as a cause of hospital infections--typing of clinical isolates using pulsed field gel electrophoresis] ]. / Stenotrophomonas maltophilia kao uzrocnik bolnickih infekcija--tipizacija klinickih izolata metodom elektroforeze u pulzirajucem polju (PFGE).

Stenotrophomonas maltophilia (S. maltophilia) has been recognised now as an important cause of hospital infections. As S. maltophilia is resistant to many antibiotics, attempts have been made to identify the sources of S. maltophilia infection and route of its transmission. From July till October 1998, 22 isolates of S. maltophilia were obtained from 20 patients hospitalised at eight different wards. Strain typing was performed by macrorestriction analysis of chromosomal DNA by use of PFGE (XbaI and SpeI enzymes, in a CHEF DR III drive module). PFGE analysis of 22 S. maltophilia isolates revealed 9 different types designated by letters A to I. The source and route of the spread of infection could not be identified. These results may indicate that we had clusters of S. maltophilia infection in cardiosurgery ward and ICU by types A, B, C and D; in neurosurgical ICU by type E and in urology ICU by type H.

[Guidelines for cleaning and disinfection/sterilization of endoscopes]. / Preporuke za ciscenje i dezinfekciju/sterilizaciju endoskopa.

Endoscopy is a diagnostic and therapeutic method which is being increasingly used in various fields of medicine, especially in minimal invasive surgery. During the endoscopic procedure, endoscopes are contaminated with patient's microbial flora. After each procedure and before the next patient, endoscope should be reprocessed in a way to be safe from post-procedural infection. Endoscopes are divided in two categories (the borders between them are not always clear-cut): high-risk category endoscopes which enter the sterile tissue, and medium-risk category which come in contact with mucosal surface. High-risk endoscopes should be sterilized or high-level disinfected, and medium-risk should be high-level disinfected. The first and the most important step in endoscope reprocessing is thorough manual cleaning of all parts of dismantled endoscope and of all channels in water and (enzymatic) detergent. The second step is disinfection of endoscope fully immersed in 2% glutaraldehyde for 20 minutes at room temperature. The third step is thorough rinsing in sterile water or tap water followed by 70% ethanol, depending on the next endoscopic procedure. Steps 2-4 can be done in the machine. During endoscopy as well as during endoscope reprocessing, strict preventive measures should be followed for health care workers protection.

Helicobacter pylori: in vitro induction of resistance to azithromycin.

Helicobacter pylori resistance to macrolides is possibly an important factor for the failure of macrolide therapy for H. pylori infection. The aim of this study was to assess the propensity of H. pylori to develop in vitro resistance to azithromycin. In 73 clinical isolates taken from patients before starting antimicrobial therapy of H. pylori infection, MIC was determined using an agar dilution method (Müller-Hinton agar with 7.5% unlysed horse blood, pH = 7.2, at 35 degrees C, during 72 h in a humid microaerobic atmosphere). Each strain was first cultivated at half minimal inhibitory concentration (MIC) then in doubling concentrations until growth arrest. All experiments for induction of resistance were performed on the same media, incubation temperature, atmosphere and time of MIC determination. MIC interpretative standards for sensitivity, intermediate sensitivity and resistance of H. pylori to azithromycin were < or = 2, 4 and > or = 8 mg/l, respectively. Of 73 strains, 5 died during the experiments, and in the remaining 68 strains, serial passage with increasing azithromycin concentrations resulted in the development of resistance in 19 (26.9%) strains. Two strains had an MIC of 16 mg/l azithromycin. Thirty-three (48.5%) strains kept the same MIC or doubled their MIC, 16 (23.5%) strains had 4- to 16-fold MIC but still remained sensitive, 2 resistant strains had 128-fold MICs and 17 resistant strains had increased their MICs more than 128 times. Seventeen highly resistant strains (MIC > 128 mg/l) were kept frozen at -70 degrees C for 3 months in a brain-heart infusion broth with 15% glycerol. MIC was assessed again to determine the stability of resistance. Eleven strains kept MICs > 128 mg/l, 2 became sensitive and 1 intermediate, but reverted easily, after only 2 passages, to an MIC of > 128 mg/l azithromycin. Although macrolides are very active against H. pylori, the propensity to develop resistance in a high proportion of strains has a clear impact on the choice of the right combinations of macrolides with other agents as well as the dosage of the macrolide antibiotics.