Insights into the Mechanism of Action of Bactericidal Lipophosphonoxins.

The advantages offered by established antibiotics in the treatment of infectious diseases are endangered due to the increase in the number of antibiotic-resistant bacterial strains. This leads to a need for new antibacterial compounds. Recently, we discovered a series of compounds termed lipophosphonoxins (LPPOs) that exhibit selective cytotoxicity towards Gram-positive bacteria that include pathogens and resistant strains. For further development of these compounds, it was necessary to identify the mechanism of their action and characterize their interaction with eukaryotic cells/organisms in more detail. Here, we show that at their bactericidal concentrations LPPOs localize to the plasmatic membrane in bacteria but not in eukaryotes. In an in vitro system we demonstrate that LPPOs create pores in the membrane. This provides an explanation of their action in vivo where they cause serious damage of the cellular membrane, efflux of the cytosol, and cell disintegration. Further, we show that (i) LPPOs are not genotoxic as determined by the Ames test, (ii) do not cross a monolayer of Caco-2 cells, suggesting they are unable of transepithelial transport, (iii) are well tolerated by living mice when administered orally but not peritoneally, and (iv) are stable at low pH, indicating they could survive the acidic environment in the stomach. Finally, using one of the most potent LPPOs, we attempted and failed to select resistant strains against this compound while we were able to readily select resistant strains against a known antibiotic, rifampicin. In summary, LPPOs represent a new class of compounds with a potential for development as antibacterial agents for topical applications and perhaps also for treatment of gastrointestinal infections.

Lipophosphonoxins: new modular molecular structures with significant antibacterial properties.

Novel compounds termed lipophosphonoxins were prepared using a simple and efficient synthetic approach. The general structure of lipophosphonoxins consists of four modules: (i) a nucleoside module, (ii) an iminosugar module, (iii) a hydrophobic module (lipophilic alkyl chain), and (iv) a phosphonate linker module that holds together modules i-iii. Lipophosphonoxins displayed significant antibacterial properties against a panel of Gram-positive species, including multiresistant strains. The minimum inhibitory concentration (MIC) values of the best inhibitors were in the 1-12 µg/mL range, while their cytotoxic concentrations against human cell lines were significantly above this range. The modular nature of this artificial scaffold offers a large number of possibilities for further modifications/exploitation of these compounds.

Phenotypic detection of broad-spectrum beta-lactamases in microbiological practice.

BACKGROUND: Enterobacteriaceae producing ESBL and AmpC enzymes can be associated with failure of antibiotic therapy and related morbidity and mortality. Their routine detection in microbiology laboratories is still a problem. The aim of this study was to compare the sensitivity of selected phenotypic methods. MATERIAL/METHODS: A total of 106 strains of the Enterobacteriaceae family were tested, in which molecular biology methods confirmed the presence of genes encoding ESBL or AmpC. In ESBL-positive strains, the sensitivity of the ESBL Etest (AB Biodisk) and a modified double-disk synergy test (DDST) were evaluated. AmpC strains were tested by a modified AmpC disk method using 3-aminophenylboronic acid. For simultaneous detection of ESBL and AmpC, the microdilution method with a modified set of antimicrobial agents was used. RESULTS: The sensitivity of the ESBL Etest was 95%; the modified DDST yielded 100% sensitivity for ESBL producers and the AmpC test correctly detected 95% of AmpC-positive strains. The sensitivity of the modified microdilution method was 87% and 95% for ESBL and AmpC beta lactamases, respectively. CONCLUSIONS: The detection of ESBL and AmpC beta lactamases should be based on specific phenotypic methods such as the modified DDST, ESBL Etest, AmpC disk test and the modified microdilution method.

[In vitro diagnostic medical devices--the legal context]. / In vitro diagnostické zdravotnické prostredky--legislativní souvislosti.

In vitro diagnostics is the basic principle of most laboratory activities. It influences three quarters of diagnostic decisions, affecting more than a half of direct costs of provided health care. Production, storing and distribution of in vitro diagnostic medical devices, as well as the laboratory diagnostic process itself (use of in vitro diagnostics) must strictly adhere to all legislative provisions relating to in vitro diagnostics. The article provides a detailed explanation of (i) Directive 98/79/CE on in vitro diagnostic medical devices, (ii) Act No. 22/1997 Coll. on technical requirements for products, (iii) Act No. 123/2000 Coll. on medical devices and (iv) Government Regulation No. 453/2004 on technical requirements for in vitro diagnostic medical devices.

[Prevalence of ESBL-positive strains of Klebsiella pneumoniae in the Czech Republic and their molecular biology analysis]. / Prevalence ESBL-pozitivních kmenu Klebsiella pneumoniae v Ceské republice a jejich molekulárne-biologická analýza.

BACKGROUND: One of the problems of contemporary medicine is an increasing number of bacterial strains with hazardous phenotypes of resistance. The feared bacterial pathogens include Klebsiella pneumoniae strains producing AmpA extended-spectrum beta-lactamases. The study focused on the molecular biological characteristics of ESBL-positive strains of Klebsiella pneumoniae collected in the Czech Republic. MATERIALS AND METHODS: Clinical material from patients hospitalized in 16 Czech hospitals in September and October 2004 was used to isolate and determine Klebsiella pneumoniae strains by standard identification procedures. Their susceptibility to antibiotics was tested using a dilution micromethod. A Double-Disk Synergy Test was used for phenotype determination of ESBL production. The blaTEM, blaSHV and blaOXA genes coding ESBL production were demonstrated by PCR. Molecular biological characteristics of ESBL-positive strains utilized the genomic DNA isolation, XbaI restrictase digestion and PFGE differentiation. The acquired restriction maps of individual isolates were compared using GelCompar II software and their relationship was determined. RESULTS: During the monitored period, 913 Klebsiella pneumoniae strains causing clinically detectable diseases were isolated. Of these, 234 (25.6 %) were determined as ESBL-positive strains. The prevalence of ESBL-positive strains was 38.5 % in ICUs and 15.8 % in standard wards. More than 50 % of ESBL-positive isolates were effectively treated only with meropenem (98 %), cefoperazone/sulbactam (61 %) and amikacin (54 %). Conversely, ESBL-negative strains showed high susceptibility to all tested antibiotics (76-99 %). The molecular biological analysis identified 18 clonal types containing 2-6 identical strains. 17 clones usually contained isolates from one hospital and only in one clone strains from two hospitals were identified. CONCLUSION: Based on the above mentioned results, the prevalence of ESBL-positive strains of Klebsiella pneumoniae in the Czech Republic can be perceived as relatively high, especially in the ICUs. An extensive spread of epidemic clones within Czech hospitals and, to a limited extent, between them can be demonstrated.

Frequency of Gram-negative bacterial pathogens in bloodstream infections and their resistance to antibiotics in the Czech Republic.

A study performed at 12 hospitals in the Czech Republic in 2001 evaluated the Gram-negative bacterial pathogens most frequently associated with bloodstream infections and their susceptibility to a selection of antimicrobial agents. Of 831 Gram-negative strains, the most frequently isolated organisms were Escherichia coli (32%), Klebsiella pneumoniae (24%) and Pseudomonas aeruginosa (10%). E. coli isolates were relatively susceptible to the antibiotics tested, whereas K. pneumoniae were relatively resistant to all agents except meropenem, and P. aeruginosa to all agents except gentamicin and amikacin. Other agents showed variable rates of resistance to penicillins, third-generation cephalosporins, aminoglycosides and ciprofloxacin.