Resistance gene transfer: induction of transducing phage by sub-inhibitory concentrations of antimicrobials is not correlated to induction of lytic phage.

Objectives: Horizontal gene transfer of antimicrobial resistance (AMR) genes between clinical isolates via transduction is poorly understood. MRSA are opportunistic pathogens resistant to all classes of antimicrobial agents but currently no strains are fully drug resistant. AMR gene transfer between Staphylococcus aureus isolates is predominantly due to generalized transduction via endogenous bacteriophage, and recent studies have suggested transfer is elevated during host colonization. The aim was to investigate whether exposure to sub-MIC concentrations of antimicrobials triggers bacteriophage induction and/or increased efficiency of AMR gene transfer. Methods: Isolates from MRSA carriers were exposed to nine antimicrobials and supernatants were compared for lytic phage particles and ability to transfer an AMR gene. A new technology, droplet digital PCR, was used to measure the concentration of genes in phage particles. Results: All antibiotics tested induced lytic phage and AMR gene transduction, although the ratio of transducing particles to lytic particles differed substantially for each antibiotic. Mupirocin induced the highest ratio of transducing versus lytic particles. Gentamicin and novobiocin reduced UV-induced AMR transduction. The genes carried in phage particles correlated with AMR transfer or lytic particle activity, suggesting antimicrobials influence which DNA sequences are packaged into phage particles. Conclusions: Sub-inhibitory antibiotics induce AMR gene transfer between clinical MRSA, while combination therapy with an inhibiting antibiotic could potentially alter AMR gene packaging into phage particles, reducing AMR transfer. In a continually evolving environment, pathogens have an advantage if they can transfer DNA while lowering the risk of lytic death.

Within-host diversity of MRSA antimicrobial resistances.

OBJECTIVES: MRSA is a major antimicrobial resistance (AMR) pathogen. The reservoir of infecting isolates is colonization, which is the site of evolutionary selection. The aim was to identify if AMRs in colonizing MRSA populations diversified and potential mechanisms of resistance gene transfer in vivo. METHODS: Nasal swabs from 38 MRSA carriers admitted to hospital were plated and 20 individual colonies from each patient tested for phenotypic antibiotic susceptibility and genetically for lineage, carriage of four prophages and three plasmid families. Free bacteriophages were detected in swabs as well as their capacity for transducing resistance genes. RESULTS: Nine (24%) patients carried phenotypic AMR variants and 24 (63%) carried prophage and plasmid variants. If a single colony was selected for testing, the probability of detecting all AMR in that patient was 87%. Sixty-four different AMR and mobile genetic element (MGE) profiles were detected, mostly in the MRSA CC22 background (where CC stands for clonal complex), with up to 8 profiles per patient. Nearly half of the patients carried detectable free bacteriophages and phages successfully transduced resistance genes between laboratory and patient isolates in vitro. WGS showed MRSA core genomes were stable, while AMR and MGEs varied. CONCLUSIONS: 'Clouds' of MRSA variants that have acquired or lost AMR and MGEs are common in nasal colonizing populations and bacteriophages may play an important role in gene transfer. Accurate estimation of AMR and genetic variability has implications for diagnostics, epidemiology, antimicrobial stewardship and understanding the evolutionary selection of AMR in colonizing populations.

[Application of Western blotting for the detection of uncoupling protein-2 (UCP-2) in mitochondria from smokers and non-smokers]. / Zastosowanie metody Western blot do oznaczania bialka rozprzegajacego 2 (UCP-2) w mitochondriach osób palacych i niepalacych.

INTRODUCTION: Uncoupling proteins (UCPs) are a family of transmembrane anion transporters present in the inner mitochondrial membrane. UCP-2, which exhibits the widest distribution in various tissues, plays an important role in many physiological processes. Human UCP-2 studies have been hampered by the lack of a method for measuring this protein in an easily accessible human tissue, e.g. blood. The aim of this study was to develop such a method and test its utility by comparing UCP-2 levels in smokers and non-smokers. MATERIAL AND METHODS: Venous blood samples from 10 smoking and seven non-smoking volunteers were used for the study; lymphocytes were isolated employing Lymphoprep. UCP-2 levels were measured by Western blotting combined with chemoluminescence detection. RESULTS: Total lymphocyte homogenates were found useless for measuring UCP-2 levels, but it was possible to measure UCP-2 in homogenates of purified lymphocyte mitochondria. There was a significant, though moderate, linear correlation between UCP-2 level and daily cigarette use. UCP-2 level in peripheral blood lymphocytes from smokers was higher than that in non-smokers. CONCLUSION: The method for measuring UCP-2 in peripheral blood lymphocytes opens the possibility of UCP-2 screening studies in humans and thus may be useful for studying the role of the protein in human physiology and pathology.

CDP-choline (citicoline) attenuates brain damage in a rat model of birth asphyxia.

To estimate protective potential of citicoline in a model of birth asphyxia, the drug was given to 7-day old rats subjected to permanent unilateral carotid artery occlusion and exposed for 65 min to a hypoxic gas mixture. Daily citicoline doses of 100 or 300 m/kg, or vehicle, were injected intraperitoneally for 7 consecutive days beginning immediately after the end of the ischemic-hypoxic insult, and brain damage was assessed by gross zorphology score and weight deficit two weeks after the insult. Caspase-3, alpha-fodrin, Bcl-2, and Hsp70 levels were assessed at 0, 1, and 24 h after the end of the hypoxic insult in another group of rat pups subjected to the same insult and given a single dose of 300 m/kg of citicoline or the vehicle. Citicoline markedly reduced caspase-3 activation and Hsp70 expression 24 h after the insult, and dose-dependently attenuated brain damage. In the context of the well-known excellent safety profile of citicoline, these data suggest that clinical evaluation of the efficacy of the drug in human birth asphyxia may be warranted.