• Lyons Herring posted an update 6 months, 3 weeks ago

    Although there was some variation at the transposon level (mostly Tn4401a, 584/604 (97%) isolates; predominantly with ATTGA-ATTGA target site duplications, 465/604 77% isolates), bla KPC spread appears to have been supported by highly fluid, modular exchange of larger genetic segments amongst plasmid populations dominated by IncFIB (580/604 isolates), IncFII (545/604 isolates) and IncR replicons (252/604 isolates). The subset of reconstructed plasmid sequences (21 isolates, 77 plasmids) also highlighted modular exchange amongst non-bla KPC and bla KPC plasmids, and the common presence of multiple replicons within bla KPC plasmid structures (>60%). The substantial genomic plasticity observed has important implications for our understanding of the epidemiology of transmissible carbapenem resistance in Enterobacterales, for the implementation of adequate surveillance approaches, and for control. Copyright © 2020 American Society for Microbiology.Capsid assembly is a critical step in the hepatitis B virus (HBV) life cycle, mediated by the core protein. Core is a potential target for new antiviral therapies, the capsid assembly modulators (CAMs). JNJ-56136379 (JNJ-6379) is a novel and potent CAM currently in phase II trials. We evaluated the mechanism of action (MOA) and antiviral properties of JNJ-6379 in vitro Size exclusion chromatography and electron microscopy studies demonstrated that JNJ-6379 induced formation of morphologically intact viral capsids devoid of genomic material (‘primary’ MOA). JNJ-6379 accelerated the rate and extent of HBV capsid assembly in vitro JNJ-6379 specifically and potently inhibited HBV replication; median 50% effective concentration (EC50) 54 nM (HepG2.117 cells). In HBV-infected primary human hepatocytes (PHHs), JNJ-6379, when added with the viral inoculum, dose-dependently reduced extracellular HBV DNA levels (median EC50 93 nM) and prevented covalently closed circular DNA (cccDNA) formation, leading to a dose-dependent reduction of intracellular HBV RNA levels (median EC50 876 nM) and reduced antigen levels (‘secondary’ MOA). Adding JNJ-6379 to PHHs 4/5 days post infection reduced extracellular HBV DNA and did not prevent cccDNA formation. Time-of-addition PHH studies revealed that JNJ-6379 most likely interfered with post-entry processes. Collectively, these data demonstrate that JNJ-6379 has a dual MOA on the early and late steps of the HBV life cycle, which is different to the MOA of nucleos(t)ide analogues. JNJ-6379 is in development for chronic hepatitis B treatment, and may translate into higher HBV functional cure rates. Copyright © 2020 American Society for Microbiology.Plazomicin was active against 97.0% of 8,783 Enterobacterales isolates collected in the United States (2016-2017) and only 6 isolates carried 16S rRNA methyltransferases encoding resistance to virtually all aminoglycosides. Plazomicin (89.2-95.9% susceptible) displayed greater activity compared to amikacin (72.5-78.6%), gentamicin (30.4-45.9%) and tobramycin (7.8-22.4%) against carbapenem-resistant and extensively drug-resistant isolates. The discrepancies among the susceptibility rates for these agents was greater when applying breakpoints generated using the same stringent contemporary methods applied to determine plazomicin breakpoints. Copyright © 2020 American Society for Microbiology.Enterococcus faecium (Efm) strains are commonly resistant to vancomycin and β-lactams. In addition, Efm often causes biofilm-associated infections and these infections are difficult to treat. In this context, we investigated the activity of DAP dosing regimens (8, 10, 12 and 14 mg/kg/d) alone and in combination with ceftaroline (CPT), ampicillin (AMP), ertapenem (ERT) and rifampin (RIF) against 2 clinical strains of biofilm-producing vancomycin-resistant Enterococcus faecium (VREfm) S447 and HOU503 in an in vitro biofilm model. HOU503 harbors common LiaS and LiaR substitutions whereas S447 lacks mutations associated with the LiaFSR pathway. AT13387 clinical trial Minimum inhibitory concentrations (MIC) results demonstrated that both strains were susceptible to DAP and resistant to CPT, AMP, ERT and RIF. The 168-h pharmacokinetic/pharmacodynamic (PK/PD) CDC biofilm reactor models (simulating human antibiotic exposures) with titanium and polyurethane coupons were used to evaluate the efficacy of antibiotic combinations. DAP 12 and 14 achieved bactericidal activity against S447 but lacked such effect against HOU503. Addition of ERT and RIF enhanced DAP activity, allowing DAP 8 and 10 + ERT or RIF to produce bactericidal activity against both strains at 168 h. While, DAP 8 and 10 + CPT improved killing they did not reach bactericidal reduction against S447. Combination of CPT with DAP 8 and 10 enhanced DAP activity and showed bactericidal killing against HOU503 at 168h. Our data provides further support for combinations of DAP with AMP, ERT, CPT and RIF in infections caused by biofilm producing VREfm. Further research involving DAP combinations against biofilm-producing enterococci is warranted. Copyright © 2020 American Society for Microbiology.Nine hundred Haemophilus influenzae clinical isolates from 83 U.S. and European medical centers were tested for susceptibility by reference broth microdilution methods against ceftolozane-tazobactam and comparators. Results were stratified by β-lactamase production and infection type. Overall, ceftolozane-tazobactam MIC50/90 values were 0.12/0.25 mg/L and 99.0% of isolates were inhibited at the susceptible breakpoint of ≤0.5 mg/L; the highest MIC value was only 2 mg/L. Our results support using ceftolozane-tazobactam to treat H. influenzae infections. Copyright © 2020 American Society for Microbiology.Quinolones, such as the antimalarial atovaquone, are inhibitors of the malarial mitochondrial cytochrome bc 1 complex, a target critical to the survival of both liver and blood stage parasites, making these drugs useful as both prophylaxis and treatment. Recently, several derivatives of endochin have been optimised to produce novel quinolones that are active in vitro and in animal models. While these quinolones exhibit potent ex vivo activity against Plasmodium falciparum and P vivax, their activity against the zoonotic P knowlesi is unknown. We screened several of these novel endochin-like quinolones (ELQs) for their activity against P. knowlesi in vitro, and compared this with their activity against P. falciparum tested under identical conditions. We demonstrate that ELQs are potent against P. knowlesi (EC50 values less then 117 nM), and equally effective against P falciparum We then screened select quinolones and partner drugs using a longer exposure (2.5 life cycles), and show that proguanil is 10-fold less potent against P knowlesi when compared with P falciparum, while the quinolones demonstrate similar susceptibility.

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