Newly Detected Transmission of blaKPC-2 by Outer Membrane Vesicles in Klebsiella Pneumoniae.

OBJECTIVE: The prevalence of carbapenem-resistant Klebsiella pneumoniae (CR-KP) is a global public health problem. It is mainly caused by the plasmid-carried carbapenemase gene. Outer membrane vesicles (OMVs) contain toxins and other factors involved in various biological processes, including ß-lactamase and antibiotic-resistance genes. This study aimed to reveal the transmission mechanism of OMV-mediated drug resistance of Klebsiella (K.) pneumoniae. METHODS: We selected CR-KP producing K. pneumoniae carbapenemase-2 (KPC-2) to study whether they can transfer resistance genes through OMVs. The OMVs of CR-KP were obtained by ultracentrifugation, and incubated with carbapenem-sensitive K. pneumoniae for 4 h. Finally, the carbapenem-sensitive K. pneumoniae was tested for the presence of blaKPC-2 resistance gene and its sensitivity to carbapenem antibiotics. RESULTS: The existence of OMVs was observed by the electron microscopy. The extracted OMVs had blaKPC-2 resistance gene. After incubation with OMVs, blaKPC-2 resistance gene was detected in sensitive K. pneumoniae, and it became resistant to imipenem and meropenem. CONCLUSION: This study demonstrated that OMVs isolated from KPC-2-producing CR-KP could deliver blaKPC-2 to sensitive K. pneumoniae, allowing the bacteria to produce carbapenemase, which may provide a novel target for innovative therapies in combination with conventional antibiotics for treating carbapenem-resistant Enterobacteriaceae.

ZD7288, a selective hyperpolarization-activated cyclic nucleotide-gated channel blocker, inhibits hippocampal synaptic plasticity.

The selective hyperpolarization-activated cyclic nucleotide-gated (HCN) channel blocker 4-(N-ethyl-N-phenylamino)-1,2-dimethyl-6-(methylamino) pyrimidinium chloride (ZD7288) blocks the induction of long-term potentiation in the perforant path-CA3 region in rat hippocampus in vivo. To explore the mechanisms underlying the action of ZD7288, we recorded excitatory postsynaptic potentials in perforant path-CA3 synapses in male Sprague-Dawley rats. We measured glutamate content in the hippocampus and in cultured hippocampal neurons using high performance liquid chromatography, and determined intracellular Ca(2+) concentration [Ca(2+)]i) using Fura-2. ZD7288 inhibited the induction and maintenance of long-term potentiation, and these effects were mirrored by the nonspecific HCN channel blocker cesium. ZD7288 also decreased glutamate release in hippocampal tissue and in cultured hippocampal neurons. Furthermore, ZD7288 attenuated glutamate-induced rises in [Ca(2+)]i in a concentration-dependent manner and reversed 8-Br-cAMP-mediated facilitation of these glutamate-induced [Ca(2+)]i rises. Our results suggest that ZD7288 inhibits hippocampal synaptic plasticity both glutamate release and resultant [Ca(2+)]i increases in rat hippocampal neurons.

[The spontaneous YMDD mutation rate in chronic hepatitis B patients].

OBJECTIVE: To investigate the spontaneous YMDD mutation rate. METHODS: Serum samples collected from 196 untreated chronic HBV patients were detected by primer-specific real-time PCR. RESULTS: Among 196 patients, spontaneous YMDD variants were detected in 21 subjects (20 YVDD mutants and 1 YIDD mutant). YMDD variants account for more than 50%, 25% to 50%, 9% to 25% of total virus load in 1, 5 and 15 patients, respectively. Gender, age, HBeAg status, serum viral load, the state of disease and duration of infection were not associated with spontaneous YMDD mutation. Genotype B had higher spontaneous YMDD rate than genotype C (20.00% vs 7.38%, x(2) = 6.28, P < 0.05). CONCLUSION: Spontaneous YMDD variants exist in chronic hepatitis B patients, Genotype B is associated with higher spontaneous YMDD rate.