Development of rabbit models of ventilator-associated bacterial pneumonia produced by carbapenem-resistant Pseudomonas aeruginosa.

Ventilator-associated bacterial pneumonia (VABP) is among the most intractable of carbapenem-resistant Gram-negative bacterial infections. New antimicrobial agents are critically needed for the treatment of VABP. However, current conventionally used animal model systems are inadequate to meet this challenge. We, therefore, developed rabbit models of VABP caused by carbapenem-resistant Pseudomonas aeruginosa. Persistently neutropenic New Zealand White rabbits were used throughout the study. The early-phase intubated model (0-24 h) received mechanical ventilation, while the late-phase intubated model (72-96 h) was ambulatory. The following outcome parameters were studied: survival, residual tissue bacterial burden (CFU/g), residual BAL bacterial burden (CFU/mL), lung weights, pulmonary lesion score, histology, O2 saturation, radiographic imaging, and histology. Each anesthetized rabbit received a predetermined endotracheal bacterial inoculum, and ventilators were set to FiO2 = 40% and PEEP = 8 mmHg. Within the first 12 h post-inoculation, mean bacterial burdens in lung tissue and BAL fluid, respectively, were established at approximately 107 CFU/g and 106 CFU/mL, persisted through 24 h in the early-phase model and increased in the late-phase model to approximately 108 CFU/g and 107 CFU/mL. Mean max SpO2 was ≥98 mmHg, and mean nadir SpO2 was ≥68 mmHg. Serial thoracic radiographs demonstrated progressive multilobar pneumonic infiltrates. Lung histology revealed progressive focal bronchopneumonia, coagulative necrosis, intra-alveolar hemorrhage, alveolar epithelial cell necrosis, and bacterial microcolonies. The new rabbit model of VABP produced by carbapenem-resistant Pseudomonas aeruginosa recapitulates the pathophysiological, microbiological, diagnostic imaging, and histological patterns of human disease by which to assess critically needed new antimicrobial agents against this lethal infection.

Neuroprotective Effect of a Novel ATP-Synthase Inhibitor Bedaquiline in Cerebral Ischemia-Reperfusion Injury.

Mitochondrial dysfunction during ischemic stroke ultimately manifests as ATP depletion. Mitochondrial ATP synthase upon loss of mitochondrial membrane potential during ischemia rapidly hydrolyses ATP and thus contributes to ATP depletion. Increasing evidence suggests that inhibition of ATP synthase limits ATP depletion and is protective against ischemic tissue damage. Bedaquiline (BDQ) is an anti-microbial agent, approved for clinical use, that inhibits ATP synthase of Mycobacteria; however recently it has been shown to act on mitochondrial ATP synthase, inhibiting both ATP synthesis and hydrolysis in low micromolar concentrations. In this study, we investigated whether preconditioning with BDQ can alleviate ischemia/reperfusion-induced brain injury in Wistar rats after middle cerebral artery occlusion-reperfusion and whether it affects mitochondrial functions. We found that BDQ was effective in limiting necrosis and neurological dysfunction during ischemia-reperfusion. BDQ also caused inhibition of ATPase activity, mild uncoupling of respiration, and stimulated mitochondrial respiration both in healthy and ischemic mitochondria. Mitochondrial calcium retention capacity was unaffected by BDQ preconditioning. We concluded that BDQ has neuroprotective properties associated with its action on mitochondrial respiration and ATPase activity.

Pharmacokinetics and Efficacy of Ceftazidime-Avibactam in the Treatment of Experimental Pneumonia Caused by Klebsiella pneumoniae Carbapenemase-Producing K. pneumoniae in Persistently Neutropenic Rabbits.

Klebsiella pneumoniae carbapenemase-producing Klebsiella pneumoniae (KPC-Kp) is an emerging global public health threat that causes life-threatening pneumonia and bacteremia. Ceftazidime-avibactam (CZA) represents a promising advance for the treatment of serious infections caused by KPC-Kp We investigated the pharmacokinetics and efficacy of ceftazidime-avibactam in the treatment of experimental KPC-Kp pneumonia in persistently neutropenic rabbits. For single-dose and multidose (administration every 8 h) pharmacokinetics, rabbits received ceftazidime-avibactam intravenous infusions at 60/15, 90/22.5, and 120/30 mg/kg of body weight. Ceftazidime mean area under the concentration-time curves (AUCs) ranged from 287 to 608 µg·h/ml for a single dose and from 300 to 781 µg·h/ml for multiple doses. Avibactam AUCs ranged from 21 to 48 µg·h/ml for a single dose and from 26 to 48 µg·h/ml for multiple doses. KPC-Kp pneumonia was established by direct endotracheal inoculation. Treatments consisted of ceftazidime-avibactam at 120/30 mg/kg every 6 h, a polymyxin B (PMB) loading dose of 2.5 mg/kg followed by 1.5 mg/kg every 12 h q12h, or no treatment (untreated controls [UC]). There were significant reductions in the residual bacterial burden, lung weights, and pulmonary hemorrhage scores in CZA- and PMB-treated rabbits for a 7-day or a 14-day (P ≤ 0.01) course in comparison with those in the UC. These results corresponded to significant decreases in the bacterial burden in bronchoalveolar lavage fluid after a 7-day or a 14-day treatment (P ≤ 0.01). The outcomes demonstrated an improved response at 14 days versus that at 7 days. There was significantly prolonged survival in rabbits treated with CZA for 14 days in comparison with that in the PMB-treated or UC rabbits (P ≤ 0.05). This study demonstrates that ceftazidime-avibactam displays linear dose-proportional exposures simulating those seen from human plasma pharmacokinetic profiles, is active for the treatment of experimental KPC-Kp pneumonia in persistently neutropenic rabbits, and provides an experimental foundation for the treatment of severely immunocompromised patients with this life-threatening infection.

The effect of induced sputum and bronchoalveolar lavage fluid from patients with chronic obstructive pulmonary disease on neutrophil migration in vitro.

OBJECTIVE: The aim of study was to investigate a chemotactic effect of induced sputum and bronchoalveolar lavage fluid on blood neutrophils in patients with chronic obstructive pulmonary disease (COPD) and healthy individuals. MATERIAL AND METHODS: Forty-three smokers with COPD, 19 ex-smokers with COPD, 13 healthy smokers, and 17 healthy nonsmokers were recruited to the study. Neutrophils were isolated from peripheral blood of study individuals. For the same experimental conditions, pooled induced sputum and bronchoalveolar lavage fluid of 20 COPD patients were used. Neutrophil chemotaxis in vitro was performed in cell-transmigration chamber. Substances tested for chemoattraction (interleukin-8, induced sputum, bronchoalveolar lavage fluid directly or in addition to interleukin-8) were added to lower wells. Upper wells were filled with 2.5 x 10(6)/mL of neutrophil culture and incubated for 2 hours. Migration was analyzed by flow cytometry. RESULTS: Interleukin-8 (10-100 ng/mL) induced a dose-dependant neutrophil migration in all the groups. Only 100 ng/L of interleukin-8 induced more intensive chemotaxis of neutrophils from COPD smokers as compared to ex-smokers (P<0.05). Such difference between healthy individuals was obtained using 30 ng/mL of interleukin-8 (P<0.05). Induced sputum/interleukin-8 (10-100 ng/mL), as well as induced sputum directly, induced neutrophil migration (P<0.05). Chemotaxis of neutrophils isolated from COPD patients and healthy nonsmokers did not depend on additional interleukin-8 concentration. Bronchoalveolar lavage fluid/interleukin-8 (30-100 ng/mL) induced more intensive migration of neutrophils from COPD patients than bronchoalveolar lavage fluid (P<0.05) alone. CONCLUSIONS: Migration of neutrophils isolated from patients with COPD was more intensive compared to healthy individuals. Induced sputum and bronchoalveolar lavage fluid directly and with addition of interleukin-8 stimulated chemotaxis, and it was higher in neutrophils from COPD patients. Migration of neutrophils did not depend on smoking status.

Gender-Related Effect of Sodium Dichloroacetate on the Number of Hassall's Corpuscles and RNA NKCC1 Expression in Rat Thymus.

The aim was to investigate the effect of dichloroacetate (DCA) on thymus weight, Hassall's corpuscle number (HCs), and NKCC1 RNA expression in Wistar rats aged 4-5 weeks. They were investigated in the controls and DCA-treated gonad-intact and castrated males and females. The treatment lasted 4 weeks with DCA 200 mg/kg/day. At the end of the experiment, rat thymus was weighted, and its lobe was taken for the expression of NKCC1 RNA determined by the PCR method and of Hassall's corpuscles by immunohistochemistry. DCA caused a thymus weight decrease in DCA-treated gonad-intact rats of both genders as compared with their controls (p < 0.05), and no such impact was found in castrated DCA-treated males and females. DCA caused an increase of the HCs in gonad-intact males (p < 0.05), and no such increase in the DCA-treated gonad-intact females was found. There was gender-related difference in the HCs when comparing DCA-treated gonad-intact males and females: males showed significantly higher HCs (p < 0.05); no gender-related differences were found in the castrated DCA-treated groups. The Slc12a2 gene RNA expression level was found to be significantly decreased only in gonad-intact and in castrated DCA-treated males. The authors discuss the gender-related DCA effects on the thymus.

Real-time gene expression analysis in carp (Cyprinus carpio L.) skin: inflammatory responses to injury mimicking infection with ectoparasites.

We studied a predictive model of gene expression induced by mechanical injury of fish skin, to resolve the confounding effects on the immune system induced by injury and skin parasite-specific molecules. We applied real time quantitative PCR (RQ-PCR) to measure the expression of the pro-inflammatory cytokines CXCa, CXCb, interleukin (IL)1-beta, tumor necrosis factor alpha (TNFalpha), and the receptors IL1R1, CXCR1 and CXCR2 in skin of Cyprinus carpio after mechanical injury. We also studied the expression of the anti-inflammatory cytokine IL-10. Most obvious, specific up-regulation of the chemokine CXCa, the chemokine receptor CXCR1 and the pro-inflammatory cytokine IL-beta was detected at 2-3h after injury. In order to correlate gene expression patterns after injury with cell migration, we studied chemotaxis of head kidney leukocytes towards lysates of epithelioma papulosum cyprini (EPC) cells. Neutrophilic granulocytes were shown to migrate towards epithelial lysates. Using immunohistochemistry we observed that the early inflammatory response after injury involved an influx of cells, most probably neutrophilic granulocytes, into the injured area. This suggests that the increased expression of pro-inflammatory genes is related to a rapid influx of neutrophilic granulocytes.

Modulation of carp (Cyprinus carpio) neutrophil functions during an infection with the haemoparasite Trypanoplasma borreli.

Trypanoplasma borreli is an extracellular blood parasite of common carp (Cyprinus carpio) transmitted by fish-biting leeches. The infestation with this parasite in juvenile carp may range between 75% and 100%, especially in fish recovering from the first hibernation period. T. borreli is perfectly adapted to its prolonged survival in a cyprinid host. Elevated numbers of activated neutrophils in peripheral blood and tissues are reported during T. borreli infection, but in context of the disease, the direct reason for elevated neutrophil numbers and their role during the infection remain unclear. In this study, a quantitative transmigration system, permitting the harvest of highly pure (> or = 97%) neutrophil populations was applied to investigate the modulation of carp neutrophil functions during T. borreli infection. We demonstrate time-dependent kinetics of a serum-induced down-regulation of neutrophil chemotaxis and an up-regulation of ROS production during the course of infection. With highly pure neutrophil populations, we could show that this divergent alteration of neutrophil functions was neither caused by T. borreli metabolites nor by the parasite itself. Moreover, when added to highly purified neutrophils, parasite metabolites did not alter the leukotriene B4-induced neutrophil chemotaxis nor the Staphylococcus aureus-induced ROS production. We conclude that the haemoparasite T. borreli does not interact with neutrophils directly, but indirectly modulates their functions via serum factors induced by parasite interaction with other components of the immune system.

Quantitative and qualitative assessment of serum- and inflammatory mediator-induced migration of carp (Cyprinus carpio) head kidney neutrophils in vitro.

A quantitative transmigration system, permitting the harvest of transmigrated cells for further analysis, was used to study carp head kidney (HK) granulocyte migration in vitro. Pooled carp serum and leukotriene B4 (LTB-4), but not recombinant human C-X-C chemokine ligand 8 (rhCXCL8), recombinant human complement component 5a (rhC5a) or N-formyl-methionyl-leucyl-phenylalanine (FMLP) induced strong migration (up to 70%) of carp HK granulocytes. The transmigrated cells were viable (>or=96%) and uniform (purity >or=97%). After serum- as well as LTB-4-induced transmigration granulocytes produced the same amounts of reactive oxygen species (ROS) as non-migrated cells in HK cell suspension. Their morphology, staining characteristics and flow cytometric scatter characteristics, plus their ability to produce ROS characterised the transmigrated granulocytes as neutrophils. The quantitative transmigration system described here could also serve as an excellent tool for the selective attraction and isolation of highly purified carp neutrophils from HK cell suspensions.