Objective A comparative study of in-hospital mortality and risk factors of ventilator-associated pneumonia (VAP) caused by carbapenem-resistant gram-negative bacteria (CRGNB) and non-carbapenem-resistant gram-negative bacteria (nCRGNB) in China was conducted to investigate whether there is a higher in-hospital mortality of VAP caused by CRGNB and its unique associated risk factors. Methods Relevant literatures published at home and abroad in PubMed, EMBASE, Cochrane library, Web of Science, CNKI and Wanfang databases were retrieved from the date of establishment to June 1, 2021, and the quality of the included literatures was evaluated using Newcastle-Ottawa scale. Meta-analysis of literatures meeting the criteria was performed using RevMan 5.3 software. Results A total of 5 literatures were included, all of which were case-control studies with a total of 574 cases, including 302 cases in the CRGNB group and 272 cases in the nCRGNB group. The results showed that the in-patient mortality of VAP caused by CRGNB infection was significantly increased compared with that of VAP caused by nCRGNB infection (OR=2.51, 95%CI 1.71 - 3.67, P<0.00001). Risk factor analysis of CRGNB infection showed that statistically significant risk factors included mechanical ventilation duration ≥7 days (OR=2.66, 95%CI 1.23 - 5.75, P=0.01), secondary intubation (OR=4.48, 95%CI 2.61 - 7.69], P<0.00001), combined with antibiotics (OR=2.83, 95%CI 1.76 - 4.54, P<0.0001), using carbapenem antibiotics (OR=2.78, 95%CI 1.76 - 4.40, P<0.0001). In addition, two studies showed that tigecycline was sensitive to CRGNB in vitro. Conclusions Compared with nCRGNB-induced VAP, CRGNB infection significantly increases the in-hospital mortality of VAP patients in China, indicating that the in-hospital mortality of CRGNB infection is related to drug resistance, and had little relationship with region and drug resistance mechanism. Among them, mechanical ventilation duration ≥7 days, secondary intubation, combined use of antibiotics and carbapenem antibiotics are risk factors for CRGNB infection in VAP patients. Tigecycline is sensitive to most CRGNB strains in China and is an important choice for the treatment of CRGNB in China.
The properties of mucus in a person with asthma can alter with disease process so that it may lead to the airway embolism. Fe2O3 nanoparticles can be used for drug delivery. Up till now, however, little is known about how the Fe2O3 nanoparticles influence the properties of airway mucus. In this study, Fe2O3 nanoparticles were dispersed with ultrasound, and the morphological properties were measured with scanning electron microscope, atomic force microscope and nanometer laser particle size and zeta potential analyzer. Then the dispersed Fe2O3 nanoparticles were added to the simulated asthma airway mucus with different final concentration (0.03, 0.3, and 0.4 mg/mL). The measurements of flow curve, yield stress, large amplitude oscillatory shear (LAOS) and shock scanning were carried out with a rotational rheometer. Experimental results showed that the Fe2O3 nanoparticles reduced the zero shear viscosity of simulated asthma airway mucus. With increase of shear rate, the wind speed of mucus was reduced. The yield stress of simulated asthma airway mucus was 19.0 Pa, but the yield stresses of experimental group (0.03, 0.3 and 0.4 mg/mL) were 17.0, 0.99, and 0.7 Pa, respectively. The results showed that the viscoelastic modulus of asthma airway mucus treated with Fe2O3 nanoparticles were changed obviously as measured with large amplitude scanning and frequency scanning. By adopting the method of optical phase microscopy, we found that different structures of simulated airway mucus were absorbed. The results showed Fe2O3 nanoparticles distroyed mucus structure. The experimental results proved that Fe2O3 nanoparticles could change the rheological characteristics of simulated asthma airway mucus. This experimental result would lay a foundation for the further development of airway mucus sticky agent based on the function of Fe2O3 nanoparticles.