Altered susceptibility to air sampling stress by filtration is related to colistin resistance development in Acinetobacter baumannii

Improved measurement of airborne viruses using a two-stage highly virus-enriching electrostatic particle concentrator with electric-field-enhancing wire electrodes

High enrichment of airborne viruses during sampling is critical for their rapid measurement and requires a high sampling flow rate (or velocity), small collection areas, and high collection efficiency; however, high collection efficiency can rarely be achieved at high flow velocities and in small collection areas in electrostatic sampling. Herein, we present improved measurement of airborne viruses using a two-stage highly virus-enriching electrostatic particle concentrator (HEPC) with wire electrodes and high values of the-inlet-velocity-to-collection-electrode-width ratio. This sampler was evaluated using MS2 viruses and 0.05-2.0 µm diameter polystyrene latex particles at 20 liters/min. Computer simulations and experiments agreed well, showing that the wire electrodes increased collection efficiency (by up to 37 % than the without-wire-electrodes case) without high viability losses through local electric field enhancement for high-flow-velocity regions over the collection electrode and minimization of local corona discharge. The relative infectious virus concentrations of the HEPC were 41-70 times higher than those of the BioSampler. Airborne influenza A viruses at field-level concentrations (1.8 × 105 and 2.6 × 104 copies/m3) were also detected at 10-min sampling due to the high enrichment capability of HEPC. The HEPC has strong potential as a rapid airborne virus monitoring system in the field.

Three-dimensional composite electrospun nanofibrous membrane by multi-jet electrospinning with sheath gas for high-efficiency antibiosis air filtration

Three-dimensional (3D) composite polyvinylidene fluoride (PVDF)/polyacrylonitrile (PAN) electrospun nanofibrous membranes combining both thick and thin nanofibers have been fabricated by the method of multi-jet electrospinning with sheath gas to realize high-efficiency air filtration under a low pressure drop. The thin PAN nanofibers form a dense membrane, with a strong capturing ability on the ultra-fine particles, while the thick PVDF nanofibers play a 3D supporting effect on the thin PAN nanofibers. In this case, the combination results in a fluffy membrane with higher porosity, which could achieve the airflow passing through the membrane without the air pressure drop. The effects of the composite manner of thick nanofibers and thin nanofibers are investigated, in order to optimize the air filtration performance of the 3D composite nanofibrous membrane. As a result, the maximum quality factor for air filtration could reach up to 0.398 Pa^-1. The particle-fiber interaction model was used to simulate the air filtration process as well, and the simulation results were fairly consistent with the experimental results, providing a guidance method for the optimization of composite nanofibrous membrane for high-efficiency air filtration. More interestingly, a cationic poly[2-(N,N-dimethyl amino) ethyl methacrylate] (PDMAEMA) was added in the PVDF solution to obtain a composite air filtration membrane with excellent antibiosis performance, which achieved the highest inhibition rate of approximately 90%. In short, this work provides an effective way to promote antibiosis air filtration performance by using an electrospun nanofibrous membrane, and might also effectively accelerate the biological protection application of current air filtration membranes.

Size distribution and antibiotic-resistant characteristics of bacterial bioaerosol in intensive care unit before and during visits to patients

Airborne bacteria in hospitals have been implicated in nosocomial infections. This investigation studied the characteristics of airborne bacteria and the effect of patient visitation on the bacteria profile in intensive care units (ICUs). Air at a medical ICU and surgical ICU was sampled for one year. Airborne bacteria before and during visits to patients in ICUs were collected using a Six-Stage Viable Andersen Cascade Impactor to analyze the concentration and size distribution of airborne bacteria and the percentage thereof that were antibiotic-resistant. During patient visitation in the ICUs in this study, the number of visitors was 20-80. Airborne bacteria concentration during visiting hours (total averaging 168.5 CFU/m³) was three to four times than before visiting hours (p = 0.043). With increasing the visitors, most of the airborne human-associated bacteria (HAB) concentrations during visitations were higher than before visitations in each season. The two-way ANOVA of HAB concentration before and during visitation (p = 0.028) of combining MICU and SICU in various season (p = 0.007) all revealed statistical agreement. The proportion of particles, from 1.1 to 4.7 µm, during the visits was almost 1-2.4 times that before the visits in most sampling periods (p = 0.028). In addition, the opportunistic pathogens such as Micrococcus spp., Staphylococcus spp. and Acinetobacter spp. were found in the air during visiting times. Small proportions of some environmental strains with a high antibiotic-resistance percentage (42-78%), including Brevundimonas spp., Elizabethkingia spp. and others, were detected during patient visitation. Patient visitation activities affect the bacterial profile in air in ICUs. During the visitation, visitors might bring or generate bacteria into ICUs. Limiting the number of patient visitors to ICUs, wearing respirators and gowns or increasing ventilation rate during and after patient visitation is required to maintain indoor air quality and probably decrease the risk of patient infection.