With widespread abuse of antibiotics, bacterial resistance has increasingly become a serious threat. Acinetobacter baumannii has emerged as one of the most important hospital-acquired pathogens worldwide. Bacteriophages (also called “phages”) could be used as a potential alternative therapy to meet the challenges posed by such pathogens. Endolysins from phages have also been attracting increasing interest as potential antimicrobial agents. Here, we isolated 14 phages against A. baumannii, determined the lytic spectrum of each phage, and selected one with a relatively broad host range, named vB_AbaP_PD-6A3 (PD-6A3 for short), for its biological characteristics. We over-expressed and purified the endolysin (Ply6A3) from this phage and tested its biological characteristics. The PD-6A3 is a novel phage, which can kill 32.4% (179/552) of clinical multidrug resistant A. baumannii (MDRAB) isolates. Interestingly, in vitro, this endolysin could not only inhibit A. baumannii, but also that of other strains, such as Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA). We found that lethal A. baumannii sepsis mice could be effectively rescued in vivo by phage PD-6A3 and endolysin Ply6A3 intraperitoneal injection. These characteristics reveal the promising potential of phage PD-6A3 and endolysin Ply6A3 as attractive candidates for the control of A. baumannii-associated nosocomial infections.

IntroductionAssociation has been reported between ambient fine particulate matter (PM) and adverse outcomes of cerebrovascular events. However, it remains unclear that whether short-term exposure to PM relates to stroke and the lag of health effects. This triggers us to examine the relationship between PM and population stroke morbidity in Chengdu.MethodsThe daily average concentration of atmospheric pollutants and meteorological factors and daily morbidity of stroke in Chengdu (2013–2015) were collected. Based on time series analysis-generalized additive models (GAM), single-pollutant, two-pollutant and multi-pollutant model were established. The effects of atmospheric PM2.5 (defined as PM less than 2.5μm in aerodynamic diameter), PMc(defined as PM less than 10μm and more than 2.5μm in aerodynamic diameter) and PM10 (defined as PM less than 10μm in aerodynamic diameter) concentration on the daily mortality of stroke were analyzed, respectively.ResultsThe three-year mean concentrations of PM2.5, PMc and PM10 for air pollutants were 75.9, 43.9 and 119.7 μg/m3, respectively. PM2.5 on the current day (lag0) and with a moving average of 0–1 days were significantly associated with the increasing risk of stroke morbidity, and PM2.5 with a lag of 0–1 days had greater association, whereas for PMc and PM10 there were no significant association observed. In our study, every 10μg/m3 increase of PM2.5 was associated with 0.69% percent change in stroke morbidity (95%CI: 0.01~1.38). For females, every 10μg/m3 increase of PM2.5 contributes to 0.80% percent change of onset. And for the group of age less than 65, we observed 0.78% higher risk every 10μg/m3 increase of PM2.5.ConclusionsThese findings suggest that short-term exposure to PM2.5 within 1 day is associated with the onset of stroke, and the younger people (age<65) and females are more sensitive than older people and males.

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