Broad-host-range plasmids are frequently associated with antibiotic resistance genes and can quickly spread antibiotic resistant phenotypes among diverse bacterial populations. Wastewater treatment plants have been id...Broad-host-range plasmids are frequently associated with antibiotic resistance genes and can quickly spread antibiotic resistant phenotypes among diverse bacterial populations. Wastewater treatment plants have been identified as reservoirs for broad-host-range plasmids carrying resistance genes. The threat of broad-host-range plasmids released into the environment from wastewater treatment plants has identified the need for disinfection protocols to target broad-host- range plasmid destruction. Here we evaluate the efficacy of dissolved ozone at 2 and 8 mg·L–1 as a primary means for the destruction of broad-host-range plasmid and chromosomal DNA in simulated effluent. Pilot-scale tests using an experimental unit were carried out in municipal wastewater treatment plant effluent and compared with ultraviolet (UV)-irradiation and chlorination methodologies. Genes specific to Escherichia coli (uidA) and IncP broad-host-range plasmids (trfA) were monitored using real-time quantitative polymerase chain reaction (qPCR), and total DNA was monitored using absorbance spectroscopy. In wastewater treatment plant experiments, E. coli qPCR results were compared to a recognized culture-based method (Colilert?) for E. coli. In laboratory experiments, dissolved ozone at 8 mg·L–1 significantly destroyed 93% total, 98% E. coli, and 99% of broad-host-range plasmid DNA. Ozonation, UV-irradiation, and chlorination significantly reduced DNA concentrations and culturable E. coli in wastewater treat- ment plant effluent. Chlorination and UV disinfection resulted in 3-log decreases in culture-based E. coli concentrations in wastewater treatment plant effluent while changes were not significant when measured with qPCR. Only ozonation significantly decreased the IncP broad-host-range plasmid trfA gene, although concentrations of 2.2 × 105 copies trfA·L–1 remained in effluent. Disinfection processes utilizing high dissolved ozone concentrations for the destruction of emerging contaminants such as broad-host-range plasmid and total DNA may have utility as methods to ensure downstream environmental health and safe water reuse become more important.展开更多
目的研究自医院污水中分离的宽噬噬菌体,治疗小鼠产超广谱β-内酰胺酶(ESBLs)大肠埃希菌感染的疗效。方法从医院污水中分离筛选出宽噬噬菌体,建立小鼠全身感染模型,观察宽噬噬菌体治疗小鼠的细菌感染的疗效。结果细菌感染的小鼠立即腹...目的研究自医院污水中分离的宽噬噬菌体,治疗小鼠产超广谱β-内酰胺酶(ESBLs)大肠埃希菌感染的疗效。方法从医院污水中分离筛选出宽噬噬菌体,建立小鼠全身感染模型,观察宽噬噬菌体治疗小鼠的细菌感染的疗效。结果细菌感染的小鼠立即腹腔注射纯化的Φ9882(MOI≥10-4,multiple of infection,感染复数),小鼠生存率为100%;Φ9882(MOI,200)延迟1 h治疗感染的小鼠仍有60%的生存率;热失活Φ9882治疗感染的小鼠生存率为0。结论通过噬菌体治疗剂量、延迟治疗、热失活、体内分布和免疫反应方面的研究,宽噬噬菌体Φ9882能有效地治疗小鼠产ESBLs大肠埃希菌感染,无不良副作用,从而为进一步应用噬菌体进行临床抗感染治疗奠定基础。展开更多
Xanthomonas oryzea pv.oryzae(Xoo)is the causal agent of bacterial blight of rice,which is a significant threat to many of rice-growing regions.The type Ⅲ secretion system(T3SS)is an essential virulence factor in Xoo....Xanthomonas oryzea pv.oryzae(Xoo)is the causal agent of bacterial blight of rice,which is a significant threat to many of rice-growing regions.The type Ⅲ secretion system(T3SS)is an essential virulence factor in Xoo.Expression of the T3SS is often induced in the host environment or in hrp-inducing medium but is repressed in nutrient-rich medium.The elucidation of molecular mechanism underlying induction of T3SS genes expression is a very important step to lift the veil on global virulence regulation network in Xoo.Thus,an efficient and reliable genetic tool system is required for detection of the T3SS proteins.In this study,we constructed a protein expression vector pH3-flag based on the backbone of pHM1,a most widely used vector in Xoo strains,especially a model strain PXO99A.This vector contains a synthesized MCS-FLAG cassette that consists of a multiple cloning site(MCS),containing a modified pUC18 polylinker,and Flag as a C-terminal tag.The cassette is flanked by transcriptional terminators to eliminate interference of external transcription enabling detection of accurate protein expression.We evaluated the potential of this expression vector as T3SS proteins detection system and demonstrated it is applicable in the study of T3SS genes expression regulation in Xoo.This improved expression system could be very effectively used as a molecular tool in understanding some virulence genes expression and regulation in Xoo and other Xanthomonas spp.展开更多
文摘Broad-host-range plasmids are frequently associated with antibiotic resistance genes and can quickly spread antibiotic resistant phenotypes among diverse bacterial populations. Wastewater treatment plants have been identified as reservoirs for broad-host-range plasmids carrying resistance genes. The threat of broad-host-range plasmids released into the environment from wastewater treatment plants has identified the need for disinfection protocols to target broad-host- range plasmid destruction. Here we evaluate the efficacy of dissolved ozone at 2 and 8 mg·L–1 as a primary means for the destruction of broad-host-range plasmid and chromosomal DNA in simulated effluent. Pilot-scale tests using an experimental unit were carried out in municipal wastewater treatment plant effluent and compared with ultraviolet (UV)-irradiation and chlorination methodologies. Genes specific to Escherichia coli (uidA) and IncP broad-host-range plasmids (trfA) were monitored using real-time quantitative polymerase chain reaction (qPCR), and total DNA was monitored using absorbance spectroscopy. In wastewater treatment plant experiments, E. coli qPCR results were compared to a recognized culture-based method (Colilert?) for E. coli. In laboratory experiments, dissolved ozone at 8 mg·L–1 significantly destroyed 93% total, 98% E. coli, and 99% of broad-host-range plasmid DNA. Ozonation, UV-irradiation, and chlorination significantly reduced DNA concentrations and culturable E. coli in wastewater treat- ment plant effluent. Chlorination and UV disinfection resulted in 3-log decreases in culture-based E. coli concentrations in wastewater treatment plant effluent while changes were not significant when measured with qPCR. Only ozonation significantly decreased the IncP broad-host-range plasmid trfA gene, although concentrations of 2.2 × 105 copies trfA·L–1 remained in effluent. Disinfection processes utilizing high dissolved ozone concentrations for the destruction of emerging contaminants such as broad-host-range plasmid and total DNA may have utility as methods to ensure downstream environmental health and safe water reuse become more important.
文摘目的研究自医院污水中分离的宽噬噬菌体,治疗小鼠产超广谱β-内酰胺酶(ESBLs)大肠埃希菌感染的疗效。方法从医院污水中分离筛选出宽噬噬菌体,建立小鼠全身感染模型,观察宽噬噬菌体治疗小鼠的细菌感染的疗效。结果细菌感染的小鼠立即腹腔注射纯化的Φ9882(MOI≥10-4,multiple of infection,感染复数),小鼠生存率为100%;Φ9882(MOI,200)延迟1 h治疗感染的小鼠仍有60%的生存率;热失活Φ9882治疗感染的小鼠生存率为0。结论通过噬菌体治疗剂量、延迟治疗、热失活、体内分布和免疫反应方面的研究,宽噬噬菌体Φ9882能有效地治疗小鼠产ESBLs大肠埃希菌感染,无不良副作用,从而为进一步应用噬菌体进行临床抗感染治疗奠定基础。
基金supported by the National Key R&D Program of China (2017YFD0200400)the National Natural Science Foundation of China (31772122 and 31470235)
文摘Xanthomonas oryzea pv.oryzae(Xoo)is the causal agent of bacterial blight of rice,which is a significant threat to many of rice-growing regions.The type Ⅲ secretion system(T3SS)is an essential virulence factor in Xoo.Expression of the T3SS is often induced in the host environment or in hrp-inducing medium but is repressed in nutrient-rich medium.The elucidation of molecular mechanism underlying induction of T3SS genes expression is a very important step to lift the veil on global virulence regulation network in Xoo.Thus,an efficient and reliable genetic tool system is required for detection of the T3SS proteins.In this study,we constructed a protein expression vector pH3-flag based on the backbone of pHM1,a most widely used vector in Xoo strains,especially a model strain PXO99A.This vector contains a synthesized MCS-FLAG cassette that consists of a multiple cloning site(MCS),containing a modified pUC18 polylinker,and Flag as a C-terminal tag.The cassette is flanked by transcriptional terminators to eliminate interference of external transcription enabling detection of accurate protein expression.We evaluated the potential of this expression vector as T3SS proteins detection system and demonstrated it is applicable in the study of T3SS genes expression regulation in Xoo.This improved expression system could be very effectively used as a molecular tool in understanding some virulence genes expression and regulation in Xoo and other Xanthomonas spp.
