Inventory building of phages against extensively drug-resistant Acinetobacter baumannii isolated from wounds of patients with severe burn and related characteristic analysis
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摘要: 目的 建立烧伤ICU住院患者创面分离泛耐药鲍氏不动杆菌噬菌体库并分析相关特征。 方法 2014、2015年,重庆市1家医院烧伤ICU住院患者创面分离出131株泛耐药鲍氏不动杆菌;2015年,广东省6家医院烧伤ICU住院患者创面分离出98株泛耐药鲍氏不动杆菌。收集前述229株菌进行如下实验。(1)分析重庆市、广东省来源菌株的多位点序列分型(MLST)。(2)采用污水共培养法选用上述菌株及两地来源污水分离噬菌体,记录分离噬菌体的数量及成功次数、失败次数。(3)根据2015年重庆市和广东省分型比例最大的菌株,选用其对应噬菌体与来源地所有菌株进行交叉感染,观察噬菌体与同型或不同型菌株交叉感染时的裂解情况并计算裂解比。(4)任取一型别噬菌体液等分为3份,通过倍比稀释法测定噬菌体的滴度。将每份噬菌体液再分为3小份,分别于-20 ℃、4 ℃、室温条件下采用LB液体培养基保存,保存1、2个月时检测噬菌体滴度,评价噬菌体的稳定性。对数据行Fisher确切概率法检验、
χ 2检验、单因素方差分析。 结果 (1)2014年重庆市来源的菌株以序列型368(45%,31/69)为主,2015年重庆市来源的菌株以序列型75(26%,16/62)、序列型195(24%,15/62)为主。2015年广东省来源的菌株以序列型977(46%,45/98)为主。(2)以重庆市来源的菌株为基础使用当地来源的污水分离噬菌体的效果(成功分离8次、分离失败1次、分离9株噬菌体)明显优于使用广东省来源的污水(成功分离1次、分离失败7次、分离1株噬菌体),以广东省来源的菌株为基础使用当地来源的污水分离噬菌体的效果(分离8次均成功,分离6株噬菌体)明显优于使用重庆市来源的污水(分离7次均失败,分离0株噬菌体),差异均有统计学意义(P <0.05或P <0.01)。以两地来源菌株为基础使用各自来源地的污水分离噬菌体的效果比较,差异无统计学意义(P >0.05)。(3)序列型75、序列型977泛耐药鲍氏不动杆菌噬菌体对同型菌株的裂解比分别为13/16、8/9,均明显高于它们对不同型菌株的裂解比(分别为11/115、3/53,χ 2值分别为48.23、68.46,P 值均小于0.001)。(4)与保存前比较,-20 ℃、4 ℃和室温条件保存1个月噬菌体滴度降低约1个数量级,保存2个月噬菌体滴度降低约2个数量级。保存1、2个月,3种储存条件噬菌体的滴度相近(F 值分别为1.29、1.07,P 值均大于0.05)。 结论 本研究成功建立229株泛耐药鲍氏不动杆菌噬菌体库。不同地域、不同时间的泛耐药鲍氏不动杆菌的MLST各异,使用与菌株同一地区来源的污水分离噬菌体的效果好,噬菌体的裂解能力与菌株MLST关系密切,可按照地域划分建立噬菌体库。此外,噬菌体在LB液体培养基中稳定性良好且对储存条件无特殊要求。Abstract: Objective To build inventory of phages against extensively drug-resistantAcinetobacter Baumannii isolated from wounds of inpatients of burn ICU and analyze related characteristics. Methods In 2014 and 2015, 131 strains of extensively drug-resistantAcinetobacter Baumannii were isolated from wounds of inpatients of burn ICU from one hospital in Chongqing. In 2015, 98 strains of extensively drug-resistantAcinetobacter Baumannii were isolated from wounds of inpatients of burn ICU from 6 hospitals in Guangdong province. Above-mentioned 229 strains were collected for conducting experiments as follows: (1) Multilocus sequence typing (MLST) of strains isolated from Chongqing and Guangdong province was analyzed. (2) Sewage co-culture method was applied for isolation of phages with above-mentioned strains and sewage from Chongqing and Guangdong province. Numbers of isolated phages and times of successful isolation and unsuccessful isolation were recorded. (3) The most prevalent subtypes of strains from Chongqing and Guangdong province in 2015 were collected, and their phages respectively underwent cross infection with all strains from Chongqing and those from Guangdong province. The lysis ability of phage was observed when phage underwent cross infection with the same subtype of strain or not the same, and the lytic ratio was calculated. (4) Fluid of phage in one type was randomly selected and equally divided into 3 parts, and its titer was determined by double dilution method. Then each part of phage fluid was subdivided into 3 small parts, which were cultured with LB fluid medium and respectively stored under the condition of -20 ℃, 4 ℃, and room temperature. After being stored for 1 month and 2 months, the titer of phage was determined for evaluating stability of phage. Data were processed with Fisher′s exact test, chi-square test, and one-way analysis of variance. Results (1) The major type of strains from Chongqing in 2014 was ST368 (45%, 31/69), and major types of strains from Chongqing in 2015 were ST75 (26%, 16/62) and ST195 (24%, 15/62), while that from Guangdong province in 2015 was ST977 (46%, 45/98). (2) For strains from Chongqing, isolation effect of phage with sewage of Chongqing (8 times of successful isolation with 9 strains of phages and 1 time of unsuccessful isolation) was better than that with sewage of Guangdong province (1 time of successful isolation with 1 strain of phage and 7 times of unsuccessful isolation). For strains from Guangdong province, isolation effect of phage with sewage of Guangdong province (8 times of successful isolation with 6 strains of phages) was better than that with sewage of Chongqing (7 times of unsuccessful isolation with no phage). These differences were statistically significant (P <0.05 orP <0.01). There was no obvious difference in isolation effect of phage between strains from Chongqing with sewage of Chongqing and strains from Guangdong province with sewage of Guangdong province (P >0.05). (3) The ratios of phages of ST75 and ST977 extensively drug-resistantAcinetobacter Baumannii strains lysing the strains with the same type were respectively 13/16 and 8/9, which were obviously higher than those lysing the strains with different type (respectively 11/115 and 3/53, withχ 2 values respectively 48.23 and 68.46,P values below 0.001). (4) Compared with that before storage, titer of phage under storage condition of -20 ℃, 4 ℃, and room temperature for 1 month decreased by approximately 1 order of magnitude, and that for 2 months decreased by approximately 2 orders of magnitude. After being stored for 1 month and 2 months, there were no statistically significant differences in titer of phage among 3 storage conditions (withF values respectively 1.29 and 1.07,P values above 0.05). Conclusions This study has successfully built an inventory covering 229 strains of phages of extensively drug-resistantAcinetobacter Baumannii . MLST of extensively drug-resistantAcinetobacter baumannii varies in different area and different time. Phage can be well isolated using sewage with the same source as that of strain. The lysis ability of phage is closely related to the MLST of strains. Inventory of phages should be built according to regional division. Moreover, phage cultured with LB fluid medium shows good stability without special requirements for storage conditions.
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