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不动杆菌属(Acinetobacter spp.)细菌广泛存在于自然界的条件致病菌[1],目前已正式命名62个菌种(http://www.bacterio.net/acinetobacter.html)。依据细菌生化特征的商品化全自动菌种鉴定系统是临床上鉴定不动杆菌菌种的常用方法。通常醋酸钙不动杆菌(Acinetobacter calcoaceticus)、鲍曼不动杆菌(Acinetobacter baumannii)、Acinetobacter nosocomialis和Acinetobacter pittii通过鉴定技术很难区分,因而合称为醋酸钙-鲍曼不动杆菌复合体(ACB复合体)。后来陆续有其他不动杆菌也被纳入其中,包括Acinetobacter seifertii(曾称为近13TU型)、Acinetobacter lactucae(曾称为NB14型)以及不动杆菌基因型介于1~3之间的菌种等。因此,该复合物内菌种间遗传上密切相关、表型上难以区分[2]。
虽然ACB复合体各成员菌种表型相近,但流行病学特征却有很大不同。鲍曼不动杆菌是医院与社区获得性感染的最常见病原体之一;而A.pittii和A.nosocomialis、A.calcoaceticus等主要从土壤、水中分离出来,其是否导致临床感染仍不清楚;A. seifertii、A.lactucae和不动杆菌基因型介于1~3之间的菌种也有从临床标本中分离出[3-5]。由于ACB复合体成员异质性明显,不同的临床意义也容易引起临床误导,因此,准确鉴定ACB复合体各菌种具有科研和临床价值[6]。
除了以生化反应为基础的商品化鉴定系统,还有以下鉴定策略,如:仅存在于鲍曼不动杆菌的碳青霉烯酶基因blaOXA-51-like,用于对鲍曼不动杆菌的鉴定[7-8];16S rRNA基因高度保守、普遍存在、高稳定性等特性,其序列具有的细菌属、种的特征,使得其一度在系统发育学研究中成为细菌鉴定和分类的“金标准”[9];gyrB基因编码DNA回旋酶的B亚单位蛋白(GyrB),是惟一能诱导DNA负超螺旋的拓扑异构酶。因细菌GyrB具有种属特异性[10-11],gyrB基因可作为ACB复合体的基因鉴定的基因序列[12-14]。本文拟采用以上不同菌种鉴定方法对20株ACB复合体进行菌种鉴定,以期确定最有效的菌种鉴定方法。
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收集蚌埠医学院第一附属医院自2012年2月至2013年4月自痰液、血液、手术及伤口分泌物、尿液等各种标本中无重复分离的ACB复合体20株。
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金黄色葡萄球菌ATCC29213、嗜麦芽窄食单胞菌ATCC17666、大肠埃希菌ATCC25933、鲍曼不动杆菌ATCC19606,由我院微生物实验室提供。醋酸钙不动杆菌ATCC23055,购于上海复祥生物科技有限公司。
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VITEK 2 Compact微生物鉴定/药敏系统、VITKE比浊仪(法国生物梅里埃公司);梯度PCR仪(TGradient型:Biometra公司);GIS凝胶成像分析系统(上海天能科技有限公司);SmartSpecTM紫外分光光度计(Bio RAD);PCR引物(见表 1)、DNA Marker、5×TBE(上海生工生物工程有限公司);PCR扩增试剂盒(天根生化科技有限公司);琼脂糖、EB(加拿大Ferments公司)。
目的基因 引物序列(5′-3′) 退火温度/℃ 产物大小/bp 备注 OXA-51 F:TAA TGC TTT GAT CGG CCT TG 53.0 353 [15] R:TGG ATT GCA CTT CAT CTT GG 菌种特异性 gyrB基因* A.pittii D16:GAT AAC AGC TAT AAA GTT TCA GGT GGT 51.0 194 [16] D8:CAA AAA CGT ACA GTT GTA CCA CTG C A.calcoaceticus D14:GAC AAC AGT TAT AAG GTT TCA GGT G 47.2 428 [16] D19:CCG CTA TCT GTA TCC GCA GT A.baumanni Sp2F:GTT CCT GAT CCG AAA TTC TCG 54.0 490 [16] Sp4R:AAC GGA GCT TGT CAG GGT TA A.baumannii和 Sp4F:CAC GCC GTA AGA GTG CAT TA 55.0 294 [16] A.nosocomialis Sp4R:AAC GGA GCT TGT CAG GGT TA 16S rRNA F:AGA GTT TGA TCC TGG CTC AG 54.9 1400 [12] R:GGT TAC CTT GTT ACG ACT T *注:菌种特异性gyrB基因:引物Sp2F/Sp4R扩增产物为A.baumannii所特有;引物Sp4F/sp4R扩增产物仅在A.baumannii及A.nosocomialis为阳性;引物D14/D19特异性扩增A.calcoacelicus的gyrB基因;引物D16/D8特异性扩增GS 3的gyrB基因。 表 1 引物合成序列表
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取-80 ℃冻存菌株,以三分区法血平板接种,CO2培养箱培养12~24 h。挑选单个菌落,0.45%无菌氯化钠溶液调配1.0麦氏管浊度(Mcfarland)菌液。以VITEK 2 Compact微生物鉴定/药敏系统进行菌种鉴定。
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刮取新鲜菌落于150 μL无菌双蒸水,混匀后煮沸10 min,于4 ℃ 12 000 r/min离心10 min,留取含有粗提取细菌总DNA的上清液,SmartSpecTM紫外分光光度计检测并调节提取DNA的吸光度A260/280比值为1.8~2.0。
PCR Master MIX(2×)12.5 μL、上游引物1.0 μL,下游引物1.0 μL, 模板DNA 1.0 μL, 无核酸酶水8.5 μL构成反应体系,94 ℃预变性3 min、94 ℃变性30 s、退火30 s(OXA-51 53 ℃、GS3 gyrB 51 ℃、A.calcoaceticus gyrB 47.2 ℃,A.baumanni gyrB 54 ℃,A.baumannii和GS13TU gyrB 55 ℃、16S rRNA 54.9 ℃)、72 ℃延伸1 min,共30个循环,最后72 ℃延伸5 min。
PCR产物以1%琼脂糖凝胶电泳,GIS凝胶成像系统读取结果,拍摄并记录结果。PCR扩增的16S rDNA产物经琼脂糖凝胶电泳初步检测后,由上海生工生物工程技术公司进行纯化和序列测定。所得片段序列运用在线序列比对BLASTn与GenBank上的基因序列进行比对分析。
对一组醋酸钙-鲍曼不动杆菌复合体细菌的基因型鉴定
Study on genotyping in clinical Acinetobacter calcoaceticus-Acinetobacter baumannii complex
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摘要:
目的 探讨鉴定醋酸钙-鲍曼不动杆菌复合体各菌种的有效方法。 方法 运用全自动细菌鉴定系统联合分子生物学方法,经聚合酶链式反应(PCR)扩增鲍曼不动杆菌特异表达的D类碳青霉烯酶基因OXA-51、16S rRNA及醋酸钙-鲍曼不动杆菌复合体各菌种特异表达的gyrB基因,以准确鉴定醋酸钙-鲍曼不动杆菌复合体各菌种种属。 结果 20株醋酸钙-鲍曼不动杆菌复合体经全自动细菌鉴定及药敏分析系统鉴定均与原始种属相一致;经分子生物学方法鉴定结果为Acinetobacter baumannii 16株,Acinetobacter calcoaceticus 3株,Acinetobacter nosocomialis 1株。 结论 全自动菌种鉴定系统辅以分子生物学基因分型方法可较为准确地鉴定醋酸钙-鲍曼不动杆菌复合体各个菌种。gyrB基因作为到种鉴定标志物对于高度亲缘性菌种的鉴定价值更大。 -
关键词:
- 醋酸钙-鲍曼不动杆菌复合体 /
- 基因分型鉴定 /
- OXA-51基因 /
- gyrB基因 /
- 16S rRNA基因
Abstract:Objective To investigate the effective methods for identification of all the genotypes of Acinetobacter speciese, including Acinetobacter calcoaceticus-Acinetobacter baumannii (ACB) complex. Methods For all ACB complex strains, bacterial identification was carried out using automatic bacteria identification system.Additionally, for more accurate discrimination between ACB complex species, Molecular Biology methods has been combined? with, all ACB complex strains were further subjected to polymerase chain reaction (PCR) amplification to detect the A.baumannii-specific expression of the class D carbapenemase gene OXA-51, 16S rRNA gene and ACB complex gyrB genes, which specifically expressed in each species. Results Totally all 20 ACB complex strains were identified as ACB complex by automatic bacteria identification system; which were identified by the method in Molecular Biology by PCR, of them 3 A.calcoaceticus strains and 1 A.nosocomialis strain were detected in ACB complex, together with 16 Acinetobacter baumannii strains. Conclusions The combination of automatic bacteria identification system and Molecular Biology methods can provide more accurate genospecies identification in ACB complex.gyrB gene might be a more effective marker in the identification of highly phylogenetic related species. -
表 1 引物合成序列表
目的基因 引物序列(5′-3′) 退火温度/℃ 产物大小/bp 备注 OXA-51 F:TAA TGC TTT GAT CGG CCT TG 53.0 353 [15] R:TGG ATT GCA CTT CAT CTT GG 菌种特异性 gyrB基因* A.pittii D16:GAT AAC AGC TAT AAA GTT TCA GGT GGT 51.0 194 [16] D8:CAA AAA CGT ACA GTT GTA CCA CTG C A.calcoaceticus D14:GAC AAC AGT TAT AAG GTT TCA GGT G 47.2 428 [16] D19:CCG CTA TCT GTA TCC GCA GT A.baumanni Sp2F:GTT CCT GAT CCG AAA TTC TCG 54.0 490 [16] Sp4R:AAC GGA GCT TGT CAG GGT TA A.baumannii和 Sp4F:CAC GCC GTA AGA GTG CAT TA 55.0 294 [16] A.nosocomialis Sp4R:AAC GGA GCT TGT CAG GGT TA 16S rRNA F:AGA GTT TGA TCC TGG CTC AG 54.9 1400 [12] R:GGT TAC CTT GTT ACG ACT T *注:菌种特异性gyrB基因:引物Sp2F/Sp4R扩增产物为A.baumannii所特有;引物Sp4F/sp4R扩增产物仅在A.baumannii及A.nosocomialis为阳性;引物D14/D19特异性扩增A.calcoacelicus的gyrB基因;引物D16/D8特异性扩增GS 3的gyrB基因。 -
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