玫瑰单胞菌一株的鉴定及分析

Identification and characterization of one Roseomonas strain

目的 确定临床脓液标本中1株革兰阴性球杆菌K8756的分类学位置.方法 抽取患者深部脓肿物,置于Amies培养基室温保存、运输.脓液标本分区划线接种血平板、巧克力平板,置于35 ℃含5%CO2培养箱.采用API、Vitek2细菌鉴定系统,结合传统形态学检查、手工生化实验对分离株进行鉴定.从纯培养物提取脂肪酸、甲基化,采用气相色谱仪分析脂肪酸成分.PCR扩增16SrRNA基因并测序,对所测得的核酸序列进行同源性比对及系统发育分析.结果 血平板、巧克力平板分离到1株缓慢生长的革兰阴性球杆菌K8756.API 20NE生化编码为1245045（72 h）,提示为人苍白杆菌;Vitek2 GN鉴定卡重复实验3次,提示为皮氏罗尔斯顿菌或支气管炎鲍特菌.但基于16SrRNA基因序列的系统发育分析表明,菌株K8756属于玫瑰单胞菌的成员,与该属的合格发表种黏液玫瑰单胞菌MDA5527T核酸匹配度高达100%（菌株K8756的GenBank登录号为GU207841）.其菌落形态、表型特征及主要细胞脂肪酸成分亦与黏液玫瑰单胞菌相似.结论 菌株K8756（=GIMCC 1.0030）在分类学上属于黏液玫瑰单胞菌.16S rRNA基因序列分析是鉴定临床疑难菌株及新发现菌株的重要手段.

Objective To identify one runny mucoid-like Gram-negative bacteria with pink pigment isolated from clinical pus sample. Methods The pus sample was aseptically extracted from a deep lesions of one patient, then stored in Amies medium at room temperature for transportation. One sheep blood plate and one chocolate plate were used to detect the possible pathogens from the specimens. After inoculation, the plates were placed in a humidified incubator with 5% CO2 at 35 ℃. To identify the obtained isolates, we used the commercial Vitek2 and API systems, combining some traditional morphological examination and classical biochemical and physiological characteristics. For pure cultures, the cellular fatty acids were extracted, methylated, and determined by gas chromatography method. The 16S rRNA gene was amplified and sequenced by a commercial broad-spectrum PCR primers. The phylogenetic tree based on 16S rRNA gene was constructed by Mega 4.1 software using the neighbour-joining methods with 1 000 bootstrap replications. Results One runny mucoid-like Gram-negative bacterium, named K8756, was isolated both on sheep blood and chocolate plates after 72 h incubation. The API 20NE profile was 1245045 after a 3-day culture, which would be identified as Ochrobactrum anthropi with a good confidence of 98% probability. It was identified as Ralstonia pickettii and Bordetella bronchiseptica by VITEK 2 GN kits. However, further comparative 16S rRNA gene sequences showed that strain K8756 was closely related to the valid published Roseomonas mucosa MDA 5527 with 100% identity. Colonial morphologic features, phenotypic characteristics and major cellular fatty acid composition were also with high similarity to Roseomonas mucosa. Conclusions Strain K8756（ = GIMCC 1.0030 ） is identified as Roseomonas mucosa by the polyphasic phenotypic and genotypic characteristics. The comparative analysis based on 16S rRNA gene sequences is a useful method for identifying the problematic and newly named bacteria.