The first documented nosocomial outbreak caused by Serratia marcescens in Spain occurred in 1969 at the neonatal intensive care unit (NICU) of the tertiary La Paz Children's Hospital in Madrid, Spain, and based on the available phenotyping techniques at this time, it was considered as a monoclonal outbreak. Only 47 years later, another S. marcescens outbreak of an equivalent dimension occurred at the same NICU. The aim of the present study was to study isolates from these historical and contemporary outbreaks by phenotypic analysis and whole-genome sequencing techniques and to position these strains along with 444 publicly available S. marcescens genomes, separately comparing core genome and accessory genome contents. Clades inferred by both approaches showed high correlation, indicating that core and accessory genomes seem to evolve in the same manner for S. marcescens. Nine S. marcescens clusters were identified, and isolates were grouped in two of them according to sampling year. One exception was isolate 13F-69, the most genetically distant strain, located in a different cluster. Categorical functions in the annotated accessory genes of both collections were preserved among all isolates. No significant differences in frequency of insertion sequences in historical (0.18-0.20)-excluding the outlier strain-versus contemporary isolates (0.11-0.19) were found despite the expected resting effect. The most dissimilar isolate, 13F-69, contains a highly preserved plasmid previously described in Bordetella bronchiseptica. This strain exhibited a few antibiotic resistance genes not resulting in a resistant phenotype, suggesting the value of gene down expression in adaptation to long-term starvation.

中文翻译：

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粘质沙雷氏菌的基因组学使同一儿科疾病暴发隔离了47年：在物种更新系统发育中的地位。

由西班牙粘质沙雷氏菌引起的首次医院爆发是在1969年发生在西班牙马德里拉巴斯儿童三级医院的新生儿重症监护病房（NICU），根据当时可用的表型分析技术，该病被认为是单克隆爆发。仅仅47年后，同一重症监护病房又发生了同样大小的marces marcescens暴发。本研究的目的是通过表型分析和全基因组测序技术研究来自这些历史和当代暴发的分离株，并将这些菌株与444个公开可用的粘菌链球菌基因组一起定位，分别比较核心基因组和辅助基因组的内容。通过这两种方法推断出的进化枝显示出高度相关性，表明核心基因组和辅助基因组似乎以相同的方式进化。鉴定了九个marcescens簇，并根据采样年将分离株分为两个。一个例外是分离的13F-69，这是遗传距离最远的菌株，位于另一个簇中。在所有分离物中，两个集合的注释辅助基因中的分类功能均得以保留。尽管有预期的静息作用，但在历史序列（0.18-0.20）中，除异常菌株与当代分离株（0.11-0.19）外，未发现插入序列的频率有显着差异。最不相似的分离株13F-69包含先前在支气管败血波氏杆菌中描述的高度保存的质粒。该菌株显示出一些抗生素抗性基因，未导致抗性表型，