Serratia marcescens is a global spread nosocomial pathogen. This rod-shaped bacterium displays a broad host range and worldwide geographical distribution. Here we analyze an international collection of this multidrug-resistant, opportunistic pathogen from 35 countries to infer its population structure. We show that S. marcescens comprises 12 lineages; Sm1, Sm4, and Sm10 harbor 78.3% of the known environmental strains. Sm5, Sm6, and Sm7 comprise only human-associated strains which harbor smallest pangenomes, genomic fluidity and lowest levels of core recombination, indicating niche specialization. Sm7 and Sm9 lineages exhibit the most concerning resistome; bla_KPC-2 plasmid is widespread in Sm7, whereas Sm9, also an anthropogenic-exclusive lineage, presents highest plasmid/lineage size ratio and plasmid-diversity encoding metallo-beta-lactamases comprising bla_NDM-1. The heterogeneity of resistance patterns of S. marcescens lineages elucidated herein highlights the relevance of surveillance programs, using whole-genome sequencing, to provide insights into the molecular epidemiology of carbapenemase producing strains of this species.

粘质沙雷氏菌是一种全球传播的医院病原体。这种杆状细菌具有广泛的宿主范围和全球地理分布。在这里，我们分析了来自 35 个国家的这种多重耐药、机会性病原体的国际收集，以推断其人口结构。我们表明S. marcescens包含 12 个谱系；Sm1、Sm4 和 Sm10 包含 78.3% 的已知环境菌株。Sm5、Sm6 和 Sm7 仅包含与人类相关的菌株，它们具有最小的泛基因组、基因组流动性和最低水平的核心重组，表明生态位专业化。Sm7 和 Sm9 谱系表现出最令人担忧的抗性组；bla _KPC-2质粒在 Sm7 中广泛存在，而 Sm9 也是人为独有的谱系，具有最高的质粒/谱系大小比和编码包含bla _NDM-1的金属-β-内酰胺酶的质粒多样性。本文阐明的粘质沙门氏菌谱系的抗性模式的异质性突出了监测计划的相关性，使用全基因组测序，以提供对该物种产碳青霉烯酶菌株的分子流行病学的见解。