Fatal Outbreak of an Emerging Clone of Extensively Drug-Resistant Acinetobacter baumannii with Enhanced Virulence

Crystal L. Jones*, Megan Clancy, Cary Honnold, Shweta Singh, Erik Snesrud, Fatma Onmus-Leone, Patrick McGann, Ana C. Ong, Yoon Kwak, Paige Waterman, Daniel V. Zurawski, Robert J. Clifford, Emil Lesho

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

78 Scopus citations


Background. Severe Acinetobacter baumannii infections in immunocompetent patients are uncommon, and the virulence mechanisms of this organism are not fully understood. Methods. Following an outbreak of fatal A. baumannii infections in a cohort of relatively immunocompetent patients (low comorbidity and illness severity scores), isolates were investigated with comparative genomics and in animal models. Results. Two unrelated A. baumannii clades were associated with the outbreak. The clone associated with the majority of patient deaths, clade B, is evolutionarily distinct from the 3 international clonal complexes, belongs to multilocus sequence type (MLST) 10, and is most closely related to strains isolated from the Czech Republic, California, and Germany in 1994, 1997, and 2003, respectively. In 2 different murine models, clade B isolates were more virulent than comparator strains, including the highly virulent reference strain AB5075. The most virulent clade B derivative, MRSN 16897, was isolated from the patient with the lowest combined comorbidity/illness severity score. Clade B isolates possess a unique combination of putative virulence genes involved in iron metabolism, protein secretion, and glycosylation, which was leveraged to develop a rapid and specific clinical assay to detect this clade that cannot be distinguished by MLST. Conclusions. Clade B warrants continued surveillance and investigation.

Original languageEnglish
Pages (from-to)145-154
Number of pages10
JournalClinical Infectious Diseases
Issue number2
StatePublished - 15 Jul 2015
Externally publishedYes


  • Acinetobacter baumannii
  • extensively drug resistant
  • outbreak
  • virulence


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