title: Fatal outbreak of an emerging clone of extensively drug-resistant Acinetobacter baumannii with enhanced virulence.
abstract: 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.
authors.affiliation: Department of Wound Infections, Walter Reed Army Institute of Research, Silver Spring, Maryland.
authors.forename: Crystal L
authors.initials: CL
authors.lastname: Jones
authors.affiliation: Providence Alaska Medical Center, Anchorage.
authors.forename: Megan
authors.initials: M
authors.lastname: Clancy
authors.affiliation: Department of Pathology.
authors.forename: Cary
authors.initials: C
authors.lastname: Honnold
authors.affiliation: Department of Wound Infections, Walter Reed Army Institute of Research, Silver Spring, Maryland.
authors.forename: Shweta
authors.initials: S
authors.lastname: Singh
authors.affiliation: Multidrug-Resistant Organism Repository and Surveillance Network, Walter Reed Army Institute of Research, Silver Spring, Maryland.
authors.forename: Erik
authors.initials: E
authors.lastname: Snesrud
authors.affiliation: Multidrug-Resistant Organism Repository and Surveillance Network, Walter Reed Army Institute of Research, Silver Spring, Maryland.
authors.forename: Fatma
authors.initials: F
authors.lastname: Onmus-Leone
authors.affiliation: Multidrug-Resistant Organism Repository and Surveillance Network, Walter Reed Army Institute of Research, Silver Spring, Maryland.
authors.forename: Patrick
authors.initials: P
authors.lastname: McGann
authors.affiliation: Multidrug-Resistant Organism Repository and Surveillance Network, Walter Reed Army Institute of Research, Silver Spring, Maryland.
authors.forename: Ana C
authors.initials: AC
authors.lastname: Ong
authors.affiliation: Multidrug-Resistant Organism Repository and Surveillance Network, Walter Reed Army Institute of Research, Silver Spring, Maryland.
authors.forename: Yoon
authors.initials: Y
authors.lastname: Kwak
authors.affiliation: Multidrug-Resistant Organism Repository and Surveillance Network, Walter Reed Army Institute of Research, Silver Spring, Maryland.
authors.forename: Paige
authors.initials: P
authors.lastname: Waterman
authors.affiliation: Department of Wound Infections, Walter Reed Army Institute of Research, Silver Spring, Maryland.
authors.forename: Daniel V
authors.initials: DV
authors.lastname: Zurawski
authors.affiliation: Multidrug-Resistant Organism Repository and Surveillance Network, Walter Reed Army Institute of Research, Silver Spring, Maryland.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Clifford
authors.affiliation: Multidrug-Resistant Organism Repository and Surveillance Network, Walter Reed Army Institute of Research, Silver Spring, Maryland.
authors.forename: Emil
authors.initials: E
authors.lastname: Lesho
mesh_terms: D000151:Acinetobacter Infections / Q000453:epidemiology* / Q000235:genetics / Q000382:microbiology / Q000401:mortality*; D040981:Acinetobacter baumannii / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity*; D000328:Adult; D000369:Aged, 80 and over; D000818:Animals; D002140:California; D018153:Czech Republic; D004195:Disease Models, Animal; D004196:Disease Outbreaks; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D005260:Female; D023281:Genomics; D005858:Germany; D006801:Humans; D007121:Immunocompetence; D008297:Male; D051379:Mice; D008875:Middle Aged; D058885:Multilocus Sequence Typing; D010802:Phylogeny; D062606:Tertiary Care Centers / Q000706:statistics & numerical data; D014481:United States / Q000453:epidemiology; D014774:Virulence / Q000235:genetics
keywords: Acinetobacter baumannii; extensively drug resistant; outbreak; virulence