title: Misidentification of a mucoid strain of Salmonella enterica serotype choleraesuis as Hafnia alvei by the Vitek GNI+ card system.
abstract: Nontyphoidal salmonellae are among the most common causes of bacterial gastroenteritis worldwide. They are also notable causes of extraintestinal infections, including bacteremia and vascular infections. Salmonella enterica serotype Choleraesuis is typically associated with invasive infections. We report a patient who had an infected intra-abdominal aortic aneurysm due to an unusually mucoid strain of Salmonella enterica serotype Choleraesuis. The isolate was erroneously identified as Hafnia alvei by the Vitek GNI+ card system. A blood culture isolate taken from the same patient 9 months earlier was also identified as H. alvei by the Vitek GNI+ card system. Despite an apparent cure with intravenous amoxicillin-clavulanic acid at that time, the Salmonella infection had not been cleared and manifested as a ruptured infected abdominal aortic aneurysm. Repeated passage of the strain yielded nonmucoid colonies, which were correctly identified by the API and PHOENIX systems. The isolates from the aneurysm and the former bacteremic episode were found to be identical using pulsed field gel electrophoresis. The fallibility of automated bacterial identification systems is highlighted. Such errors are especially important for isolates in which in vitro antibiotic susceptibility testing does not correlate with the clinical success of treatment, as illustrated by Salmonella infections.
authors.affiliation: Department of Microbiology, The University of Hong Kong, 4/F University Pathology Building, Queen Mary Hospital, 102 Pokfulam Road, Hong Kong.
authors.forename: Teresa K F
authors.initials: TK
authors.lastname: Wang
authors.forename: Wing-Cheong
authors.initials: WC
authors.lastname: Yam
authors.forename: Kwok-Yung
authors.initials: KY
authors.lastname: Yuen
authors.forename: Samson S Y
authors.initials: SS
authors.lastname: Wong
mesh_terms: D000368:Aged; D019980:Amoxicillin-Potassium Clavulanate Combination / Q000627:therapeutic use; D017544:Aortic Aneurysm, Abdominal / Q000382:microbiology*; D001431:Bacteriological Techniques; D001769:Blood / Q000382:microbiology; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000235:genetics; D003951:Diagnostic Errors; D016521:Electrophoresis, Gel, Pulsed-Field; D004756:Enterobacteriaceae Infections / Q000175:diagnosis* / Q000188:drug therapy / Q000382:microbiology; D020611:Hafnia alvei / Q000145:classification / Q000302:isolation & purification*; D006801:Humans; D008297:Male; D012480:Salmonella Infections / Q000175:diagnosis* / Q000188:drug therapy / Q000382:microbiology; D019779:Salmonella enterica / Q000145:classification / Q000302:isolation & purification* / Q000502:physiology
chemical_list: D004269:DNA, Bacterial; D019980:Amoxicillin-Potassium Clavulanate Combination