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. CASE REPORTA 75-year-old man was admitted to our hospital in March 2006 because of persistent back pain and abdominal distention lasting for 2 days. He had a history of hypertension, transient ischemic attack, and pulmonary tuberculosis complicated with bronchiectasis. At the time of admission, his oral temperature was 37.5°C, with a blood pressure of 163/87 mmHg and heart rate of 85 beats per minute. A physical examination revealed distension and tenderness in the lower abdomen.

Detection of Escherichia coli O157:H7 in Human patients Stool and Food by Using Multiplex PCR Assays Targeting the rfbE and the eaeAGenes compared with Detection by Biochemical Test and Serological Assay

“…[9]. In the present study, PCR assays using two combinations of primers were designed for the detection of E.…”

A Colanic Acid Operon Deletion Mutation Enhances Induction of Early Antibody Responses by Live Attenuated Salmonella Vaccine Strains

“…Most of this research on CA was carried out with E. coli strains (5), such as different laboratory K-12 strains, including MC4100, MG1655, and W3310 (6,8,17,30,31,(37)(38)(39)(40), K1 (41), K5 (41), K92 (42), extraintestinal isolate O4/K54/H5 (35,43), different O8 and O9 pathovars (44), enterohemorrhagic E. coli O157:H7 (18,26,27,36,37,45), and uropathogenic E. coli (33). Although it was reported that CA in Salmonella is not important for biofilm formation in vitro (46), some reports indicated that CA in Salmonella may play a role in vivo (4,47,48). The divergence of CA gene clusters between Salmonella and E. coli is slightly higher than the average for other genes of the two species (4).…”

“…Mucoid Salmonella strains were not lysed by P22, indicating the inaccessibility to the P22 receptor LPS O antigen (49). A mucoid variant of Salmonella has been isolated from a clinical specimen, which indicated that CA overexpression in vivo may help Salmonella escape antibiotic treatment (48). Although the physiological stimuli in vivo that induce CA synthesis are not fully understood (50), mutation of wcaM, one of the CA synthesis genes in Salmonella, resulted in reduced biofilm formation on HEp-2 cells and on chicken intestinal tissue at 37°C in vitro (47), which indicated that the CA can be produced at 37°C when bacteria are exposed to eukaryotic cells.…”

Role of RNA polymerase sigma-factor (RpoS) in induction of glutamate-dependent acid-resistance of Escherichia albertii under anaerobic conditions

“…The commercial systems, often used by clinical and food laboratories to identify gram‐negative rods, identified E. albertii isolates as Hafnia, E. coli, Salmonella , or Yersinia ruckeri (Abbott et al , 2003). Automated bacterial identification systems have limitations as documented in a recent report where a clinical mucoid strain of Salmonella enterica serovar choleraesuis was identified as H. alvei (Wang et al , 2006). Since E. albertii has just been described, the lack of biochemical identification of these strains may have jeopardized the scope of research involving its occurrence and association with food‐borne illness.…”