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Lim, Kweon, Lee, and Park: Two Cases of Enterobacter hormaechei Infection Misidentified as Cedecea davisae Infection

Abstract

Enterobacteriaceae is a family of gram-negative, rod-shaped bacteria that consists of various species. Among these, members of the genus Cedecea has been reported as relatively rare causative pathogens of human infections. Commercially available automated identification systems that use biochemical reactions are known to accurately identify Enterobacteriaceae species. However, the accurate identification of some organisms with diverse biochemical profiles by these automated identification systems may be problematic. In this study, we report two cases of isolate misidentification, from patients with acute cholecystitis and deep vein thrombosis, as Cedecea davisae with VITEK II system. Both the isolates were correctly identified as Enterobacter hormaechei using gyrB gene sequence analysis. We also performed 16S rRNA sequence analyses and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analyses; however, indeterminate results were obtained from both the assays. Therefore, the sequence analysis of alternative genes, like gyrB, might be useful for accurate identification of species that belong to the family of Enterobacteriaceae.

Figures and Tables

Table 1

Results of 16S rRNA sequencing

lmo-5-223-i001
Case No. ID Identities Gaps
1 Enterobacter hormaechei VIT-SNSJ 479/488 (98.16%) 0/488 (0%)
Enterobacter cloacae ECNIH2 479/488 (98.16%) 0/488 (0%)
Enterobacter ludwigii VVS01-S1 479/488 (98.16%) 0/488 (0%)
2 Enterobacter hormaechei Nuan 5 489/490 (99.80%) 0/490 (0%)
Enterobacter cloacae ECNIH2 489/490 (99.80%) 0/490 (0%)
Lactobacillus plantarum AU5-800R 489/490 (99.80%) 0/490 (0%)
Table 2

Results of MALDI-TOF MS identification

lmo-5-223-i002
Case No. Bruker Biotyper VITEK MS system
ID Score ID Confidence value
1 Enterobacter cloacae 2.117 Enterobacter cloacae 50
Enterobacter cloacae 1.991 Enterobacter asburiae 50
Enterobacter homaechei 1.989
2 Enterobacter cloacae 2.207 Enterobacter cloacae 50
Enterobacter cloacae 2.200 Enterobacter asburiae 50
Enterobacter homaechei 2.146
Table 3

Results of rpoB sequencing

lmo-5-223-i003
Case No. ID Identities Gaps
1 Enterobacter hormaechei ATCC 49162 981/983 (99.80%) 0/983 (0%)
Enterobacter cloacae EN-291 981/983 (99.80%) 0/983 (0%)
Enterobacter cloacae EN-280 981/983 (99.80%) 0/983 (0%)
2 Enterobacter hormaechei ATCC 49162 969/971 (99.79%) 0/971 (0%)
Enterobacter cloacae EN-291 969/971 (99.79%) 0/971 (0%)
Enterobacter cloacae EN-280 969/971 (99.79%) 0/971 (0%)
Table 4

Results of gyrB sequencing

lmo-5-223-i004
Case No. ID Identities Gaps
1 Enterobacter hormaechei ATCC 49162 1,171/1,178 (99.41%) 0/1,178 (0%)
Enterobacter cloacae NCTC 9394 1,150/1,178 (97.62%) 0/1,178 (0%)
Enterobacter cloacae SSM 2554 1,147/1,178 (97.37%) 0/1,178 (0%)
2 Enterobacter hormaechei ATCC 49162 1,150/1,159 (99.22%) 0/1,159 (0%)
Enterobacter cloacae NCTC 9394 1,129/1,159 (97.41%) 0/1,159 (0%)
Enterobacter cloacae SSM 2554 1,126/1,159 (97.15%) 0/1,159 (0%)

Notes

This article is available from http://www.labmedonline.org

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