MSACL 2019 EU Abstract

Enterobacter: When MALDI-TOF (VITEK® MS) and New Taxonomy Speak as One Voice

Sophie Polsinelli, Delphine Jacob, Françoise Allard, Christophe Meunier, Sandrine Arend, Béatrice Cellière, Pierre-Jean Cotte-Pattat, Priscillia Courault, Géraldine Durand, Victoria Girard, Valérie Monnin.
bioMérieux, La Balme Les Grottes, France

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Valérie Monnin (Presenter) bioMérieux

Relevant Financial Disclosures (within past 24 months) No relevant financial relationship(s) to disclose. Conflict mitigation NOT REQUIRED.

Introduction: The species belonging to the Enterobacter genus are responsible for 5 to 10% of infections among patients hospitalized in intensive care units and are primarily due to the members of the Enterobacter cloacae complex (ECC). This complex is divided into 13 clusters with 6 defined species E. asburiae, E. cloacae, E. hormaechei, E. kobei, E. ludwigii and E. nimipressuralis.
New Enterobacter species and sub-species have also recently been described such as
E. bugandensis associated with neonatal sepsis.

Objectives: In this study, we demonstrate that the use of MALDI-TOF technology coupled with well characterized strains improves Enterobacter genus identification and is in accordance with the new genus taxonomy.
Methods: 76 Enterobacter strains were characterized by sequencing of the gyrB gene. MALDI-TOF acquisitions were performed by direct deposit after addition of 1µL of CHCA, bioMérieux, and within the mass range of 3.000-17.000 Da.
Data were analyzed using dendrograms and performances were evaluated using a cross-validation approach.
Results: The dendrogram showed that a clear differentiation is possible between the different Enterobacter species or even sub-species. The clustering obtained using MALDI-TOF corresponds to the newly described taxonomy of this genus (Int J Syst Evol Microbiol 2018;68:3379–3393 DOI 10.1099/ijsem.0.003071).
Cross validation study was performed to evaluate the performance of the updated database, containing 40.458 spectra covering 1199 bacterial species.
Species within the ECC could be separated using MALDI-TOF. They could even be identified at sub species level for E. cloacae and E. hormaechei. The preliminary performances showed 83.8 to 100% of correct identification for all Enterobacter species including new species except E. kobei for which a high rate of NoID results (29.8%) was observed, probably due to heterogeneity of the species as demonstrated by the existence of two different type strains.

Conclusions: This study demonstrates that MALDI TOF is a reliable tool to differentiate close species of Enterobacter like species within the ECC and also to identify new highly pathogenic species like E. bugandensis such helping patient care and reducing time to appropriate antibiotic therapy.