MALDI-TOF MS Identification and Clustering Applied to Enterobacter Species in Nosocomial Setting.

Lucia De Florio,Eleonora Cella,Elisabetta Riva,Silvia Spoto,Annalisa Giona,Marta Fogolari,Etleva Dedej,Alessia Lai,Silvia Angeletti,Massimo Ciccozzi,Gianguglielmo Zehender

doi:10.3389/fmicb.2018.01885

Lucia De Florio, Eleonora Cella + Show 9 more

Open Access

https://doi.org/10.3389/fmicb.2018.01885

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Abstract

Enterobacter microorganisms cause important bacterial infections in humans. Recently, carbapenem resistant isolates carrying the blaKPC gene were described and their clonal transmission in different nosocomial outbreaks reported. In this study, the relative numbers of Enterobacter species, their antimicrobial susceptibility along 3 years of observation and the identification ability of the two most common MALDI-TOF platforms were evaluated. A clustering analysis was performed to identify changes in the microbial population within the nosocomial environment. Enterobacter were identified using two platforms (MALDI-TOF Biotyper and VITEK MS). Antimicrobial susceptibility was tested by Vitek2 Compact and MIC50 and MIC90 was evaluated using GraphPad software. Clustering analysis was performed by MALDI-TOF and a dendrogram was built with both platforms and compared. The most frequent species isolated were Enterobacter cloacae and Enterobacter aerogenes with a gradual increase of Enterobacter asburiae in 2017. MALDI-TOF platforms showed a very good sensitivity and specificity except for E. asburiae identification that was reliable only by MALDI-TOF MS Biotyper. An increase of resistance for Enterobacter, confirmed by the isolation of extended spectrum beta-lactamase (ESBL) strains and the emergence of E. cloacae multidrug-resistant (MDR) and carbapenem resistant strains, was observed. A clonal route of transmission involving general surgery and geriatric wards was evidenced as previously described for Klebsiella pneumoniae MDR strains in the same nosocomial setting. These data represent an important source of information about the spreading of Enterobacter in the nosocomial environment.

Highlights

Enterobacter species are gram-negative bacilli belonging to the family of Enterobacteriaceae and to the “ESKAPE” pathogens including Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species
Four hundreds and forty-five strains of Enterobacter species have been isolated at the University Hospital Campus Bio-Medico of Rome, Italy, from the year 2015 to the year 2017
The number of E. cloacae remained constant during the years whereas a decrease of E. aerogenes and a gradual increase of E. asburiae was observed in the year 2017 (Table 1)

Summary

Introduction

Enterobacter species are gram-negative bacilli belonging to the family of Enterobacteriaceae and to the “ESKAPE” pathogens including Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species. An increasing prevalence of multidrug-resistant (MDR) Enterobacter strains has been observed and in many cases nosocomial strains acquired carbapenemases as blaNDM-1 and blaKPC limiting the availability of appropriate antimicrobial treatments (Pottumarthy et al, 2003; Deshpande et al, 2006; Blanco et al, 2013). These strains are frequently isolated in course of bloodstream infections and severe local infection as pneumonia, especially in critically ill patients (Fridkin, 2001; Marchaim et al, 2008; Castanheira et al, 2011). The study revealed that these strains, evolving from a unique ancestor, follow a clonal spread and that plasmids harboring blaKPC gene were horizontally transferred between strains (Chavda et al, 2016)

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