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

Lucia De Florio¹, Elisabetta Riva², Annalisa Giona¹

¹Unit of Clinical Laboratory Science, University Campus Bio-Medico of Rome, Rome, Italy.

Frontiers in Microbiology

|August 30, 2018

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.

Insights

This study tracked Enterobacter species, antimicrobial resistance, and MALDI-TOF identification over three years. Carbapenem-resistant Enterobacter cloacae emerged, spreading through hospital wards via clonal transmission.

Area of Science:

Clinical Microbiology
Infectious Diseases
Antimicrobial Resistance

Background:

Enterobacter species are significant causes of human infections.
Carbapenem-resistant Enterobacter isolates, particularly those with the blaKPC gene, have been reported with evidence of clonal transmission in nosocomial outbreaks.
Understanding the dynamics of Enterobacter populations and their resistance patterns in healthcare settings is crucial for infection control.

Purpose of the Study:

To evaluate the relative abundance of Enterobacter species over three years.
To assess antimicrobial susceptibility trends and the emergence of resistance, including multidrug-resistant (MDR) and carbapenem-resistant strains.
To compare the identification capabilities of two common MALDI-TOF mass spectrometry platforms for Enterobacter species.

Main Methods:

Identification of Enterobacter species using MALDI-TOF MS Biotyper and VITEK MS platforms.
Antimicrobial susceptibility testing using Vitek2 Compact, with MIC50 and MIC90 evaluation.
Clustering analysis using MALDI-TOF data to build and compare dendrograms for microbial population dynamics.

Main Results:

Enterobacter cloacae and Enterobacter aerogenes were the most frequent species, with a noted increase in Enterobacter asburiae in 2017.
MALDI-TOF platforms demonstrated high sensitivity and specificity, though E. asburiae identification was only reliable with MALDI-TOF MS Biotyper.
An increase in Enterobacter resistance was observed, including extended-spectrum beta-lactamase (ESBL) producing strains and the emergence of MDR and carbapenem-resistant E. cloacae.
Clonal transmission of resistant strains was identified between general surgery and geriatric wards.

Conclusions:

The study highlights a concerning rise in antimicrobial resistance within Enterobacter species in a nosocomial environment.
MALDI-TOF MS Biotyper offers superior identification accuracy for certain species like E. asburiae compared to VITEK MS.
Evidence of clonal transmission underscores the need for enhanced infection control measures to prevent the spread of resistant Enterobacter strains in hospitals.

Read full analysis

Keywords:

Enterobacter MALDI-TOF mass spectrometry clustering analysis nosocomial infection resistance

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