What is the classification of Enterobacteriaceae (a family of Gram-negative bacteria) from 1937 to 2020?

From the Guidelines

The classification of Enterobacteriaceae has undergone significant changes from 1937 to 2020, with a shift from a simple family-based system to a complex taxonomic framework based on molecular phylogenetic relationships, as evident from the most recent study in 2017 1.

Key Developments in Classification

• Initially, in 1937, the family was defined by phenotypic characteristics such as gram-negative staining, facultative anaerobic metabolism, and fermentation of glucose.
• The 1950s-60s saw the introduction of biochemical tests for classification, recognizing genera like Escherichia, Salmonella, Shigella, Klebsiella, and Proteus.
• The 1970s-80s introduced DNA hybridization techniques for more precise differentiation between closely related species.
• The 1990s brought 16S rRNA gene sequencing, revolutionizing bacterial taxonomy by providing molecular phylogenetic relationships.
• Major reclassification occurred in the 2000s with whole genome sequencing, leading to the splitting of Enterobacteriaceae into multiple families within the order Enterobacterales in 2016, as supported by a study in 2018 1.

Implications of Taxonomic Evolution

• This evolution reflects our deepening understanding of bacterial relationships.
• It has important implications for clinical diagnostics, antimicrobial therapy, and epidemiological surveillance of these human pathogens, as highlighted in a study published in the World Journal of Emergency Surgery in 2017 1.
• The classification changes are crucial for managing infections caused by Enterobacteriaceae, including intra-abdominal infections, where appropriate antibiotic therapy is critical, as discussed in the management guidelines for intra-abdominal infections 1.

Current Understanding and Future Directions

• By 2020, the original Enterobacteriaceae family was significantly narrowed, with many former members reassigned to new families like Yersiniaceae, Erwiniaceae, Pectobacteriaceae, Hafniaceae, and Morganellaceae.
• The continued evolution of bacterial taxonomy, driven by advances in molecular techniques, will further refine our understanding of Enterobacteriaceae and inform clinical practice, as noted in recent studies 1.

From the Research

Classification of Enterobacteriaceae

• The family Enterobacteriaceae has undergone significant changes in its classification over the years, with the development of new molecular methods and laboratory techniques leading to the discovery of new species and the reclassification of existing ones 2.
• Studies have identified six main clades within the family Enterobacteriaceae, which can be reliably demarcated using molecular markers such as conserved signature indels (CSIs) 3.
• The classification of Enterobacteriaceae has been revised in recent years, with 19 new genera described since 2000, and some genera such as Yersinia, Morganella, and Erwinia no longer belonging to the family 4.

Taxonomic Changes

• The taxonomic changes in the Enterobacteriaceae family have significant implications for clinical and epidemiological interpretation, and it is essential to update the libraries of commercial systems used for microorganism identification and to train staff on these changes 4.
• The reclassification of Enterobacteriaceae has also led to the proposal of new genera, such as Pseudescherichia and Metakosakonia, and the transfer of some species to new genera 3.

Enterobacteriaceae and Human Disease

• Enterobacteriaceae are a large family of Gram-negative bacteria that can cause both intestinal and extraintestinal diseases in humans, with some species such as Salmonella, Escherichia, Shigella, and Yersinia being important human pathogens 5.
• The emergence of antimicrobial resistance among Enterobacteriaceae has become a significant concern, with the spread of multidrug-resistant clones limiting therapeutic options and making some infections untreatable with existing antimicrobials 6.