Leclercia pneumoniae sp. nov., a bacterium isolated from clinical specimen in Leipzig, Germany

Area of Science:

• Microbiology
• Genomics
• Clinical Bacteriology

Background:

• The genus *Leclercia* currently comprises a single species, *Leclercia adecarboxylata*.
• Bacterial infections in infants, such as pneumonia and septicemia, require accurate identification and classification of causative agents.

Purpose of the Study:

• To characterize a bacterial isolate, strain 49125^T, obtained from an infant with pneumonia and septicemia.
• To determine if strain 49125^T represents a new species within the *Leclercia* genus.

Main Methods:

• Phenotypic characterization including biochemical profiling and MALDI-TOF mass spectrometry.
• Genomic analysis involving hybrid Illumina and Nanopore sequencing for genome reconstruction.
• Phylogenetic analysis using 172 marker genes and k-mer-based searches.
• In silico DNA-DNA hybridization for genomic relatedness assessment.

Main Results:

• Strain 49125^T exhibited phenotypic characteristics similar to *Leclercia adecarboxylata*.
• Genome sequencing revealed a 4.4 Mbp circular genome with 55.0 mol% G+C content.
• Phylogenetic and genomic analyses showed average nucleotide identity below 95% with known species.
• These findings indicate strain 49125^T represents a distinct species.

Conclusions:

• Strain 49125^T is proposed as a new species, *Leclercia pneumoniae* sp. nov.
• This discovery expands the taxonomic diversity of the *Leclercia* genus.
• Accurate classification is crucial for understanding the clinical significance of novel bacterial pathogens.