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Pathogenetic characterization of a Micrococcus luteus strain isolated from an infant
Xiaolu Shi1,2, Shuxiang Qiu1, Liyin Ji2
1Department of Public Health Laboratory Sciences, School of Public Health, Hengyang Medical School, University of South China, Hengyang, China.
Purpose:
To explore the clinical characteristics of Micrococcus luteus bloodstream infection in an infant and characterize the phenotype and genotype of the isolated strains, as well as seek suitable infection models for assessing virulence.
Methods:
Clinical data was collected from an infant patient diagnosed with M. luteus bloodstream infection. Metagenomic sequencing was performed on the isolated blood sample. The strain was isolated and underwent mass spectrometry, biochemical tests, antibiotic susceptibility assays, and whole-genome sequencing. The Galleria mellonella infection model was used to assess M. luteus virulence.
Results:
Patient responded poorly to cephalosporins, but recovered after Linezolid treatment. Metagenomic sequencing identified M. luteus as the predominant species in the sample, confirming infection. They were identified as M. luteus with a high confidence level of 98.99% using mass spectrometry. The strain showed positive results for Catalase, Oxidase, and Urea tests, and negative results for Mannose, Xylose, Lactose, Mannitol, Arginine, and Galactose tests, consistent with the biochemical profile of M. luteus reference standards. M. luteus susceptibility to 15 antibiotics was demonstrated and no resistance genes were detected. Predicted virulence genes, including clpB, were associated with metabolic pathways and the type VI secretion system. The infection model demonstrated dose-dependent survival rates.
Conclusion:
The infant likely developed a bloodstream infection with M. luteus due to compromised immunity. Although the isolated strain is sensitive to cephalosporin antibiotics and has low pathogenicity in infection models, clinical treatment with cephalosporins was ineffective. Linezolid proved to be effective, providing valuable guidance for future clinical management of such rare infections.
Insights
Micrococcus luteus bloodstream infection in an infant was identified. Despite antibiotic susceptibility, cephalosporins failed, but Linezolid treatment was effective, guiding future rare infection management.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Genomics
Background:
- Bacterial bloodstream infections (BSIs) pose significant risks, particularly in infants.
- Micrococcus luteus is an opportunistic pathogen rarely causing severe infections.
Purpose of the Study:
- To detail the clinical presentation of M. luteus BSI in an infant.
- To characterize the isolated M. luteus strain's phenotype and genotype.
- To evaluate M. luteus virulence using an infection model.
Main Methods:
- Clinical data analysis of an infant with M. luteus BSI.
- Metagenomic sequencing and whole-genome sequencing of the isolate.
- Phenotypic characterization including biochemical tests and antibiotic susceptibility assays.
- Galleria mellonella infection model for virulence assessment.
Main Results:
- Metagenomic sequencing confirmed M. luteus as the causative agent.
- The isolate was identified by mass spectrometry and biochemical tests.
- The strain was susceptible to 15 antibiotics, with no detected resistance genes.
- Virulence factors including clpB and type VI secretion system were predicted.
- The Galleria mellonella model showed dose-dependent mortality.
Conclusions:
- M. luteus BSI in an immunocompromised infant occurred.
- Clinical treatment with cephalosporins was ineffective despite in vitro susceptibility.
- Linezolid treatment led to patient recovery, offering crucial clinical insights.
