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Whole Genome Analysis Reveals New Insights into Macrolide Resistance in Mycoplasma pneumoniae
Shao Li Li1, Hong Mei Sun1, Bao Li Zhu2
1Department of Bacteriology, Capital Institute of Pediatrics (CIP), Beijing 100020, China.
Objective:
Mutations in 23S rRNA gene are known to be associated with macrolide resistance in Mycoplasma pneumoniae (M. pneumoniae). However, these mutations alone do not fully explain the high resistance rates in Asia. The aim of this study was to investigate other possible mutations involved in macrolide resistance in M. pneumoniae.
Methods:
The whole genomes of 10 clinical isolates of M. pneumoniae with macrolide resistance were sequenced by Illumina HiSeq2000 platform. The role of the macrolide-specific efflux transporter was assessed by efflux-pump inhibition assays with reserpine and carbonyl cyanide m-chlorophenyl-hydrazone (CCCP).
Results:
A total of 56 single nucleotide polymorphisms (SNPs) were identified in 10 clinical isolates in comparison to the reference strains M129 and FH. Strikingly, 4 of 30 SNPs causing non-synonymous mutations were clustered in macrolide-specific efflux system gene macB encoding macrolide-specific efflux pump protein of the ATP-binding cassette transporter family. In assays of the minimal inhibitory concentrations (MIC) of macrolide antibiotics in the presence of the efflux pump inhibitors caused a significant decrease of MICs, even under detectable levels in some strains.
Conclusion:
Our study suggests that macrolide efflux pump may contribute to macrolide resistance in M. pneumoniae in addition to the common point mutations in 23S rRNA gene.
Insights
Macrolide resistance in Mycoplasma pneumoniae is not solely due to 23S rRNA gene mutations. This study found that macrolide efflux pumps, involving the macB gene, also contribute significantly to resistance. Further research into these efflux mechanisms is warranted.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- Macrolide resistance in Mycoplasma pneumoniae is a growing concern, particularly in Asia.
- Known resistance mechanisms primarily involve mutations in the 23S rRNA gene.
- These known mutations do not fully account for the observed high resistance rates.
Purpose of the Study:
- To investigate novel genetic mutations contributing to macrolide resistance in Mycoplasma pneumoniae.
- To explore the role of efflux pumps in mediating macrolide resistance.
Main Methods:
- Whole-genome sequencing of 10 macrolide-resistant Mycoplasma pneumoniae clinical isolates using Illumina HiSeq2000.
- Efflux-pump inhibition assays were performed using reserpine and CCCP to assess transporter activity.
- Minimal inhibitory concentrations (MICs) were determined in the presence and absence of efflux pump inhibitors.
Main Results:
- Fifty-six single nucleotide polymorphisms (SNPs) were identified compared to reference strains.
- Four non-synonymous SNPs were found in the macB gene, encoding a macrolide-specific efflux pump.
- Efflux pump inhibitors significantly reduced macrolide MICs, indicating the involvement of efflux pumps in resistance.
Conclusions:
- Macrolide efflux pumps, in addition to 23S rRNA mutations, play a role in Mycoplasma pneumoniae macrolide resistance.
- The macB gene and its encoded efflux pump are implicated in this resistance mechanism.
- Understanding these additional resistance pathways is crucial for effective treatment strategies.
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