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Macrolide resistance in Mycoplasma pneumoniae in adult patients

Panpan Xie1,2, Yue Zhang1,3, Yanhong Qin1,3

  • 1Department of Respiratory and Critical Care Medicine, Senior Department of Infectious Diseases, the Fifth Medical Center of PLA General Hospital, Beijing, China.

Frontiers in Cellular and Infection Microbiology
|April 1, 2025
PubMed

Insights

Macrolide-resistant Mycoplasma pneumoniae is common in adults, primarily due to 23S rRNA gene mutations. Efflux pumps also contribute to resistance, suggesting midecamycin as a potential alternative treatment.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Antimicrobial Resistance

Background:

  • Mycoplasma pneumoniae causes significant respiratory infections.
  • Macrolides are first-line treatments, but resistance is increasing.
  • Resistance mechanisms in adults remain understudied compared to pediatric cases.

Purpose of the Study:

  • To investigate macrolide resistance in M. pneumoniae from adult patients.
  • To elucidate the underlying resistance mechanisms in adult isolates.
  • To evaluate potential alternative treatments.

Main Methods:

  • Collected pharyngeal swabs from adult patients with respiratory infections.
  • Isolated and identified M. pneumoniae strains.
  • Assessed antimicrobial susceptibility using broth microdilution.
  • Sequenced 23S rRNA genes and performed PCR for resistance genes (erm, mef, mphC).
  • Determined Minimum Inhibitory Concentrations (MICs) with and without reserpine.

Main Results:

  • 41.7% of 72 M. pneumoniae isolates were macrolide-resistant.
  • All resistant strains had mutations at the 2063 site in the 23S rRNA gene.
  • Efflux pump genes (msrA/B, mefA) were found in two isolates.
  • Reserpine reduced azithromycin MICs by 75% in these two strains.
  • Midecamycin showed the greatest activity against M. pneumoniae (MIC90: 16 µg/ml).

Conclusions:

  • Macrolide-resistant M. pneumoniae is prevalent in adult patients in Beijing.
  • Point mutations in the 23S rRNA gene are the primary resistance mechanism.
  • Efflux pumps play a partial role in macrolide resistance.
  • Midecamycin is a promising alternative for treating M. pneumoniae infections, especially azithromycin-resistant cases.
Keywords:
Mycoplasma pneumoniaeefflux pumpmacrolide resistancepoint mutationsresistant mechanism

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