Is Mycoplasma pneumoniae part of the normal flora?

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Last updated: April 11, 2025View editorial policy

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From the Guidelines

No, Mycoplasma pneumoniae is not considered normal flora in humans. It is a pathogenic bacterium that causes respiratory infections, most notably atypical pneumonia (sometimes called "walking pneumonia") 1. Unlike normal flora bacteria that colonize the body without causing disease, M. pneumoniae is an opportunistic pathogen that spreads through respiratory droplets from person to person. When infection occurs, it typically causes symptoms like persistent cough, fever, fatigue, and headache. M. pneumoniae lacks a cell wall, which makes it naturally resistant to beta-lactam antibiotics like penicillins and cephalosporins.

Key Characteristics of M. pneumoniae

  • Causes atypical pneumonia
  • Spreads through respiratory droplets
  • Naturally resistant to beta-lactam antibiotics
  • Treatment typically involves macrolide antibiotics, tetracyclines, or fluoroquinolones for 7-14 days, depending on severity 1.

Treatment Considerations

  • Macrolide resistance is a concern, especially in Asia 1
  • Tetracyclines and fluoroquinolones are alternative treatment options, but may have adverse effects in certain patient populations 1
  • Clinicians should weigh the possible adverse effects and clinical benefits before starting treatment 1 The bacterium's small size and unique characteristics allow it to evade some immune responses, which explains why infections can persist for weeks without appropriate treatment. According to the most recent guidelines, the treatment of choice for M. pneumoniae infection is a macrolide, but alternative antibiotics such as tetracyclines and fluoroquinolones may be considered in cases of macrolide resistance or intolerance 1.

From the Research

Mycoplasma pneumoniae as Normal Flora

  • There is no evidence to suggest that Mycoplasma pneumoniae is a normal flora in the human body 2, 3, 4, 5, 6.
  • Mycoplasma pneumoniae is a pathogenic mycoplasma responsible for respiratory tract infections in humans, which occurs worldwide in children and adults 2.
  • The bacterium is known to cause community-acquired pneumonia, and its clinical presentation and manifestations can vary widely, affecting all organs of the body 3, 6.

Pathogenicity and Infections

  • Mycoplasma pneumoniae is an important cause of respiratory tract infections in children as well as adults, ranging in severity from mild to life-threatening 4.
  • The bacterium can cause extrapulmonary manifestations and severe pulmonary manifestations, leading to long-term sequelae 6.
  • The increasing emergence of Mycoplasma pneumoniae that is resistant to macrolides in some areas of the world and increased world travel could add to the difficulty of controlling and treating Mycoplasma pneumoniae infections 6.

Treatment and Antibiotic Resistance

  • Mycoplasma pneumoniae is susceptible to macrolides and related antibiotics, tetracyclines, and fluoroquinolones 2.
  • Macrolides and related antibiotics are the first-line treatment for respiratory infections caused by Mycoplasma pneumoniae, but strains with acquired resistance to macrolides have emerged worldwide 2, 5.
  • Minocycline and tosufloxacin have shown good in vitro activities against macrolide-resistant Mycoplasma pneumoniae, and minocycline has been effective in shortening the duration of fever in pediatric patients infected with macrolide-resistant Mycoplasma pneumoniae 5.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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