What antibiotics cover Moraxella (M.) catarrhalis infections?

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Last updated: May 7, 2025View editorial policy

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From the Guidelines

Moraxella catarrhalis infections are best treated with amoxicillin with clavulanic acid 625 mg three times a day for 14 days, as recommended by the British Thoracic Society guideline for bronchiectasis in adults 1. This recommendation is based on the most recent and highest quality study available, which suggests that amoxicillin with clavulanic acid is an effective first-line treatment for Moraxella catarrhalis infections. Some key points to consider when treating Moraxella catarrhalis infections include:

  • The importance of using beta-lactam antibiotics with beta-lactamase inhibitors, such as amoxicillin with clavulanic acid, to overcome the beta-lactamase resistance mechanism produced by nearly all M. catarrhalis strains.
  • Alternative treatment options, such as clarithromycin, doxycycline, or ciprofloxacin, may be considered in cases where amoxicillin with clavulanic acid is not suitable or effective.
  • Treatment duration typically ranges from 5-14 days, depending on the infection site and severity, with respiratory infections usually requiring 7-10 days of therapy.
  • It is essential to consider local resistance patterns and patient factors, such as allergy history and renal function, when selecting an antibiotic regimen.
  • The British Thoracic Society guideline for bronchiectasis in adults provides a comprehensive overview of the recommended antimicrobial agents for various organisms, including Moraxella catarrhalis, and should be consulted for further guidance 1.

From the FDA Drug Label

Gram-Negative Bacteria Enterobacter cloacae Escherichia coli Haemophilus influenzae Haemophilus parainfluenzae Klebsiella pneumoniae Legionella pneumophila Moraxella catarrhalis Proteus mirabilis Pseudomonas aeruginosa Serratia marcescens

Levofloxacin covers Moraxella catarrhalis 2.

  • Key points:
    • Levofloxacin has in vitro activity against Moraxella catarrhalis.
    • The drug label does not provide information on the minimum inhibitory concentrations (MICs) of levofloxacin against Moraxella catarrhalis.
    • Azithromycin also covers Moraxella catarrhalis 3.

From the Research

Antibiotics Effective Against Moraxella Catarrhalis

  • Amoxicillin/clavulanate is effective against Moraxella catarrhalis, including beta-lactamase-producing strains 4, 5, 6, 7
  • Cefpodoxime proxetil is also effective against Moraxella catarrhalis, including beta-lactamase-producing strains 8
  • Cefuroxime is effective against Moraxella catarrhalis, with a sensitivity rate of 99% 5, 6
  • Erythromycin and clarithromycin are effective against Moraxella catarrhalis, with a sensitivity rate of 93% and 100% respectively 5, 6, 7
  • Levofloxacin and trimethoprimsulfamethoxazole are also effective against Moraxella catarrhalis, with a sensitivity rate of 99% and 100% respectively 6
  • Doxycycline is effective against Moraxella catarrhalis, with a sensitivity rate of 100% 6, 7

Resistance Patterns

  • Moraxella catarrhalis strains often produce beta-lactamase, which can confer resistance to penicillin and ampicillin 4, 5, 7
  • However, amoxicillin/clavulanate and other antibiotics such as cefuroxime, cefpodoxime proxetil, and levofloxacin remain effective against these strains 4, 8, 5, 6, 7

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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