Moraxella species

MICROBIOLOGY

• Gram-negative diplococcus [Fig], appears identical to N. gonorrhoeae.
  • Previously known as Branhamella.
  • M. catarrhalis is the major human pathogen.
    • Occasional cases of other Moraxella species have been described.
      • M. nonliquefaciens has been seen in highly immunocompromised patients. It may occasionally be misidentified in the lab as N. cinerea, N. flavescens, or as a glucose-negative strain of N. gonorrhoeae.
  • Frequently missed in respiratory cultures because colonies resemble commensal Neisseria, which are normal flora.
• Grows easily on blood chocolate agar, grows well at 28ºC.
• Colonizes the upper airways in 5-15% of the population; found only in humans.
  • It is most frequently found as part of normal flora for infants and children (25-75% in healthy children) and decreases in adults.
  • Higher prevalence of pharyngeal colonization during winter.
• Commonly produces beta-lactamase; 95% of strains are resistant to amoxicillin.