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 described.
      • M. nonliquefaciens has been seen in highly immunocompromised patients. 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 28º C.
• Colonizes upper airways in 5-15% of the population, found only in humans.
  • Most frequently found as part of normal flora for infants and children, decreases in adults.
• Commonly produces beta-lactamase, 95% of strains resistant to amoxicillin.