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Moraxella spp

• atlantae
• catarrhalis - lacunata
• lincolnii
• nonliquefaciens
• osloensis |

History

• Moraxella - named for Victor Morax, swiss ophthalmologist who first discovered the genera
• Catarrhalis - from Greek “catarrh” = “to flow down”. Named for profuse discharge from eyes and nose

Etymology

• Produce endotoxin
• Iron binding surface proteins | | Clinical syndromes | - Otitis media (15-20% cases in children)
• bronchitis
• sinusitis
• laryngitis
• COPD exacerbations (~10% exacerbations).
• CAP (immunocompromised host). Rarely invasive - bacteraemia, meningitis, septic arthritis |

Lab diagnostics

https://microbe-canvas.com/Bacteria/gram-negative-cocci/oxidase-positive-3/moraxella-catarrhalis.html - for microscopy and agar images

Microbiology

• Microscopy:
  • GN cocco-bacilli, resistant to decolourisation (can appear GP)
    • More coccoid: M. catarrhalis
    • More rod-shaped: M. atlantae, M. lacunata, M. nonliquefaciens, M. osloensis
  • Pairs or short chains. occasionally tetrads
• Culture:
  • aerobic growth ideally 33-35 C
  • Nutritionally fastidious, poor growth on blood agar. Improved on chocolate. No growth on MacConkey
  • Colony:
    • White or buff
    • Convex
    • “hockey puck” motility - stay intact and glide over agar when pushed with loop
• Species ID
  • Biochemical tests:
    • Catalase +
    • Oxidase +
    • Nitrase variable
    • Usually beta-lactamase positive
    • Tributyrin test:
      • differentiates M. catarrhalis (+) from Neisseria spp. (-)
      • Note, other Moraxella spp are Tributyrin + as well, so not useful to differentiate Moraxella spp.
      • Important as Moraxella and Neisseria are both oxidase positive GN cocco-bacilli found in respiratory tract samples
    • DNAse test:
      • differentiates M. catarrhalis (+) from other Moraxella spp. (-)
• MALDI-TOF