Moraxella spp

• M. atlantae
• M. canis
• M. lacunata
• M. lincolnii
• M. nonliquefaciens
• M. osloensis

Gram Stain

• Gram negative coccobacilli (plump) in pairs and short chains - nonfermenter

Clinical Significance

Many of these species can colonize human skin and mucous membranes (including the genital tract). They are considered low level pathogens.

M. atlantae - associated with bacteremia in immunocompromised patients.

M. canis - part of the upper respiratory flora of dogs and cats and has been associated with bacteremia and wound infections following dog bites.

M. lacunata - associated with conjunctivitis, keratitis, chronic sinusitis, and endocarditis.

M. lincolnii - isolated from human respiratory tract samples where its pathogenic role is uncertain.

M. nonliquefaciens - associated with endophthalmitis and septic arthritis. Mucoid strains (difficult to eradicate) are often found in patients with chronic lung disease.

M. osloensis - associated with sinusitis, conjunctivitis, pulmonary infections, septic arthritis, osteomyelitis, peritonitis, meningitis, endocarditis, bacteremia/septicemia, and intravascular device related infections.

Usual Susceptibility Pattern

These organisms are usually susceptible to ampicillin, cephalosporins, tetracyclines, quinolones, TMP/SMX, and macrolides. 

Occasional strains of M. nonliquefaciens and M. lacunata produce a beta-lactamase resulting in resistance to amoxicillin and 1st generation cephalosporins.