- Stain: gram-negative
- Morphology: diplococcus
- Growth and culture:
- Oxidase-positive, catalase-positive
- Asaccharolytic (does not ferment carbohydrates)
M. catarrhalis and M. lacunata are the most clinically relevant species within this genus.
- Humans are the primary reservoir.
- M. catarrhalis spreads from person to person via respiratory droplets.
- Nasopharyngeal colonization:
- Common in infancy, but declines with age
- Bacteria can migrate to the middle ear from the nasopharynx via the Eustachian tube.
- ↑ Rate of colonization noted with increased pneumococcal vaccination (which is believed to cause shifts in respiratory microbiome).
- Opportunistic pathogen:
- Infection occurs in the setting of a weakened immune system or owing to existing respiratory disease (i.e., chronic obstructive pulmonary disease (COPD)).
- Bacterial stress (i.e., cold shock response) causes expression of pathogenic mechanisms within M. catarrhalis.
- Pathogenic mechanisms:
- Adhesins allow the bacteria to bind to the mucosa.
- Inhibits toll-like receptor 2 signaling (responsible for foreign substance recognition), allowing for immune system evasion
- Aggregates and creates a biofilm, making it difficult for antibiotics to reach the bacteria
- Tracheobronchitis and pneumonia:
- Noted in susceptible individuals, most commonly manifesting as acute COPD exacerbations
- M. catarrhalis causes 10%–20% of COPD exacerbations.
- Otitis media: M. catarrhalis causes 15%–20% of cases of otitis media in children.
- Uncommon cause of acute bacterial sinusitis
M. lacunata is a common cause of chronic angular blepharoconjunctivitis in humans.
- Clinical features of the diseases are often sufficient in arriving at the diagnosis.
- Microbiologic studies are often reserved for recurrent, severe conditions or for cases in which therapy has failed.
- Other tests are determined by clinical presentation (chest X-ray for suspected pneumonia).
- Moraxella: > 90% produce β-lactamase and thus are resistant to penicillin, ampicillin, and amoxicillin.
- Susceptible to amoxicillin–clavulanate, macrolides, extended-spectrum cephalosporins, tetracyclines, fluoroquinolones
- Aebi, C. (2011). Moraxella catarrhalis—pathogen or commensal? Adv Exp Med Biol 697:107–116.
- Goldstein, E. J. C., Murphy T. F. (2009). Moraxella catarrhalis: a human respiratory tract pathogen. Clin Infect Dis 000:000–000. https://academic.oup.com/cid/article/49/1/124/371116
- Heiniger, N., Troller, R., Meier, P.Ss, Aebi, C. (2005). Cold shock response of the UspA1 outer membrane adhesin of Moraxella catarrhalis. Infect Immun 000:000–000. https://pubmed.ncbi.nlm.nih.gov/16299321/
- Murphy, T. F., File, T. M. (2019). Moraxella catarrhalis infections. UpToDate. Retrieved 23 April 2021, from https://www.uptodate.com/contents/moraxella-catarrhalis-infections
- Pelton, S., Tahtinen, P., Kaplan, S.L., Isaacson, G.C. (2020). Acute otitis media in children: dpidemiology, microbiology, and complications. UpToDate. Retrieved 23 April 2021, from https://www.uptodate.com/contents/acute-otitis-media-in-children-epidemiology-microbiology-and-complications