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Previously known as: Branhamella catarrhalis, Neisseria catarrhalis or Micrococcus catarrhalis.
This is a Gram-negative, aerobic, oxidase-positive diplococcus. The genera Moraxella (including the former Branhamella), Acinetobacter and Psychrobacter currently belong to the family Moraxellaceae; the classification is currently under review.
Moraxella catarrhalis is an exclusively human commensal and mucosal pathogen.
It is a common commensal organism of the upper respiratory tract, particularly in children; however, it is increasingly being recognised as a pathological organism causing otitis media, sinusitis, ocular infection and occasionally laryngitis.It may cause bronchitis or pneumonia in adults and children with underlying lung disease.[3, 4]
Rarely, it may lead to bacteraemia and meningitis in the immunocompromised. Bacteraemic infection can lead to localised complications such as osteomyelitis and septic arthropathy. It can also cause nosocomial infection in a hospital setting, particularly in respiratory, paediatric and intensive care units.
- The prevalence of M. catarrhalis colonisation is highly dependent on age.
- Healthy adults are rarely colonised with this organism, whereas most infants have upper respiratory tract colonisation at some time in the first several years of life.
- Carriage rates among populations of children vary from 28% to100%.[5, 6]
- M. catarrhalis has been shown to be positively cultured in at least one site in 42% of patients with sinusitis and 27% of well adults.
- In healthy adults the carriage rate is much lower at 1-10%. Carriage rates among those with underlying lung disease and the elderly are higher.
- It is a leading cause of otitis media in children.
- Only a proportion of positive bacteriological cultures occurring in children are thought to be of clinical significance (~9% in those aged <5 years and ~33% in those aged 6-10 years).
- M. catarrhalis is estimated to cause ~10% of exacerbations in chronic obstructive pulmonary disease (COPD) patients.
It may present with typical clinical features of:
- Upper respiratory tract infection.
- Otitis media.
- Lower respiratory tract infection.
- Bacteraemia (usually in the immunocompromised).
In those with underlying respiratory disease such as COPD, it may present as:
- Nosocomial outbreaks of infection (thought to be transferred from carers/visitors).
In the immunocompromised
This includes patients with cystic fibrosis. It rarely causes:
- Neonatal ophthalmic infection.
- Urinary tract infection.
- Wound infection.
- Peritonitis in patients undergoing chronic ambulatory peritoneal dialysis (CAPD).
There are no examination findings peculiar to, or discriminatory for, infection with M. catarrhalis and findings will be as expected for each of the disease entities it causes. Differentiation from other pathogens is on microbiological grounds.
Bacteriological differential diagnosis is between those conditions that commonly cause infection in the sites listed above such as:
- Streptococcus pneumoniae.
- Haemophilus influenzae.
- Causes of atypical pneumonia.
- Viral causes of upper/lower respiratory tract infection.
- Fungal infection (should be considered as a possible cause of illness in the immunocompromised).
- FBC may reveal elevated WCC (predominantly neutrophils).
- Gram-staining of sputum, middle-ear effusion fluid/aspirate, nasopharyngeal aspirate, sinus aspirate, transtracheal/transbronchial aspirate, blood, peritoneal fluid, wounds or urine will reveal Gram-negative diplococci.
- The organism may be cultured from the same sources.
- It may be difficult to discriminate M. catarrhalis from Neisseria spp. but use of differential culture media can help.
- Serological tests are not of much use due to significant cross-reactivity with Neisseria spp.
- Imaging may be used to determine the site and extent of infection - eg, CT scan of sinuses and CXR.
- Lumbar puncture and blood cultures are useful in diagnosing bacteraemic infection and meningitis.
- The vast majority of isolates of M. catarrhalis are penicillin-resistant through the production of beta-lactamase.
- Trimethoprim resistance is also common.
- Macrolide antibiotics such as erythromycin and clarithromycin are useful. However, there is some resistance to these antibiotics.
- There is less resistance with newer macrolides such as azithromycin.
- There is also low resistance with amoxicillin with clavulanate.
- Quinolones such as ciprofloxacin and ofloxacin can be effective.
- Second- or third-generation cephalosporins may be used.
- Tetracyclines are also active against this pathogen - eg, doxycycline.
- Recurrence/failure to respond to antibiotic therapy.
- Bacteraemia/systemic sepsis (mainly in the immunocompromised).
- Meningitis (mainly in the immunocompromised).
- Mastoiditis complicating otitis media.
- Hearing impairment complicating otitis media.
- Pleural effusion complicating pneumonia.
- Death in advanced cases.
The vast majority of cases of community-acquired upper respiratory tract infection will recover spontaneously or respond to antibiotics, without complications or sequelae.
Prognosis among the immunocompromised, those with underlying lung disease, those in hospital, the elderly and the very young is variable but tends to be worse.
- Nosocomial outbreaks can be prevented by good hygiene techniques in hospitals, particularly hand washing/use of alcohol gel hand rubs.
- It is thought that the infection may spread from person to person via droplet infection from expectorated sputum; it may help to isolate confirmed cases in hospital where this is possible and give attention to general hygiene measures to prevent spread in community cases.
- Smoking cessation should reduce susceptibility to infection in those with respiratory disease.
- Vaccines are currently in development.
Further reading and references
; Moraxella catarrhalis - pathogen or commensal? Adv Exp Med Biol. 2011697:107-16.
; Prevalence and resistance pattern of Moraxella catarrhalis in community-acquired lower respiratory tract infections. Infect Drug Resist. 2015 Jul 318:263-7. doi: 10.2147/IDR.S84209. eCollection 2015.
; Vaccine targets against Moraxella catarrhalis. Expert Opin Ther Targets. 2015 Aug 23:1-15.
; Characterization of the molecular interplay between Moraxella catarrhalis and human respiratory tract epithelial cells. PLoS One. 2013 Aug 68(8):e72193. doi: 10.1371/journal.pone.0072193. Print 2013.
; Population density profiles of nasopharyngeal carriage of five bacterial species in pre-school children measured using quantitative PCR offer potential insights into the dynamics of transmission. Hum Vaccin Immunother. 2015 Sep 14:0.
; Evaluation of swabbing methods for estimating the prevalence of bacterial carriage in the upper respiratory tract: a cross sectional study. BMJ Open. 2014 Oct 304(10):e005341. doi: 10.1136/bmjopen-2014-005341.
; Bacterial pathogens in the nasopharynx, nasal cavity, and osteomeatal complex during wellness and viral infection. Am J Rhinol Allergy. 2013 Jan27(1):39-42. doi: 10.2500/ajra.2013.27.3835.
; Moraxella catarrhalis: from emerging to established pathogen. Clin Microbiol Rev. 2002 Jan15(1):125-44.
; Molecular mechanisms of moraxella catarrhalis-induced otitis media. Curr Allergy Asthma Rep. 2013 Oct13(5):512-7. doi: 10.1007/s11882-013-0374-8.
; Genetic analysis of a pediatric clinical isolate of Moraxella catarrhalis with resistance to macrolides and quinolones. J Infect Chemother. 2015 Apr21(4):308-11. doi: 10.1016/j.jiac.2014.11.002. Epub 2014 Nov 14.
; Ceftaroline in the management of complicated skin and soft tissue infections and community acquired pneumonia. Ther Clin Risk Manag. 2015 Apr 711:565-79. doi: 10.2147/TCRM.S75412. eCollection 2015.