''Moraxella'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

gram-negative Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is that their cell envelope consists ...

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

in the family Moraxellaceae. It is named after the Swiss

ophthalmologist Ophthalmology (, ) is the branch of medicine that deals with the diagnosis, treatment, and surgery of eye diseases and disorders. An ophthalmologist is a physician who undergoes subspecialty training in medical and surgical eye care. Following a ...

Victor Morax. The organisms are short rods, coccobacilli, or as in the case of '' Moraxella catarrhalis'', diplococci in morphology, with asaccharolytic, oxidase-positive, and

catalase Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting ...

-positive properties.Ala'Aldeen, D. A. A. (2007). "Neisseria and moraxella". In Greenwood, David; Slack, Richard; Peitherer, John; & Barer, Mike (Eds.), ''Medical Microbiology'' (17th ed.), p. 258. Elsevier. . ''M. catarrhalis'' is the clinically most important species under this genus.

Roles in disease

The organisms are commensals of mucosal surfaces and sometimes give rise to

opportunistic infection An opportunistic infection is an infection that occurs most commonly in individuals with an immunodeficiency disorder and acts more severe on those with a weakened immune system. These types of infections are considered serious and can be caused b ...

. * '' M. catarrhalis'' usually resides in respiratory tract, but can gain access to the

lower respiratory tract The respiratory tract is the subdivision of the respiratory system involved with the process of conducting air to the alveoli for the purposes of gas exchange in mammals. The respiratory tract is lined with respiratory epithelium as respirator ...

in patients with chronic chest disease or compromised host defenses, thus causing tracheobronchitis and

pneumonia Pneumonia is an Inflammation, inflammatory condition of the lung primarily affecting the small air sacs known as Pulmonary alveolus, alveoli. Symptoms typically include some combination of Cough#Classification, productive or dry cough, ches ...

. For example, it causes a significant proportion of lower respiratory tract infections in elderly patients with

COPD Chronic obstructive pulmonary disease (COPD) is a type of progressive lung disease characterized by chronic respiratory symptoms and airflow limitation. GOLD defines COPD as a heterogeneous lung condition characterized by chronic respiratory s ...

and

chronic bronchitis Bronchitis is inflammation of the bronchi (large and medium-sized airways) in the lungs that causes coughing. Bronchitis usually begins as an infection in the nose, ears, throat, or sinuses. The infection then makes its way down to the bronchi. ...

. It is also one of the notable causes of

otitis media Otitis media is a group of Inflammation, inflammatory diseases of the middle ear. One of the two main types is acute otitis media (AOM), an infection of rapid onset that usually presents with ear pain. In young children this may result in pullin ...

and

sinusitis Sinusitis, also known as rhinosinusitis, is an inflammation of the mucous membranes that line the sinuses resulting in symptoms that may include production of thick nasal mucus, nasal congestion, facial congestion, facial pain, facial pressure ...

. It causes similar symptoms to ''

Haemophilus influenzae ''Haemophilus influenzae'' (formerly called Pfeiffer's bacillus or ''Bacillus influenzae'') is a Gram-negative, Motility, non-motile, Coccobacillus, coccobacillary, facultative anaerobic organism, facultatively anaerobic, Capnophile, capnophili ...

'', although it is much less virulent. Unlike '' Neisseria meningitidis'', which is a morphological relative of ''M. catarrhalis'', it hardly ever causes

bacteremia Bloodstream infections (BSIs) are infections of blood caused by blood-borne pathogens. The detection of microbes in the blood (most commonly accomplished by blood cultures) is always abnormal. A bloodstream infection is different from sepsis, wh ...

meningitis Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, intense headache, vomiting and neck stiffness and occasion ...

. * '' Moraxella lacunata'' is one of the causes of blepharoconjunctivitis in human. * '' Moraxella bovis'' is the cause of infectious bovine keratoconjunctivitis, known colloquially in the United Kingdom as New Forest eye. As a strict aerobe, ''M. bovis'' is confined to the cornea and conjunctiva, resulting in a progressive, nonself-limiting keratitis, ulceration, and – ultimately – rupture of the cornea. The disease is relatively common, infecting cattle only. Treatment is the use of either subconjunctival injection of a tetracycline, or topical application of cloxacillin, the former being more effective. The bacterium can be transmitted by flies, so fly control may be necessary on farms throughout the summer. Rupture of the eye is more serious, and requires immediate enucleation, though the procedure itself carries a good prognosis.

Roles in disease

References

Further reading