Moraxella catarrhalis

Moraxella catarrhalis Moraxella catarrhalis is a bacteria belonging to subgenus Branhamella of the genus Moraxella. The bacteria are gram negative and aerobic. It was first described in 1896 and causes infections of the middle ear, respiratory system, central nervous system joints and the eyes in human beings. The oxidase positive bacteria are known to be a causative agent to inflammations of the middle ear, throat, paranasal sinuses and bronchopneumonia in elderly patients and chronic smokers.
Pathogenicity of Moraxella catarrhalis
The bacteria can live commensally within the human respiratory tract only becoming infective with increase in a number or the presence of a pre-existing complication of the respiratory system such as COPD. The infection is most common as a nosocomial infection or in children with weakened immune system and immunocompromised adults.
Virulence factors and teratogenicity
Moraxella catarrhalis has a beta-lactamase positive strain that is highly resistance to antibiotic activity. Further, the bacteria has outer membrane surface proteins such as CopB, OMP CD, OMP E, uspA1 and uspA2 that limit the extent to which the normal protective mechanisms of the body and drugs affect the proliferation and existence of the bacteria in the system.
The possibility of the bacteria, to cross the placental barrier and cause infections in-utero, has not been established. However, the high prevalence of otitis media caused by the bacteria is suggestive of a close relationship.
Morphology: Moraxella catarrhalis is a non-motile single-celled bacterium which is oxidase positive and nonsaccharolytic. It is a gram-negative diplococcic bacterium that is non-sporeforming and catalase positive. It occurs as spherical organisms appearing in pairs or in linear clusters.
Staining, sensitivity and treatment: The bacteria is negative on gram stain. The bacteria is not sensitive to common antibiotics that cannot break the beta-lactam ring. The most effective treatment involves fluoroquinolones, second- and third-generation cephalosporins, erythromycin, and amoxicillin-clavulanic acid antibiotics.
At risk population, prevention and precaution: Children with weak immune system, pre-existing respiratory conditions and immunocompromised individuals are at high risk. There is no known vaccine against Moraxella catarrhalis. However, control measures include personal protective equipment in the hospital setting, such as gloves, face masks and hand washing to prevent contamination. In the hospital setting, the patients should be isolated in special rooms and anybody with weak immune status or children must not come into contact with the patient.
Wirth T, Morelli G, Kusecek B, van Belkum A, van der Schee C, Meyer A, Achtman M: The rise and spread of a new pathogen: seroresistant Moraxella catarrhalis. Genome Res. 2007. 17: 11: 1647-56