Moraxella catarrhalis is a bacterium belonging to the Neisseriaceae family. It was first described in 1896 as Mikrokokkus catarrhalis. It has since been named Micrococcus catarrhalis, Neisseria catarrhalis, and Branhamella catarrhalis but is commonly known by Moraxella catarrhalis. It was originally considered a saprophyte of the upper respiratory tract with no major pathogenic consequences. Now however, after much research, it is considered the third most common cause of middle ear infections and sinusitis in children, and lower respiratory infections in adults. It has also been attributed to pneumonia, bronchitis, meningitis, neonatal ophthalmia, and urinary tract infections.
This bacterium is an aerobic, gram negative diplococcus. It is kidney bean shaped and is 0.6 - 1.0 um in diameter and often appears in pairs or tetrads. Different strains have pili and fimbrae. Identification of M. catarrhalis is done by CBC blood testing, gram staining, and culturing. The microbe can cause high white blood cell counts and can be grown on chocolate and blood agar plates. Colonies do not adhere to the agar and can be pushed around.
This bacterium is both a pathogen and non-pathogen commonly found in the human lungs. What makes it one or the other is not completely understood. The current theory is that increased numbers of the bacteria in a certain area, i.e. the eustacian tube or throat cause this bacteria to become pathogenic.
It is estimated that 95% of M. catarrhalis produce beta lactamase. This makes those 95% resistant to penicillin, ampicillin, and amoxicillin. Recommended treatment is with Augmentin and second and third generation oral cephalosporins.
Infections tend to be most prevalent in children, immunosuppresent patients and elderly. Mortality rates of patients with underlying conditions who then develop pneumonia as a result of M. catarrhalis are 45%.
Current research is being done to create a vaccine against pathogenic M. catarrhalis. Researchers are trying to develop a vaccine that attacks the protein coats of the bacteria. One such researcher, Dr. Timothy Murphy of the State University of New York at Buffalo has been given a 1.5 million dollar grant to produce antigens. Through email correspondence, Dr. Murphy said that there have been two possible antigens developed and that human trials on those will begin within the next year. His team is trying to produce more antigens currently and is hoping that one will work. The estimate time frame for vaccine production is still ten years from now.
Murphy, Timothy F.( 1996). Branhamella catarrhalis: Epidemiology, Surface Antigenic Structure, and Immune Response. Microbiological Reviews, 60,267- 279.
Murphy, Timothy F. (2003) Email correspondence
Baker, Lois.(l999, March 4). Murphy awarded $1.5 million grant to develop vaccine against ear infections. University at Buffalo Reporter.[On-line]. [URL: http://www.buffalo.edu/reporter/vol30/vol30n23/n3.html]
Constantinescu, MD, Michael.(2002, December 12). Moraxella catarrhalis Infections. EMedicine.[On-line].
[URL: http://www.emedicine.com/med/topic1500.htm]
*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.
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