mycoplasma pneumonia

mycoplasma pneumonia - Learning Issue: Mycoplama Pnemoniae...

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Learning Issue: Mycoplama Pnemoniae Name: Michael Holmes Definition Mycoplasma pneumoniae is a member of the class Mollicutes, which includes bacterial pathogens and commensals found in many animals and plants. These pathogens comprise the smallest self-replicating prokaryotes known to cause infection in humans. M. pneumoniae is approximately 120 to 150 nm, about the size of myxoviruses, and passes easily through membrane filters intended to prevent contamination by other bacteria. Sequencing of the entire 816,394 base- pair genome was reported in 1996. Humans are the only known natural host for M. pneumoniae. Causes The organism gains access to the respiratory tract through aerosolized droplets spread among close contacts. Risk Factors Once considered to occur primarily among adolescents and young adults, M. pneumoniae is increasingly being recognized as a cause of lower respiratory tract disease in young children. In a study of community-acquired pneumonia in Finland, M. pneumoniae was the causative pathogen in 9% of children 0 to 4 years of age and in 40% of children 5 to 9 years of age. Although the frequency of pneumonia due to any respiratory pathogen decreases in children older than 5 years of age, the relative importance of M. pneumoniae as a cause of pneumonia increases with age. M. pneumoniae accounts for approximately 20% to 40% of cases of acute pneumonia in junior high and high school students and for up to 50% of cases among college students and military recruits. Endemic incidence rates for M. pneumoniae pneumonia range from 1 to 2 per 1000 children < 5 years of age, 3 to 4 per 1000 children 5 to 15 years of age, and < 1 per 1000 adults < 70 years of age. Pathophysiology Specific attachment to the respiratory epithelial tissue occurs primarily through interaction between a host epithelial cell receptor and the organism's P1 attachment protein, a 169-kd surface antigen. Other structures that participate in cytadherence also have been identified. Following attachment, hydrogen peroxide and superoxide radicals synthesized by M. pneumoniae act in concert with endogenous toxic oxygen molecules generated by host cells to induce oxidative stress in the respiratory epithelium. Once M. pneumoniae reaches the lower respiratory tract, the organism may be opsonized by complement or antibodies. Activated macrophages begin phagocytosis and undergo chemotactic
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mycoplasma pneumonia - Learning Issue: Mycoplama Pnemoniae...

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