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Proteins of Chlamydia pneumoniae immunodominant in humans were characterized with the sera of 13 patients who were not likely to have been exposed to C. trachomatis or C. psittaci. The serological responses among these patients were similar on a qualitative basis, but some differences were found quantitatively. However, the serological responses of the patients who were infected with C. pneumoniae differed markedly from those of two patients who were infected with C. trachomatis and two who were infected with C. psittaci and those of mice that were transtracheally infected with C. pneumoniae. Among proteins immunodominant in the patients who were infected with C. pneumoniae, a 40-kDa major outer membrane protein was genus specific and 53-, 46-, and 43-kDa proteins were species specific in their reactions with the majority of the human sera used. A few sera reacted strongly with a 73-kDa protein genus specifically. Some proteins with weak immunogenicity exhibited species specificity. An antigenic analysis with human sera and murine monoclonal antibodies against the 53-kDa protein showed that the antigenicities were strictly conserved among the seven strains of C. pneumoniae tested. The genus-specific 73-kDa protein was solubilized with octylglucoside. All of the speciesspecific immunodominant proteins were solubilized with sodium dodecyl sulfate, but the genus-specific major outer membrane protein was not. These results suggest that a serological diagnosis of C. pneumoniae infection could be achieved species specifically by comparison of the serum responses to sodium dodecyl sulfate-and octylglucoside-soluble fractions. Members of genus Clhlamydia are gram-negative, obligate intracellular bacteria which cause diseases such as lymphogranuloma venereum, trachoma, and acute respiratory infections. The genus Chlamydia has a unique developmental cell cycle which alternates between the rigid elementary body (EB) and the relatively fragile large reticulate body (RB). The EB is infectious and nonvegetative, whereas the RB is noninfectious and vegetative (24, 32). The genus Chlanmydia is classified into three species, Chlamnydia trachomatis, C. psittaci, and C pneuln71oniiae. Recently, Fukushi and Hirai (10) proposed the establishment of a new

Objective To evaluate the clinical features, etiology, and outcome of patients over 65 years old hospitalized for community-acquired pneumonia.Patients Eighty-four patients (50 males, 34 females) hospitalized for community-acquired pneumonia in Kawasaki Medical School Kawasaki Hospital between April 1998 and March 2000.Results Most of the patients had respiratory symptoms or signs, but over one-third also had atypical symptomsof pneumonia such as dyspnea, consciousness disturbance, and gastrointestinal symptoms.The causative microorganisms were identified in 48%of these patients. Streptococcus pneumoniae (13%), respiratory viruses (13%), Haemophilus influenzae (8 %) and Mycobacterium tuberculosis (8%) were frequently identified, but Mycoplasma pneumoniaewas less frequently noted in the elderly. Double infection was recognized in 19 %and a combination of some virus and bacteria in 13%. Treatment consisted of the administration of second or third generation cephalosporin antibiotics intravenously, because antibiotics had already been preadministered in 39%. The prognosis was poor (mortality rate 9%) for the elderly with community-acquired pneumonia despite mechanical ventilation in 8 %.Conclusions Although the range of microorganisms causing community-acquired pneumonia differed slightly from that in previous reports; namely, lower frequency of Chlamydia pneumoniae and Legionella pneumophila, it is suggested that the initial antibiotic treatment should always cover S. pneumoniaeand H. influenzae. In addition, since a prevalence of virus infections related to the increase in community-acquired pneumonia in the elderly was found in this study, the routine use of influenza vaccine and pneumococcal vaccines in the elderly is recommendedto reduce the high mortality rate. (Internal Medicine 40: 703-707, 2001)

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