An 81-year-old woman with no underlying systemic illness was hospitalized with fever, muscle weakness, and sputum without cough for 2 days. Chest imaging showed consolidation in the left lower lobe. Real-time polymerase chain reaction (PCR) for six respiratory bacteria and 12 respiratory viruses performed on sputum obtained on admission showed Mycoplasma pneumoniae DNA, with no evidence of other pathogens. M. pneumoniae was confirmed to be the causative agent by serologic data. Variation of mycoplasma quantity in subsequent sputa was analyzed because of persistent sputum production despite treatment with minocycline. Mycoplasma DNA gradually decreased, becoming undetectable 1 week after the completion of 2 weeks of minocycline therapy. Two weeks after the completion of the minocycline therapy, mycoplasma DNA in sputum was strongly detectable again, and oral treatment with clarithromycin was initiated. No pathogen DNA was detected during 2 weeks of clarithromycin therapy or at 2 weeks after completion of this therapy. Although susceptibility tests on three isolates (on admission, 1 week after starting minocycline, and 2 weeks after minocycline cessation), showed no resistance to minocycline or clarithromycin, the infection was, nonetheless, prolonged. Some elderly subjects with mycoplasma pneumonia may show a longer course than that in young persons with pneumonia.
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