Two Cases of Mycoplasma pneumoniae Pneumonia with A2063G Mutation in the 23S rRNA Gene in Siblings
A previously healthy 9-yr-old boy with a cough and sputum since 7 days and a fever since 3 days visited the outpatient department (OPD) of Wonju Medical Center. He took cough medication for 2 days before admission but did not take any antibiotics. He was an elementary school student, and there was no recent history of sick contacts, travel, or illness.\nAuscultation of the lungs revealed coarse crackles with right side rhonchi. Laboratory results showed that complete blood cell count, white blood cell differential count, electrolyte level, liver function tests, and urinalysis were normal. C-reactive protein (CRP) was 12.0 mg/L (reference range: 0-5 mg/L). The chest radiograph showed pneumonic consolidation on the right upper lung field. Sputum culture showed growth of normal flora. Sputum smears were negative for acid-fast bacilli, and a tuberculin skin test was negative. Blood culture showed no growth after 7-day incubation. The serologic test for detecting anti-mycoplasma IgM antibody (SERODIA®-MYCO II, Fujirebio, Tokyo, Japan) was negative, but the patient's cold agglutinins titer was 1 :128. A PCR test of a nasopharyngeal swab specimen was positive for M. pneumoniae. Gene amplification of M. pneumoniae was performed by MyGenie 32 Thermal Block (Bioneer, Daejeon, Korea), and we used 20 µL of high fidelity PCR premix (AccuPower®Premix, Bioneer, Daejeon, Korea) as the reactive agent. PCR primers were designed for detecting known M. pneumoniae single point mutations (A2063G, A2064G, T2611C, and C2617A). In this case, the resistant strains displayed a point mutation in the 23S rRNA: A-to-G transition mutation at nucleotide 2063.\nInitial treatment with flomoxef was given intravenously (70 mg/kg/day, divided into 3 doses). The result of PCR for M. pneumoniae was positive, and roxithromycin (7 mg/kg/day, divided into 2 doses) was added on the 2nd day of hospitalization. On the 5th day of hospitalization, neither respiratory symptoms nor follow-up chest radiography findings improved. Treatment was, therefore, switched from roxithromycin to azithromycin (10 mg/kg/day, once a day for 3 days). On the 9th day of hospitalization, clinical symptoms and chest radiography findings improved, so the patient was discharged. Four days later, he was symptom-free with no detectable complications on OPD follow-up. The M. pneumoniae isolated from this patient carried an A2063G mutation.