Additional corticosteroids or alternative antibiotics for the treatment of macrolide-resistant Mycoplasma pneumoniae pneumonia

Mycoplasma pneumoniae (MP) pneumonia has occurred in periodic epidemics of 3–4 years in Korea. The peak prevalent age group has become younger in recent epidemics (2–4 years) compared to that in past epidemics in Korea. The infection rates in each age group have decreased with increasing age, with corresponding positive rates of anti-MP IgG detected in the populations. We have observed that there is no serologically confirmed reinfected MP pneumonia case during the 3 most recent epidemics, by using a repeated serologic test performed at presentation and again at discharge. Thus, adolescent and young adult patients are rarer in Korea, but older children and young adults are prone to developing severe pneumonia. The epidemiological characteristics of MP infection suggest that it may act like a viral infection, such as measles in the prevaccination era. During an epidemic, the majority of MP infected patients may present as asymptomatic or with mild symptoms such as fever and myalgia. Among infected patients, a small proportion of patients manifest pneumonia, and a small part in pneumonia patients affect severe pneumonia or extrapulmonary manifestations such as encephalopathy and other organ involvement. These clinical characteristics are similar to those observed in viral infections such as influenza. Although MP is believed to be an extracellular small bacterium, it may invade host cells in vivo. Recently, Hegde et al. demonstrated that a MP species, Mycoplasma agalactiae, is capable of entering host cells and systemically disseminates to distant organ cells, using in vitro and in vivo studies in the sheep infection model. Therefore, it is possible that lung or other organ cell injury in MP infection may be caused by pathogen-derived substances and/or the host cell-derived substances produced during MP replication in the host cells, like that in other respiratory viral infections. The prevalent MP strains during each epidemic may be different, and the main MP strain causing the 2015–2016 epidemic in Korea might be a macrolide-resistant MP (MRMP) strain, similar to that in Japan and China. Considering the epidemiological and clinical similarity of MP infection with viral infections, it is natural that the effect of antibiotics on MP pneumonia in children and adults has been controversial for some time. The majority of MP pneumonia patients present a self-limited clinical course without antibiotics, although macrolides are still recommended as the first-line antibiotic for MP infection. There are no differences in the outcomes of MP pneumonia patients between those treated with a beta-lactam only and those treat ed with additional macrolides, and some patients present progressive pneumonia despite early treatment with adequate antibiotics for macrolide-sensitive MP (MSMP) or MRMP strains. The recent appearance of MRMP strains in Korea has presented an opportunity to discuss this issue once again. Yang et al. reviewed the mechanism of resistance acquisition by MP, and discussed the issue of alternative antibiotics or additional immune-modulators for treating MRMP pneumonia. For patients with severe progressive MRMP pneumonia, Yang et al. recommend the use of alternative antibiotics, and/or the addition of systemic immune-moCorresponding author: Kyung-Yil Lee, MD Department of Pediatrics, Daejeon St. Mary's Hospital, College of Medicine, The Catholic University of Korea, 64 Daeheung-ro, Jung-gu, Daejeon 34943, Korea Tel: +82-42-220-9541 Fax: +82-42-221-2925 E-mail: leekyungyil@catholic.ac. kr