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      Mycoplasma pneumoniae pneumonia in children

      review-article
      , MD, , MD
      Korean Journal of Pediatrics
      The Korean Pediatric Society
      Mycoplasma pneumoniae, Pneumonia, Macrolides, Drug resistance, Child, Corticosteroids

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          Abstract

          Mycoplasma pneumoniae (MP), the smallest self-replicating biological system, is a common cause of upper and lower respiratory tract infections, leading to a wide range of pulmonary and extra-pulmonary manifestations. MP pneumonia has been reported in 10 to 40% of cases of community-acquired pneumonia and shows an even higher proportion during epidemics. MP infection is endemic in larger communities of the world with cyclic epidemics every 3 to 7 years. In Korea, 3 to 4-year cycles have been observed from the mid-1980s to present. Although a variety of serologic assays and polymerase chain reaction (PCR) techniques are available for the diagnosis of MP infections, early diagnosis of MP pneumonia is limited by the lack of immunoglobulin (Ig) M antibodies and variable PCR results in the early stages of the infection. Thus, short-term paired IgM serologic tests may be mandatory for an early and definitive diagnosis. MP infection is usually a mild and self-limiting disease without specific treatment, and if needed, macrolides are generally used as a first-choice drug for children. Recently, macrolide-resistant MP strains have been reported worldwide. However, there are few reports of apparent treatment failure, such as progression of pneumonia to acute respiratory distress syndrome despite macrolide treatment. The immunopathogenesis of MP pneumonia is believed to be a hyperimmune reaction of the host to the insults from MP infection, including cytokine overproduction and immune cell activation (T cells). In this context, immunomodulatory treatment (corticosteroids or/and intravenous Ig), in addition to antibiotic treatment, might be considered for patients with severe infection.

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          Most cited references52

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          Molecular biology and pathogenicity of mycoplasmas.

          The recent sequencing of the entire genomes of Mycoplasma genitalium and M. pneumoniae has attracted considerable attention to the molecular biology of mycoplasmas, the smallest self-replicating organisms. It appears that we are now much closer to the goal of defining, in molecular terms, the entire machinery of a self-replicating cell. Comparative genomics based on comparison of the genomic makeup of mycoplasmal genomes with those of other bacteria, has opened new ways of looking at the evolutionary history of the mycoplasmas. There is now solid genetic support for the hypothesis that mycoplasmas have evolved as a branch of gram-positive bacteria by a process of reductive evolution. During this process, the mycoplasmas lost considerable portions of their ancestors' chromosomes but retained the genes essential for life. Thus, the mycoplasmal genomes carry a high percentage of conserved genes, greatly facilitating gene annotation. The significant genome compaction that occurred in mycoplasmas was made possible by adopting a parasitic mode of life. The supply of nutrients from their hosts apparently enabled mycoplasmas to lose, during evolution, the genes for many assimilative processes. During their evolution and adaptation to a parasitic mode of life, the mycoplasmas have developed various genetic systems providing a highly plastic set of variable surface proteins to evade the host immune system. The uniqueness of the mycoplasmal systems is manifested by the presence of highly mutable modules combined with an ability to expand the antigenic repertoire by generating structural alternatives, all compressed into limited genomic sequences. In the absence of a cell wall and a periplasmic space, the majority of surface variable antigens in mycoplasmas are lipoproteins. Apart from providing specific antimycoplasmal defense, the host immune system is also involved in the development of pathogenic lesions and exacerbation of mycoplasma induced diseases. Mycoplasmas are able to stimulate as well as suppress lymphocytes in a nonspecific, polyclonal manner, both in vitro and in vivo. As well as to affecting various subsets of lymphocytes, mycoplasmas and mycoplasma-derived cell components modulate the activities of monocytes/macrophages and NK cells and trigger the production of a wide variety of up-regulating and down-regulating cytokines and chemokines. Mycoplasma-mediated secretion of proinflammatory cytokines, such as tumor necrosis factor alpha, interleukin-1 (IL-1), and IL-6, by macrophages and of up-regulating cytokines by mitogenically stimulated lymphocytes plays a major role in mycoplasma-induced immune system modulation and inflammatory responses.
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            Methylprednisolone pulse therapy for refractory Mycoplasma pneumoniae pneumonia in children

            Summary Objectives To determine the efficacy of methylprednisolone pulse therapy for children with Mycoplasma pneumoniae pneumonia (MP) that is refractory to antibiotic treatment. Methods Refractory patients were defined as cases showing clinical and radiological deterioration despite appropriate antibiotic therapy for 7 days or more. We identified 6 such children (male/female: 3/3) aged 3–9 years who were treated between 1998 and 2006. During the same period, 190 children with MP were admitted to our institution. Results Common laboratory findings of the patients included cytopenia, elevated serum lactate dehydrogenase and ferritin levels, and elevated urine β2-microglobulin levels, suggesting complication of hypercytokinemic condition. We initiated intravenous methylprednisolone at a dose of 30 mg/kg on 10.2 ± 2.8 clinical days and administered it once daily for 3 consecutive days. Fever subsided 4–14 h after initiation of steroid pulse therapy in all patients. This dramatic effect was accompanied by rapid improvement of radiological abnormalities including infiltrates and pleural effusion, followed by improvement of laboratory abnormalities. There were no adverse events of steroid therapy. Conclusions This is the first case-series study showing an effect of 3-day methylprednisolone pulse therapy on refractory MP in children. This therapy is apparently an efficacious and well-tolerated treatment for refractory MP.
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              Macrolide-resistant Mycoplasma pneumoniae: characteristics of isolates and clinical aspects of community-acquired pneumonia.

              Mycoplasma pneumoniae is one of the main pathogens causing community-acquired respiratory tract infections in children and adults. Macrolide (ML) antibiotics are recognized generally as first-choice agents for M. pneumoniae infections, and these antibiotics were thought to have excellent effectiveness against M. pneumoniae for many years. In 2000, however, M. pneumoniae showing resistance to macrolides was isolated from clinical samples obtained from Japanese pediatric patients with community-acquired pneumonia (CAP). Since then, prevalence of ML-resistant M. pneumoniae isolates in pediatric patients has increased rapidly. In 2007, ML-resistant M. pneumoniae isolates were obtained from Japanese adults with CAP; numbers of such isolates also have gradually increased in Japan. Recently, similar antimicrobial resistance in M. pneumoniae has begun to emerge worldwide. In this review, we focus on changes of ML-resistant M. pneumoniae from year to year and consider resistance mechanisms as well as clinical features of patients with resistant M. pneumoniae infection.
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                Author and article information

                Journal
                Korean J Pediatr
                KJP
                Korean Journal of Pediatrics
                The Korean Pediatric Society
                1738-1061
                2092-7258
                February 2012
                14 February 2012
                : 55
                : 2
                : 42-47
                Affiliations
                Department of Pediatrics, College of Medicine, The Catholic University of Korea, Seoul, Korea.
                Author notes
                Corresponding author: Kyung-Yil Lee, MD. Department of Pediatrics, The Catholic University of Korea, Daejeon St. Mary's Hospital, 64 Daeheung-ro, Jung-gu, Daejeon 301-723, Korea. Tel: +82-42-220-9541, Fax: +82-42-221-2925, leekyungyil@ 123456catholic.ac.kr
                Article
                10.3345/kjp.2012.55.2.42
                3286761
                22375148
                3ed71602-190a-46fb-8d10-4db0537ee0b2
                Copyright © 2012 by The Korean Pediatric Society

                This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 15 December 2011
                : 11 January 2012
                Categories
                Review Article

                Pediatrics
                macrolides,corticosteroids,drug resistance,mycoplasma pneumoniae,pneumonia,child
                Pediatrics
                macrolides, corticosteroids, drug resistance, mycoplasma pneumoniae, pneumonia, child

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