Pediatric respiratory infections by Mycoplasma pneumoniae

Mycoplasma pneumoniae is one of the most common agents of community-acquired pneumonia in children and young adults. Although M. pneumoniae is a small bacterium that can reproduce in an artificial culture medium and is known to be sensitive to certain antibiotics in vitro as well as in vivo, the immunopathogenesis of M. pneumoniae in the human host is not fully understood. The epidemiologic characteristics, including periodic epidemics, and some clinical characteristics of M. pneumoniae are similar to those observed in systemic viral infections. Many experimental and clinical studies have suggested that the pathogenesis of lung injuries in M. pneumoniae infection is associated with a cell-mediated immune reaction, including high responsiveness to corticosteroid therapy. This paper presents an overview of M. pneumoniae infections, with emphasis on epidemiology, pathogenesis and treatment.     

Macrolide-resistant Mycoplasma pneumoniae

Mycoplasma pneumoniae (M. pn) is one of the main pathogens causing community-acquired pneumonia (CAP) in children. In Japan, macrolide (ML)-resistant M. pn was firstly isolated from clinical samples collected from pediatric patients with CAP in 2000, and the agents have rapidly increased. All ML-resistant strains had a point mutation in domain V of the 23S rRNA. Among the patients with ML-resistant M. pn, the duration of fever was significantly longer than in patients with ML-susceptible M. pn infection. The antimicrobial agent was often changed from ML as a first choice agent to minocycline or levofloxacin, because of unimproved clinical symptoms. Further clinical studies are needed to establish appropriate chemotherapy.     

Surface parasitism by Mycoplasma pneumoniae of respiratory epithelium

Identification of the attachment factor on virulent Mycoplasma pneumoniae organisms which permits surface parasitism of respiratory epithelium was attempted. Brief pretreatment of M. pneumoniae monolayers with protease prevented mycoplasma attachment ot sensitive host cells without reducing viability of the microorganisms. Gel electrophoretic analysis of mycoplasma proteins before and after exposure of intact mycoplasmas to protease revealed the absence of a major protein species (P1) in enzyme-treated preparations while other protein bands with the exception of P2 were virtually unaffected. The absence of P1 correlated with the failure of enzyme-treated mycoplasmas to attach to tracheal explants. P1 regeneration after protease treatment of mycoplasma monolayers was directly associated with reattachment capabilities in M. pneumoniae. Erythromycin inhibited P1 resynthesis, thus preventing resumed attachment activity by mycoplasmas. Lactoperoxidase-catalyzed iodination of intact M. pneumoniae organisms further confirmed that P1 was an external membrane protein and suggested that his surface component was required for the successful membrane-membrane interaction between host and parasite.     

Optimized serodiagnosis of Mycoplasma pneumoniae infections

Serologic methods are well established for the diagnosis of Mycoplasma pneumoniae infections in humans, but they are less sensitive than polymerase chain reaction (PCR). To improve their sensitivity, a new panel of antigens was tested. Compared with PCR results, up to 92% of PCR-positive patients were confirmed by our immunoblotting approach having a specificity between 92.6% and 100%.     

Epidemiology of macrolide-resistant Mycoplasma pneumoniae by age distribution in Japan

IntroductionMycoplasma pneumoniae (M. pneumoniae) is the major pathogen involved in community-acquired pneumonia in all age groups. Resistance to macrolides, the first-line treatment for M. pneumoniae infection, is a major global public health concern. However, studies evaluating macrolide-resistant M. pneumoniae infection simultaneously in all ages are limited. This study aimed to determine the prevalence and clinical characteristics of macrolide-resistant M. pneumoniae infection in terms of age distribution.MethodsWe enrolled 292 patients in Tokyo, Japan, who visited Eiju General Hospital or Zama Children's Clinic in 2015–2016. Patients were tested using real-time PCR for M. pneumoniae DNA. PCR-positive patients (n = 151) were further selected and sequentially divided into preschool-aged children (≤5 years, n = 31), school-aged children (6–15 years, n = 101), adolescents (16–19 years, n = 5), and adults (≥20 years, n = 14). We then analyzed the M. pneumoniae infection clinical characteristics, prevalence of macrolide-resistant infection, and 23S rRNA domain V resistance-associated mutation status.ResultsWe found insignificant differences in the prevalence of macrolide-resistant M. pneumoniae infection among all groups, clinical characteristics, and resistance-associated mutation status in patients with macrolide-resistant M. pneumoniae infection. We also found statistically higher prevalence of mutation-positive (n = 85) M. pneumoniae in patients previously treated with macrolide compared to the mutation-negative group (n = 66); 63.8% vs 11.1% (p < 0.001), respectively.ConclusionsWe found no significant differences in both clinical characteristics and prevalence of macrolide-resistant M. pneumoniae infection among all ages. Also, previous macrolide treatment contributes to drug-resistance.     

Chlamydophila pneumoniae serology: cross-reaction with Mycoplasma pneumoniae infection

Atypical pathogens Mycoplasma pneumoniae and Chlamydophila pneumoniae play an important role in community-acquired pneumonia. However, it has been pointed out that positive enzyme-linked immunosorbent assay (ELISA, Hitazyme C. pneumoniae) IgM reactivity is frequent among M. pneumoniae pneumonia patients. To clarify the reactivity of ELISA IgM in M. pneumoniae pneumonia, findings were compared with immunoblotting, ELNAS Plate C. pneumoniae (ELNAS) and the micro-immunofluorescence (MIF) test. Ninety-eight serologically confirmed cases with M. pneumoniae pneumonia and 10 cases with C. pneumoniae pneumonia were enrolled in this study. C. pneumoniae IgM-positive cases measured by the ELISA were observed in 30 (30 %) patients with M. pneumoniae pneumonia. However, there were no positive cases by immunoblotting, ELNAS, or MIF test. These cases determined to be IgM positive only in the ELISA were all negative by another serological test, recombinant enzyme immunoassay (rEIA), and these positive results in the ELISA were considered to be false-positive reactions. In contrast, IgM-positive findings in patients with C. pneumoniae pneumonia did not show any positive reaction in M. pneumoniae antibody titer. ELISA showed a high frequency of false-positive findings in patients with M. pneumoniae pneumonia, which included false-positive cases with a high titer for IgM. To accurately diagnose C. pneumoniae infection in various studies, including respiratory infections, researchers should consider the IgM false-positive reaction with ELISA in patients with suspected atypical pneumonia.     

间接免疫荧光法检测肺炎支原体 IgM 的临床意义

目的：探讨肺炎支原体（MP）抗体（MP-IgM）检测在诊断呼吸道感染中的临床价值。方法采用间接免疫荧光法检测1924例呼吸道感染患者血清肺炎支原体 IgM。结果1924例患者中共检出阳性617例,阳性率32．07％,男女患者阳性率分别为26．67％和39．56％,男女阳性率差异有统计学意义（P ＜0．001）。夏季检出阳性率最高,为45．00％,春夏两季的阳性率显著高于秋冬两季。儿童组的阳性率高于成人组（P ＜0．001）。结论呼吸道感染患者中 MP 感染率较高;MP-IgM 检测有利于呼吸道感染患者的早期诊断,为临床合理用药提供帮助,避免抗生素的滥用。     

小儿肺炎支原体合并肺炎链球菌性肺炎与单纯肺炎支原体体液免疫功能及CT表现比较

目的  探讨小儿肺炎支原体（MP）合并肺炎链球菌（SP）性肺炎与单纯MP体液免疫功能及胸部CT表现的差异。方法  选取本院2020年3月~2022年3月收治的肺炎患儿70例,其中MP感染46例,MP合并SP感染24例,通过检测患儿机体体液免疫指标和观察CT表现,分析两种不同感染类型患儿体液免疫和CT表现间的差异。结果  在病灶分布上两组差异无统计学意义（P＞0.05）;与SP组比较,MP合并SP组支气管血管束增厚、支气管壁增厚、网状影、磨玻璃影和扇形薄片影等影像征象发生率较低,实变影发生率较高,差异有统计学意义（P＜0.05）,MP合并SP组胸腔积液厚度较厚、淋巴结最大横径较大（P＜0.05）;两组患儿IgA、IgG、IgM水平的差异无统计学意义（P＞0.05）。结论  与单纯SP感染相比,MP合并SP感染引起的小儿肺炎体液免疫功能紊乱差异不明显,但在CT影像征象上差异较大,有助于鉴别诊断。     

Host discrimination of Mycoplasma pneumoniae proteinaceous immunogens

The immune response of experimentally infected hamsters and human patients to Mycoplasma pneumoniae was examined by radioimmunoprecipation in conjunction with gel electrophoresis and fluorography. Both intrinsically and extrinsically labeled mycoplasma proteins were coincubated with acute and convalescent sera in a radioimmunoprecipitation assay. Two M. pneumoniae proteins were selectively precipitated by convalescent sera. These predominant immunogens were trypsin-sensitive, antibody-accessible surface proteins that co-migrate on polyacrylamide gels with proteins P1 and P2, which were previously implicated by us as mediators of cytadsorption. Anti-M. pneumoniae antiserum did not precipitate radiolabeled antigens derived from Mycoplasma orale or Mycoplasma salivarium. These data indicate that M. pneumoniae infection stimulates a specific and highly targeted host antibody response to key proteinaceous immunogens.     

Atelectasis caused by macrolide-resistant Mycoplasma pneumoniae pneumonia in an adult patient

A 27-year-old, previously healthy woman was admitted to our hospital for mild pneumonia. After 2 days ceftriaxone sodium administration, her chest radiograph revealed a rightward mediastinal shift caused by atelectasis of the upper portion of the right lung. Bronchoscopic examination showed swelling in the right upper lobe bronchus and obstruction in the B¹ segmental bronchus caused by complete edematous swelling. Histopathology showed acute cellular bronchitis with edema of the bronchial wall containing lymphocytes, plasma cells, and macrophages. Mycoplasma pneumoniae was detected by culture and a polymerase chain reaction test using sputum collected during bronchoscopy, and treatment was changed to minocycline. After 7 days antibiotic therapy, her condition improved and no relapse was observed. Identification of point mutations in domain V of the 23S rRNA for macrolide-resistant M. pneumoniae was performed, and an A-to-G transition at position 2063 in domain V of the 23S rRNA gene was identified. Atelectasis caused by M. pneumoniae is thought to be a common associated finding in pediatric patients, but it is rare in adults. In addition, our patient showed extremely unusual findings with obstruction caused by complete edematous swelling.