Mycoplasma pneumoniae: características clínicas diferenciales y dificultades diagnósticas de las neumonías atípicas en niños / Mycoplasma pneumoniae: differential clinical features and diagnostic challenges in atypical pneumonias in children

Introducción: la neumonía por Mycoplasma pneumoniae continúa estando infradiagnosticada en las consultas de Pediatría de Atención Primaria, especialmente en los niños más pequeños. Material y métodos: estudio prospectivo en 9 cupos pediátricos, sobre niños desde 1 mes a 14 años con neumonía diagnosticada mediante radiografía y clínica compatible. Diagnóstico etiológico mediante serología en la fase aguda. Se analiza la relación de diferentes variables con la etiología atípica y no atípica. Resultados: de los 92 pacientes incluidos, un 30,4% fueron neumonías atípicas que, a pesar de no ser raras en menores de 2 años (26% del total a esta edad), predominaron en los mayores de 5 años (80,9%). La edad media en meses fue significativamente mayor en atípicas (74,2 ± 42,2), que en las no atípicas (35,9 ± 33,8; p <0,0001). La congestión nasal (42,8%; OR: 1,8; p <0,01) y la taquipnea (64,2%; OR: 2,4; p <0,014) fueron significativamente más frecuentes en las no atípicas. El patrón alveolar se observó en el 53,6% de las neumonías atípicas, sin diferencias con las no atípicas. Solamente un 25% de las neumonías atípicas fueron correctamente tratadas inicialmente con macrólidos en monoterapia sin existir diferencias en cuanto a su evolución con respecto a la elección de un tipo u otro de terapia antibiótica. Las neumonías no atípicas precisaron antibioterapia intravenosa con una mayor frecuencia (15,6%) de forma no estadísticamente significativa. Conclusión: las neumonías por gérmenes atípicos parecen más prevalentes en niños pequeños de lo previamente descrito, en ocasiones en coexistencia con virus. Su mejor diagnóstico y tratamiento continúan siendo un reto por resolver (AU)

Introduction: pneumonia caused by Mycoplasma pneumoniae continues to be underdiagnosed in paediatric primary care, especially in younger children.Material and methods: prospective study conducted in 9 primary care paediatric caseloads, including children aged 1 month to 14 years with pneumonia diagnosed based on compatible radiographic findings and clinical features. The aetiological diagnosis was made by acute-phase serological testing. We analysed the association of different variables with atypical and typical aetiologies.Results: of the 92 patients in the sample, 30.4% had atypical pneumonias which, while not rare in children under 2 years (26%) predominated in children over 5 years (80.9%). The mean age in months was significantly higher in cases with an atypical (74.2±42.2) versus typical (35.9±33.8) aetiology (p<0.0001). Nasal congestion (42.8%; OR 1.8; p<0.01) and tachypnoea (64.2%; OR 2.4; p<0.014) were significantly more frequent in typical pneumonia. The alveolar pattern was observed in 53.6% of atypical pneumonias, with no differences compared to typical pneumonias. Only 25% of atypical pneumonia cases were treated correctly with first-line macrolide monotherapy, with no differences in outcomes based on the choice of antibiotherapy. Patients with typical pneumonia required intravenous antibiotic therapy more frequently (15.6%), but the difference was not statistically significant.Conclusion: atypical germs were more frequent at younger ages than previously described, in some cases with concomitant detection of viruses. Improving the diagnosis and treatment of atypical pneumonia remains a challenge. (AU)

Neutrophil-Mediated Lung Injury Both via TLR2-Dependent Production of IL-1α and IL-12 p40, and TLR2-Independent CARDS Toxin after Mycoplasma pneumoniae Infection in Mice.

Mycoplasma pneumoniae (Mp) residing extracellularly in the respiratory tract is the primary cause of bacterial community-acquired pneumonia in humans. However, the detailed pathological mechanism of Mp infection, especially inflammation in the lung, remains unclear. This study examined the role of the neutrophils in the inflammation of Mp-induced pneumonia in mice and the mechanism of neutrophil infiltration into the lungs in the Mp-induced pneumonia. We observed massive infiltration of neutrophils in the bronchoalveolar lavage fluid (BALF) and lung injury after the Mp challenge. The neutrophils were shown to contribute to lung injury in Mp pneumonia but were not involved in eliminating Mp, suggesting that neutrophils are detrimental to the host in Mp pneumonia. Mp also induced the production of inflammatory cytokines and chemokines in the BALF in a toll-like receptor 2 (TLR2)-dependent manner. Particularly, both interleukin (IL)-1α and IL-12 p40 played a crucial role in neutrophil infiltration into the BALF in a coordinated manner. Both IL-1α and IL-12 p40 were released from the alveolar macrophages depending on the TLR2 and reactive oxygen species. In addition, the community-acquired respiratory distress syndrome (CARDS) toxin from Mp were found to induce neutrophil infiltration into BALF in a TLR2-independent and IL-1α-dependent manner. Collectively, the TLR2-dependent production of both IL-1α and IL-12 p40, and CARDS toxin have been elucidated to play an important role in neutrophil infiltration into the lungs subsequently leading to the lung injury upon Mp infection in mice. These data will aid in the development of therapeutics and vaccines for Mp pneumonia. IMPORTANCE Although Mp-induced pneumonia is usually a self-limiting disease, refractory life-threatening pneumonia is often induced. In addition, the development of alternative therapeutic strategies for Mp is expected because of the emergence of antibiotic-resistant Mp. However, the lack of knowledge regarding the pathogenesis of Mp-induced pneumonia, especially inflammation upon the Mp infection, makes it tedious to design novel therapeutics and vaccines. For example, although neutrophil infiltration is widely recognized as one of the characteristics of Mp-induced pneumonia, the precise role of neutrophils in the aggravation of Mp pneumonia remains unclear. This study showed that the infiltration of neutrophils in the lungs is detrimental to the host in Mp-induced pneumonia in mice. Furthermore, the TLR2-dependent IL-1α and IL-12 p40 production, and CARDS toxin play important roles in neutrophil infiltration into the lung, following lung injury. Our findings apply to the rational design of novel therapeutics and vaccines against Mp.

Mycoplasma pneumoniae Seroprevalence and Total IgE Levels in Patients with Juvenile Idiopathic Arthritis.

BACKGROUND: Mycoplasma pneumoniae (M. pneumoniae) is implicated in several immune-mediated extrapulmonary manifestations, including reactive arthritis. Recently, increased total serum IgE were reported in children developing M. pneumoniae-related extrapulmonary diseases (MpEPDs). Here, we aimed at analyzing these aspects in children affected with rheumatic disorders and, in detail, Juvenile Idiopathic Arthritis (JIA). METHODS: M. pneumoniae serology (IgG and IgM) and total serum IgE were concomitantly analyzed in 139 pediatric patients diagnosed with: JIA (Group 1, n = 85), or any rheumatic disease other than JIA (Group 2, n = 27), or non-inflammatory endocrinological disorders (Group 3, n = 27). RESULTS: Overall, 19.4% M. pneumoniae seroprevalence was observed in this hospitalized pediatric population, without signicant differences among the three groups. No significant differences in total serum IgE levels were noted among these groups; however, a second analysis excluding children with very high (and clearly abnormal) IgE levels suggested that JIA patients and, in detail, those with oligopolyarticular forms may have higher serum IgE concentrations. This relative difference among groups in serum IgE level seems to be more pronounced in M. pneumoniae seropositive children. CONCLUSIONS: M. pneumoniae infection should be actively sought in children developing immune-mediated diseases, including patients affected with JIA and, especially, in oligopolyarticular forms. There is some evidence that total serum IgE levels may tend to be increased in patients with oligopolyarticular JIA subtype and especially in those resulting as M. pneumoniae seropositive. However, further and focused research is needed to confirm these preliminary results and to clarify the relation between M. pneumoniae infection, atopic status, and immune-mediated arthritis.

Mycoplasma genitalium and M. pneumoniae Regulate a Distinct Set of Protein-Coding Genes in Epithelial Cells.

Mycoplasma genitalium and M. pneumoniae are two significant mycoplasmas that infect the urogenital and respiratory tracts of humans. Despite distinct tissue tropisms, they both have similar pathogenic mechanisms and infect/invade epithelial cells in the respective regions and persist within these cells. However, the pathogenic mechanisms of these species in terms of bacterium-host interactions are poorly understood. To gain insights on this, we infected HeLa cells independently with M. genitalium and M. pneumoniae and assessed gene expression by whole transcriptome sequencing (RNA-seq) approach. The results revealed that HeLa cells respond to M. genitalium and M. pneumoniae differently by regulating various protein-coding genes. Though there is a significant overlap between the genes regulated by these species, many of the differentially expressed genes were specific to each species. KEGG pathway and signaling network analyses revealed that the genes specific to M. genitalium are more related to cellular processes. In contrast, the genes specific to M. pneumoniae infection are correlated with immune response and inflammation, possibly suggesting that M. pneumoniae has some inherent ability to modulate host immune pathways.

IL-17 stimulates neutrophils to release S100A8/A9 to promote lung epithelial cell apoptosis in Mycoplasma pneumoniae-induced pneumonia in children.

Mycoplasma pneumoniae-induced pneumonia (MPP) is a common cause of community-acquired respiratory tract infections, increasing risk of morbidity and mortality, in children. However, diagnosing early-stage MPP is difficult owing to the lack of good diagnostic methods. Here, we examined the protein profile of bronchoalveolar lavage fluid (BALF) and found that S100A8/A9 was highly expressed. Enzyme-linked immunosorbent assays used to assess protein levels in serum samples indicated that S100A8/A9 concentrations were also increased in serum obtained from children with MPP, with no change in S100A8/A9 levels in children with viral or bacterial pneumonia. In vitro, S100A8/A9 treatment significantly increased apoptosis in a human alveolar basal epithelial cell line (A549 cells). Bioinformatics analyses indicated that up-regulated S100A8/A9 proteins participated in the interleukin (IL)-17 signaling pathway. The origin of the increased S100A8/A9 was investigated in A549 cells and in neutrophils obtained from children with MPP. Treatment of neutrophils, but not of A549 cells, with IL-17A released S100A8/A9 into the culture medium. In summary, we demonstrated that S100A8/A9, possibly released from neutrophils, is a new potential biomarker for the clinical diagnosis of children MPP and involved in the development of this disease through enhancing apoptosis of alveolar basal epithelial cells.

Comparison of Mycoplasma pneumoniae IgM and IgE Antibody Levels in Asthmatic and Non-Asthmatic Adults.

OBJECTIVE: Mycoplasma pneumoniae (M. pneumoniae), an extracellular pathogen lacking a cell wall, causes respiratory infection in adults and children and has been implicated in asthma exacerbation; immunoglobulin (Ig) E may be involved in these exacerbations. Specific IgM and IgG immune response to M. pneumoniae has been reported, but less is known about IgE M. pneumoniae antibody (Ab) responses in asthma. Previous studies in our laboratory demonstrated that asthmatic children have increased IgM M. pneumoniae levels, but not IgE. Thus, we sought to investigate whether past M. pneumoniae infection triggers production of M. pneumoniae-specific IgE Abs in adult subjects with/without asthma. METHODS: M. pneumoniae- IgE and -IgM Ab responses were studied in adult asthmatic (N=22) and non-asthmatic (N=22) subjects (ELISA). Data are reported as antibody index. Threshold detection levels: IgE, IgM: 0.2, 0.9, respectively. RESULTS: M. pneumoniae-IgE Ab levels were low and below the threshold of detection in both asthmatic and non-asthmatics (0.002±0.008 vs. 0.02±0.03; P=0.021). However, specific-IgM levels were slightly higher in non-asthmatics compared with asthmatics (0.96±0.37 vs. 0.79±0.31; P=0.054). M. pneumoniae-IgM Ab positivity was similar in both groups (P=1.0). CONCLUSION: IgM M. pneumoniae Abs may play an important role in non-asthma and persist for months after acute infection. IgE M. pneumoniae Abs may play a less important role in both groups.

Baicalin relieves Mycoplasma pneumoniae infection­induced lung injury through regulating microRNA­221 to inhibit the TLR4/NF­κB signaling pathway.

Mycoplasma pneumoniae (MP) is a common pathogen that can cause respiratory infections. MP pneumonia (MPP) leads to numerous complications, including lung injury and even death. The present study aimed to investigate the protective effects of Baicalin treatment on MP infection­induced lung injury and the molecular mechanism underlying these effects. Briefly, after mice were infected intranasally by MP and treated with Baicalin (80 mg/kg), serum levels of MP­immunoglobulin M (IgM) were detected by ELISA. The expression levels of C­reactive protein (CRP) in lung tissue were detected by immunohistochemistry and the bronchoalveolar lavage fluid (BALF) was examined by ELISA. Inflammatory factors and inflammatory cells in the BALF were assessed. The expression levels of microRNA (miR)­221 in lung tissue were examined by reverse transcription­quantitative PCR and pathological changes in lung tissue were detected by H&E staining. Cell apoptosis was evaluated by TUNEL assay and the protein expression levels of TLR4, MyD88 and NF­κB were detected by western blotting. Baicalin treatment significantly reduced serum levels of MP­IgM and CRP expression in lung tissue during MP infection. In addition, Baicalin decreased the levels of IL­1ß, IL­6, IL­18 and TNF­α in the BALF, and the number of inflammatory cells. Baicalin also reduced the inflammatory infiltration in lung tissue induced by MP infection, improved the pathological changes detected in lung tissue, reduced apoptosis, and downregulated the protein expression levels of TLR4, MyD88 and NF­κB. Furthermore, Baicalin treatment downregulated the expression of miR­221 and the protective effects of Baicalin were attenuated by miR­221 overexpression. In conclusion, Baicalin has a therapeutic effect on mice with MP infection­induced lung injury, which may be related to inhibition of miR­221 expression and regulation of the TLR4/NF­κB signaling pathway.

Biological functions of IL-17-producing cells in mycoplasma respiratory infection.

Mycoplasmas are the smallest and simplest bacteria that lack a cell wall but have the capability of self-replication. Among them, Mycoplasma pneumoniae is one of the most common causes of community-acquired pneumonia. The hallmark of mycoplasma respiratory diseases is the persistence of lung inflammation that involves both innate and adaptive immune responses. In recent years, a growing body of evidence demonstrates that IL-17 plays an important role in respiratory mycoplasma infection, and associates with the pathologic outcomes of infection, such as pneumonitis and asthma. Numerous studies have shown that a variety of cells, in particular Th17 cells, in the lung can secrete IL-17 during respiratory mycoplasma infection. In this article, we review the biological functions of distinct IL-17-producing cells in mycoplasma respiratory infection with a focus on the effect of IL-17 on the outcomes of infection.

A Previously Healthy 18-Year-Old Male With Fever, Arrhythmia, and Shock.

A male individual aged 18 years with no significant past medical history presented with fever, headache, dry cough, and chest pain. On clinical examination, he had tachycardia and hypotension needing intravenous fluid resuscitation and inotropic support. A chest radiograph revealed streaky lung opacities, and he was treated with antibiotics for suspected community-acquired pneumonia complicated by septic shock. Significant elevation of cardiac enzymes was noted, and there was a continued need for inotropes to maintain normotension. He also developed intermittent bradycardia, with serial electrocardiograms showing first-degree atrioventricular block, low-voltage QRS complexes, and ST-T wave changes and telemetry demonstrating junctional and ventricular escape rhythm. A complete workup for sepsis and acute myocarditis were performed to find the etiologic agent. Intravenous immunoglobulins were started to treat myocarditis, with eventual clinical improvement. He was eventually diagnosed with an unusual etiology for his illness. He was noted to still have intermittent ventricular escape rhythm on electrocardiograms on follow-up 2 weeks after discharge but continues to remain asymptomatic and in good health.

T-B cell epitope peptides induce protective immunity against Mycoplasma pneumoniae respiratory tract infection in BALB/c mice.

Mycoplasma pneumoniae is the most common pathogen of community-acquired pneumonia in humans. Due to its high rates of antibiotic resistance, vaccination has become the best method to control the dissemination of M. pneumoniae. The recombinant carboxyl terminus of the P1 (P1C) protein is an immunodominant antigen, but it has negative effects such as poor stability and lower purity. In the current study, T-B epitopes of the P1C protein were predicted according to bioinformatics analysis and assessed for efficacy in peptide vaccination. BALB/c mice were subcutaneously inoculated with the T-B epitope peptides four times and then infected with M. pneumoniae through the respiratory tract. The results showed that the T-B epitope peptides of the P1C protein (P1C103-117, P1C155-169, P1C224-238 and P1C244-258) induced strong antigen-specific serum antibody responses and cellular immune responses with high levels of serum IgG, IgA antibodies and Th1-biased (IFN-γ and IL-2) cytokines. Immunization with T-B epitope peptides significantly reduced the M. pneumoniae burden and the degree of inflammation in the challenged mice. Furthermore, the levels of IFN-γ and TNF-α in the supernatants of lung homogenates were observably reduced compared to those in the PBS group. Overall, our findings demonstrate that T-B epitopes (P1C103-117, P1C155-169, P1C224-238 and P1C244-258) play significant roles in the P1C protein and can be used to induce powerful humoral and cellular immune responses to provide significant protection against M. pneumoniae pulmonary infection, which provides new insight into the design of potential multiepitope vaccines to prevent host infection by M. pneumoniae.

Prevalence and clinical characteristics of hospitalized children with community-acquired Mycoplasma pneumoniae pneumonia during 2017/2018, Chengde, China.

ABSTRACT: Community acquired-pneumonia (CAP) has varying causative pathogens and clinical characteristics. This study investigated the prevalence of Mycoplasma pneumoniae (M pneumoniae) and evaluated the clinical characteristics in infected hospitalized children by disease severity.From throat swabs of hospitalized children (5 months to 14 years) with CAP collected between November 2017 and May 2018, M pneumoniae and other CAP pathogens were identified using polymerase chain reaction (PCR). Differences in clinical and laboratory test data were compared between severe and mild case groups.Of 333 hospitalized children enrolled, 221/333 (66.4%) tested positive for M pneumoniae and 24/221 (10.9%) patients were (n = 9, aged <5 years vs n = 15, ≥5 years) single infection by PCR, however, only 170/333 (51.1%) patients were presented with M pneumoniae IgM-positive. M pneumoniae detection rate by PCR was higher than by immunoglobulin (IgM) serology. In 123/221 (55.7%) M pneumoniae infected patients, coinfection with bacterial pathogens (n = 61, <5 years vs n = 62, ≥5 years) occurred. Children (aged 3-8 years) had most M pneumoniae infection. Severe M pneumoniae pneumonia (MPP) in children occurred mostly in older age (7 [interquartile ranges {IQR}, 6-8] years; P < .0001), with longer cough days (14 [IQR, 10-19.5] days; P = .002) and hospitalization duration (9.5 [IQR, 7-12.3] days; P < .0001), lower lymphocyte ratio (24.1, [IQR, 20.0-31.1] %; P = .001), higher neutrophils ratio (66.0, [IQR, 60.2-70.3]%; P < .0001), and serum C-reactive protein (CRP) level (3.8, [IQR, 1.3-10.9] mg/L; P = .027).M pneumoniae is the most commonly detected pathogen in CAP. High coinfection prevalence increases diagnosis difficulty by clinically nonspecific characteristics. M pneumoniae detection by PCR with IgM may improve precise and reliable diagnosis of community-acquired MPP.

Prediction of risk factors of bronchial mucus plugs in children with Mycoplasma pneumoniae pneumonia.

BACKGROUND: Recently, many cases of pneumonia in children with Mycoplasma pneumoniae infection have been shown to have varying degrees of intrabronchial mucus plug formation. The clinical, laboratory, radiological characteristics, and treatment of patients with Mycoplasma infection are analyzed in this study. The risk factors for M. pneumoniae pneumonia (MPP) mucus plug formation in children are explored, and a risk factor scoring system is established. METHODS: MPP patients treated with bronchoscopy were retrospectively enrolled in the study from February 2015 to December 2019. The children were divided into a mucus plug group and a control group according to the presence or absence of mucus plug formation. The clinical, laboratory, radiological characteristics, and treatment of the two groups of children were compared. Univariate and multivariate logistic regression models were used to identify the risk factors for MPP mucus plug formation. The receiver operating characteristic (ROC) curve was drawn to evaluate the regression model and establish the MPP mucous plug risk factor scoring system. RESULTS: A univariate analysis showed that the children in the mucous group were older and had a longer fever duration, longer hospital stay, higher fever peak, more cases of wheezing symptoms and allergies, and azithromycin or corticosteroids were administered later. In addition, neutrophil, C-reactive protein (CRP), lactate dehydrogenase (LDH), D-dimer (DD), sputum MP-DNA copy number, and total immunoglobulin A (IgA) levels were higher, while prealbumin (PA) levels were lower. The ROC curve analysis showed that children with MPP had PA ≤144.5 mg/L, had used corticosteroids during the course of the illness of ≥4.5 days, CRP ≥12.27 mg/L, an LDH ≥ 462.65 U/L, and there was a possibility of intra-airway mucus formation. The independent risk factors were scored according to their odds ratio (OR) value. Among the 255 children with MPP, the high-risk group had 44 (83.02%) mucus plugs out of 53; the middle-risk group had 35 (34.3%) mucus plugs out of 102; and the low-risk group had 11 (11%) mucus plugs out of 100. CONCLUSIONS: PA levels, timing of corticosteroid use (use in the first few days), CRP levels, and LDH levels were independent risk factors for MPP mucus plug formation. This provides a basis for the early identification of MPP in children combined with mucus plug formation.

Association between infectious burden and cerebral microbleeds: a pilot cross-sectional study.

OBJECTIVE: Cerebral microbleeds (CMBs) is a subtype of cerebral small vessel disease. Their underlying pathogenesis remains unclear. The aim of this study was to investigate the association between infectious burden (IB) and CMBs. METHODS: Seven hundred and seventy-three consecutive patients who were hospitalized in the Department of Neurology in General Hospital of Western Theater Command without severe neurological symptoms were recruited and selected in this pilot cross-sectional study. CMBs were assessed using the susceptibility-weighted imaging sequence of magnetic resonance imaging. Immunoglobulin G antibodies against common pathogens, including herpes simplex virus (HSV)-1, HSV-2, cytomegalovirus (CMV), Chlamydia pneumoniae (C. pneumoniae), Mycoplasma pneumoniae (M. pneumoniae), Epstein-Barr virus (EBV), Helicobacter pylori (HP), and Borrelia burgdorferi (B. burgdorferi), were measured by commercial ELISA assays. IB was defined as a composite serologic measure of exposure to these common pathogens. RESULTS: Patients with and without CMBs were defined as the CMBs group (n = 76) and the non-CMBs group (n = 81), respectively. IB was significantly different between the CMBs and non-CMBs groups. After adjusted for other risk factors, the increased IB was independently associated with the presence of CMBs (P = 0.031, OR = 3.00, 95% CI [1.11-8.15]). IB was significantly positively associated with the number of CMBs (Spearman ρ = 0.653, P < 0.001). The levels of serum inflammatory markers were significantly different between the CMBs and non-CMBs groups and among the categories of IB. INTERPRETATION: IB consisting of HSV-1, HSV-2, CMV, C. pneumoniae, M. pneumoniae, EBV, HP, and B. burgdorferi was associated with CMBs. All the findings suggested that pathogen infection could be involved in the pathogenesis of CMBs.

Altered chemokine profile in Refractory Mycoplasma pneumoniae pneumonia infected children.

BACKGROUND: Mycoplasma pneumoniae is one of the major pathogens causing community-acquired pneumonia in children. Although usually self-limited, Mycoplasma pneumoniae pneumonia (MPP) may lead to complicated morbidity that can even be life-threatening. Upon MPP infection, alveolar macrophage becomes attracted and activated and will induce subsequent cytokine and chemokine reaction. Refractory Mycoplasma pneumoniae pneumonia (RMPP) is manifested by clinical or radiological deterioration despite proper antibiotic therapy. RMPP is characterized with excessive inflammation and may need subsequent glucocorticoid treatment. AIM: The aim of this study was to investigate the change of plasma chemokines in non-refractory Mycoplasma pneumoniae pneumonia (NRMPP) and RMPP before and after antibiotic or methylprednisolone treatment. METHOD: A total of 42 children with MPP were enrolled in this study. Plasma specimens were collected at admission and one to two weeks after antibiotic or methylprednisolone treatment with declined fever. Plasma specimens were then indicated to chemokines detection. RESULTS: Mycoplasma pneumoniae pneumonia altered the chemokine profile through the observation of decreased plasma M1 related chemokines (CCL2, CCL8 and CXCL10) and increased M2 related chemokines (CCL17 and CCL22) after treatment.When the patients were divided into RMPP and NRMPP groups and the chemokines before treatment were compared, the RMPP group showed higher CXCL10 but lower CCL3 and CCL11 than the NRMPP group. CONCLUSION: Unique changes in macrophage related chemokines is observed in the course of MPP infection. NRMPP and RMPP infection in children showed distinct manifestation in chemokine profiles.

Mycoplasma pneumoniae lipids license TLR-4 for activation of NLRP3 inflammasome and autophagy to evoke a proinflammatory response.

Mycoplasma pneumoniae is an obligate pathogen that causes pneumonia, tracheobronchitis, pharyngitis and asthma in humans. It is well recognized that membrane lipoproteins are immunostimulants exerting as lipopolysaccharides (LPS) and play a crucial role in the pathogenesis of inflammatory responses upon M. pneumoniae infection. Here, we report that the M. pneumoniae-derived lipids are another proinflammatory agents. Using an antibody-neutralizing assay, RNA interference or specific inhibitors, we found that Toll-like receptor 4 (TLR-4) is essential for M. pneumoniae lipid-induced tumour necrosis factor (TNF)-α and interleukin (IL)-1ß production. We also demonstrate that NLR family pyrin domain containing 3 inflammasome (NLRP3) inflammasome, autophagy and nuclear factor kappa B (NF-κB)-dependent pathways are critical for the secretion of proinflammatory cytokines, while inhibition of TLR-4 significantly abrogates these events. Further characterization revealed that autophagy-mediated inflammatory responses involved the activation of NF-κB. In addition, the activation of NF-κB promoted lipid-induced autophagosome formation, as revealed by assays using pharmacological inhibitors, 3-methyladenine (3-MA) and Bay 11-7082, or silencing of atg5 and beclin-1. These findings suggest that, unlike the response to lipoprotein stimulation, the inflammation in response to M. pneumoniae lipids is mediated by the TLR-4 pathway, which subsequently initiates the activation of NLRP3 inflammasome and formation of a positive feedback loop between autophagy and NF-κB signalling cascade, ultimately promoting TNF-α and Il-1ß production in macrophages.

Immunodominant proteins P1 and P40/P90 from human pathogen Mycoplasma pneumoniae.

Mycoplasma pneumoniae is a bacterial human pathogen that causes primary atypical pneumonia. M. pneumoniae motility and infectivity are mediated by the immunodominant proteins P1 and P40/P90, which form a transmembrane adhesion complex. Here we report the structure of P1, determined by X-ray crystallography and cryo-electron microscopy, and the X-ray structure of P40/P90. Contrary to what had been suggested, the binding site for sialic acid was found in P40/P90 and not in P1. Genetic and clinical variability concentrates on the N-terminal domain surfaces of P1 and P40/P90. Polyclonal antibodies generated against the mostly conserved C-terminal domain of P1 inhibited adhesion of M. pneumoniae, and serology assays with sera from infected patients were positive when tested against this C-terminal domain. P40/P90 also showed strong reactivity against human infected sera. The architectural elements determined for P1 and P40/P90 open new possibilities in vaccine development against M. pneumoniae infections.

Diagnostic utility of serology and polymerase chain reaction for detection of Mycoplasma pneumoniae and Chlamydophila pneumoniae in paediatric community-acquired lower respiratory tract infections.

Purpose: Mycoplasma pneumoniae (M. pneumoniae) and Chlamydophila pneumoniae (C. pneumoniae) play a significant role in children of all ages with lower respiratory tract infections (LRTIs). This study was conducted to detect M. pneumoniae and C. pneumoniae in children with community-acquired LRTIs employing serology, polymerase chain reaction (PCR) and nested PCR analysis. Material and Methods: This study included 75 children with acute LRTIs for detection of M. pneumoniae and C. pneumoniae. Blood was obtained for M. pneumoniae and C. pneumoniae antibodies and nasopharyngeal aspirates for M. pneumoniae PCR and C. pneumoniae nested PCR. Results: M. pneumoniae infection was positive in 9 (64.21%) children aged 2-6 months and in 5 (35.79%) aged 7 months-12 years, and this difference was statistically significant (P = 0.002). C. pneumoniae infection was comparable within the age group and statistically insignificant (P = 0.43). Clinical and radiological profiles of M. pneumoniae- and C. pneumoniae-positive and negative patients were numerically comparable. Serology and PCR together detected M. pneumoniae infection in 14 (18.6%) children. The sensitivity, specificity and positive and negative predictive values of serology were 77.78%, 92.42%, 58.33% and 96.83%, respectively. C. pneumoniae infection was positive in 11 (14.6%) children by serology and nested PCR with 50% sensitivity, 87.67% specificity, 10% positive predictive value and 98.46% negative predictive value. Conclusions: Our study confirms that M. pneumoniae and C. pneumoniae play a significant role in community-acquired LRTIs and a combination of serology and nested PCR is useful for its diagnosis.