Cytoadherence-dependent induction of inflammatory responses by Mycoplasma pneumoniae

Predictive value of immune-related parameters in severe Mycoplasma pneumoniae pneumonia in children

Background

The severity of Mycoplasma pneumoniae pneumonia (MPP) is strongly correlated with the extent of the host's immune-inflammatory response. In order to diagnose the severity of MPP early, this study sought to explore the predictive value of immune-related parameters in severe MPP (sMPP) in admitted children.

Methods

We performed a database analysis consisting of patients diagnosed at our medical centers with MPP between 2021 and 2023. We included pediatric patients and examined the association between complete blood cell count (CBC), lymphocyte subsets and the severity of MPP. Binary logistic regression was performed to identify the independent risk factors of sMPP. Receiver operating characteristic (ROC) curves were used to estimate discriminant ability.

Results

A total of 245 MPP patients were included in the study, with 131 males and 114 females, median aged 6.0 [interquartile range (IQR), 4.0-8.0] years, predominantly located in 2023, and accounted for 64.5%. Among them, 79 pediatric patients were diagnosed as sMPP. The parameters of CBC including white blood cell (WBC) counts, neutrophil counts, monocyte counts, platelet counts, and neutrophil-to-lymphocyte ratio (NLR), were higher in the sMPP group (all P<0.05). The parameters of lymphocyte subsets including CD3+ T cell ratio (CD3+%) and CD3+CD8+ T cell ratio (CD3+CD8+%), were lower in the sMPP group (all P<0.05). And CD3-CD19+ B cell ratio (CD3-CD19+%) was higher in the sMPP group. Logistic regression analysis showed that age, CD3-CD19+%, and monocyte counts were identified as independent risk factors for the development of sMPP (all P<0.001). The three factors were applied in constructing a prediction model that was tested with 0.715 of the area under the ROC curve (AUC). The AUC of the prediction model for children aged ≤5 years was 0.823 and for children aged >5 years was 0.693.

Conclusions

The predictive model formulated by age, CD3-CD19+%, and monocyte counts may play an important role in the early diagnosis of sMPP in admitted children, especially in children aged ≤5 years.

Mycoplasma pneumoniae: Among the smallest bacterial pathogens with great clinical significance in children

BACKGROUND

Mycoplasmas are the smallest prokaryotic microorganisms found in nature. Mycoplasma pneumoniae (M. pneumoniae) is the most commonly studied among human mycoplasmas.

OBJECTIVES

In this review, we briefly focus on the recent developments that have enhanced our understanding of M. pneumoniae, one of the smallest pathogenic bacteria of great clinical importance in children.

CONTENT

M. pneumoniae infections may involve either upper or lower respiratory tract or both of them. Extrapulmonary manifestations have been reported in almost every organ, including the skin and the hematologic, cardiovascular, musculoskeletal, and nervous system due to direct local effects, after dissemination of bacteria or indirect effects. The correct identification of M. pneumoniae infections is vital for prescription of the appropriate therapy.There are scarce specific findings of clinical laboratory results for the diagnosis of M. pneumoniae infection. Detection of M. pneumoniae infections can be achieved using culture, serology, or molecular-based methods. Culture is time-consuming, laborious, and expensive. The major types of serological tests for M. pneumoniae include the microtiter plate enzyme immunoassay (EIA), the membrane EIA, indirect immunofluorescence, and particle agglutination. Nucleic acid amplification tests (NAATs) include traditional PCR, nested PCR, real-time quantitative PCR, nucleic acid sequence-based amplification (NASBA), loop-mediated isothermal amplification (LAMP) technology, and RNA simultaneous amplification and testing (SAT). Macrolides have been the drug of choice for treating M. pneumoniae infection in past years. Clinically significant acquired macrolide-resistant M. pneumoniae (MRMP)has emerged worldwide which may be associated with more extrapulmonary complications, and severe clinical and radiological features. Since molecular-based assays can detect M. pnueumoniae in clinical specimens, there is a need for real point of care testing for fast detection of M. pneumoniae or its DNA and mutations in macrolide resistance gene. It is necessary to develop safe vaccines that provide protective immunity against M.pneumoniae infection.

Clinical features and “early” corticosteroid treatment outcome of pediatric mycoplasma pneumoniae pneumonia

Background

Many children with mycoplasma pneumoniae (MP) pneumonia (MPP) developed sequelae such as bronchiolitis/bronchitis obliterans (BO). Early corticosteroid therapy might prevent disease progression. This study aimed to use “early” corticosteroid and observe the treatment outcome in patients with MPP.

Methods

Patients who had pulmonary infiltrations on chest imaging within 5 days of the disease course and were suspected of having MP infection on admission were enrolled. Among them, patients whose disease course was within 10 days on admission were ultimately enrolled. We analyzed their data including the clinical features, the starting time and dose of corticosteroid therapy, and the treatment outcome. According to chest imaging, we divided patients into two groups (Group A: bronchiolitis-associated lesions or ground-glass opacities; Group B: pulmonary segmental/lobar consolidation).

Results

A total of 210 patients with confirmed MPP were ultimately enrolled. There were 59 patients in Group A and 151 patients in Group B. Patients in Group A were more prone to have allergy histories, hypoxemia, wheezing sound, and wet rales on auscultation than those in Group B. Corticosteroid treatment was initiated between 5 and 10 days of disease onset in all patients and 6–7 days in most patients. Methylprednisolone was prescribed in all patients within 10 days of disease onset, and the highest prescribed dose was at least 2 mg/kg/day. In Group A, methylprednisolone &gt;2 mg/kg/day was prescribed in 22 patients, and among them, 8 patients with diffuse bronchiolitis-associated lesions received high-dose methylprednisolone therapy. After 3 months, lung CT revealed slightly segmental ground-glass opacity in three patients. In Group B, methylprednisolone &gt;2 mg/kg/day was prescribed in 76 patients, and among them, 20 patients with pulmonary lobar consolidation received high-dose methylprednisolone therapy. After 3 months, chest imaging revealed incomplete absorption of pulmonary lesions in seven patients. Among them, five patients with consolidation in more than one pulmonary lobe ultimately had slight BO.

Conclusion

In hospitalized patients with MPP, particularly severe MPP, the ideal starting time of corticosteroid treatment might be 5–10 days, preferably 6–7 days, after disease onset. The initial dosage of corticosteroid therapy should be decided according to the severity of the disease. MPP patients with diffuse bronchiolitis-associated lesions/whole lobar consolidation on imaging might require high-dose corticosteroid therapy.

Regulatory functional role of NLRP3 inflammasome during Mycoplasma hyopneumoniae infection in swine

Mycoplasma hyopneumoniae causes enzootic pneumonia, a highly contagious respiratory disease in swine that causes significant economic losses worldwide. It is unknown whether the nucleotide oligomerization domain-like receptor (NLR) family pyrin domain containing 3 (NLRP3) inflammasome regulates the immune response in swine during M. hyopneumoniae infection. The current study utilized an in vivo swine model of M. hyopneumoniae infection to investigate the regulatory functional role of the NLRP3 inflammasome during M. hyopneumoniae infection. Notable histopathological alterations were observed in M. hyopneumoniae-infected swine tissues, which were associated with an inflammatory response and disease progression. Swine M. hyopneumoniae infection was associated with an increase in the expression of the NLRP3 inflammasome, which stimulated pro-inflammatory cytokines such as tumor necrosis factor-alpha, interleukin 18, and interleukin 1 beta (IL-1β). The impact of the NLRP3 inhibitor, MCC950 on NLRP3 and pro-inflammatory cytokines in M. hyopneumoniae-infected swine was examined to investigate the relationship between the NLRP3 inflammasome and M. hyopneumoniae infection. Taken together, our findings provide strong evidence that the NLRP3 inflammasome plays a critical regulatory functional role in M. hyopneumoniae infection in swine.

Investigation of the relationship between community-acquired respiratory distress syndrome toxin and the high-mobility group box protein 1-toll-like receptors-myeloid differentiation factor 88 signaling pathway in Mycoplasma pneumoniae pneumonia

BACKGROUND

In recent years, reports of refractory Mycoplasma pneumoniae pneumonia (RMPP) have gradually increased, including reports on how these conditions threaten the lives of children. However, the specific mechanism of Mycoplasma pneumoniae pneumonia (MPP) remains unclear. This study aimed to investigate the relationship between community-acquired respiratory distress syndrome toxin (CARDS TX) and High-mobility group box protein 1-Toll-like receptors-Myeloid differentiation factor 88 (HMGB1-TLRs-MyD88) in MPP and to examine the immune pathogenesis of Mycoplasma pneumoniae infection.

METHODS

Children who were diagnosed with MPP and examined by bronchoscopy were included in the MPP group. Additionally, children who underwent bronchoscopy because of bronchial foreign bodies in the same period were included in the control group. Gene expression of CARDS TX, HMGB1, Toll-like receptor 2 (TLR2), Toll-like receptor 4 (TLR4), MyD88, and cluster of differentiation 14 (CD14) in bronchoalveolar lavage fluid (BALF) were detected using real-time reverse transcription-polymerase chain reaction. Correlations between CARDS TX and HMGB1-TLRs-MyD88 were analyzed.

RESULTS

CARDS TX, HMGB1, TLR2, MyD88, and CD14 mRNA expression in BALF in the MPP group was significantly higher than that in the control group (all P < 0.05). CARDS TX mRNA expression was positively correlated with HMGB1, TLR2, MyD88, and CD14 mRNA expression (all P < 0.05). Furthermore, HMGB1 mRNA expression was positively correlated with TLR2, MyD88, and CD14 mRNA expression (all P < 0.05).

CONCLUSIONS

CARDS TX may participate in the immune pathogenesis of MPP through the HMGB1-TLRs/CD14-MyD88 pathway.

Multiple bacterial virulence factors focused on adherence and biofilm formation associate with outcomes in cirrhosis

BACKGROUND & AIMS

Altered gut microbiota is associated with poor outcomes in cirrhosis, including infections and hepatic encephalopathy (HE). However, the role of bacterial virulence factors (VFs) is unclear. Aim: Define association of VFs with cirrhosis severity and infections, their linkage with outcomes, and impact of fecal microbiota transplant (FMT).

METHODS

VF abundances were determined using metagenomic analysis in stools from controls and cirrhosis patients (compensated, HE-only, ascites-only, both and infected). Patients were followed for 90-day hospitalizations and 1-year death. Stool samples collected before/after a placebo-controlled FMT trial were also analyzed. Bacterial species and VFs for all species and selected pathogens (Escherichia, Klebsiella, Pseudomonas, Staphylococcus, Streptococcus, and Enterococcus spp) were compared between groups. Multi-variable analyses were performed for clinical biomarkers and VFs for outcome prediction. Changes in VFs pre/post-FMT and post-FMT/placebo were analyzed. Results: We included 233 subjects (40 controls, 43 compensated, 30 HE-only, 20 ascites-only, 70 both, and 30 infected). Decompensated patients, especially those with infections, had higher VFs coding for siderophores, biofilms, and adhesion factors versus the rest. Biofilm and adhesion VFs from Enterobacteriaceae and Enterococcus spp associated with death and hospitalizations independent of clinical factors regardless of when all VFs or selected pathogens were analyzed. FMT was associated with reduced VF post-FMT versus pre-FMT and post-placebo groups.

CONCLUSIONS

Virulence factors from multiple species focused on adhesion and biofilms increased with decompensation and infections, associated with death and hospitalizations independent of clinical factors, and were attenuated with FMT. Strategies focused on targeting multiple virulence factors could potentially impact outcomes in cirrhosis.

PRESENTATIONS

Portions of this manuscript were an oral presentation in the virtual International Liver Congress 2021.

ABBREVIATIONS

VF: virulence factors, HE: hepatic encephalopathy, FMT: Fecal microbiota transplant, PPI: proton pump inhibitors, LPS: lipopolysaccharides, VFDB: Virulence factor database, OTU: operational taxonomic units, SBP: spontaneous bacterial peritonitis, UTI: urinary tract infections, MRSA: methicillin resistant Staphylococcus aureus, VRE: vancomycin-resistant Enterococcus, MAAsLin2: Microbiome Multivariable Associations with Linear Models, LPS: lipopolysaccharides, AKI: acute kidney injury.

Development of a scale for early prediction of refractory Mycoplasma pneumoniae pneumonia in hospitalized children

Now there is no clinical scale for early prediction of refractory Mycoplasma pneumoniae pneumonia (RMPP). The aim of this study is to identify indicators and develop an early predictive scale for RMPP in hospitalized children. First we conducted a retrospective cohort study of children with M. pneumoniae pneumonia admitted to Children's Hospital of Nanjing Medical University, China in 2016. Children were divided into two groups, according to whether their pneumonia were refractory and the results were used to develop an early predictive scale. Second we conducted a prospective study to validate the predictive scale for RMPP in children in 2018. 618 children were included in the retrospective study, of which 73 with RMPP. Six prognostic indicators were identified and included in the prognostic assessment scale. The sensitivity of the prognostic assessment scale was 74.0% (54/73), and the specificity was 88.3% (481/545) in the retrospective study. 944 children were included in the prospective cohort, including 92 with RMPP, the sensitivity of the prognostic assessment scale was 78.3% (72/92) and the specificity was 86.2% (734/852). The prognostic assessment scale for RMPP has high diagnostic accuracy and is suitable for use in standard clinical practice.

Mycoplasma pneumoniae Infections: Pathogenesis and Vaccine Development

Mycoplasma pneumoniae is a major causative agent of community-acquired pneumonia which can lead to both acute upper and lower respiratory tract inflammation, and extrapulmonary syndromes. Refractory pneumonia caused by M. pneumonia can be life-threatening, especially in infants and the elderly. Here, based on a comprehensive review of the scientific literature related to the respective area, we summarize the virulence factors of M. pneumoniae and the major pathogenic mechanisms mediated by the pathogen: adhesion to host cells, direct cytotoxicity against host cells, inflammatory response-induced immune injury, and immune evasion. The increasing rate of macrolide-resistant strains and the harmful side effects of other sensitive antibiotics (e.g., respiratory quinolones and tetracyclines) in young children make it difficult to treat, and increase the health risk or re-infections. Hence, there is an urgent need for development of an effective vaccine to prevent M. pneumoniae infections in children. Various types of M. pneumoniae vaccines have been reported, including whole-cell vaccines (inactivated and live-attenuated vaccines), subunit vaccines (involving M. pneumoniae protein P1, protein P30, protein P116 and CARDS toxin) and DNA vaccines. This narrative review summarizes the key pathogenic mechanisms underlying M. pneumoniae infection and highlights the relevant vaccines that have been developed and their reported effectiveness.

Evaluation on blood coagulation and C-reactive protein level among children with mycoplasma pneumoniae pneumonia by different chest imaging findings

Mycoplasma pneumoniae infection may induce a systemic hypercoagulable abnormality, like organ embolism and infarction. Indexes of blood coagulation and C-reactive protein (CRP) have been reported different between healthy people and mycoplasma pneumoniae pneumonia (MPP) patients, but this difference in MPP patients with different chest imaging findings has rarely been reported.We performed a retrospective study of 101 children with MPP and 119 controls, combined with radiological examination and blood tests, to compare the blood coagulation and CRP level among MPP children with different chest imaging findings.For the MPP children with different chest imaging findings, there were significant differences in CRP, fibrinogen (FIB) and D-dimer (D-D) levels among subgroups (P = .004, P = .008 and P < .001 respectively). The CRP level in group of interstitial pneumonia was significantly higher than that in groups of bronchopneumonia and hilar shadow thickening (P = .003 and P = .001 respectively). And the FIB and D-D values in group of lung consolidation were significantly higher than that in the other 3 groups (all P < .05). When compared with controls, the white blood cell, CRP, FIB, and D-D levels in MPP children were significantly higher, and the activated partial thromboplastin time and thrombin time levels were significantly lower (all P < .05).Our results showed that CRP level changed most significantly in group of interstitial pneumonia, whereas FIB, D-D levels changed most significantly in the lung consolidation group.

Investigation of acute-phase proteins and cytokines response in goats with contagious caprine pleuropneumonia with special reference to their diagnostic accuracy

Acute-phase proteins (APPs) have always had valued diagnostic potentialities in response to infection. This study aimed to evaluate the diagnostic accuracy of selected APPs and proinflammatory cytokines (PIC) in goats with contagious caprine pleuropneumonia (CCPP) under field conditions. Moreover, to highlight the role of tested biomarkers in CCPP pathogenesis. Fifty-eight goats (38 confirmed cases with CCPP and 20 healthy controls) were involved in this investigation. C-reactive protein (CRP), procalcitonin (PCT), haptoglobin (HP), fibrinogen (Fb), serum amyloid A (SAA), selected PIC (IL1-α, IL1-β, IL-6, interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α)) levels were investigated in serum samples from all goats under investigation. Latex agglutination test was used for diagnosis of goats with CCPP. For microbiological investigations, nasopharyngeal swabs (from all goats), lung tissues and pleural fluids (from only necropsied goats) were collected. This study revealed that all tested parameters have a high to moderate degree of diagnostic performance for CCPP. Magnitudes of increase in levels of APPs (CRP, HP and SAA) were stronger than PIC, IFN-γ, Fb and PCT. All tested parameters showed high diagnostic accuracy (AUROC >90%), except HP (AUROC = 87.3%) and IFN-γ (AUROC = 78.8%) showed moderate accuracy in differentiation of goats with and without CCPP infection. For detecting goats with and without CCPP infection, HP had the lowest sensitivity (Se = 81.6%) and Fb had the lowest specificity (Sp = 85.0%) among the APPs parameters tested. However, PCT showed the highest Se (100%) and Sp (95.0%) to detect goats with and without CCPP infection among tested parameters. Conclusively, this study endorses the significance of selected APPs and PIC as additional screening diagnostic parameters for naturally occurring CCPP in goats. However, it does not replace traditional methods for diagnosis of CCPP in goats. Furthermore, APPs and PIC have an important role in disease pathogenesis in goats.

Mycoplasma gallisepticum triggers immune damage in the chicken thymus by activating the TLR-2/MyD88/NF-κB signaling pathway and NLRP3 inflammasome

Previous studies reported that Mycoplasma gallisepticum (MG) causes immune dysregulation in chickens. However, the underlying mechanisms of immune dysregulation in chickens are still unclear. The thymus is a primary lymphoid organ where the proliferation, differentiation and selection of T-lymphocytes occur, whereas T-lymphocytes play a crucial role in innate immune responses. To evaluate the effects of MG-infection on chicken thymus, White Leghorn chickens were divided into (1) control group and (2) MG-infection group. ATPase activities were detected by commercial kits. The hallmarks of inflammation, autophagy and energy metabolism were examined in chicken thymus tissues by histopathology, transmission electron microscopy, immunofluorescence microscopy, RT-PCR and western blotting. Immunofluorescence examination revealed that the number of CD8⁺ lymphocytes has significantly reduced in MG-infection group. In addition, morphological analysis revealed that MG induced inflammatory cells infiltration. The mitochondria were swollen and chromatin material was condensed in MG-infection group. The mRNA and protein expression results showed that MG-infection triggered the nucleotide-binding oligomerization domain, leucine rich repeat and pyrin domain containing 3 (NLRP3) inflammasome through TLR-2/MyD88/NF-κB signaling pathway. Meanwhile, the expressions of autophagy-related genes were reduced both at mRNA and protein level in MG-infection group. While, ATPase activities and the expression of energy metabolism-related genes were reduced in the thymus of MG-infected chickens. These results showed that MG-infection triggered inflammatory response through TLR-2/MyD88/NF-κB signaling pathway, activated NLRP3 inflammasome, reduced the level of autophagy and impaired energy metabolism, which then lead to tissue damage in chicken thymus. The data provide new insights in MG-infection-mediated immune damage and provide possible therapeutic targets for future targeted therapy.

Efficacy of glucocorticoids for the treatment of macrolide refractory mycoplasma pneumonia in children: meta-analysis of randomized controlled trials

Background

Mycoplasma pneumoniae is one of the most common pathogens causing community acquired pneumonia in children. Although the rate of macrolide-refractory Mycoplasma pneumoniae (MRMP) has increased, systemic glucocorticoids as a treatment option has not been validated yet. The purpose of this study was to assess the efficacy of glucocorticoids add-on in the treatment of MRMP in children through systematic review and meta-analysis.

Methods

Data sources

A systematic literature search was conducted using ten electronic bibliographic databases including English, Korean, Chinese and Japanese languages, up to March 8, 2018.

Study selection

The study was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist and selected randomized control trials which compared the efficacy of glucocorticoids add-on to macrolide in the treatment of MRMP in children.

Data extraction

Two independent reviewers extracted: primary outcomes as hospital days, fever duration, and change in C-reactive protein (CRP) and main analysis was performed through meta-analysis with random effects model.

Results

Twenty-four unique randomized controlled trials met the inclusion criteria. The mean length of hospital stay in glucocorticoids treatment group was significantly shorter than that in conventional macrolide-treatment group (Weighted mean difference (WMD) = − 4.03 days). The mean length of fever duration was significantly shorter in the glucocorticoid treatment group in comparison with the conventional treatment group (WMD = -3.32 days). Level of CRP after treatment was significantly lower in the glucocorticoid treatment group than that in the conventional treatment group (WMD = -16.03). Sensitivity analysis and subgroup analysis showed no significant improvement in heterogeneity. As limitations of the study, most of the studies included were from a single country and we were unable to control for heterogeneity across interventions, lack of standardized measures, and different time points of assessments across studies.

Conclusions

Glucocorticoid add-on treatment for MRMP can significantly shorten the duration of fever and hospital stay and decrease the level of CRP. These results should be confirmed by adequately powered studies in the future.

Extracellular methemoglobin promotes cyto-adherence of uninfected RBC to endothelial cells: Insight into cerebral malaria pathology

The endothelial cell barrier is tightly regulated, and disruption or the leaky behavior of the barrier leads to pathology. Disturbance of blood-brain barrier is observed during viral infection, cerebral malaria, and acute hemorrhagic encephalitis. Red blood cells (RBCs) bind to the endothelial cells (ECs) and their affinity towards ECs enhances in the presence of Plasmodium falciparum infection. ECs stimulated with methemoglobin (MetHb; 20 µM) for 1 hour exhibit high levels of cyto-adherence receptors CD36 and ICAM-1 on their cell surface compared with unstimulated cells. These ECs have acquired affinity towards uninfected RBCs in flow at arterial shear stress. SEM analysis indicates that EC-RBC cyto-adherence involved multiple attachment points. Initially, ECs bind single layer of RBCs and the number of RBCs increases over time to give high-order cyto-adherence with more than 30 RBCs adhered to each endothelial cell. The cyto-adherence complexes are stable to high shear stress and can withstand shear stress up to 450 dyne/cm ² . MetHb-treated ECs exhibited high reactive oxygen species level, and preincubation of ECs with antioxidant (NAC or mannitol) abolished the formation of EC-RBC cyto-adherence complexes. In addition, gallic acid (present in red wine) and green tea extract has inhibited the formation of EC-RBC cyto-adherence complex. A better understanding of gallic acid and tea polyphenol targeting pathological cyto-adherence may allow us to develop a better adjuvant therapy for cerebral malaria and other noninfectious diseases.

β2 microglobulin and lactate dehydrogenase are indices of different features of Mycoplasma pneumoniae-associated community-acquired lower respiratory tract infection for severity evaluation in children

Using the hospital records, we retrospectively assessed whether urinary β2 microglobulin/creatinine ratio (UBCR) and lactate dehydrogenase (LD) values could be used to estimate the severity of Mycoplasma pneumoniae-associated lower respiratory tract infection (MP-LRTI). We studied 48 patients with MP-LRTI (median age, 7.5 years; range, 3-14 years) admitted to Kagoshima City Hospital and examined the relationships of the UBCR or LD values with fever and pulmonary tissue damage (hypoxemia and severity assessments on chest radiographs). Patients were assigned to four groups based on whether they had fever and/or hypoxemia. Patients with high fever showed significantly higher UBCR values than those without (P < 0.05), whereas those with hypoxemia showed higher LD values than those without (P = 0.001). The maximum body temperature on admission was closely associated with the UBCR but not with LD levels. In chest radiography assessments, LD levels were significantly higher in patients with severe than mild or moderate MP-LRTI. A cut-off LD level of 530 IU/L showed a very high sensitivity (100%) and specificity (93%). Although UBCR values were higher in patients with severe MP-LRTI, the differences were not statistically significant. Our study shows that the UBCR is associated with body temperature, whereas LD levels may serve as an index of pulmonary tissue damage in children with MP-LRTI.

Immunosuppression Reduces Lung Injury Caused by Mycoplasma pneumoniae Infection

The underlying mechanisms of Mycoplasma pneumoniae pneumonia (MPP) pathogenesis are not clearly understood. This study aimed to investigate the correlation between immune response and lung injury in MPP. The clinical characteristics of MPP were compared between patients treated with and without immunosuppressive chemotherapy, and demographic, clinical, and laboratory data were compared between patients with severe and mild MPP. To determine the effect of immune response on lung lesions, mouse MPP and immunosuppression models were established by intranasal inoculation of M129 and intraperitoneal injection of cyclophosphamide, respectively. Myeloperoxidase and oxidant-antioxidant enzyme activities were evaluated for mechanism studies. The immunosuppressant group had a lower incidence of MPP and fewer cases of severe MPP than the non-immunosuppressant group. The severe MPP group had a greater incidence of severe immune disorders than the mild MPP group. Relative to immunosuppressed mice, wild mice exhibited more severe inflammatory infiltration and lung injury as well as a significant increase in myeloperoxidase and malondialdehyde levels and a decrease in superoxide dismutase level after MP infection. In conclusion, immunological responses likely play a vital role in MPP pathogenesis. Lung injury occurring after MP infection-which might be caused by oxidant-antioxidant imbalance-can be reduced by immunosuppression.

Bacteria in Asthma Pathogenesis

The airways are under continuous assault from aerosolized bacteria and oral flora. The bacteria present in the airways and gastrointestinal tract of neonates promote immune maturation and protect against asthma pathogenesis. Later bacterial infections and perturbations to the microbiome can contribute to asthma pathogenesis, persistence, and severity.

Mycoplasma pneumoniae protects infected epithelial cells from hydrogen peroxide-induced cell detachment

Epithelial cell shedding is a defence mechanism against infectious microbes that use these cells as an infection foothold and that eliminate microbes from infection foci by removing infected cells. Mycoplasma pneumoniae, a causative agent of respiratory infections, is known to adhere to and colonise the surface of ciliated airway epithelial cells; it produces a large amount of hydrogen peroxide, indicating its capability of regulating hydrogen peroxide-induced infected cell detachment. In this study, we found that M. pneumoniae reduces exogenous hydrogen peroxide-induced detachment of the infected cells from culture plates. This cell detachment occurred dependently of DNA damage-initiated, poly (ADP-ribose) polymerase 1 (PARP1)-mediated cell death, or parthanatos. In cells infected with M. pneumoniae, exogenous hydrogen peroxide failed to induce DNA damage-initiated poly (ADP-ribose) (PAR) synthesis and concomitant increased cytoplasmic membrane rupture, both of which are biochemical hallmarks of parthanatos. The impairment of PAR synthesis was attributed to a reduction in the amount of cytosolic nicotinamide adenine dinucleotide (NAD), a substrate of PARP1, caused by M. pneumoniae. On the other hand, nonadherent mutant strains of M. pneumoniae showed a lower ability to reduce cell detachment than wild-type strains, but the extent to which NAD was decreased in infected cells was comparable to that seen in the wild-type strain. We found that NAD depletion could induce PARP1-independent cell detachment pathways following stimulation with hydrogen peroxide and that M. pneumoniae could also regulate PARP1-independent cell detachment in a cytoadhesion-dependent manner. These results suggest that M. pneumoniae might regulate infected cell detachment induced by hydrogen peroxide that it produces itself, and such a mechanism may contribute to sustaining the bacterial infection.

Activation of NLRP3 inflammasome in macrophages by mycoplasmal lipoproteins and lipopeptides

The NLRP3 inflammasome, an intracellular sensor consisting of the nucleotide-binding oligomerization domain-like receptor family, pyrin domain containing 3 (NLRP3), the adaptor protein apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC), and procaspase-1, plays critical roles in host defense against microbial pathogens by inducing production of interleukin-1β (IL-1β) and IL-18. Mycoplasma salivarium and Mycoplasma pneumoniae cells activated murine bone marrow-derived macrophages (BMMs) to induce production of IL-1α, IL-1β, and IL-18. The IL-1β production-inducing activities of these mycoplasmas toward BMMs from Toll-like receptor 2 (TLR2)-deficient mice were significantly attenuated compared with those from C57BL/6 mice (B6BMMs). This result suggests the possibility that their lipoproteins as TLR2 agonists are involved in the activity. Lipoproteins of M. salivarium and M. pneumoniae (MsLP and MpLP), and the M. salivarium-derived lipopeptide FSL-1 induced IL-1β production by B6BMMs, but not by BMMs from caspase-1-, NLRP3- or ASC-deficient mice. The activities of MsLP and MpLP were not downregulated by the proteinase K treatment, suggesting that the active sites are their N-terminal lipopeptide moieties. B6BMMs internalized the mycoplasmal N-terminal lipopeptide FSL-1 at least 30 min after incubation, FSL-1-containing endosomes started to fuse with the lysosomes around 2 hours, and then FSL-1 translocated into the cytosol from LAMP-1⁺ endosomes. The artificial delivery of FSL-1 into the cytosol of B6BMMs drastically enhanced the IL-1β production-inducing activity. FSL-1 as well as the representative NLRP3 inflammasome activator nigericin induced the NLRP3/ASC speck, but FSL-1 located in a compartment different from the NLRP3/ASC speck.

Low Bacterial Co-infection Invalidates the Early Use of Non-anti-Mycoplasma pneumoniae Antibiotics in Pediatric Refractory Mycoplasma pneumoniae Pneumonia Patients

Background: Childhood refractory mycoplasma pneumoniae (MP) pneumonia (RMPP) is a lung disease with elevated level of C-reactive protein and severe clinical and radiological deterioration. Whether bacterial co-infection contributes to disease of RMPP and whether inclusion of non-anti-MP antibiotics in treatment regimen would benefit RMPP patients remains elusive. Methods: We retrospectively reviewed the medical records of 675 RMPP children. Traditional bacterial culture and next generation sequencing (NGS) were used to detect bacteria in bronchoalveolar lavage fluid in all the 675 patients and 18 patients respectively. Antibiotics used and clinical outcomes were analyzed along with other clinical measurements. Results: Positive bacterial cultures were only found in 18 out of 675 cases (2.67%) and NGS analyses of another 18 cases did not revealed positive bacterial infection, which were consistent with the results of bacterial cultures. Non-anti-MP antibiotics were utilized in 630 cases (93.33%), even last-line antibiotics, such as glycopeptides or carbapenems, were frequently used. Conclusion: Bacterial co-infection in RMPP was rare and non-anti-MP antibiotics didn't show any efficacy for early treatment of RMPP patients, which may provide a rationale for restricting the use of non-anti-MP antibiotics in RMPP patients and preventing antibiotic resistance globally.

NLRP3 Is a Critical Regulator of Inflammation and Innate Immune Cell Response during Mycoplasma pneumoniae Infection

Mycoplasma pneumoniae is an atypical bacterial respiratory pathogen known to cause a range of airway inflammation and lung and extrapulmonary pathologies. We recently reported that an M. pneumoniae-derived ADP-ribosylating and vacuolating toxin called community-acquired respiratory distress syndrome (CARDS) toxin is capable of triggering NLRP3 (NLR-family, leucine-rich repeat protein 3) inflammasome activation and interleukin-1β (IL-1β) secretion in macrophages. However, it is unclear whether the NLRP3 inflammasome is important for the immune response during M. pneumoniae acute infection. In the current study, we utilized in vitro and in vivo models of M. pneumoniae infection to characterize the role of the NLRP3 inflammasome during acute infection. M. pneumoniae-infected macrophages deficient for inflammasome components NLRP3, ASC (apoptosis speck-like protein containing a caspase activation and recruitment domain), or caspase-1 failed to process and secrete IL-1β. The MyD88/NF-κB signaling pathway was found to be critical for proinflammatory gene expression in macrophages infected with M. pneumoniae C57BL/6 mice deficient for NLRP3 expression were unable to produce IL-1β in the airways during acute infection, and lack of this inflammatory response led to deficient immune cell activation and delayed bacterial clearance. These findings are the first to report the importance of the NLRP3 inflammasome in regulating the inflammatory response and influencing the progression of M. pneumoniae during acute infection.

ATF3 inhibits the inflammation induced by Mycoplasma pneumonia in vitro and in vivo

OBJECTIVES

Activating transcription factor-3 (ATF3) is a key regulator of inflammatory responses. We aimed to investigate the effects and mechanisms of ATF3 on the inflammatory cytokines are induced by Mycoplasma pneumonia (MP).

STUDY DESIGN

RAW264.7 and mouse peritoneal macrophages were exposed to various time with or without MP infection (3, 6, 12, 24, and 48 h), and detect the expression of ATF3. Adenovirus-expression of ATF3 (Ad/ATF3) or Ad/βgal was transfected into cells which were exposed to MP for 48 h, RT-PCR and ELISA was used to evaluate the expression and secretion of TNF-α, IL-1β, IL-6, and IL-18. In addition, intravenous administration Ad/ATF3 or Ad/βgal into the mice, the secretion of inflammatory cytokines were detected using ELISA. ChIP assay was used to determine whether ATF3 can bind to the promoter of Early growth response protein 1 (Egr-1). Western blot was used to detect the expression of Egr-1 and Fyn.

RESULTS

ATF3 was increased at 3, 6, 12, and 24 h and the highest expression levels occurs in 6 h, there is no significant differences at 24 and 48 h compared with 0 h or CON group in RAW 264.7. Similar results were seen in mouse peritoneal macrophages. Overexpression of ATF3 resulted in the reduction of inflammatory cytokines. ChIP assay revealed that ATF3 can bind to the promoter of Egr-1. Overexpression of ATF3 inhibited the protein expression of Egr-1 and Fyn; conversely, ATF3-deficiency promoted the expression of Egr-1 and Fyn. Overexpression of Egr-1 reduced the anti-inflammatory action of ATF3.

CONCLUSIONS

ATF3 inhibit the expression and release of TNF-α, IL-1β, IL-6, and IL-18 induced by MP in vitro and in vivo, which is associated with its negative regulation of Egr-1/Fyn signaling pathway.

Effects of methylprednisolone or immunoglobulin when added to standard treatment with intravenous azithromycin for refractory Mycoplasma pneumoniae pneumonia in children

BACKGROUND

The prevalence of Mycoplasma pneumoniae pneumonia has increased considerably in recent years. To evaluate the efficacy of combined treatment of azithromycin with intravenous immunoglo-bulin (IVIG) or methylprednisolone in children with refractory Mycoplasma pneumoniae pneumonia (RMPP).

METHODS

Children with RMPP were randomly allocated to group A [intravenous azithromycin (IA)+ methylprednisolone], group B (IA+IVIG) or group C (IA alone). Following a 7-day treatment, group C patients were randomly separated into two sub-groups: group C₁ (IA+methylprednisolone) and group C₂ (IA+IVIG). Temperature, respiratory symptoms and signs were examined. The average febrile period after treatment (F₂), average total febrile period (F₃), infiltration absorption, atelectasis resolution, pleural effusion disappearance were determined. The levels of C-reactive protein (CRP), D-dimer, and lactate dehydrogenase (LDH) were measured.

RESULTS

Seven days after enrollment, the average F₂ after treatment of group A was the shortest. Compared with the control group C, the combined treatment group A and B showed higher rates of infiltration absorption, atelectasis resolution and pleural effusion disappearance, while lower levels of serum CRP, D-dimer and LDH. Fourteen days after enrollment, all children with combined therapy clinically improved, and presented better laboratory results. Group C₁ showed shorter F₃ and lower levels of CRP and LDH than those of group C₂. Overall, group A showed the shortest F₃, also has the lowest CRP and LDH.

CONCLUSIONS

Azithromycin with IVIG or methylprednisolone was better treatment for children with RMPP than azithromycin alone. IVIG treatment may be beneficial, especially when the efficacy of corticosteroids is insecure, thus could be considered as an alternative of primary therapeutic approaches.

Mycoplasma pneumoniae 23S rRNA A2063G mutation does not influence chest radiography features in children with pneumonia

Objective

To measure the rate of the A2063G mutation in the Mycoplasma pneumoniae (M. pneumoniae) 23S rRNA domain V in children with pneumonia and to determine the correlation between radiographic findings and the presence of the A2063G mutation.

Methods

Patients who were hospitalized with a confirmed diagnosis of M. pneumoniae pneumonia were enrolled in this study. M. pneumoniae strains were collected for genotype analysis. Chest radiography was performed on all children prior to and following macrolide treatment. Clinical and imaging data were obtained.

Results

Of 211 patients, 195 (92.42%) harboured M. pneumoniae with the A2063G mutation. No significant differences were identified in inflammation score, chest radiography inflammation absorption grade before and after macrolide treatment, or pulmonary complications (atelectasis, hydrothorax, or pleuritis) prior to macrolide treatment when children were stratified based on the presence or absence of the A2063G mutation.

Conclusions

A high proportion of children with pneumonia harboured strains of M. pneumoniae with the A2063G mutation in the 23S rRNA domain V. However, no obvious chest radiographic features of M. pneumoniae pneumonia were associated with the A2063G variant.

Interaction of Mycoplasma hominis PG21 with Human Dendritic Cells: Interleukin-23-Inducing Mycoplasmal Lipoproteins and Inflammasome Activation of the Cell

Mycoplasma hominis lacks a cell wall, and lipoproteins anchored to the extracellular side of the plasma membrane are in direct contact with the host components. A Triton X-114 extract of M. hominis enriched with lipoproteins was shown to stimulate the production of interleukin-23 (IL-23) by human dendritic cells (hDCs). The inflammasome activation of the host cell has never been reported upon M. hominis infection. We studied here the interaction between M. hominis PG21 and hDCs by analyzing both the inflammation-inducing mycoplasmal lipoproteins and the inflammasome activation of the host cell. IL-23-inducing lipoproteins were determined using a sequential extraction strategy with two nondenaturing detergents, Sarkosyl and Triton X-114, followed by SDS-PAGE separation and mass spectrometry identification. The activation of the hDC inflammasome was assessed using PCR array and enzyme-linked immunosorbent assay (ELISA). We defined a list of 24 lipoproteins that could induce the secretion of IL-23 by hDCs, 5 with a molecular mass between 20 and 35 kDa and 19 with a molecular mass between 40 and 100 kDa. Among them, lipoprotein MHO_4720 was identified as potentially bioactive, and a synthetic lipopeptide corresponding to the N-terminal part of the lipoprotein was subsequently shown to induce IL-23 release by hDCs. Regarding the hDC innate immune response, inflammasome activation with caspase-dependent production of IL-1β was observed. After 24 h of coincubation of hDCs with M. hominis, downregulation of the NLRP3-encoding gene and of the adaptor PYCARD-encoding gene was noticed. Overall, this study provides insight into both protagonists of the interaction of M. hominis and hDCs.IMPORTANCEMycoplasma hominis is a human urogenital pathogen involved in gynecologic and opportunistic infections. M. hominis lacks a cell wall, and its membrane contains many lipoproteins that are anchored to the extracellular side of the plasma membrane. In the present study, we focused on the interaction between M. hominis and human dendritic cells and examined both sides of the interaction, the mycoplasmal lipoproteins involved in the activation of the host cell and the immune response of the cell. On the mycoplasmal side, we showed for the first time that M. hominis lipoproteins with high molecular mass were potentially bioactive. On the cell side, we reported an activation of the inflammasome, which is involved in the innate immune response.

Capsular Polysaccharide is a Main Component of Mycoplasma ovipneumoniae in the Pathogen-Induced Toll-Like Receptor-Mediated Inflammatory Responses in Sheep Airway Epithelial Cells

Mycoplasma ovipneumoniae (M. ovipneumoniae) is characterized as an etiological agent of primary atypical pneumonia that specifically infects sheep and goat. In an attempt to better understand the pathogen-host interaction between the invading M. ovipneumoniae and airway epithelial cells, we investigated the host inflammatory responses against capsular polysaccharide (designated as CPS) of M. ovipneumoniae using sheep bronchial epithelial cells cultured in an air-liquid interface (ALI) model. Results showed that CPS derived from M. ovipneumoniae could activate toll-like receptor- (TLR-) mediated inflammatory responses, along with an elevated expression of nuclear factor kappa B (NF-κB), activator protein-1 (AP-1), and interferon regulatory factor 3 (IRF3) as well as various inflammatory-associated mediators, representatively including proinflammatory cytokines, such as IL1β, TNFα, and IL8, and anti-inflammatory cytokines such as IL10 and TGFβ of TLR signaling cascade. Mechanistically, the CPS-induced inflammation was TLR initiated and was mediated by activations of both MyD88-dependent and MyD88-independent signaling pathways. Of importance, a blockage of CPS with specific antibody led a significant reduction of M. ovipneumoniae-induced inflammatory responses in sheep bronchial epithelial cells. These results suggested that CPS is a key virulent component of M. ovipneumoniae, which may play a crucial role in the inflammatory response induced by M. ovipneumoniae infections.

Acute respiratory distress syndrome caused by Mycoplasma pneumoniae without elevated pulmonary vascular permeability: a case report

Sporadic patients with acute respiratory distress syndrome (ARDS) caused by Mycoplasma pneumoniae have been reported. However, knowledge about the pathophysiology and pharmacological treatment of this condition is insufficient. Moreover, the pulmonary vascular permeability in ARDS related to M. pneumoniae infection has not been reported. We report a case of ARDS caused by Mycoplasma pneumoniae without elevated pulmonary vascular permeability, which was successfully treated using low-dose short-term hydrocortisone, suggesting that pulmonary infiltration in ARDS caused by Mycoplasma pneumoniae does not match the criteria of permeability edema observed in typical ARDS.

Inflammation-inducing Factors of Mycoplasma pneumoniae

Mycoplasma pneumoniae, which causes mycoplasmal pneumonia in human, mainly causes pneumonia in children, although it occasionally causes disease in infants and geriatrics. Some pathogenic factors produced by M. pneumoniae, such as hydrogen peroxide and Community-Acquired Respiratory Distress Syndrome (CARDS) toxin have been well studied. However, these factors alone cannot explain this predilection. The low incidence rate of mycoplasmal pneumonia in infants and geriatrics implies that the strong inflammatory responses induced by M. pneumoniae coordinate with the pathogenic factors to induce pneumonia. However, M. pneumoniae lacks a cell wall and does not possess an inflammation-inducing endotoxin, such as lipopolysaccharide (LPS). In M. pneumoniae, lipoproteins were identified as an inflammation-inducing factor. Lipoproteins induce inflammatory responses through Toll-like receptors (TLR) 2. Because Mycoplasma species lack a cell wall and lipoproteins anchored in the membrane are exposed, lipoproteins and TLR2 have been thought to be important for the pathogenesis of M. pneumoniae. However, recent reports suggest that M. pneumoniae also induces inflammatory responses also in a TLR2-independent manner. TLR4 and autophagy are involved in this TLR2-independent inflammation. In addition, the CARDS toxin or M. pneumoniae cytadherence induces inflammatory responses through an intracellular receptor protein complex called the inflammasome. In this review, the inflammation-inducing factors of M. pneumoniae are summarized.

Activation of inflammasomes in dendritic cells and macrophages by Mycoplasma salivarium

Interleukin-1β (IL-1β) plays crucial roles in the pathogenesis of periodontal disease. It is produced after the processing of pro-IL-1β by caspase-1, which is activated by the inflammasome-a multiprotein complex comprising nucleotide-binding domain leucine-rich repeat-containing receptor (NLR), the adaptor protein apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC), and procaspase-1. Mycoplasma salivarium preferentially inhabits the gingival sulcus and the incidence and number of organisms in the oral cavity increase significantly with the progression of periodontal disease. To initially clarify the association of this organism with periodontal diseases, this study determined whether it induces IL-1β production by innate immune cells such as dendritic cells or macrophages by using Mycoplasma pneumoniae as a positive control. Both live and heat-killed M. salivarium and M. pneumoniae cells induced IL-1β production by XS106 murine dendritic cells as well as pyroptosis. The activities were significantly downregulated by silencing of caspase-1. Bone-marrow-derived macrophage (BMMs) from wild-type and NLR-containing protein 3 (NLRP3)-, ASC-, and caspase-1-deficient mice were examined for IL-1β production in response to these mycoplasmas. Live M. salivarium and M. pneumoniae cells almost completely lost the ability to induce IL-1β production by BMMs from ASC- and caspase-1-deficient mice. Their activities toward BMMs from NLRP3-deficient mice were significantly but not completely attenuated. These results suggest that live M. salivarium and M. pneumoniae cells can activate several types of inflammasomes including the NLRP3 inflammasome. Both M. salivarium and M. pneumoniae cells can activate THP-1 human monocytic cells to induce IL-1β production. Hence, the present finding that M. salivarium induces IL-1β production by dendritic cells and macrophages may suggest the association of this organism with periodontal diseases.

Setting a standard for the initiation of steroid therapy in refractory or severe Mycoplasma pneumoniae pneumonia in adolescents and adults

Serum interleukin (IL)-18 level was thought to be a useful as a predictor of refractory or severe Mycoplasma pneumoniae pneumonia, and steroid administration is reported to be effective in this situation. The serum levels of IL-18 correlated significantly with those of lactate dehydrogenase (LDH). The purpose of this study was to set a standard for the initiation of steroid therapy in M. pneumoniae pneumonia using a simple serum marker. We analyzed 41 adolescent and adult patients with refractory or severe M. pneumoniae pneumonia who received steroid therapy, and compared them with 108 patients with M. pneumoniae pneumonia who responded to treatment promptly (control group). Serum LDH levels were significantly higher in the refractory and severe group than in the control group at the initiation of steroid therapy (723 vs 210 IU/L, respectively; p < 0.0001). From receiver operating characteristic curve analysis, we calculated serum LDH cut-off levels of 364 IU/L at initiation of steroid therapy and 302 IU/L at 1-3 days before the initiation of steroid therapy. The administration of steroids to patients in the refractory and severe group resulted in the rapid improvement of symptoms and a decrease in serum LDH levels in all patients. Serum LDH level can be used as a useful parameter to determine the initiation of steroid therapy in refractory or severe M. pneumoniae pneumonia. A serum LDH level of 302-364 IU/L seems to be an appropriate criterion for the initiation of steroid therapy.

Effect of Ureaplasma parvum co-incubation on Chlamydia trachomatis maturation in human epithelial HeLa cells treated with interferon-γ

Chlamydia trachomatis is an obligate intracellular bacterium that causes a sexually transmitted disease. Ureaplasma parvum is commensal in the human genital tract, with a minimal contribution to urogenital infection. We have recently found that U. parvum has a significant effect on the presence of C. trachomatis in the genital tract of healthy women. We therefore assessed the effect of U. parvum co-incubation on C. trachomatis maturation from reticulate bodies (RBs) to elementary bodies (EBs) in HeLa cells in the absence or presence of interferon (IFN)-γ, which is a critical host defense factor. IFN-γ stimulation of viable U. parvum significantly prompted chlamydial growth with an increase in infectious particles, EBs, in HeLa cells. IFN-γ treatment of killed U. parvum had a similar effect on C. trachomatis maturation in HeLa cells. There was no change in expression of indoleamine 2,3-dioxygenase (IDO) in cultures of viable or killed U. parvum. We concluded that U. parvum co-incubation by IFN-γ helped C. trachomatis to mature from RBs to EBs in HeLa cells, independent of IDO expression. This suggests a novel survival strategy of C. trachomatis against IFN-γ exposure, prompting secondary infection of the genital mucosa, with possible clinical implications.

Cytadherence of Mycoplasma pneumoniae induces inflammatory responses through autophagy and toll-like receptor 4

Mycoplasma pneumoniae causes pneumonia, tracheobronchitis, pharyngitis, and asthma in humans. The pathogenesis of M. pneumoniae infection is attributed to excessive immune responses. We previously demonstrated that M. pneumoniae lipoproteins induced inflammatory responses through Toll-like receptor 2 (TLR2). In the present study, we demonstrated that M. pneumoniae induced strong inflammatory responses in macrophages derived from TLR2 knockout (KO) mice. Cytokine production in TLR2 KO macrophages was increased compared with that in the macrophages of wild-type (WT) mice. Heat-killed, antibiotic-treated, and overgrown M. pneumoniae failed to induce inflammatory responses in TLR2 KO macrophages. 3-Methyladenine and chloroquine, inhibitors of autophagy, decreased the induction of inflammatory responses in TLR2 KO macrophages. These inflammatory responses were also inhibited in macrophages treated with the TLR4 inhibitor VIPER and those obtained from TLR2 and TLR4 (TLR2/4) double-KO mice. Two mutants that lacked the ability to induce inflammatory responses in TLR2 KO macrophages were obtained by transposon mutagenesis. The transposons were inserted in atpC encoding an ATP synthase F0F1 ε subunit and F10_orf750 encoding hypothetical protein MPN333. These mutants showed deficiencies in cytadherence. These results suggest that cytadherence of M. pneumoniae induces inflammatory responses through TLR4 and autophagy.

Effects of Methylprednisolone Pulse Therapy on Refractory Mycoplasma pneumoniae Pneumonia in Children

Purpose

Mycoplasma pneumoniae (M. pneumoniae) is one of the most common causes of community-acquired pneumonia in children. The clinical course is typically self-limited and benign; however, rare cases of severe pneumonia can develop despite appropriate antibiotic therapy. We studied the effects of methylprednisolone pulse therapy on severe refractory M. pneumoniae pneumonia in children.

Methods

The clinical effects of methylprednisolone therapy were evaluated retrospectively in 12 children with severe refractory M. pneumoniae pneumonia, which was diagnosed serologically. All patients developed respiratory distress, high fever, and initial lobar pneumonic consolidation based on radiological findings. All clinical symptoms deteriorated despite appropriate antibiotic therapy. Thus, children were treated with intravenous methylprednisolone pulse therapy in addition to antibiotics.

Results

The average febrile period before admission was 4.9±1.7 days, and fever persisted in all children until steroid administration. Methylprednisolone pulse therapy (30 mg/kg) was given 5.4±2.5 days after admission. After methylprednisolone pulse therapy, clinical symptoms improved in all patients without adverse events. The fever subsided 0-2 h after initiation of corticosteroid therapy. The abnormal radiological findings resolved within 2.6±1.3 days, and the high C-reactive protein levels (6.7±5.9 mg/dL) on admission decreased to 1.3±1.7 mg/dL within 3.0±1.1 days after starting corticosteroid therapy.

Conclusions

Three-day methylprednisolone pulse therapy could be applied to treatment of refractory M. pneumoniae pneumonia despite appropriate antibiotic therapy and appeared to be efficacious and well-tolerated.

Soluble B7-H3 elevations in hospitalized children with Mycoplasma pneumoniae pneumonia

The purpose of this study is to explore the associations between soluble B7-H3 (sB7-H3) and cytokines, clinical characteristics and laboratory findings. Thirty-two children with Mycoplasma pneumoniae pneumonia diagnosed by both positive serology and PCR were admitted to Children's Hospital affiliated to Soochow University. These children were enrolled and evaluated from May 2012 through September 2012. Soluble B7-H3 level and cytokines (tumor necrosis factor-α (TNF-α), interferon-γ, interleukin (IL)-4, IL-10) were determined by enzyme-linked immunosorbent assay technique. Meanwhile, clinical parameters including laboratory findings were obtained. Soluble B7-H3 level was significantly increased in patients with M. pneumoniae pneumonia compared with the levels of sB7-H3 in control subjects (4.94 ± 2.69 vs. 3.42 ± 1.48, ng/mL; P = 0.032). Furthermore, level of sB7-H3 was correlated with TNF-α level in plasma in patients with M. pneumoniae pneumonia (rp = 0.667; P < 0.001) as well as level of sB7-H3 in M. pneumoniae pneumonia subjects was also correlated with duration of symptoms (rp = 0.607; P < 0.001), percentage of neutrophil cells (rp = 0.657; P < 0.001), and C-reactive protein level (rs = 0.445; P = 0.011). Level of sB7-H3 was decreased after treatment (6.08 ± 3.07 vs. 3.55 ± 1.58, ng/mL; P = 0.019). Soluble B7-H3 maybe plays an important role in immunopathogenesis of M. pneumoniae pneumonia, especially for increasing TNF-α concentration and activation neutrophils.

Mycoplasma pneumoniae pneumonia in children

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.

In Mycoplasma hominis the OppA-mediated cytoadhesion depends on its ATPase activity

Background

In Mycoplasma hominis, a facultative human pathogen of the human genital tract, OppA, the substrate-binding domain of the oligopeptide permease, is a multifunctional protein involved in nutrition uptake, cytoadhesion and hydrolysis of extracellular ATP.

Results

To map the function-related protein regions the ATPase activity and adhesive behavior of OppA mutants were analyzed. Mutations of the Walker BA motifs resulted in an inhibition of up to 8% of the OppA ATPase activity, whereas deletion of the N-terminal CS1 or the CS2 region, structural motifs that are conserved in bacterial OppA proteins, reduced ATPase activity to 60% and deletion of CS3, the third conserved region adjacent to the Walker B motif led to a reduction to 42% ATPase activity.

Interestingly, adhesion of the OppA mutants to immobilized HeLa cells demonstrated that two distal regions are mainly involved in adherence of OppA: the CS1 region, deletion of which led to 35% of the cytoadhesion, and the Walker BA with the adjacent upstream region CS3, deletion of which led to 25% of the cytoadhesion. The influence of the ATPase activity on the adherence of M. hominis to HeLa cells was confirmed by the use of ATPase inhibitors which reduced mycoplasmal cytoadhesion to 50%.

Conclusions

These findings suggest that the OppA-mediated cytoadherence of Mycoplasma hominis depends on both, the topology of the neighbouring CS1 and ATPase domain regions and the functionality of the ecto-ATPase activity in addition.