Expert consensus on the diagnosis and treatment of macrolide-resistant Mycoplasma pneumoniae pneumonia in children

Background Mycoplasma pneumoniae(M.pneumoniae)is a significant contributor to community-acquired pneumonia among children.Since 1968,when a strain of M.pneumoniae resistant to macrolide antibiotics was initially reported in Japan,macrolide-resistant M.pneumoniae(MRMP)has been documented in many countries worldwide,with varying incidence rates.MRMP infections lead to a poor response to macrolide antibiotics,frequently resulting in prolonged fever,extended antibiotic treatment,increased hospitalization,intensive care unit admissions,and a significantly higher proportion of patients receiving glucocorticoids or second-line antibiotics.Since 2000,the global incidence of MRMP has gradually increased,especially in East Asia,which has posed a serious challenge to the treatment of M.pneumoniae infections in children and attracted widespread attention from pediatricians.However,there is still no global consensus on the diagnosis and treatment of MRMP in children.Methods We organized 29 Chinese experts majoring in pediatric pulmonology and epidemiology to write the world’s first consensus on the diagnosis and treatment of pediatric MRMP pneumonia,based on evidence collection.The evidence searches and reviews were conducted using electronic databases,including PubMed,Embase,Web of Science,CNKI,Medline,and the Cochrane Library.We used variations in terms for“macrolide-resistant”,“Mycoplasma pneumoniae”,“MP”,“M.pneumoniae”,“pneumonia”,“MRMP”,“lower respiratory tract infection”,“Mycoplasma pneumoniae infection”,“children”,and“pediatric”.Results Epidemiology,pathogenesis,clinical manifestations,early identification,laboratory examination,principles of antibiotic use,application of glucocorticoids and intravenous immunoglobulin,and precautions for bronchoscopy are highlighted.Early and rapid identification of gene mutations associated with MRMP is now available by polymerase chain reaction and fluorescent probe techniques in respiratory specimens.Although the resistance rate to macrolide remains high,it is fortunate that M.pneumoniae still maintains good in vitro sensitivity to second-line antibiotics such as tetracyclines and quinolones,making them an effective treatment option for patients with initial treatment failure caused by macrolide antibiotics.Conclusions This consensus,based on international and national scientific evidence,provides scientific guidance for the diagnosis and treatment of MRMP in children.Further studies on tetracycline and quinolone drugs in children are urgently needed to evaluate their effects on the growth and development.Additionally,developing an antibiotic rotation treatment strategy is necessary to reduce the prevalence of MRMP strains.

Chinese herbal medicine combined with Western medicine for Mycoplasma pneumoniae pneumonia in children:An overview of systematic reviews

Objective:To summarize the characteristics and evaluate the quality of the methodology and evidence within systematic reviews(SRs)of Chinese herbal medicine(CHM)for Mycoplasma pneumoniae pneumonia(MPP)inchildren.Methods:SRs of randomized controlled trials were searched using PubMed,the Cochrane Library,Embase,the Chinese National Knowledge Infrastructure Databases(CNKI),the Chinese Scientific Journals Database(VIP),Wanfang,and the SinoMed Database.SRs on the use of CHM alone or in combination with Western medications for MPP in children were included.The study compared the effects of Western medicine alone with those of CHM.The evidence quality using the A Measurement Tool to Assess Systematic Reviews(AMSTAR)2,the Preferred Reporting Items for Systematic Reviews and Meta-Analyses(PRISMA)2020,and the Grading of Recommendations,Assessment,Development,and Evaluation(GRADE)criteria.The primary indicators were the total effective rate,fever subsidence time,and cough disappearance time.The secondary outcomes were pulmonary rale disappearance time,average hospitalization time,lung X-ray infiltrate disappearance time,immunological indices,and inflammatory cytokine levels.Results:Twelve relevant SRs were included;75%(9/12)were assessed as very low quality,and 25%(3/12)Were rated as low quality using the AMSTAR 2 criteria.According to the PRISMA 2020 checklist,the average SR score was 20.3 out of a 27 point maximum.In all SRs,CHM demonstrated improvement in symptoms and signs among children with MPP.The evidence quality using the GRADE criteria ranged from"very low"(>50%)to"moderate"(<5%).The most common downgrading factor was imprecision,followed by publication bias and inconsistency.Conclusion:This overview highlights the limited quality of the methodology and evidence of the included SRs.Although the included studies showed the beneficial effects of CHM on MPP in children,it was difficult to draw firm conclusions owing to methodological flaws.

Serum inflammatory markers in children with Mycoplasma pneumoniae pneumonia and their predictive value for mycoplasma severity

BACKGROUND Mycoplasma pneumoniae pneumonia(MPP)significantly impacts pediatric health,necessitating markers for early severe disease identification.AIM To investigate the correlation between serum inflammatory marker and the severity of MPP in children.METHODS A prospective study was carried out from January 2023 to November 2023.A total of 160 children with MPP who underwent treatment were selected:80 had severe MPP and 80 had mild MPP.Clinical and laboratory data were collected at the time of hospital admission and during hospitalization.Receiver operating characteristic curves were utilized to assess the diagnostic and prognostic for severe MPP.RESULTS Fever duration and length of hospitalization in pediatric patients with severe MPP exceeded those with mild MPP.The incidence of pleural effusion,lung consolidation,and bronchopneumonia on imaging was markedly elevated in the severe MPP cohort compared to the mild MPP cohort.In contrast to the mild cohort,there was a notable increase in C-reactive protein(CRP),procalcitonin(PCT),erythrocyte sedimentation rate,lactic dehydrogenase,D-dimer,and inflammatory cytokines[interleukin(IL)-6,IL-8,IL-10 and tumor necrosis factor(TNF)-α]in the severe MPP group were significantly higher.CONCLUSION Serum inflammatory markers(CRP,PCT,IL-6,D-dimer,IL-10 and TNF-α)were considered as predictors in children with severe MPP.

Evaluating the role of interleukin-2 and interleukin-12 in pediatric patients with concurrent Mycoplasma pneumoniae and Epstein-Barr virus infections

BACKGROUND Mycoplasma pneumoniae(MP)frequently causes respiratory infections in children,whereas Epstein-Barr virus(EBV)typically presents subclinical manifestations in immunocompetent pediatric populations.The incidence of MP and EBV coinfections is often overlooked clinically,with the contributory role of EBV in pulmonary infections alongside MP remaining unclear.AIM To evaluate the serum concentrations of interleukin-2(IL-2)and interleukin-12(IL-12)in pediatric patients with MP pneumonia co-infected with EBV and assess their prognostic implications.METHODS We retrospectively analyzed clinical data from patients diagnosed with MP and EBV co-infection,isolated MP infection,and a control group of healthy children,spanning from January 1,2018 to December 31,2021.Serum IL-2 and IL-12 levels were quantified using enzyme-linked immunosorbent assay.Logistic regression was employed to identify factors influencing poor prognosis,while receiver operating characteristic(ROC)curves evaluated the prognostic utility of serum IL-2 and IL-12 levels in co-infected patients.RESULTS The co-infection group exhibited elevated serum IL-2 and C-reactive protein(CRP)levels compared to both the MP-only and control groups,with a reverse trend observed for IL-12(P<0.05).In the poor prognosis cohort,elevated CRP and IL-2 levels,alongside prolonged fever duration,contrasted with reduced IL-12 levels(P<0.05).Logistic regression identified elevated IL-2 as an independent risk factor and high IL-12 as a protective factor for adverse outcomes(P<0.05).ROC analysis indicated that the area under the curves for IL-2,IL-12,and their combination in predicting poor prognosis were 0.815,0.895,and 0.915,respectively.CONCLUSION Elevated serum IL-2 and diminished IL-12 levels in pediatric patients with MP and EBV co-infection correlate with poorer prognosis,with combined IL-2 and IL-12 levels offering enhanced predictive accuracy.

Understanding serum inflammatory markers in pediatric Mycoplasma pneumoniae pneumonia

This editorial reflects on the research,which investigates the potential of serum markers to predict the severity of Mycoplasma pneumoniae infections.Mycoplasma pneumoniae pneumonia(MPP)is a prevalent cause of respiratory infections in children,often leading to significant morbidity.Predicting the severity of MPP can significantly enhance patient management and outcomes.This editorial reviews the role of specific laboratory markers:(1)Lactate dehydrogenase;(2)Interleukin(IL)-6;(3)IL-10;(4)Tumor necrosis factor-α;and(5)D-dimer in predicting the severity of MPP in pediatric patients.Elevated levels of these markers are strongly associated with severe cases of MPP,providing clinicians with valuable tools for early diagnosis and targeted intervention.

Analysis of the Role of D-Dimer,Interleukin-6,and Interleukin-18 in Differential Diagnosis of Pediatric Refractory Mycoplasma pneumoniae Pneumonia

Objective:To analyze the value of D-dimer(D-D),interleukin-6(IL-6),and IL-18 in the differential diagnosis of children with refractory Mycoplasma pneumoniae pneumonia(RMPP).Methods:The medical records of 92 children with Mycoplasma pneumoniae pneumonia(MPP)treated in the hospital were selected for retrospective analysis from January 2023 to January 2024.After comprehensive examinations such as computed tomography examination of the chest,48 children with general Mycoplasma pneumoniae pneumonia(GMPP)were put in the GMPP group and 44 children with RMPP were grouped in the RMPP group.The IL-6,IL-18,and D-D levels were compared between the two groups,and the receiver operating characteristic(ROC)curves were plotted to analyze their value for differential diagnosis of RMPP.Results:The levels of IL-6,IL-18,and D-D in the RMPP group were higher than those in the GMPP group(P<0.05);the ROC curves showed that the specificity of the differential diagnosis of IL-6,IL-18,and D-D was higher,and their diagnostic value was significant.Conclusion:Determination of IL-6,IL-18,and D-D levels in children with MPP can further diagnose the children’s condition,which can help physicians formulate targeted treatment plans,and is of great significance to the improvement of the children’s condition,which is worthy of attention.

Research Progress on Combined Chinese and Western Medicine Treatment of Mycoplasma pneumoniae Pneumonia in Children

With the continuous development of medical technology,combined treatment of Chinese and Western medicine has gradually become a research hotspot.As a common disease in pediatrics,the treatment of Mycoplasma pneumoniae pneumonia(MPP)in children is also being explored and improved.This article summarizes the research progress of combined Chinese and Western medicine treatment of MPP in children in recent years,aiming to provide a useful reference for the combined treatment of MPP in children.The article firstly introduces the etiology and pathogenesis of MPP in children,thereafter briefly introduces the Western anti-infective treatment and traditional Chinese medicine(TCM)diagnosis and treatment of MPP in children,and lastly introduces the methods of combined treatment of TCM and Western medicine in detail.The article points out that the combination of Chinese and Western medicine can give full play to the overall regulation of Chinese medicine and the precise treatment advantages of Western medicine,improve the therapeutic effect,reduce the use of antibiotics,and lower the recurrence rate of the disease,which is worthy of further research and promotion.

The Predictive Value of NLR, IL-6, CRP, and PCT in Mycoplasmal Pneumonia with Complicated Myocardial Injury

Objective:To evaluate the dynamic changes in neutrophil-to-lymphocyte ratio(NLR),interleukin-6(IL-6),C-reactive protein(CRP),and procalcitonin(PCT)levels in children with Mycoplasma pneumoniae pneumonia(MPP)complicated by myocardial injury and to determine their predictive value both individually and in combination.Methods:150 children diagnosed with MPP at Jiujiang Maternal and Child Health Hospital between June 2023 and June 2024 were selected.Patients were divided into the myocardial damage group(MD group,n=65)and the non-myocardial damage group(non-MD group,n=85),based on the presence of myocardial injury.Ninety hospitalized children without MPP served as the control group(Con group).Myocardial enzyme profile indicators,including lactate dehydrogenase(LDH),α-hydroxybutyrate dehydrogenase(α-HBDH),aspartate aminotransferase(AST),high-sensitivity cardiac troponin I(hs-cTnI),creatine kinase(CK),and creatine kinase-MB(CK-MB),were measured using a chemiluminescent immunoassay analyzer.Serum NLR,IL-6,CRP,and PCT levels were determined using appropriate analyzers.The correlation between these markers and myocardial enzyme indicators was analyzed using Spearman correlation analysis.Multivariate logistic regression was applied to identify risk factors for myocardial injury in MPP patients.Results:Serum levels of NLR,IL-6,CRP,and PCT in the MD and non-MD groups were significantly higher than in the Con group(P<0.05),with the MD group showing higher levels than the non-MD group(P<0.05).These markers were positively correlated with myocardial enzyme indicators.Logistic regression identified elevated NLR,IL-6,CRP,PCT,LDH,α-HBDH,AST,hs-cTnI,CK,and CK-MB as risk factors for myocardial injury in MPP patients(P<0.05).Conclusion:Elevated levels of NLR,IL-6,CRP,PCT,and myocardial enzymes are significant risk factors for myocardial injury in children with MPP,offering valuable insights for prevention and prognosis.

Clinical characteristics of community-acquired pneumonia in children caused by mycoplasma pneumoniae with or without myocardial damage:A single-center retrospective study

BACKGROUND Mycoplasma pneumoniae(MP)is a prevalent pathogen that causes respiratory infections in children and adolescents.AIM To assess the differences in the clinical features of MP-associated communityacquired pneumonia(CAP)in children who presented with mild or severe mycoplasma pneumoniae pneumonia(MPP);to identify the incidence of myocardial damage between the two groups.METHODS This work is a retrospective study.We identified children between 2 mo and 16 years of age with clinical and radiological findings consistent with CAP.We admitted patients to the inpatient department of the Second Hospital of Jilin University,Changchun,China,from January 2019 to December 2019.RESULTS A total of 409 hospitalized patients were diagnosed with MPP.Among them were 214(52.3%)males and 195(47.7%)females.The duration of fever and cough was the longest in severe MPP cases.Similarly,plasma levels of highly sensitive Creactive protein(t=-2.834,P<0.05),alanine transaminase(t=-2.511,P<0.05),aspartate aminotransferase(t=-2.939,P<0.05),and lactate dehydrogenase(LDH)(t=-2.939,P<0.05)were all elevated in severe MPP cases compared with mild MPP cases,and these elevations were statistically significant(P<0.05).Conversely,the neutrophil percentage was significantly lower in severe MPP cases than in mild MPP cases.The incidence of myocardial damage was significantly higher in severe MPP cases than in mild MPP cases(χ^(2)=157.078,P<0.05).CONCLUSION Mycoplasma pneumoniae is the main cause of CAP.The incidence of myocardial damage was higher and statistically significant in severe MPP cases than in mild MPP cases.

Advances in the Detection of Mycoplasma hyopneumoniae by Polymerase Chain Reaction (PCR) Technology

Mycoplasma hyopneumoniae is an important pathogen causing Mycoplasmal pneumonia of swine, which generally causes secondary infections and mixed infections, thus seriously threats the development of swine industry and resulting in huge economic losses. Using PCR technology has very important significance to the correct diagnosis of Mycoplasmal pneumonia at the early stage. In this paper, specific target genes of Mycoplasma hyopneumoniae, methods for clinical sample collection, key technical factors of DNA sample processing method, and the research progress, main advantages and disadvantages, and application of general PCR technology, multiple PCR technology, nested-PCR technology, real-time fluorescence quantitative PCR technology, gene chip detection technology and loop-mediated isothermal amplification in detection of Mycoplasma hyopneumoniae were summarized, which provided convenience for the effective diagnosis and prevention of Mycoplasmal pneumonia of swine.

Comparative Analysis for the Detection and Monitoring of Mycoplasma hyopneumoniae Infection by Nested PCR(n-PCR) and Real time PCR(q-PCR) from Field Swine Herds

[Objective] 303 nasal swabs samples were collected from pigs in farms located in Taizhou city, Jiangsu Province, China from March to December 2012 for the purpose of detecting the presence of Mycoplasma hyopneumoniae, the primary agent of Enzootic porcine pneumonia （EPP） in pig herds using the nested PCR and Real time PCR techniques. [Method] Nasal swabs were collected from pigs of different ages＇ i.e. 7, 14, 21, 28, 30 and 35 days old, soaked in sterile 1 xPBS overnight at 4 ℃ and DNA extracted using the TIANamp（R） bacterial DNA kit. The DNA samples underwent amplification under the Mhyo 183 q-PCR and P36 primer Nested PCR systems. [Result] With the Nested PCR assay, 38 （12.5%） out of 303 samples tested positive for the presence of M. hyopneumoniae; with the real time PCR assay 152 （50.2%） tested positive for M. hyopneumoniae. The two assays matched to positively detect Mhyo in 22 （7.3%） samples and again matched in 127 （41.9%） samples negative for Mhyo infection. The pattern of infection in both assays was similar where 7- and 35-day-old piglets in both assays had the highest rates of infection i.e. 15.6% and 18.4% for n-PCR and 53.1% and 56.6% for q-PCR for 7- and 35-day-old piglets respectively. [Conclusion] The results highlight the suitability of both PCR assays in establishing the herd infection status of pigs in field conditions.

The Effect of Azithromycin in Treating Mycoplasma Pneumonia in Children

Objective:To discuss and analyze the effect of azithromycin in the treatment of mycoplasma pneumonia in children.Methods:A total of 120 children with mycoplasma pneumonia who were admitted to the Department of Pediatrics of our hospital from January 2022 to December 2022 were selected as the research subjects.They were divided into an azithromycin group and a reference group according to the random number drawing method,with 60 cases in each group.The azithromycin group was treated with azithromycin,and the reference group was treated with conventional treatment.The efficacy of treatment,laboratory indicators,platelet count and D-dimer,and adverse reactions of both groups were compared.Results:The efficacy of the azithromycin group was significantly higher than that of the reference group(P<0.05).Before treatment,there were no significant differences in the laboratory indicators like ferritin,procalcitonin(PCT),and erythrocyte sedimentation rate(ESR)between the two groups(P>0.05);after treatment,the laboratory indicators of the azithromycin group were significantly better than those of the reference group(P<0.05).Before treatment,there was no statistically significant difference in platelet count and D-dimer between the groups(P>0.05);after medication,the platelet count,and D-dimer in the azithromycin group were significantly better than those in the reference group(P<0.05).The total incidence of adverse reactions in the azithromycin group was significantly lower than that in the reference group(P<0.05).Conclusion:Azithromycin is more effective in treating mycoplasma pneumonia in children,and has certain clinical value.

Evaluation of a New Real-time PCR Assay for Detection of Mycoplasma Pneumoniae in Clinical Specimens

Objective To establish and evaluate a real-time PCR assay to detect Mycoplasma pneumoniae （M.pneumoniae） in clinical specimens. Methods By analysing the whole pl gene sequence of 60 M.pneurnoniae clinical isolates in Beijing of China, an optimized real-time PCR assay （MpP1） using pl gene conserved region was designed. The specificity and sensitivity of this assay were evaluated and compared with other two reported assays （RepMpl and Mp181） using 40 positive and 100 negative clinical specimens. Results The detection limit of the new assay was 8.1 fg （about 1-3CFU） M.pneumoniae DNA. The sensitivity of MpP1, RepMpl, and Mp181 assays appeared to be 100%, 100%, and 85%, respectively. Conclusion MpP1 assay is suitable for the detection of M.pneumoniae in Chinese clinical specimens.

Correlation Between the Clinical Severity, Bacterial Load, and Inflammatory Reaction in Children with Mycoplasma Pneumoniae Pneumonia

Given the lack of defining features in the clinical manifestations and radiographic findings for children with mycoplasma pneumoniae pneumonia(MPP),quantitative polymerase chain reaction(qPCR)has become a useful diagnostic method.This study was performed to explore the relationship between the qPCR findings,clinical symptoms,and inflammatory markers in children with MPP.Four hundred children with MPP have been enrolled in this retrospective analysis.All clinical and analytical information,including mycoplasma pneumoniae(MP)PCR results,has been collected.Based on the PCR results,the patients were divided into groups with load values(copy number)<105(54 cases),2105 and<106(71 cases),2106 and<107(112 cases),>107 and<108(114 cases),and>108(49 cases).The clinical features(including symptoms and signs)and inflammatory indicators were compared among the groups.The incidence of high fever(above 39℃),thermal peak during the entire hospitalization period,fever duration,days of hospitalization,and plasma lactate dehydrogenase(LDH)levels were statistically correlated with the MP PCR load value in children with MPP.The analysis of relevance degree showed the correlative order as a thermal peak of hospitalization>duration of fever>period of hospitalization>LDH value>C-reactive protein value.The host immune response was significantly greater in the complication group than in the non-complication group.

Mycoplasma pneumoniae Macrolide Resistance and MLVA Typing in Children in Beijing,China,in 2016:Is It Relevant?

Objective The aim of this study is to investigate the macrolide resistance rate and molecular type with multiple-locus variable-number tandem-repeat analysis(MLVA)of Mycoplasma pneumoniae of Beijing in 2016 in pediatric patients.Methods Real-time quantitative polymerase chain reaction(PCR)was used to identify M.pneumoniae,and MLVA was performed.The domain V of the 23 S rRNA was sequenced to detect macrolide-resistant point mutations.We also investigated the activities of antibiotics against M.pneumoniae isolates in vitro.Results The PCR detection rate of M.pneumoniae in children in Beijing was 40%,and the macrolide resistance rate was 66%.The A2063 G mutation in the 23 S rRNA V region is the dominant mutation(137/146,93.84%),whereas the A2064 G mutation is rare(9/146,6.16%).Seventy-three samples were typed successfully by MLVA typing,including 86.3%(63/73)were MLVA type 4-5-7-2,and 13.7%(10/73)were MLVA type 3-5-6-2.No other types were found.No strains were resistant to levofloxacin or tetracycline.Conclusion In 2016,a specific decrease in the macrolide resistance rate occurred in Beijing.The detection rate and macrolide resistance rate of outpatients are lower than those of inpatients.The A2063 G mutants M.pneumoniae have high levels of resistance to erythromycin and azithromycin.The primary MLVA type is 4-5-7-2,followed by 3-5-6-2.No other MLVA types were detected.No strains resistant to tetracycline or levofloxacin were found in vitro.

Using 16S rDNA Sequencing Technology to Preliminarily Analyze Intestinal Flora in Children with Mycoplasma pneumoniae Pneumonia

Objective We investigated changes in the intestinal flora of children with Mycoplasma pneumoniae pneumonia(MPP).Methods Between September 2019 and November 2019,stool samples from 14 children with MPP from The Fourth Hospital of Baotou city,Inner Mongolia Autonomous Region,were collected and divided into general treatment(AF)and probiotic(AFY)groups,according to the treatment of“combined Bifidobacterium,Lactobacillus,Enterococcus,and Bacillus cereus tablets live”.Highthroughput 16S rDNA sequencing was used to identify intestinal flora.Results Intestinal flora abundance and diversity in children with MPP were decreased.Both Shannon and Simpson indices were lower in the AF group when compared with healthy controls(P<.05).When compared with healthy controls,the proportion of Enterorhabdus was lower in the AF group,while the proportion of Lachnoclostridium was higher(P<0.05).The proportion of Bifidobacteria and Akkermansia was lower in the AFY group but Enterococcus,Lachnoclostridium,Roseburia,and Erysipelatoclostridium proportions were higher.The proportion of Escherichia coli-Shigella in the AFY group after treatment was decreased(P<0.05).Conclusions The intestinal flora of children with MPP is disturbed,manifested as decreased abundance and diversity,and decreased Bifidobacteria.Our probiotic mixture partly improved intestinal flora disorders.

Establishment of a Predictive Diagnostic Model for Acute Mycoplasma Pneumoniae Infection in Elderly Patients with Community-acquired Pneumonia

We established a diagnostic model to predict acute Mycoplasma pneumoniae （M. pneumonia） infection in elderly Community-acquired pneumonia （CAP） patients. We divided 456 patients into acute and non-acute M. pneumoniae infection groups. Binary logistic regression and receiver operating characteristic （ROC） curves were used to establish a predictive model. The following independent factors were identified： age 〉 70 years; serum cTNT level 〉 0.0S ng/mL; lobar consolidation; mediastinal lymphadenopathy; and antibody titer in the acute phase 〉 1：40. The area under the ROC curve of the model was 0.923 and a score of 2 7 score predicted acute M. pneumoniae infection in elderly patients with CAP. The predictive model developed in this study has high diagnostic accuracy for the identification of elderly acute M. pneumoniae infection.

The Expression of PDGF-B Chain mRNA in Lung Tissue from Rats Repeatedly Infected with Mycoplasma Pneumoniae

In order to investigate the role played by platelet derived growth factor-BB (PDGF-BB) in the pathogenesis of pulmonary interstitial fibrosis in rats repeatedly infected with mycoplasma pneumoniae (MP), a rat MP infection model was developed by infecting rats with MP for 9 times during a period of 24 weeks with a technique of ultrasonic nebulizing inhalation. Then in situ hybridization was performed with PDGF-B chain cDNA probe and the results were quantitatively analyzed to measure the changes in PDGF-B chain mRNA expression in the lung tissue. The results showed that: (1) MP polymerase chain reaction (PCR) tests showed positive results in the bronchoalveolar lavage fluid (BALF ) from all of the MP-infected rats (n = 4) while they were all negative in BALF from the control animals (n = 4, P<0. 05) and in BALF from those rats both infected with MP and, at the same time, treated with erythromycin (n = 4, P<0. 05). Bacterial cultures of the bronchial and lung tissue were negative in all three groups. The observation under a transmission electron microscope indicated that the interalveo-lar septa were widened with increased amount of collagen in the MP-infected rats while there were no obvious abnormalities in the other two groups. (2) Strong positive expression of PDGF-B chain mRNA was found in the plasma of mono-cytes and macrophages located in the locally widened interalveolar septa and alveolar spaces in the lung tissue from the MP-infected animals with the integral optical densities being 37. 42 ±9. 05 (n = 4) which was significantly higher than the values of control group (0. 42 + 0. 08, n = 4, P<0. 01) and of the group with MP-infec-tion plus erythromycin treatment (1. 62 ± 0. 40, n = 4, P<0. 01). These results suggest that PDGF-BB may be involved in the process of the development of pulmonary interstitial fibrosis caused by the repeated MP-infection. It may be an important growth factor for mediating the roles of monocytes and macrophages to promote the aggregation and proliferation of fibroblasts which can then secrete collagen in large quantity in the pulmonary interstitium.

The Effect of Vitamin A on Secretion of IFN-γ and IL-4 in A549 Cells Induced by Mycoplasma Pneumoniae

In order to investigate the effect of vitamin A （VA） on the secretion of IFN-γ and IL-4 in Mycoplasma Pneumoniae （MP）-induced A549 cells, A549 cells were co-cultured with MP for different time lengths and then the levels of IFN-γ and IL-4 in the cell culture supernatants were detected before and after treatment with different concentrations of VA by using the enzyme-linked immu-nosorbent assay （ ELISA）. The results showed that the level of IFN-γ and IL-4 in the supernatants of MP-induced A549 cells was much higher than that in non-induced cells （P〈0.01）. After application of VA, IL-4 level was not increased until the concentration of VA was up to 0.5×10-5 mol/L （P〈0.01）. However, with concentration of VA increased up to 1×10-4 mol/L, IL-4 was significantly suppressed （P〈0.01）. It was concluded that MP could induce the secretion of IFN-γ and IL-4 in A549 cells. VA could inhibit the secretion of IFN-γ and increase the IL-4 level in MP-induced A549 cells. However, high concentration of VA had an inhibitory effect on the secretion of IL-4 as well as on the IFN-γ. These data provided a theoretical basis for the application of VA in MP pneumonia in the clinical practice.

Whole Genome Analysis Reveals New Insights into Macrolide Resistance in Mycoplasma pneumoniae

Objective Mutations in 23 S rRNA gene are known to be associated with macrolide resistance in Mycoplasma pneumoniae（M. pneumoniae）. However, these mutations alone do not fully explain the high resistance rates in Asia. The aim of this study was to investigate other possible mutations involved in macrolide resistance in M. pneumoniae. Methods The whole genomes of 10 clinical isolates of M. pneumoniae with macrolide resistance were sequenced by Illumina Hi Seq2000 platform. The role of the macrolide-specific efflux transporter was assessed by efflux-pump inhibition assays with reserpine and carbonyl cyanide m-chlorophenyl-hydrazone（CCCP）. Results A total of 56 single nucleotide polymorphisms（SNPs） were identified in 10 clinical isolates in comparison to the reference strains M129 and FH. Strikingly, 4 of 30 SNPs causing non-synonymous mutations were clustered in macrolide-specific efflux system gene mac B encoding macrolide-specific efflux pump protein of the ATP-binding cassette transporter family. In assays of the minimal inhibitory concentrations（MIC） of macrolide antibiotics in the presence of the efflux pump inhibitors caused a significant decrease of MICs, even under detectable levels in some strains. Conclusion Our study suggests that macrolide efflux pump may contribute to macrolide resistance in M. pneumoniae in addition to the common point mutations in 23 S r RNA gene.