Etiology And Epidemiology Of Community-acquired Pneumonia In Children

OBJECTIVE:(1)To delineate the pathogens of community-acquired pneumonia(CAP)in childhood for obtaining the infectious characteristics of pathogenic microorganism,spectrum of pathogens,patterns of infection and features of antimicrobial resistance.(2)To study the characteristics of epidemiology and influential factors of childhood community-acquired pneumonia.METHODS:A prospective study was performed on 375 consecutive childhood patients with CAP eliminatting the pneumonophthisis,lung tumor,noninfectious lung interstitial disease, lung edema,pulmonary closure,lung embolism,pulmanory eosinophilia,pulmonary vasculitis. 246patients were male,129 patients were female.Samples of acute serum,acute sputum(or throat specimen)were collected for the test.At the same time,the epidemiological base line data were also collected.(1)Bacteriology detection and susceptibility test:sputum or throat specimens were collected for culture,bacteria were isolated and identified using conventional methods.(2) Mycoplasma pneumoniae(MP):antibodies of Mycoplasma pneumoniae were determined by microparticle agglutination using the commercial kit Serodia-MycoⅡ(Fujirebio,Japan).(3) Chlamydia pneumoniae(CP):antibody of Chlamydia pneumoniae were determined by indirect immunofluorescence test(IIFT)using the commercial kit(Euroimmun,Germany).(4) Respiratory virus:antibodies of respiratory syncytial virus,adenovirus,influenza virus type A,B, parainfluenza virus type 1,3 were determined by enzyme-linked immunosorbent assay(ELISA) using the commercial kit(Kesitadi,China).(5)Legionella:a genus-specific sequence of 16S ribosome gene of legionella was amplified by polymerase chain reaction(PCR).RESULTS:(1)The positive rate of sputum culture was 41.1%(148/360)and its results as follows:Streptococcus pneumoniae 28.9%(104/360),Escherichia coli 5.6%(20/360), Enterococcus pneumoniae 1.7%(6/360),Stenotrophomonasmal-tophilia 1.4%(5/360). Streptococcus pneumoniae was the most common cause of bacterial pneumonia.(2)133/350 (38.0%)childhood community-acquired pneumonia patients were infected by the common respiratory virus and the results as follows:Respiratory syncytial virus15.1%(53/350), Adenovirus 8.3%(29/350),Influenza virus type A 6.3%(22/350),Influenza virus type B 5.4% (19/350),Parainfluenza virus type 1 4.3%(15/350),Parainfluenza virus type 3 2.9%(10/350). Respiratory syncytial virus was the most common cause of viral pneumonia.(3)Pathogens were identified in 254/350 patients(72.6%)with valid sputum culture,serum samples and PCR, including a bacterial infection alone in 57(16.3%),a viral infection alone in 50(14.3%),a mycoplasma pneumoniae infection alone in 28(8.0%),a legionella infection alone in 4(1.1%), a chlamydia pneumoniae infection alone in 3(0.9%),mixed infection in 112(32.0%).(4)The resistant rate of Streptococcus pneumoniae to erythrocin,ceftazidime,cefazolin,cefuroxime and penicilin was 92.3%,89.4%,74.0%,66.3%and 60.6%respectively.(5)The detection rate of bacterial infection is higher than others in whole year,which will reach a peak on February.The infected numbers have been obviously descending since April,but that begins to rise after October.Mycoplasma pneumoniae infection is sporadic every month,however,it is the most in fall and winter.Respirovirus infection begins to go up from October and drop from the next April,which may arrive a peak from December to the next February and displays sporadic cases from May to September and is the lowest on July and August.The children below 4 years old,especially within 1 year old are the main susceptible of bacterial infection. The main infectious bacterial are the streptococcus pneumoniae and infection due to escherichia coli in each age stage.But there is not significantly discrepancy of the streptococcus pneumoniae infection in each age stage(x~2=9.45,P＞0.05).Viral infection is sporadic in each age stage,but the infection rates of respiratory syncytial virus and influenza virus from 1 year old to 4 years old are higher than others,the same as children below 6 years old.In addition, there is discrepancy of the influenza virus infection in each age stage(x~2=13.67,P＜0.05).The children below 6 years old,especially from 1 year old to 7 years old are the main susceptible of mycoplasma pneumoniae infection.And there is discrepancy of the mycoplasma pneumoniae infection in each age stage(x~2=52.9,P＜0.001).CONCLUSIONS:Bacterial infection has important role in childhood CAP and is the most cause of CAP in Taiyuan area,followed by virus and mixed infection.The identified rate of bacterial is a little more than viral,and Streptococcus pneumoniae is the most common cause of bacterial pneumonia,antibiotics resistance is very serious;Respiratory syncytial virus is the most common cause of viral pneumonia;Atypical pathogens should not be ignored.