Changes In Bacterial Spectrum And Bacterial Drug Resistance In Broncho-alveolar Lavage Fluid Of Children With Lower Respiratory Tract Infection During 2017-2021

Objective:To investigate the epidemiological distribution characteristics and drug resistance of bacteria isolated from broncho-alveolar lavage fluid（BALF）in children with lower respiratory tract infection,so as to provide a basis for clinical medication.Method:The clinical data of children with lower respiratory tract infection undergoing fiberoptic bronchoscopy from January 2017 to December 2021,and the results of bacterial culture and drug sensitivity of BALF were collected using a retrospective study.Results:1.Submitted specimens and detection During the 5 years,a total of 15,686 specimens from children with lower respiratory tract infection were submitted to BALF examination.Among them,positive bacterial culture was detected in BALF from 385 children,and 386 pathogenic strains were isolated,with a positive detection rate of 2.45%.2.Demographic characteristics Among the 385 positive cases,there were 236 boys and149 females,with a male-female ratio of 1.58: 1.The median age was 1 year and 1 month,the minimum age was 14 days,and the maximum age was 15 years.3.Endoscopic lesion distribution Among the 385 children with positive bacterial culture,endobronchial inflammation was endoscopically diagnosed in 278 children,accounting for the highest proportion（72.21%）,followed by laryngomalacia-tracheomalaciabronchomalacia（n = 41,10.65%）,other tracheal deformities（n = 27,7.01%）,bronchial foreign body（n = 26,6.75%）,bronchiectasia（n = 7,1.82%）and others（n = 6,1.56%）.4.Bacterial distribution Among the 386 pathogenic strains,a total of 15 bacterial species were isolated.The top five species accounted for 85.74%,including Streptococcus pneumoniae（45.85%）,Staphylococcus aureus（13.47%）,Haemophilus influenzae（10.62%）,Escherichia coli（8.55%）and Klebsiella pneumoniae（7.25%）successively.Other species detected included Acinetobacter baumannii（3.63%）,Moraxella catarrhalis（3.63%）,Pseudomonas aeruginosa（2.07%）,Enterobacter cloacae（1.81%）,other rare Gram-negative bacteria（0.28%）（Stenotrophomonas maltophilia,Acinetobacter junii,1strain of Burkholderia cepacia,1 strain of Serratia marcescens,1 strain of Providencia rettgeri）and Staphylococcus aureus（0.26%）successively.5.Bacterial distribution in different age groups 138（35.72%）pathogenic strains were detected in the infant group,105（27.20%）in the young children group,92（23.83%）in the preschool children group,and 51（13.21%）in the school-aged children group.Streptococcus pneumoniae showed the highest detection rate in all age groups（31.9% in the infant group,53.3% in the young children group,57.6% in the preschool children group and 47.1% in the school-aged children group）,and was the most important pathogen for lower respiratory tract infection.As for Staphylococcus aureus,15（10.9%）strains were detected in the infant group,6（5.7%）strains in the young children group,15（16.3%）strains in the preschool children group and 16（31.4%）strains in the school-aged children group.Its proportion was the highest in the school-aged children group while the lowest in the young children group.23（16.7%）strains of Escherichia coli were detected in the infant group,9（8.6%）strains in the young children group,and 1（1.1%）strain in the preschool children group,with the highest proportion in the infant group,and the detection rate reduced with age.25（18.1%）strains of Klebsiella pneumoniae were detected in the infant group,1（1%）strain in the young children group,1（1.1%）strain in the preschool children group and 1（2%）strain in the school-aged children group,with the highest proportion in the infant group.In terms of Pseudomonas aeruginosa,1（0.7%）strain was detected in the infant group,5（4.8%）strains in the young children group and2（3.9%）strains in the preschool children group,and it was mainly detected in the young children group.Streptococcus pneumoniae,Staphylococcus aureus,Escherichia coli,Klebsiella pneumoniae and Pseudomonas aeruginosa presented statistically significant differences among different age groups（P < 0.05）.6.Bacterial time distribution Streptococcus pneumoniae was prevalent throughout the year,Staphylococcus aureus was mainly prevalent in winter,Escherichia coli was mainly prevalent in spring,Haemophilus influenzae and nonfermentative Gram-negative bacilli were mainly prevalent in summer,and Klebsiella pneumoniae was mainly prevalent in summer and early autumn.Escherichia coli and nonfermentative Gram-negative bacilli showed statistically significant differences in the time of prevalence（P < 0.05）.7.Bacterial drug resistance The resistance rate of Streptococcus pneumoniae to cefotaxime,ceftriaxone and meropenem increased,and its drug resistance rate presented statistically significant differences among years（P < 0.05）.Streptococcus pneumoniae was highly resistant to erythromycin（drug resistance rate,96%-100%）,and no Streptococcus pneumoniae resistant to amoxicillin was found for five consecutive years.Staphylococcus aureus was highly resistant to clindamycin and erythromycin（drug resistance rate > 78%）.Among the 52 strains of Staphylococcus aureus from BALF,there were 22 strains of MRSA,and the prevalence of methicillin-resistant Staphylococcus aureus was 42.31%.Streptococcus pneumoniae and Staphylococcus aureus were both sensitive to vancomycin,linezolid,moxifloxacin and levofloxacin.Gram-negative bacteria were generally resistant to ampicillin.The sensitive antibiotics were mainly third-generation cephalosporins（except ceftriaxone）,fourth-generation cephalosporins and carbapenems.Escherichia coli and Pseudomonas aeruginosa had high resistance（>75%）to ceftriaxone,while Acinetobacter baumannii and Enterobacter cloacae had relatively low resistance（< 28%）to ceftriaxone.Conclusion :1.Gram-positive bacteria are dominant in BALF of lower respiratory tract infection,Streptococcus pneumoniae and Staphylococcus aureus are the main pathogenic bacteria,followed by Haemophilus influenzae,Escherichia coli and Klebsiella pneumoniae.2.The bacterial distribution in children with lower respiratory tract infections is different at different ages and seasons.3.Streptococcus pneumoniae and Staphylococcus aureus are highly resistant to erythromycin,and the main gram-negative bacilli are generally resistant to ampicillin.The drug resistance rate of the main pathogens of lower respiratory tract infection to commonly used antibiotics in clinic is still high,and the status of drug resistance is severe.