老年下呼吸道感染铜绿假单胞菌的病原学特征分析

Etiological characteristics of Lower respiratory tract infection in the elderly

目的分析本地区老年下呼吸道感染患者的病原学特征。方法选取2020-2022年张家口学院附属人民医院治疗的286例老年下呼吸道感染患者为研究对象,选取同期住院、年龄≥65岁未发生下呼吸道感染的住院患者为对照组。患者入院后未进行抗菌治疗前,采集清晨第一口痰液,接种不同培养基,培养分离纯化后用全自动细菌鉴定及药敏分析系统进行菌株鉴定及药敏分析,采用聚合酶链反应检测铜绿假单胞菌毒力基因的携带情况。结果286例老年下呼吸道感染患者中,主要为肺炎(49.65%,142/286),检出286株病原菌。212株为革兰阴性菌,主要为肺炎克雷伯菌(22.73%,22/286)和铜绿假单胞菌(14.69%,42/286)。72株为革兰阳性菌(25.17%,72/286),主要为肺炎链球菌(11.89%,34/286)。对革兰阴性菌进行药敏试验,对氨曲南、左氧氟沙星、复方新诺明的耐药率高于50%,分别为50.47%、53.77%和52.36%,对头孢他啶、莫西沙星的耐药率低于30%,分别为29.72%和24.53%,对亚胺培南、美罗培南、阿米卡星耐药率低于10%。对革兰阳性菌进行药敏试验,对青霉素、红霉素、克林霉素、复方新诺明的耐药率高于50%,分别为95.83%、72.22%、61.11%和55.56%,对莫西沙星的耐药率为26.39%,未产生对万古霉素、替考拉宁的耐药株。42株铜绿假单胞菌中,28株携带exoS基因(66.67%,28/42),11株携带exoU基因(26.19%,11/42)。携带exoU基因的铜绿假单胞菌,对环丙沙星、左氧氟沙星、莫西沙星、庆大霉素、阿米卡星的耐药率均高于携带exoS基因的铜绿假单胞菌,携带exoU基因的铜绿假单胞菌对氨曲南的耐药率低于携带exoS基因的铜绿假单胞菌,差异有统计学意义(P<0.05)。携带exoS基因与exoU基因的铜绿假单胞菌对头孢他啶、亚胺培南、美罗培南的耐药率均低于40%,对复方新诺明的耐药率均高于50%,差异无统计学意义(P>0.05)。对比三组患者血清PCT水平,细菌感染组患者高于对照组,革兰阴性菌感染者水平高于革兰阳性菌感染者,差异有统计学意义(F=351.778,P<0.05)。以老年下呼吸道感染病原菌为基准,绘制ROC曲线,血清PCT水平的曲线下面积(AUC)为0.972(95%CI:0.952~0.993),最佳截断值为1.605 ng/mL时,敏感度为95.3%,特异性为100%。结论老年下呼吸道感染患者病原菌主要为革兰阴性菌,对临床常见抗菌药物耐药率较高,exoU基因与铜绿假单胞菌的耐药性显著相关。血清PCT水平可以作为对老年下呼吸道感染的初步筛查指标,对诊断患者感染病原菌类型具有一定临床价值。

Objective To analyze the pathogenic characteristics of elderly patients with Lower respiratory tract infection in this area.Methods 286 elderly patients with Lower respiratory tract infection who were treated in the Affiliated People's Hospital of Zhangjiakou University from January 1,2020 to December 31,2022 were selected as the subjects of this study.In addition,elderly inpatients who were hospitalized in the same period and whose age was≥65 years without Lower respiratory tract infection were selected as the control group.After the patient was admitted to the hospital and before receiving antibacterial treatment,the first morning sputum was collected.Qualified sputum samples were inoculated onto different culture media,and after cultivation,separation and purification,pathogen identification and drug sensitivity analysis were carried out by a fully automated bacterial identification and drug sensitivity analysis system.The carrying of virulence genes in the isolated Pseudomonas aeruginosa were detected by Polymerase Chain reaction.Results In 286 elderly patients with Lower respiratory tract infection,pneumonia was the main cause(49.65%,142/286),and 286 strains of pathogens were detected.212 strains were Gram negative bacteria,mainly Klebsiella pneumoniae(22.73%,22/286)and P.aeruginosa(14.69%,42/286).72 strains were Gram positive bacteria(25.17%,72/286),mainly Streptococcus pneumoniae(11.89%,34/286).The drug sensitivity test of gram-negative bacteria showed that the drug resistance rate to aztreonam,Levofloxacin and Trimethoprim/sulfamethoxazole was higher than 50%(50.47%,53.77%and 52.36%respectively),the drug resistance rate to Ceftazidime,and Moxifloxacin was lower than 30%(29.72%,and 24.53%respectively),and the drug resistance rate to Imipenem,Meropenem,and Amikacin was lower than 10%.The drug sensitivity test of Gram positive bacteria showed that the drug resistance rate to penicillin,Erythromycin,Clindamycin and Trimethoprim/sulfamethoxazole was higher than 50%,which were 95.83%,72.22%,61.11%and 55.56%,respectively.The drug resistance rate to Moxifloxacin was 26.39%,and there was no drug resistance to Vancomycin and teicoplanin.Among 42 P.aeruginosa strains,28 strains carried exoS genes(66.67%,28/42),and 11 strains carried exoU genes(26.19%,11/42).The resistance rate of exoU gene carrying P.aeruginosa to Ciprofloxacin,Levofloxacin,Moxifloxacin,Gentamicin and Amikacin was higher than that of exoS gene carrying P.aeruginosa,and the resistance rate of exoU gene carrying P.aeruginosa to aztreonam was lower than that of exoS gene carrying P.aeruginosa,with statistical significance(P<0.05).The drug resistance rate of P.aeruginosa carrying exoS gene and exoU gene to Ceftazidime,Imipenem and Meropenem was lower than 40%,and the drug resistance rate to Trimethoprim/sulfamethoxazole was higher than 50%.The difference was not statistically significant(P>0.05).Comparing the serum PCT levels of three groups of patients,the levels of bacterial infection group were higher than the control group,and the levels of Gram negative bacterial infections were higher than those of Gram positive bacterial infections.The difference in comparison was statistically significant(F=351.778,P<0.05).The Receiver operating characteristic was drawn based on the pathogenic bacteria of elderly Lower respiratory tract infection.The area under the curve(AUC)of serum PCT level was 0.972(95%CI:0.952-0.993).When the optimal cut-off value was 1.605ng/mL,the sensitivity was 95.3%and the specificity was 100%.Conclusion The pathogenic bacteria in elderly patients with Lower respiratory tract infection were mainly gram-negative bacteria,and the drug resistance rate to clinical common antibiotics was high.The exoU gene was significantly related to the drug resistance of P.aeruginosa.Serum PCT level can be used as a preliminary screening indicator for Lower respiratory tract infection in the elderly,and has certain clinical value in diagnosing the type of pathogenic bacteria in patients with infection.