医院内甲氧西林耐药金黄色葡萄球菌肺部感染高危因素分析
- 来宝网2007年5月31日 13:25 点击:2612
WU Benquan, TANG Yingchun, ZHU Jiaxin.
(Department of Internal Medicine, The 3rd Affiliated Hospital of Sun YatSen University of Medical Sciences , Guangzhou 510630,China)
【Abstract】 Objective To investigate major risk factors leading to death by noscomial MRSA pulmonary infections. Method The data of hospitalized patients diagnosed as noscomial MRSA pulmonary infections were sorted out and analyzed for recent three years.Results Case mortality of 64 patients with noscomial MRSA pulmonary infections were 44%. Of these, 18 cases complicated fungi, 11 Klebsiella pneumoniae,9 Pseudomonas maltophilia and 7 Enterococcus. Case mortality of fungi and Pseudomonas maltophilia were 67% and 61%,respectively. 23 cases had fever, 18 died (case mortality 78% ) and 41 had no fever, 10 died (case mortality 24%)(χ2=15.253,P<0.005).The case mortality with reduction, normal and increase of leukocyte were 80%,24% and 45%,respectively.The comparison between three groups had obvious significance (χ2=12.554,P<0.005) and the case mortality of leukocytopenia was higher than that of other two groups (χ2=8.626,P<0.005). The case mortality of hypoproteinemia was higher than that of the control group (χ2=6.914, P<0.01). The patients who developed fulminant lesions in liver, kidneys and lungs showed higher mortality rate.Conclusions Case mortality of noscomial pneumonia caused by MRSA is very high. In addition to common causes, underling diseases, leukocytopenia, malnutrition and complex infections are also risk factors of MRSA infection.
【Key words】 Methicillin resistance; Staphylococcus aereus; Lung; Noscomial infection
甲氧西林耐药金黄色葡萄球菌(MRSA)与甲氧西林敏感金黄色葡萄球菌(MSSA)致病性相似,主要引起化脓性病变。目前只有万古霉素有效,并已出现万古霉素低敏的MRSA[1],深入研究MRSA院内感染的高危因素,对控制和减少MRSA感染具有重要意义。我们就64例MRSA严重肺部感染病例进行回顾性分析,报告如下。
材料与方法一、病例选择
1996~1998年本院住院病人标准痰标本3次以上分离出MRSA(定量培养107 cfu/ml)[2],住院48 h后发生感染,出现咳嗽、咳痰或咳痰性质改变并符合中华医学会呼吸病学分会制定的医院获得性支气管肺感染5条标准之一,结合肺部X线有肺实质炎症者[3] ,并除外血液系统病变。其中男性53例,女性11例;年龄为30~95岁,平均64岁。
二、MRSA鉴定方法
1.琼脂板稀释法:参照美国临床实验室标准委员会(NCCLS)标准,从临床分离的金黄色葡萄球菌转种至L-B培养基,培养24 h,配成107 cfu/ml的细菌悬液,沾取1.2 μl接种至M-H琼脂板上(M-H平板含4% NaCl,对倍稀释的苯唑西林)直径约5~8 mm的圆形区,32℃孵育24 h,MIC≥4 μg/ml为MRSA。
2.MRSA特异性MecA基因的聚合酶链反应(PCR)检测:用于MRSA鉴定的引物为MecA基因文库中623 bp(位置5′-1321~1943 bp-3′)的特异性片段:序列1, 5′-AGTTGTAGTTGTCGGGTTTG-3′;序列2, 5′-AGTGGAACGAAGG TACATC-3′PCR反应混合液50 μl(5 μl dNTP, 5 μl PCRbuffer(10×) 引物各2.5 μl,三蒸水25 μl,TaqDNA聚合酶0.5 μl(1.25 U),DNA模板10 μl,循环条件:变性94℃ 60 s,退火60℃ 60 s,延伸72℃ 60 s,35个周期,2%琼脂糖电泳,在623 bp处出现强荧光带为MRSA,并设阳性和阴性对照。
3.高危因素分析:分别统计基础疾病的器官、白细胞计数、血清白蛋白含量、混合感染的病原体种类和发热等,比较它们在死亡病例中的发生率,部分临床参数进行卡方检验,以期了解MRSA感染协同致死的高危因素。
结果
一、 混合感染病原菌种类及其在MRSA院内肺部感染的重要意义
58例混合感染:真菌感染18例,病死率61%;嗜麦芽假单胞菌9例,病死率67%,可能与没有有效的药物治疗有关。真菌感染的发生率28%,位于其它病原体之首,提示MRSA感染易合并真菌感染[4]。28例MRSA确诊到死亡时间平均23±8天,当合并其它病原菌感染时病程缩短,不同病原菌缩短程度不同(表1)。
二、发热、白细胞数量及营养状态对MRSA院内肺部感染的影响
所调查的64例患者发热(≥37.5℃,时间7 d以上)23例,病死率78%(18/23);体温正常41例,病死率24%(10/41)(χ2=15.253,P<0.005)。白细胞数量减少(<4.0×109)、正常和增多(≥4.0×109)时病死率分别为80%(12/15)、24%(7/29)和45%(9/20),三组比较差异有显著性(χ2=12.554,P<0.005),其中减少组与其他两组比较有显著的统计学意义(χ2=8.626,P<0.005)。血白蛋白降低组(<35 g/L)病死率65%(17/26)高于正常组(≥35 g/L)的29%(11/38)(χ2=6.914,P<0.01)。
三、MRSA院内肺部感染病死率与基础疾病的关系
表1 58例混合感染病原菌种类与64例MRSA院内肺部感染的关系
病原体 | 例数 | 死亡例数 | 病程 (d) | 病死率 (%) | 发生率 (%) |
真菌 | 18 | 11 | 19±10 | 61 | 28 |
肺炎克雷伯菌 | 11 | 4 | 14± 5 | 36 | 17 |
嗜麦芽假单胞菌 | 9 | 6 | 16± 7 | 67 | 14 |
肠球菌 | 7 | 3 | 10±10 | 43 | 11 |
聚团肠杆菌 | 4 | 0 | 0 | 0 | 6 |
绿假单胞菌 | 4 | 2 | 8± 2 | 50 | 6 |
大肠埃希菌 | 3 | 1 | 15 | 33 | 5 |
阴沟肠杆菌 | 2 | 0 | 0 | 0 | 3 |
疾病分类 | 例数 | 死亡例数 | 病死率(%) |
心血管 | 14 | 3 | 21 |
呼吸 | 21 | 10 | 48 |
消化 | 11 | 7 | 64 |
肿瘤 | 3 | 2 | 67 |
神经 | 2 | 0 | 0 |
内分泌 | 5 | 0 | 0 |
泌尿 | 8 | 6 | 75 |
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