综合医院ICU院内感染鲍曼不动杆菌耐药现状分析

目的:了解鲍曼不动杆菌在医院感染的分布及耐药现状,为临床合理使用抗菌药物提供依据。方法:收集2012-01-12月综合ICU住院患者送检的各类标本进行细菌培养分离,采用法国生物梅里埃公司ATB微生物分析系统及配套鉴定卡进行菌种鉴定,药敏试验采用K-B法,实验方法和判定标准按照CLSI2012规定进行。结果:分离鲍曼不动杆菌87株,对常用抗菌药物均出现较高的耐药率,耐药率最低的是米诺环素(13.8%),其次是头孢哌酮/舒巴坦(40.2%)。结论:鲍曼不动杆菌已成为综合ICU医院感染的主要致病菌,感染率和耐药率不断上升,应加强对鲍曼不动杆菌耐药性的监测,合理选择使用抗菌药物,对ICU采取有效的控制措施,有效控制耐药菌株在ICU的定植和传播。     

Problem pathogens (Pseudomonas aeruginosa and Acinetobacter)

A number of factors have been suspected of or identified as increasing the risk for pneumonia or colonization of the lower respiratory tract by Pseudomonas and/or Acinetobacter spp. in the intensive care unit (ICU), including advanced age, chronic lung disease, immunosuppression, surgery, use of antimicrobial agents, presence of such invasive devices as endotracheal and gastric tubes, and type of respiratory equipment. However, there is little doubt that of all these factors, extended ICU care because of severe underlying disease, prolonged respiratory therapy with mechanical ventilation, and prior antimicrobial therapy are the most important. Because the only factor amenable to prevention in this setting is antimicrobial therapy, avoiding unnecessary antibiotics should be a high priority in the management of such patients. Crude mortality rates of 30% to 75% have been reported for nosocomial pneumonia caused by Pseudomonas and/or Acinetobacter spp., with the highest rates reported in ventilator-dependent patients. It is therefore clear that the prognosis associated with this type of infection is considerably worse than that associated with infection caused by other gram-negative or gram-positive bacteria. Because bactericidal synergy against Pseudomonas and Acinetobacter spp. has been shown when carbenicillin and an aminoglycoside are combined, the use of an effective beta-lactam (piperacillin, ticarcillin, ceftazidime, or imipenem) and aminoglycoside combination remains the preferred therapeutic approach when possible. Future research efforts should also aim to improve our ability to diagnose and exclude infection in the ICU setting to avoid administering unnecessary antibiotics to patients without true pulmonary infection.     

医院感染鲍氏不动杆菌的临床分布及耐药性分析

目的:了解2008-01-20120-12临床分离的221株鲍氏不动杆菌(ABA)的标本来源、感染科室分布及耐药状况,为临床预防和治疗感染性疾病提供参考依据。方法:采用临床微生物学检验的常规方法对感染性标本进行细菌培养、鉴定和药敏试验,调查221株ABA的标本来源和感染科室,统计ABA对12种常用抗菌药物的耐药率。结果:221株ABA中有182株来自痰液,占82.4%;其次是脓液和手术切口引流物、血液等。医院感染ABA主要分布在重症监护病房(ICU),占51.6%;其次是呼吸内科24.4%和神经外科19.5%。药敏结果显示:ABA对临床常用抗生素的耐药性逐年增长,ABA耐药率最低的抗生素是头孢哌酮/舒巴坦,其次是亚胺培南、美洛培南。对青霉素类、氨基糖苷类、氟喹诺酮类、氨曲南、哌拉西林/他唑巴坦等呈高度耐药(90%),且表现出多药耐药性。结论:ABA医院获得性感染率逐年增加,并对多种抗菌药物耐药,且多药耐药性明显,应引起临床尤其是ICU病房和呼吸内科高度重视,应严格做好各种侵入性操作的无菌技术,合理使用抗生素,以降低医院感染率、提高治愈率,延缓细菌耐药性的产生。     

Antibiotic sensitivity pattern of the bacteria isolated from nosocomial infections in ICU

The incidence of nosocomial infections in ICU is 4-5 times greater than in general ward. Critically ill patients are always at higher risk of developing nosocomial infections with resistant strains. This study is an attempt to know the antibiotic sensitivity pattern of the common isolates in ICU. Samples comprising urine, blood, endotracheal secretions and throat swabs were collected from 102 ICU patients of them, 56 patients showed evidence of nosocomial infection (54.9%), from whom 120 different organisms were isolated. Antibiotic sensitivity test was done according to Kirby Bauer method. Klebsiella pneumoniae were the most prevalent isolates from respiratory tract infections followed by Proteus spp, Escherichia coli, Staphylococci spp. and Acinetobacter spp. The gram negative enteric bacilli were uniformly resistant to betalactam antibiotics as well as betalactam-betalactamase inhibitors. Resistance to Ciprofloxacin and Ceftriaxone ranged from 50-100% and 25-83.3% respectively. Staphylococci were 100% resistant to penicillin and tetracycline, 80% to cotrimoxazole, 60% to erythromycin and gentamicin and 40% to amikacin. Acinetobacter spp. were highly resistant to most of the antibacterial agents except gentamicin while Pseudomonas spp. showed 75% resistance to it. The increased prevalence of resistant organisms in ICU probably reflects lack of proper antibiotic policy resulting in prolonged and indiscriminate use of antimicrobial agent.     

2007-2010年医院鲍曼不动杆菌感染的耐药分析

目的 了解医院鲍曼不动杆菌感染的分布及耐药情况.方法 分析鲍曼不动杆菌菌株的标本来源和临床分布情况,用最低抑菌浓度(minimal inhibitory concentration,MIC)法结合纸片扩散法(K-B法)检测其对抗菌药物的敏感性.结果 2007-2010年共分离鲍曼不动杆菌62株,其中53株(占85.5%)分离自痰标本,21株(占33.9%)分离自重症监护室(intensive care units,ICU).62例患者中54.8%(34例)的患者患有严重的肺部感染疾病.分离菌对头孢哌酮/舒巴坦的耐药率为20.0%、敏感率为73.3%,对其他抗菌药物的耐药率超过60.0%.泛耐药菌占33.9%(21株),其中52.4%(11株)的泛耐药鲍曼不动杆菌感染发生在ICU病房.结论 鲍曼不动杆菌的耐药率较高,且呈多重耐药趋势.加强菌株的耐药性监测,以药敏结果指导临床用药有助于减少耐药菌株的出现.

Abstract：

Objective To investigate the prevalence and antimicrobial resistance of Acinetobacter baumannii in nosocomial infection.Methods Clinical features and the origin of A.baumannii samples were analyzed retrospectively.The minimal inhibitory concentration(MIC)and Kriby-Bauer diffusion test(K-B)were used to determine the Susceptibility to the antimicrobial agents.Results A total of 62 strains of A.baumannii were isolated from 2007 to 2010.Fifty-three strains(85.5%) of specimens were separated from respiratory tract.The isolation rate of A.baumannii was the highest in intensive care units(ICU)(21 strains,33.9%).54.8%(34/62)of patients suffered from severe lung infection.The resistance rate of cefoperazon/sulbactam was 20.0%.and the susceptible rate was 73.3%.The resistance rate to other antimicrobial agents is above 60.0%.The prevalence of multi-drug resistance of A.baumannii Was about 33.9%,and 52.4% of this kind of A.baumannii were occured in ICU.Condusion The infection of A.baumannii is more and more severe and tends to be resistant to multiple-drug and pan-drugs.The susceptible testing should be conducted to help the clinic to decrease the resistance rate.     

鲍曼不动杆菌感染的临床分布及耐药性分析

目的 了解鲍曼不动杆菌的临床分布及其对常用抗生素的耐药情况.方法 收集我院2007年7月至2010年7月的临床标本,进行鲍曼不动杆菌分离培养及药敏试验.结果 3年共分离出鲍曼不动杆菌373株,在临床标本中,痰液分布率最高,占78.6％,感染分布以ICU为主,占36.2％.药敏试验显示对碳青霉烯类、含酶抑制剂、多粘菌素E敏感性较高,对氨基糖苷类、喹诺酮类、β-内酰胺类耐药率较高,多重耐药性明显.结论 鲍曼不动杆菌主要侵犯ICU患者、慢性呼吸系统疾病患者及术后感染者.     

综合性医院重症监护室鲍曼不动杆菌耐药性分析

目的了解重症监护室病人鲍曼不动杆菌感染及耐药情况,指导临床医师选择有效抗生素进行抗感染治疗,控制院内感染的发生。方法 2008年1月～2010年1月期间,自重症监护室病人痰液等标本分离鲍曼不动杆菌,分析细菌的标本分布和科室分布,并检测细菌对常用抗生素的耐药性。细菌鉴定用VITEK-GNI+,药敏试验采用K-B法。结果分离出172株鲍曼不动杆菌,主要来自呼吸道感染病人的痰液,占87.21%;综合性重症监护室鲍曼不动杆菌的检出率较高,为43.60%(ICU-1)和29.65%(ICU-2)。药敏试验显示鲍曼不动杆菌对米诺环素、亚胺培南、含酶抑制剂的复合制剂如头孢哌酮/舒巴坦和哌拉西林/他唑巴坦以及左氧氟沙星的耐药率低,分别是1.32%、5.88%、4.71%、17.65%和23.53%,对其他抗生素有较强的耐药性。结论鲍曼不动杆菌是ICU病人呼吸道感染的常见菌,且耐药性高,建议首选米诺环素、亚胺培南、头孢哌酮/舒巴坦,哌拉西林/他唑巴坦和左氧氟沙星进行鲍曼不动杆菌的感染治疗。     

Acinetobacter baumannii:An emerging pathogenic threat to public health

Over the last three decades, Acinetobacter has gained importance as a leading nosocomial pathogen, partly due to its impressive genetic capabilities to acquire resistance and partly due to high selective pressure, especially in critical care units. This low-virulence organism has turned into a multidrug resistant pathogen and now alarming healthcare providers worldwide. Acinetobacter baumanni(A. baumannii) is a major species, contributing about 80% of all Acinetobacter hospital-acquired infections. It disseminates antibiotic resistance by virtue of its extraordinary ability to accept or donate resistance plasmids. The procedures for breaking the route of transmission are still proper hand washing and personal hygiene(both the patient and the healthcare professional), reducing patient's biofilm burden from skin, and judicious use of antimicrobial agents. The increasing incidence of extended-spectrum beta-lactamases and carbapenemases in A. baumannii leaves almost no cure for these "bad bugs".To control hospital outbreaks of multidrug resistantAcinetobacter infection, we need to contain their dissemination or require new drugs or a rational combination therapy. The optimal treatment for multidrug-resistant A. baumannii infection has not been clearly established, and empirical therapy continues to require knowledge of susceptibility patterns of isolates from one's own institution. This review mainly focused on general features and introduction to A. baumannii and its epidemiological status, potential sources of infection, risk factors, and strategies to control infection to minimize spread.     

鲍曼不动杆菌临床感染和耐药机制研究进展

鲍曼不动杆菌是一种不发酵葡萄糖的革兰阴性球杆菌,广泛分布于土壤、水体、下水道和医院环境,还能存在于人体潮湿皮肤表面。它是一种重要的条件致病菌,不仅引起医院内感染,而且还可导致严重的社区感染和野战外伤感染。近年来,随着临床上广谱抗菌药物的大量应用,出现了多重耐药菌株,并有逐年上升趋势,特别是耐碳青霉烯类菌株出现,给临床抗感染化疗提出了严峻的挑战。研究表明其耐药机制复杂,表现在不仅可产生多种灭活酶,而且还存在外膜蛋白缺失和主动外排泵机制,是临床研究的热点和难点。     

重症监护病房鲍曼不动杆菌的耐药性分析

目的对近年重症监护病房（ICU）中的鲍曼不动杆菌的耐药性进行分析,指导经验应用抗生素。方法回顾2000年1月至2004年12月自ICU患者分离的鲍曼不动杆菌,分析其药敏结果。结果5年共分离的鲍曼不动杆菌156株,以痰标本为主,占91％。常用抗生素中亚胺培南对鲍曼不动杆菌保持较高的抗菌活性（87％～90％）,对阿米卡星、氨苄西林／舒巴坦、头孢他啶、哌拉西林、环丙沙星等多种抗生素的耐药性较高,且有逐年增高的趋势。结论ICU中鲍曼不动杆菌表现为多重耐药。应重视医院致病菌的耐药性监测,根据其结果应用抗生素。     

Genotypic analysis of Acinetobacter bloodstream infection isolates in a Turkish university hospital

Acinetobacter baumannii is a significant pathogen of bloodstream infections in hospital patients that frequently causes single clone outbreaks. We aimed to evaluate the genetic relatedness and antimicrobial susceptibility of Acinetobacter spp. bloodstream isolates, in order to obtain insight into their cross-transmission. This prospective study was conducted at the Erciyes University Hospital. During a 1-y period, all patients with nosocomial BSI caused by Acinetobacter spp. were included in the study. All data with regard to the patients, underlying diseases and risk factors for BSI and the severity of disease were collected. Blood culture isolates of Acinetobacter spp. were identified according to their morphology and biochemical reactions. The antimicrobial susceptibility was determined using the Kirby-Bauer disk diffusion test according to the NCCLS; the genetic relatedness of isolates was determined by RAPD-PCR analysis and pulsed-field gel electrophoresis (PFGE). 41 patients acquired a nosocomial bloodstream infection caused by A. baumanii during this period. 88% of these infections (36 of 41) occurred while the patients were treated in the intensive care unit. Nearly 80% of the isolates belonged to 3 genotypes, suggesting cross-transmission in ICU settings where infection control practices are poor. All Acinetobacter isolates were multidrug-resistant and the crude mortality of patients infected with A. baumanii was 80.5%. We concluded that the genetic relatedness of Acinetobacter spp. causing BSI was very high, indicating cross-transmission within the ICU setting. Essential components of an infection control programme to prevent nosocomial transmission of A. baumannii are early detection of colonized patients, followed by strict attention to standard precautions and contact isolation.     

呼吸与危重症医学科5年医院感染病原学及耐药性分析

目的：了解呼吸与危重症医学科(RICU)近5年医院感染流行病学特点及细菌耐药性。方法对医院呼吸与危重症医学科2009年6月至2014年6月所分离的病原菌分布构成及耐药性进行回顾性分析。结果共分离出病原菌1411株,其中革兰阴性菌为1254株占88.87%,革兰阳性菌共分离出137株,占9.71%。最常见革兰阴性菌为鲍氏不动杆菌554株,占39.26%;最常见革兰阳性菌为屎肠球菌67株,占4.75%。多重耐药革兰阴性菌前3位是鲍曼不动杆菌、铜绿假单胞菌、肺炎克雷伯菌,检出率分别是36.36%、31.25%、24.83%;革兰阳性球菌对替加环素、万古霉素、替考拉宁及利奈唑胺仍保持较高敏感性。结论革兰阴性杆菌仍为呼吸与危重症医学科医院感染的主要病原菌,且呈多药耐药性特点,应采取行之有效的干预对策,控制细菌耐药性迅速增长的不良趋势。     

二级医院鲍曼不动杆菌感染的临床特征和同源性分析

目的：研究二级医院鲍曼不动杆菌感染患者的临床特征,对耐碳青霉烯鲍曼不动杆菌进行同源性分析,为临床治疗和医院感染控制提供依据。方法收集临床分离的115株非重复性鲍曼不动杆菌,回顾性分析患者的临床资料和细菌药敏资料。采用 Vitek2 Compact 对115株鲍曼不动杆菌进行19种抗菌药物的敏感性检测。采用肠杆菌科基因间一致重复序列聚合酶链技术(ERIC-PCR)对其中的耐碳青霉烯鲍曼不动杆菌进行基因分型和同源性分析。结果115例患者主要集中在 ICU、干部病房和呼吸科病房。患者的平均年龄为(75±16)岁。平均住院时间52.1 d。最常见的合并症为COPD 和糖尿病。72例(62.61%)患者曾接受侵入性操作。86例(74.78%)患者病程中使用过2种及以上的抗生素。48例(41.74%)患者接受机械通气。115株鲍曼不动杆菌对多黏菌素 B 耐药率最低,为0%,其次为替加环素,耐药率7.83%。仅头孢哌酮/舒巴坦、阿米卡星耐药率低于40%,对其他常用抗生素的耐药率均高于50%。对亚胺培南和美罗培南的耐药率分别达56.52%和58.26%。ERIC-PCR 技术将67株耐碳青霉烯鲍曼不动杆菌分为9个基因型。结论二级医院鲍曼不动杆菌感染患者的临床特征为：高龄,住院时间长,合并基础疾病,接受侵入性操作,接受机械通气及使用多种抗生素。对常用的抗生素高度耐药。多重耐药鲍曼不动杆菌及广泛耐药鲍曼不动杆菌存在院内接触传播的现象,因此应该提高医护人员消毒意识,加强耐药性监测及合理使用抗菌药物。     

重症监护病房常见革兰阴性杆菌耐药性监测及防控措施

目的：了解我院重症监护病房（ICU）患者感染革兰阴性杆菌的药物敏感情况,为临床合理使用抗菌药物提供依据。方法：细菌培养鉴定按照《全国临床检验操作规程》进行;药敏试验采用KB法,并制定了医院感染防控措施。结果：分离出G—菌257株,以大肠埃希菌（27.6%）、铜绿假单胞菌（25.3%）、肺炎克雷伯菌（19.8%）、鲍曼不动杆菌（16.7%）为主。药敏试验显示多数细菌呈严重耐药和多重耐药,碳青霉烯类亚胺培南、美洛培南仍为治疗革兰阴性杆菌最为敏感的药物。结论：应重视ICU细菌的耐药性监测,制定防控措施,以指导临床医生合理用药。     

多耐药鲍曼不动杆菌感染治疗方案及控制策略

鲍曼不动杆菌属于条件致病菌,是目前引起医院内及社区性感染的重要病原菌,特别是重症监护病房患者.近年来,多耐药鲍曼不动杆菌甚至是泛耐药鲍曼不动杆菌感染日益增多,治疗十分棘手.     

重症监护病房院内感染调查分析

目的 :研究重症监护病房院内感染菌群的变迁及细菌耐药的情况 ,为经验性选择抗生素提供依据 ,以达到控制院内感染的目的。方法 :对本院ICU 13 9例患者分离出的 3 10株细菌进行分析。结果 :共分离出革兰阳性 (G+)球菌 64株 ,占总数的 2 0 .6% ;革兰阴性 (G-)杆菌共 178株 ,占总数的 5 7.5 %。G-杆菌中列前三位的分别是铜绿假单胞菌 ( 2 1.6% ) ,肠杆菌 ( 6.8% ) ,大肠艾希菌( 6.5 % )。真菌共 61株 ,占总数的 19.7%。亚胺培南 西拉司丁钠、阿米卡星、头孢他啶对所有的G-杆菌保持着良好的抗菌活性 ,而环丙沙星的敏感率逐年下降。院内感染的发生部位以呼吸道最为常见。结论 :感染的细菌仍以G-杆菌为主。真菌的感染率始终较高 ,并且出现菌种的变异。菌种及细菌药敏的变化使经验性的选择抗生素变得越来越困难。临床医师应尽量减少用药的盲目性 ,以控制耐药菌的产生     

重症监护病房非发酵菌的分离及耐药性

目的了解重症监护病房（ICU）非发酵菌的临床分离状况及常见菌株的耐药性。方法分离出的非发酵菌采用VITEK-60AMS细菌鉴定仪鉴定,K—B法进行体外药敏试验。结果2005年1月～2007年8月共检出非发酵菌366株,铜绿假单胞菌（PAE）最为常见（45．36％）,其次为鲍氏不动杆菌（ABA,23．22％）和嗜麦芽寡养单胞菌（SPM,15．30％）;标本来源主要为痰液、引流液和尿液,分别占42．62％、20．77％和15．85％。PAE、ABA和SPM耐药较为严重,且呈多重耐药性。结论ICU非发酵菌以呼吸道感染常见,其耐药现象严重;应根椐药敏结果选用敏感抗菌药物。     

Risk factors for nosocomial imipenem-resistant Acinetobacter baumannii infections.

OBJECTIVES: To identify the risk factors for nosocomial imipenem-resistant Acinetobacter baumannii (IRAB) infections. METHODS: A prospective case-control study, set in an 1100-bed referral and tertiary-care hospital, of all patients who had nosocomial A. baumannii infections between January 1 and December 31, 2004. Only the first isolation of A. baumannii was considered. RESULTS: IRAB was isolated from 66 (53.7%) patients and imipenem-sensitive Acinetobacter baumannii (ISAB) was isolated from 57 (46.3%) patients during the study period. The mean duration of hospital stay until A. baumannii isolation was 20.8+/-13.6 days in IRAB infections, whereas it was 15.4+/-9.4 days in ISAB infections. Of the patients, 65.2% with IRAB infections and 40.4% with ISAB infections were followed at the intensive care unit (ICU). Previous carbapenem use was present in 43.9% of the patients with IRAB and 12.3% of the patients with ISAB infection. In univariate analysis female sex, longer duration of hospital stay until infection, ICU stay, emergent surgical operation, total parenteral nutrition, having a central venous catheter, endotracheal tube, urinary catheter or nasogastric tube, previous antibiotic use, and previous administration of carbapenems were significant risk factors for IRAB infections (p<0.05). In multivariate analysis, longer duration of hospital stay until A. baumannii isolation (odds ratio (OR) 1.043; 95% confidence interval (CI) 1.003-1.084; p=0.032), previous antibiotic use (OR 5.051; 95% CI 1.004-25.396; p=0.049), and ICU stay (OR 3.100; 95% CI 1.398-6.873; p=0.005) were independently associated with imipenem resistance. CONCLUSIONS: Our results suggest that the nosocomial occurrence of IRAB is strongly related to an ICU stay and duration of hospital stay, and that IRAB occurrence may be favored by the selection pressure of previously used antibiotics.     

中枢神经系统疾病医院获得性肺炎病原菌特点及耐药性分析

目的　探讨中枢神经系统疾病医院获得性肺炎的发病机制、病原菌菌型分布及耐药现状。方法　对 5 6例中枢神经系统疾病医院获得性肺炎患者痰液中分离的 5 9株致病菌进行菌型分类、并选用 15常用抗菌药物对其进行了体外MIC药敏试验。结果　中枢神经系统疾病医院获得性肺炎病原菌分离株数前五位分别是 :金黄色葡萄球菌 (2 3 7% )、铜绿假单胞菌 (2 2 0 % )、鲍曼不动杆菌 (18 6 % )、肺炎克雷伯菌 (8 5 % )、嗜麦芽假单胞菌 (6 8% ) ;药敏结果表明 ,所有革兰阴性菌对抗菌药物耐药率均呈上升趋势 ,尚未发现耐万古霉素的MRSA菌株。结论　住院时间长、呼吸道侵入性操作、长时间使用抗生素是中枢神经系统疾病医院获得性肺炎的易感因素 ;金黄色葡萄球菌、铜绿假单胞菌、鲍曼氏不动杆菌、肺炎克雷伯氏菌、嗜麦芽假单胞菌是中枢神经系统疾病医院获得性肺炎的主要致病菌 ,在临床治疗中 ,必须重视早期预防、及时诊断、合理使用抗菌素 ,才能预防或减少医院获得性肺炎的发生以及控制院感菌日益增高的耐药趋势     

Nosocomial Acinetobacter pneumonia

Acinetobacter spp. (A. baumannii is the prevalent genomic species, but others may cause infection) has become an increasingly important cause of nosocomial pneumonia, particularly in mechanically ventilated patients (VAP). This organism has intrinsic resistance to some antimicrobials but easily acquires resistance to many others; Acinetobacter spp. can survive for long periods of time in the environment. All of these characteristics have contributed to protracted outbreaks associated with significant morbidity and mortality. High rates of colonization are found in debilitated hospitalized patients. Infecting or colonizing organisms in nosocomial infections are more likely to be from cross-transmission or from the hospital environment than from endogenous sources. VAP caused by Acinetobacter spp. is emerging as a prominent hospital complication. The incidence of this microorganism varies from site to site, but it is the second commonest aetiological agent among the gram-negative bacteria. Longer periods of hospitalization, longer time on mechanical ventilation and prior use of antibiotics are the recognized factors increasing the risk of VAP due to Acinetobacter spp. Treatment needs to clearly differentiate infection from colonization, and the agents with the most antimicrobial activity are imipenem/cilastatin, amikacin, colistin, ampicillin/sulbactam and tigecycline. Monotherapy can be adequate if the patient does not have significant comorbidities. Infection control procedures have a major role to play in preventing transmission of this microorganism. Emphasis on initial control measures should, however, be on strict isolation of infected or colonized patients to limit dissemination of outbreak strains in the environment. The variety of potential sources of contamination with Acinetobacter spp. in the hospital environment makes control of these outbreaks one of the more difficult challenges. Persistence of Acinetobacter spp. in the environment provides ample opportunities for contamination of patients and staff and may explain continuing long-term outbreaks.