A survey of latent tuberculosis infection among laboratory healthcare workers in New York City.

OBJECTIVE: To determine the prevalence of positive tuberculin skin tests (TSTs), incidence of TST conversion, risk factors for positive TSTs, and history of active TB among HCWs in microbiology laboratories in New York City. DESIGN: Two-year survey from May 1999 to June 2001. SETTING: Nineteen microbiology laboratories. RESULTS: During the first year, interviews were conducted with 345 laboratory HCWs (mean, 18 HCWs per site; range, 2 to 51) to assess the prevalence of positive TSTs, but 3 (1%) could not recall their result and were excluded from further analyses. The mean age of the remaining 342 HCWs was 48 years; 68% (n = 233) were female, 54% (n = 183) received bacille Calmette-Guerin (BCG) vaccination, and 71% (n = 244) were foreign born. The prevalence of a positive TST was 57% (n = 196), but only 20% (n = 39) of the HCWs received isoniazid. The incidence of TST conversion in the second year of the study was 1% (1 of 108). Multivariate analysis identified age (odds ratio [OR] per year, 1.05; 95% confidence interval [CI95], 1.02-1.08), foreign birth (OR, 3.80; CI95, 1.98-7.28), BCG immunization (OR, 4.89; CI95, 2.72-8.80), and employment in a mycobacteriology laboratory (OR, 2.14; CI95, 1.25-3.68) as risk factors for a positive TST. Only one HCW had been treated for active TB. CONCLUSIONS: The prevalence of positive TSTs was high among laboratory HCWs, but the TST conversion rate was low. Higher rates of treatment for latent TB infection are desirable.     

Risk of tuberculous infection among healthcare workers in a tertiary-care hospital in Ankara, Turkey.

OBJECTIVE: To determine risk factors for tuberculin skin test (TST) positivity among healthcare workers (HCWs). DESIGN: Two-step TST was performed in 2002. SETTING: Tertiary-care hospital in Ankara, Turkey. PARTICIPANTS: A sample of 491 hospital HCWs were included. Information related to demographics, profession, work duration, department, and individual and family history of tuberculosis (TB) was obtained by a structured questionnaire. RESULTS: Four hundred eight (83%) had two-step TST positivity. On multivariate analysis, male physicians (relative risk [RR], 1.5; 95% confidence interval [CI95], 1.23-1.69; P = .001), nurses (RR, 1.5; CI95, 1.29-1.66; P = .005), radiology technicians (RR, 1.7; CI95, 1.35-1.73; P = .002), laboratory technicians (RR, 1.6; CI95, 1.3-1.74; P = .007), and male housekeepers (RR, 1.6; (HCWs). CI95, 1.38-1.7; P < .001) had a higher risk than did female physicians. Among laboratory technicians, radiology technicians had the highest TST positivity (85%). HCWs working for less than 1 year (RR, 0.8; CI95, 0.72-0.98; P = .027) had a lower risk of infection. The HCWs having bacille Calmette-Guerin vaccination (RR, 1.12; CI95, 1.08-1.45) had higher TST positivity. CONCLUSION: Male physicians, nurses, and laboratory technicians had increased risk of Mycobacterium tuberculosis infection in this setting, but community exposure likely accounted for most infections.     

Seroepidemiology of varicella-zoster virus antibodies among health-care workers and day-care-centre workers

Inclusion of live varicella vaccine in the routine occupational health vaccination schedule requires knowledge of the natural immunity to varicella zoster virus (VZV) among high-risk occupations. This study aims were to evaluate VZV antibody positivity among health-care workers (HCWs) and day-care-centre workers (DCWs) and to assess its association with potential risk factors. Three groups of workers were tested for VZV antibody positivity: hospitals and community clinic HCWs (n = 335), DCWs (n = 117) and blue-collar workers as controls (n = 121). The total VZV antibody positivity was 94.4%. There was no significant difference in VZV antibody positivity among study groups. DCWs had the lowest VZV seroprevalence (90.9%, 95% CI 85.7-96.1) and controls the highest (96.6%, 95% CI 93.2-99.9). This high VZV antibody positivity suggests that no special occupational measures are indicated in health-care or day-care occupational settings in Israel. On-going monitoring of the natural immunity to VZV is necessary to detect trends over time.     

Factors associated with tuberculin reactivity in two general hospitals in Mexico.

OBJECTIVE: To identify risk factors associated with tuberculin reactivity in healthcare workers (HCWs). DESIGN: Cross-sectional survey of tuberculin reactivity (2 TU of purified protein derivative (PPD) RT23, using the Mantoux two-step test). SETTING: Two general hospitals located in a region with a high prevalence of tuberculosis and high bacille Calmette-Guerin (BCG) coverage. PARTICIPANTS: Volunteer sample of HCWs. RESULTS: 605 HCWs were recruited: 71.2% female; mean age, 36.4 (standard deviation [SD], 8.2) years; 48.9% nurses, 10.4% physicians, 26.8% administrative personnel; mean time of employment, 10.9 (SD, 6.7) years. PPD reactivity (> or =10 mm) was found in 390 (64.5%). Multivariate analysis revealed an association of tuberculin reactivity with occupational exposure in the hospital: participation in autopsies (odds ratio [OR], 9.3; 95% confidence interval [CI95], 2.1-40.5; P=.003.), more than 1 year of employment (OR, 2.4; CI95, 1.1-5.0; P=.02), work in the emergency or radiology departments (OR, 2.0; CI95, 1.03-3.81; P=.04), being physicians or nurses (OR, 1.5; CI95, 1.04-2.11; P=.03), age (OR, 1.04; CI95, 1.02-1.07 per year of age; P<.001), and BCG scar (OR, 2.1; CI95, 1.2-3.4; P=.005). CONCLUSIONS: Although the studied population has a high baseline prevalence of tuberculosis infection and high coverage of BCG vaccination, nosocomial risk factors associated with PPD reactivity were identified as professional risks; strict early preventive measures must be implemented accordingly.     

传染病医院医务人员结核感染状况

目的了解传染病医院医务人员结核(TB)感染现况,探讨其感染TB的危险性及影响因素。方法对某传染病医院的全体医务工作者进行问卷调查和TB菌素纯蛋白衍化物（PPD）试验检测。结果该传染病医院全体职工TB感染发病率为48.18%。不同科室医务工作者的TB感染情况差异无统计学意义（P＞0.05）,不同工作年限、不同年龄、不同职称的医务工作者TB感染情况差异均有统计学意义（均P＜0.05）。文化程度、职称、目前居住情况、在结核感染门诊或病区的工作时间是TB感染的危险因素,其OR(95%CI)分别为1.70（1.03～2.80）、1.95（1.10～3.45）、1.84（1.03～3.28）、2.38（1.40～4.04）;个人防护是TB感染的保护因素［OR及OR95%CI为0.92（0.85～0.99）］。结论传染病医院的医务工作者是TB感染的高危人群,应加强自我防护意识,及早采取防护措施。     

Risk factors for tuberculosis among health care workers in South India: a nested case–control study

ObjectiveThe epidemiology of tuberculosis (TB) among health care workers (HCWs) in India remains under-researched. This study is a nested case–control design assessing the risk factors for acquiring TB among HCWs in India.Study Design and SettingsIt is a nested case–control study conducted at a tertiary teaching hospital in India. Cases (n = 101) were HCWs with active TB. Controls (n = 101) were HCWs who did not have TB, randomly selected from the 6,003 subjects employed at the facility. Cases and controls were compared with respect to clinical and demographic variables.ResultsThe cases and controls were of similar age. Logistic regression analysis showed that body mass index (BMI) <19 kg/m² (odds ratio [OR]: 2.96, 95% confidence interval [CI]: 1.49–5.87), having frequent contact with patients (OR: 2.83, 95% CI: 1.47–5.45) and being employed in medical wards (OR: 12.37, 95% CI: 1.38–110.17) or microbiology laboratories (OR: 5.65, 95% CI: 1.74–18.36) were independently associated with increased risk of acquiring TB.ConclusionHCWs with frequent patient contact and those with BMI <19 kg/m² were at high risk of acquiring active TB. Nosocomial transmission of TB was pronounced in locations, such as medical wards and microbiology laboratories. Surveillance of high-risk HCWs and appropriate infrastructure modifications may be important to prevent interpersonal TB transmission in health care facilities.     

Treatment for latent TB in correctional facilities: a challenge for TB elimination

BACKGROUND: To eliminate tuberculosis (TB) in the United States, more information is needed on how to gain access to difficult-to-reach, high-risk populations to evaluate people who would benefit from treatment for latent TB infection (LTBI). METHODS: A field study was conducted of people at risk for co-infection with TB and the human immunodeficiency virus (HIV) and to demonstrate that treating LTBI in inmates is feasible. Inmates were tested for LTBI using the Mantoux tuberculin skin test (TST). Outcomes measured were skin test results and the start and completion of treatment for LTBI. RESULTS: In 49 correctional facilities in 12 states, 198102 inmates had a skin test read. The mean skin test positivity rate among inmates was 17.0%. Of those who had a known HIV test result, 14.5% tested HIV positive. Inmates with a positive TST were 4.2 times more likely than those with a negative TST to be HIV infected (95% confidence interval [CI]=3.9-4.4). Therapy for LTBI was completed in 55.9% of patients started on treatment. Patients who were HIV positive and started on a 12-month treatment regimen were less likely than HIV-negative patients (40.0% vs 68.1%, respectively) to complete treatment (odds ratio [OR]=0.24, 95% CI=0.20-0.28). Patients treated in jails were less likely than those treated in prisons (33.6% vs 57.7%, respectively) to complete treatment (OR=0.29, 95% CI=0.26-0.32). CONCLUSIONS: Correctional facilities offer a venue for identifying and treating high-risk individuals for LTBI. However, completing treatment is more problematic in jails than in prisons.     

Influenza vaccination of healthcare workers in the United States, 1989-2002.

OBJECTIVES: We sought to estimate influenza vaccination coverage among healthcare workers (HCWs) in the United States during 1989-2002 and to identify factors associated with vaccination in this group. The Advisory Committee on Immunization Practices (ACIP) recommends annual influenza vaccination for HCWs to reduce transmission of influenza to patients at high risk for serious complications of influenza. DESIGN: Analysis of cross-sectional data from 1989-2002 surveys conducted by the National Health Interview Survey (NHIS). The outcome measure was self-reported influenza vaccination in the past 12 months. Bivariate and multivariate analysis of 2002 NHIS data. SETTING: Household interviews conducted during 1989-2002, weighted to reflect the noninstitutionalized, civilian US population. PARTICIPANTS: Adults aged 18 years or older participated in the study. A total of 2,089 were employed in healthcare occupations or settings in 2002, and 17,160 were employed in nonhealthcare occupations or settings. RESULTS: The influenza vaccination rate among US HCWs increased from 10.0% in 1989 to 38.4% in 2002, with no significant change since 1997. In a multivariate model that included data from the 2002 NHIS, factors associated with a higher rate of influenza vaccination among HCWs aged 18-64 years included age of 50 years or older (odds ratio [OR], 1.6; 95% confidence interval [CI], 1.1-2.1), hospital employee status (OR, 1.5; 95% CI, 1.2-1.9), 1 or more visits to the office of a healthcare professional in the past 12 months (OR, 1.5; 95% CI, 1.1-2.2), receipt of employer-provided health insurance (OR, 1.5; 95% CI, 1.1-2.1), a history of pneumococcal vaccination (OR, 3.9; 95% CI, 2.5-6.1), and history of hepatitis B vaccination (OR, 1.9; 95% CI, 1.4-2.4). Non-Hispanic black persons were less likely to be vaccinated (OR, 0.6; 95% CI, 0.5-0.9) than non-Hispanic white persons. There were no significant differences in vaccination levels according to HCW occupation category. CONCLUSIONS: Influenza immunization among HCWs reached a plateau during 1997-2002. New strategies are needed to encourage US HCWs to receive influenza vaccination to prevent influenza illness in themselves and transmission of influenza to vulnerable patients.     

Tuberculosis among health care workers

To assess the annual risk for latent tuberculosis infection (LTBI) among health care workers (HCWs), the incidence rate ratio for tuberculosis (TB) among HCWs worldwide, and the population-attributable fraction of TB to exposure of HCWs in their work settings, we reviewed the literature. Stratified pooled estimates for the LTBI rate for countries with low (<50 cases/100,000 population), intermediate (50-100/100,000 population), and high (>100/100,000 population) TB incidence were 3.8% (95% confidence interval [CI] 3.0%-4.6%), 6.9% (95% CI 3.4%-10.3%), and 8.4% (95% CI 2.7%-14.0%), respectively. For TB, estimated incident rate ratios were 2.4 (95% CI 1.2-3.6), 2.4 (95% CI 1.0-3.8), and 3.7 (95% CI 2.9-4.5), respectively. Median estimated population-attributable fraction for TB was as high as 0.4%. HCWs are at higher than average risk for TB. Sound TB infection control measures should be implemented in all health care facilities with patients suspected of having infectious TB.     

Tuberculosis infection in urban adolescents: results of a school-based testing program.

In 1986-87 a pilot tuberculosis (TB) skin testing program was introduced for seventh and tenth grade students in the Boston (Massachusetts) public schools. The 8.9 percent tuberculin positivity rate in tenth grade students was significantly higher than the 5.1 percent rate found in seventh graders. A majority of those who were skin test positive were born outside the United States. These results suggest that tuberculin testing in an urban school setting may identify a significant number of candidates for TB preventive therapy, particularly among tenth grade students and those who are foreign-born.     

Risk perception and attitudes towards HIV in Serbian health care workers

BACKGROUND: Health care workers (HCWs) are at risk of occupational exposure to human immunodeficiency virus (HIV). AIM: To investigate the perception of professional risk from, and the knowledge, attitudes and practice of HCWs to HIV and AIDS in Serbia. METHODS: Cross-sectional study of 1,559 Serbian HCWs using self-administered anonymous questionnaires. Chi-square testing and multiple logistic regression analysis were applied. RESULTS: Eighty-nine per cent of HCWs believed that they were at risk of acquiring HIV through occupational exposure. The perception of professional risk was higher among HCWs frequently exposed to patients' blood and body fluids (OR 7.9, 95% CI 4.4-14.5), who used additional personal protection if the HIV status of patient was known (OR 2.6, 95% CI 1.5-4.6), who had experienced sharp injuries within the last year (OR 1.9, 95% CI 1.0-3.8) or who had been tested for HIV (OR 2.1, 95% CI 1.2-3.5), and among HCWs who had treated HIV-positive patients (OR 1.7, 95% CI 1.1-2.8). The majority of respondents had deficient knowledge about modes of HIV transmission. Attitudes towards HIV-positive patients were significantly different by occupation. Seventy per cent of HCWs used appropriate protection during their daily work with patients. CONCLUSIONS: HCWs require specific educational programmes and training protocols to ensure that they are adequately protected when carrying out high quality care.     

Tuberculin skin testing among healthcare workers in the University of Malaya Medical Centre, Kuala Lumpur, Malaysia.

OBJECTIVES: To determine the occupational risk of Mycobacterium tuberculosis infection among healthcare workers (HCWs) and to examine the utility of tuberculin skin testing in a developing country with a high prevalence of bacille Calmette-Guerin vaccination. DESIGN: Tuberculin skin test (TST) survey. SETTING: A tertiary-care referral center and a teaching hospital in Kuala Lumpur, Malaysia. PARTICIPANTS: HCWs from medical, surgical, and orthopedic wards. INTERVENTION: Tuberculin purified protein derivative RT-23 (State Serum Institute, Copenhagen, Denmark) was used for the TST (Mantoux method). RESULTS: One hundred thirty-seven (52.1%) and 69 (26.2%) of the HCWs tested had indurations of 10 mm or greater and 15 mm or greater, respectively. Medical ward HCWs were at significantly higher risk of a positive TST reaction than were surgical or orthopedic ward HCWs (odds ratio, 2.18; 95% confidence interval, 1.33 to 3.57; P = .002 for TST positivity at 10 mm or greater) (odds ratio, 2.61; 95% confidence interval, 1.44 to 4.70; P = .002 for TST positivity at 15 mm or greater). A previous TST was a significant risk factor for a positive TST reaction at either 10 mm or greater or 15 mm or greater, but a duration of employment of more than 1 year and being a nurse were only significantly associated with a positive TST reaction at a cut-off point of 15 mm or greater. CONCLUSIONS: HCWs at the University of Malaya Medical Centre had an increased risk for M. tuberculosis infection that was significantly associated with the level of occupational tuberculosis exposure. A TST cut-off point of 15 mm or greater may correlate better with M. tuberculosis infection than a cut-off point of 10 mm or greater in settings with a high prevalence of bacille Calmette-Guerin vaccination.     

A MODEL FOR INTERVAL-CENSORED TUBERCULOSIS OUTBREAK DATA

As the incidence of tuberculosis (TB) has increased in the United States, occupationally acquired TB has increased among the health care workers (HCWs). This paper describes a model developed in response to the needs of an outbreak of multidrug-resistant TB. One of the goals of the outbreak investigation was to estimate the risk of tuberculin skin test (TST) conversion as a function of HCW job type and the period during which persons were employed over the study period. TST conversions were evaluated at periodic examinations and data are interval-censored. We present a generalized linear model that extends Efron's survival model for censored survival data to the case of interval-censored data. © 1997 by John Wiley & Sons, Ltd. © 1997 by John Wiley & Sons, Ltd.     

Evaluation of a western blot test as a potential screening tool for occupational exposure to Mycobacterium tuberculosis in health care workers

Health care workers (HCWs) have a higher than average risk for contracting Mycobacterium tuberculosis (MTB) infection and tuberculosis (TB). No markers of MTB-exposure are available, and TB risk assessment is performed by tuberculin screening, identifying individuals with acquired MTB infection. This study evaluated a western blot (WB) anti-M. bovis A60 complex antibody as a MTB-exposure marker. WB reactivity was evaluated on 127 exposed and 28 non-exposed HCWs from four divisions of the Policlinico Hospital of Modena, and 140 non-exposed bacille Calmette-Guérin-vaccinated controls. Excess of occupational TB risk according to the Occupational Safety and Health Administration (OSHA) was calculated in each division. WB-positivity (%) was: (1) significantly higher in exposed HCWs compared with non-exposed (72% vs 25%, P < 0.00001), (2) highly related (r = 0.99) to OSHA risk excess in all divisions, (3) higher than non-exposed in HCWs with short (< 5 years) MTB-exposure (purified protein derivative [PPD], P > 0.18; WB, P < 0.04). PPD-positivity (%) was higher than controls only in HCWs with longer (> 5 years) MTB-exposure. The study suggests that the WB antibody might represent a more sensitive biological marker of MTB contact among exposed HCWs, related to the level of TB risk and detectable earlier than the PPD skin test, thus providing new tools for TB risk assessment in health care facilities.     

Latent tuberculosis in nursing professionals of a Brazilian hospital

Tuberculosis (TB) is considered an occupational disease among health-care workers (HCWs). Direct contact with TB patients leads to an increased risk to become latently infected by Mycobacterium tuberculosis. The objective of this study is to estimate the prevalence of latent M. tuberculosis minfection among nursing professionals of a hospital in Rio Grande do Sul, Brazil, assessed by tuberculin skin test (TST). From November 2009 to May 2010, latent M. tuberculosis infection was assessed by TST in 55 nursing professionals. Epidemiological information was collected using a standardized questionnaire. A positive TST result (> or = 10 mm) was observed in 47.3% of the HCWs tested. There was no significant difference in TST positivity when duration of employment or professional category (technician or nurse) was evaluated. The results of this work reinforce the need for control measures to prevent latent M. tuberculosis infection among nursing professionals at the hospital where the study was conducted.     

Effectiveness of interventions for the control and prevention of tuberculosis in health care facilities: a review of ATS,CDC, OSHA recommendations

BACKGROUND: Health care workers (HCWs) are occupationally exposed to a multitude of biological hazards, and among these to the risk of tuberculosis (TB) infection, especially involving individuals working in specific workplace (TB and Chest divisions, Infectious Diseases wards, Microbiology laboratories) and performing thoracic endoscopy and "cough-inducing" procedures. According to national legislation (title VIII D.lgs. 626/94, 1998 Health Minister guide lines document) concerning the control and prevention of TB transmission among HCWs, health care facilities are required to (i) perform an accurate risk assessment and (ii) implement an exposure control plan and worker health surveillance program, thus involving the occupational health professionals. OBJECTIVES: The aim of this paper is to provide a general view of the epidemiological and scientific evidence related to the effectiveness of health interventions in the prevention of occupational TB infection. METHODS: Comparative evaluation and critical review of U.S. CDC (1994) guidelines, OSHA (1997) rules, and the most recent ATS and CDC (2000) "statement" documents. RESULTS: In low risk groups TCT shows decreased positive predictive value, high variability, and can be confounded by other factors (age, BCG, MNT), thus reducing its diagnostic value for latent TB infection. CONCLUSIONS: Recent recommendations on the control of TB infection in health care settings underline the need of implementing accurate risk evaluation in all hospital units, compared to the epidemiological profile in the community, and "targeted tuberculin testing" programs among high risk HCWs.     

Risk factors for hepatitis C virus infection among Egyptian healthcare workers in a national liver diseases referral centre

Little is known about the prevalence of hepatitis C virus (HCV) among healthcare workers (HCW) in Egypt, where the highest worldwide prevalence of HCV exists. The prevalence of HCV, hepatitis B virus and Schistosoma mansoni antibodies was examined in 842 HCWs at the National Liver Institute in the Nile Delta, where >85% of patients are HCV antibody-positive. The mean age of HCWs was 31.5 years and they reported an average of 0.6±1.2 needlesticks/HCW/year. The prevalence of anti-HCV, hepatitis B surface antigen (HBsAg) and co-infection was 16.6%, 1.5% and 0.2%, respectively. HCV-RNA was present in 72.1% of anti-HCV-positive HCWs, and all but one subject were infected with HCV genotype 4. Schistosoma mansoni antibodies were present in 35.1%. The anti-HCV rate increased sharply with age and employment duration, but not among those with needlestick history. After adjusting for other risk factors, the anti-HCV rate was higher among older HCWs [P<0.001; risk ratio (RR) = 1.086, 95% CI 1.063-1.11], males (P=0.002; RR=1.911, 95% CI 1.266-2.885) and those with rural residence (P<0.001; RR=2.876, 95% CI 1.830-4.52). Occupation (P=0.133), duration of employment (P=0.272) or schistosomal antibody positivity (P=0.152) were not significant risk factors for anti-HCV positivity. In conclusion, although one in six HCWs had been infected with HCV, the infections were more likely to be community-acquired and not occupationally related.     

Anxiety and depression predict musculoskeletal disorders in health care workers

Incidence of musculoskeletal disorders (MSDs) is high among health care workers (HCWs). To determine whether MSDs are associated with preexisting anxiety and/or depression, a case-control study was carried out in female HCWs (56 cases/55 controls). Cases were HCWs with a first-time clinical diagnosis of MSD within the previous 2 years. Occupation, workplace, work shift, direct patient assistance, and anxiety/depression scores (Goldberg scale) were assessed. Increased risk of incident MSDs (multivariate logistic regression) was found in workers with preexisting anxiety/depression compared to those without (OR 5.01; 95% CI 2.20–12.05; p < .01). Other significant risk factors were direct patient assistance (OR 2.59; 95% CI 1.03–6.92; p = .04) and morning work shift (OR 2.47; 95% CI 0.99–6.48; p = .05). Preexisting anxiety/depression was associated with incident MSDs in HCWs, adjusting for occupational exposure risk factors.     

综合性医院医务工作者结核分枝杆菌感染现状及职业防护

目的了解综合性医院医务工作者结核分枝杆菌（TB）感染现状及职业防护措施,分析影响因素,为综合性医疗机构结核病职业防护管理策略提供科学依据。方法采用横断面研究方法对河南省郑州市中心医院各临床科室医务工作者进行社会人口学特征、健康状况和职业防护方式的问卷调查和结核菌素皮肤试验（TST）。TB感染的影响因素分析采用单变量logistic回归和多变量逐步logistic回归,将单变量logistic回归分析中P〈0.10的变量纳入多变量logistic回归模型。采用SPSS 17.0软件对数据进行统计分析。结果 325名临床相关科室的医务工作者中,结核分枝杆菌感染率为34.2%,未发现现症肺结核患者。经多因素logistic回归分析发现,临床工作岗位（OR=2.26,95%CI：1.33~3.83）、艾滋病门诊、病房工作史（OR=6.39,95%CI：1.26~32.51）和早餐习惯（OR=3.87,95%CI：1.40~10.73）是医务工作者结核分枝杆菌感染的影响因素。结论综合性医疗机构医务工作者是结核分枝杆菌感染的重点人群,尤其应该重视其中某些高风险科室的医院感染预防控制,建立常态化的医务工作者结核分枝杆菌感染状态的体检监测制度和医疗机构内部结核病院内感染控制的评估机制。