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Intensive care units (ICUs) play an important role in the epidemiology of methicillin-resistant Staphyloccocus aureus (MRSA). Although successful interventions are multi-modal, the relative efficacy of single measures remains unknown. We developed a discrete time, individual-based, stochastic mathematical model calibrated on cross-transmission observed through prospective surveillance to explore the transmission dynamics of MRSA in a medical ICU. Most input parameters were derived from locally acquired data. After fitting the model to the 46 observed cross-transmission events and performing sensitivity analysis, several screening and isolation policies were evaluated by simulating the number of cross-transmissions and isolation-days. The number of all cross-transmission events increased from 54 to 72 if only patients with a past history of MRSA colonization are screened and isolated at admission, to 75 if isolation is put in place only after the results of the admission screening become available, to 82 in the absence of admission screening and with a similar reactive isolation policy, and to 95 when no isolation policy is in place. The method used (culture or polymerase chain reaction) for admission screening had no impact on the number of cross-transmissions. Systematic regular screening during ICU stay provides no added-value, but aggressive admission screening and isolation effectively reduce the number of cross-transmissions. Critically, colonized healthcare workers may play an important role in MRSA transmission and their screening should be reinforced.

Adults more than 40 years old are not necessarily immune to measles. A measles outbreak that involved healthcare workers occurred after contact with a 44-year-old patient. Results of a hospital-wide program of mass screening revealed that 117 (4.5%) of 2,600 individuals tested seronegative for measles; 31 (26.1%) of these 117 individuals were more than 40 years old.

The authors compared a case-crossover design, a case-time-control design, and a cohort design to evaluate the effect of nurse staffing level on the risk of nosocomial infections. They evaluated two strategies, conditional logistic regression and generalized estimating equation, to analyze the case-crossover study. The study was performed among critically ill patients in the medical intensive care unit of the University of Geneva Hospitals, Geneva, Switzerland. Of 366 patients who stayed more than 7 days in the intensive care unit between 1999 and 2002, 144 developed an infection. The main reasons for admission were infectious (35.3%), cardiovascular (32.5%), and pulmonary (19.7%) conditions. A comparison of the three study designs showed that lower nurse staffing was associated with an approximately 50% increased risk of nosocomial infections. All analyses yielded similar estimates, except that the point estimate obtained by the conditional logistic regression used in the case-crossover design was biased away from unity; the generalized estimating equation yielded unbiased results and is the most appropriate technique for case-crossover designs. The case-crossover methodology in hospital epidemiology is a promising alternative to traditional approaches, but selection of the referent periods is challenging.

Introduction: The clinical and economic burden of ventilator-associated pneumonia (VAP) is uncontested. We conducted the present study to determine whether low nurse-to-patient ratio increases the risk for VAP and whether this effect is similar for early-onset and late-onset VAP., Methods: This prospective, observational, single-centre cohort study was conducted in the medical intensive care unit (ICU) of the University of Geneva Hospitals. All patients who were at risk for ICU-acquired infection admitted from January 1999 to December 2002 were followed from admission to discharge. Collected variables included patient characteristics, admission diagnosis, Acute Physiology and Chronic Health Evaluation II score, co-morbidities, exposure to invasive devices, daily number of patients and nurses on duty, nurse training level and all-site ICU-acquired infections. VAP was diagnosed using standard definitions., Results: Among 2,470 patients followed during their ICU stay, 262 VAP episodes were diagnosed in 209/936 patients (22.3%) who underwent mechanical ventilation. Median duration of mechanical ventilation was 3 days (interquartile range 2 to 6 days) among patients without VAP and 11 days (6 to 19 days) among patients with VAP. Late-onset VAP accounted for 61% of all episodes. The VAP rate was 37.6 episodes per 1,000 days at risk (95% confidence interval 33.2 to 42.4). The median daily nurse-to-patient ratio over the study period was 1.9 (interquartile range 1.8 to 2.2). By multivariate Cox regression analysis, we found that a high nurse-to-patient ratio was associated with a decreased risk for late-onset VAP (hazard ratio 0.42, 95% confidence interval 0.18 to 0.99), but there was no association with early-onset VAP., Conclusion: Lower nurse-to-patient ratio is associated with increased risk for late-onset VAP.

Objective: There is growing evidence that low nurse staffing jeopardizes quality of patient care. The objective of the study was to determine whether low staffing level increases the infection risk in critical care., Design: Observational, single-center, prospective cohort study., Setting: Medical intensive care unit of the University of Geneva Hospitals, Switzerland., Patients: All patients admitted over a 4-yr period., Interventions: None., Measurements and Main Results: Study variables included all infections acquired in critical care, daily nurse-to-patient ratio, demographic characteristics, admission diagnosis and severity score, comorbidities, daily individual exposure to invasive devices, and selected drugs. Of a cohort of 1,883 patients totaling 10,637 patient-days, 415 (22%) developed at least one healthcare-associated infection while in critical care. Overall infection rate was 64.5 episodes per 1000 patient-days. Infected patients experienced higher mortality with a longer duration of stay both in critical care and in the hospital than noninfected patients (all p < .001). Median 24-hr nurse-to-patient ratio was 1.9. Controlling for exposure to central venous catheter, mechanical ventilation, urinary catheter, and antibiotics, we found that higher staffing level was associated with a >30% infection risk reduction (incidence rate ratio, 0.69; 95% confidence interval, 0.50-0.95). We estimated that 26.7% of all infections could be avoided if the nurse-to-patient ratio was maintained >2.2., Conclusions: Staffing is a key determinant of healthcare-associated infection in critically ill patients. Assuming causality, a substantial proportion of all infections could be avoided if nurse staffing were to be maintained at a higher level.

Objective: An important problem that arises in hospitals is the monitoring and detection of nosocomial or hospital acquired infections (NIs). This paper describes a retrospective analysis of a prevalence survey of NIs done in the Geneva University Hospital. Our goal is to identify patients with one or more NIs on the basis of clinical and other data collected during the survey., Methods and Material: Standard surveillance strategies are time-consuming and cannot be applied hospital-wide; alternative methods are required. In NI detection viewed as a classification task, the main difficulty resides in the significant imbalance between positive or infected (11%) and negative (89%) cases. To remedy class imbalance, we explore two distinct avenues: (1) a new re-sampling approach in which both over-sampling of rare positives and under-sampling of the noninfected majority rely on synthetic cases (prototypes) generated via class-specific sub-clustering, and (2) a support vector algorithm in which asymmetrical margins are tuned to improve recognition of rare positive cases., Results and Conclusion: Experiments have shown both approaches to be effective for the NI detection problem. Our novel re-sampling strategies perform remarkably better than classical random re-sampling. However, they are outperformed by asymmetrical soft margin support vector machines which attained a sensitivity rate of 92%, significantly better than the highest sensitivity (87%) obtained via prototype-based re-sampling.

Background: Focal outbreaks of sexually transmitted infections (STIs) such as syphilis and gonorrhoea have been reported in the large cities of Western Europe over the past few years. The aim of our study was to determine whether a similar trend is observed in Geneva and the situation with regard to HIV infection., Methods: We review the incidence of syphilis, gonorrhoea, Chlamydia trachomatis and HIV in Geneva from 1999 to 2004., Results: Figures indicate a steady and sustained increase in the incidence of syphilis, gonorrhoea and Chlamydia trachomatis in Geneva since 1999 that is maintained into 2004. As for HIV, the number of positive testings in Switzerland has stabilised and primary infection figures do not indicate an increase in newly acquired infections in Geneva., Conclusion: The situation in Geneva is similar to that observed elsewhere in Western Europe and indicates the need of public health interventions., (Copyright (c) 2006 S. Karger AG, Basel.)

From January to February 2005, the healthcare authorities of the Canton of Geneva were alerted to 15 cases of measles, in contrast to one single case in 2004. The adult status (17-44 years) of the affected persons years was unusual. Four were health care workers at the same hospital who were infected after contact with a 44-year-old patient in a single night during his stay in the emergency room. The presumption that measles are only a paediatric disease had made the diagnosis difficult. None of all these adults was immune according to the actual recommendations. Despite a federal vaccine policy, repetition of recommendations, good results of available vaccines and reimbursement of the cost by health insurance companies, voluntary vaccination prevalence is too small in Switzerland to prevent the outbreak of epidemics. In contrast to the goals of the World Health Organization (WHO) and the Swiss Federal Office of Public Health, the country is unfortunately far from displaying a sufficiently high herd immunity to prevent health care-associated and economic damage by sporadic epidemics.

Objectives: To describe the epidemiology of nosocomial coagulase-negative staphylococci (CoNS) bacteremia and to evaluate the clinical significance of a single blood culture positive for CoNS., Design: A 3-year retrospective cohort study based on data prospectively collected through hospital-wide surveillance. Bacteremia was defined according to CDC criteria, except that a single blood culture growing CoNS was not systematically considered as a contaminant. All clinically significant blood cultures positive for CoNS nosocomial bacteremia were considered for analysis., Setting: A large university teaching hospital in Geneva, Switzerland., Results: A total of 2,660 positive blood cultures were identified. Of these, 1,108 (41.7%) were nosocomial; CoNS were recovered from 411 nosocomial episodes (37.1%). Two hundred thirty-four episodes of CoNS bacteremia in the presence of signs of sepsis were considered clinically relevant and analyzed. Crude mortality and associated mortality were 24.4% and 12.8%, respectively. Associated mortality was similar among patients with one positive blood culture and those with two or more (16.2% vs 10.8%, respectively; P = .3). Mortality rates after bacteremia for patients with a single positive blood culture and for those with two or more were 15.3% and 7.0%, respectively, at day 14 (RR, 2.2; CI95, 0.87-5.46) and 20.8% and 11.3%, respectively, at day 28 (RR, 1.9; CI95, 0.9-3.8). On multivariate analysis, only age and a rapidly fatal disease were independently associated with death., Conclusion: CoNS bacteremia harbor a significant mortality and a single positive blood culture in the presence of signs of sepsis should be considered as clinically relevant.

Two case-control studies evaluated the prevalence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) carriage at hospital admission and characteristics of patients with CA-MRSA. Among 14,253 patients, CA-MRSA prevalence was 0.9/1,000 admissions. Although 5 CA-MRSA isolates contained Panton-Valentine leukocidin, only 1 patient had a previous skin infection. No easily modifiable risk factor for CA-MRSA was identified.

We evaluated the costs associated with a sustained and successful campaign for hand hygiene promotion that emphasized alcohol-based handrubs. The total cost of the hand hygiene promotion corresponded to less than 1% of the costs associated with nosocomial infections. Successful hand hygiene promotion is probably cost-saving.

Objective: To evaluate the dynamics of bacterial contamination of healthcare workers' (HCWs) hands during neonatal care., Setting: The 20-bed neonatal unit of a large acute care teaching hospital in Geneva, Switzerland., Methods: Structured observation sessions were conducted. A sequence of care began when the HCW performed hand hygiene and ended when the activity changed or hand hygiene was performed again. Alcohol-based handrub was the standard procedure for hand hygiene. An imprint of the five fingertips of the dominant hand was obtained before and after hand hygiene and at the end of a sequence of care. Regression methods were used to model the final bacterial count according to the type and duration of care and the use of gloves., Results: One hundred forty-nine sequences of care were observed. Commensal skin flora comprised 72.4% of all culture-positive specimens (n = 360). Other microorganisms identified were Enterobacteriaceae (n = 55, 13.8%); Staphylococcus aureus (n = 10, 2.5%); and fungi (n = 7, 1.8%). Skin contact, respiratory care, and diaper change were independently associated with an increased bacterial count; the use of gloves did not fully protect HCWs' hands from bacterial contamination., Conclusions: These data confirm that hands become progressively contaminated with commensal flora and potential pathogens during neonatal care, and identify activities at higher risk for hand contamination. They also reinforce the need for hand hygiene after a sequence of care, before starting a different task, and after glove removal.

Primary bloodstream infection (BSI) is a leading, preventable infectious complication in critically ill patients and has a negative impact on patients' outcome. Surveillance definitions for primary BSI distinguish those that are microbiologically documented from those that are not. The latter is known as clinical sepsis, but information on its epidemiologic importance is limited. We analyzed prospective on-site surveillance data of nosocomial infections in a medical intensive care unit. Of the 113 episodes of primary BSI, 33 (29%) were microbiologically documented. The overall BSI infection rate was 19.8 episodes per 1,000 central-line days (confidence interval [CI] 95%, 16.1 to 23.6); the rate fell to 5.8 (CI 3.8 to 7.8) when only microbiologically documented episodes were considered. Exposure to vascular devices was similar in patients with clinical sepsis and patients with microbiologically documented BSI. We conclude that laboratory-based surveillance alone will underestimate the incidence of primary BSI and thus jeopardize benchmarking.

Nosocomial infections (NIs)---those acquired in health care settings---are among the major causes of increased mortality among hospitalized patients. They are a significant burden for patients and health authorities alike; it is thus important to monitor and detect them through an effective surveillance system. This paper describes a retrospective analysis of a prevalence survey of NIs done in the Geneva University Hospital. Our goal is to identify patients with one or more NIs on the basis of clinical and other data collected during the survey. In this two-class classification task, the main difficulty lies in the significant imbalance between positive or infected (11%) and negative (89%) cases. To cope with class imbalance, we investigate one-class SVMs which can be trained to distinguish two classes on the basis of examples from a single class (in this case, only "normal" or non infected patients). The infected ones are then identified as "abnormal" cases or outliers that deviate significantly from the normal profile. Experimental results are encouraging: whereas standard 2-class SVMs scored a baseline sensitivity of 50.6% on this problem, the one-class approach increased sensitivity to as much as 92.6%. These results are comparable to those obtained by the authors in a previous study on asymmetrical soft margin SVMs; they suggest that one-class SVMs can provide an effective and efficient way of overcoming data imbalance in classification problems.

Objective: To determine the influence of using different denominators on risk estimates of ventilator-associated pneumonia (VAP)., Design and Setting: Prospective cohort study in the medical ICU of a large teaching hospital., Patients: All consecutive patients admitted for more than 48 h between October 1995 and November 1997., Measurements and Results: We recorded all ICU-acquired infections using modified CDC criteria. VAP rates were reported per 1,000 patient-days, patient-days at risk, ventilator-days, and ventilator-days at risk. Of the 1,068 patients admitted, VAP developed in 106 (23.5%) of those mechanically ventilated. The incidence of the first episode of VAP was 22.8 per 1,000 patient-days (95% CI 18.7-27.6), 29.6 per 1,000 patient-days at risk (24.2-35.8), 35.7 per 1,000 ventilator-days (29.2-43.2), and 44.0 per 1,000 ventilator-days at risk (36.0-53.2). When considering all episodes of VAP (n=127), infection rates were 27.3 episodes per 1,000 ICU patient-days (95% CI 22.6-32.1) and 42.8 episodes per 1,000 ventilator-days (35.3-50.2)., Conclusions: The method of reporting VAP rates has a significant impact on risk estimates. Accordingly, clinicians and hospital management in charge of patient-care policies should be aware of how to read and compare nosocomial infection rates.

To determine whether acute respiratory distress syndrome (ARDS) complicating bacteremic sepsis independently affects mortality in critically ill patients, we conducted a 3-year retrospective cohort study in a surgical intensive care unit. We included all consecutive patients with blood culture-positive sepsis and measured organ dysfunctions and mortality. Among 4,530 admissions, 196 cases of bacteremic sepsis were recorded. ARDS occurred in 31 (16%) of these patients. The case fatality rate was 58% in patients with ARDS compared with 31% in patients without ARDS. Using Cox proportional hazards regression with time-dependent variables, the unadjusted hazard ratio for death was 1.8 (95% confidence interval [CI], 1.0-3.2). After adjusting for comorbid factors that were present before the onset of sepsis, the hazard ratio was 2.2 (95% CI, 1.2-3.9). After further adjustment was made for nonpulmonary organ dysfunctions and microbiologic factors that were independently associated with mortality, the adjusted hazard ratio for ARDS was 0.6 (95% CI, 0.3-1.2). Among critically ill surgical patients, ARDS complicating bacteremic sepsis remains common, but it is not independently associated with short-term mortality, after adjusting for severity of illness and nonpulmonary organ dysfunctions evolving after the onset of sepsis.

Objective: To assess the added value of surveying patients after discharge from the intensive care unit., Design: Prospective cohort study., Setting: Medical intensive care unit of a large teaching hospital., Patients: All patients admitted to the intensive care unit for 48 hrs or more from October 1995 to November 1997., Measurements and Main Results: We prospectively surveyed 1,068 patients during their intensive care unit stay and for 5 days after intensive care unit discharge. We detected 554 intensive care unit-acquired infections, yielding an infection rate of 70.7 per 1,000 patient days. Of these, only 31 infections (5.6%) in 27 patients were detected after intensive care unit discharge. If postdischarge surveillance was targeted on patients who had had a central vascular catheter while in the intensive care unit, only one infected patient would have been missed, but only 554 out of 889 would have been followed up (sensitivity, 96.2%; specificity, 38.7%; negative predictive value, 99.7%)., Conclusions: Surveillance of all patients discharged from the medical intensive care unit is not recommended, as it is resource demanding and allows the detection of few additional infections. However, targeted postdischarge surveillance could be a rational alternative, and selection criteria need to be refined and validated.

Over the past years, there have been very few imported cases of VHF in Switzerland: one confirmed and four suspected cases of Ebola fever in Basel in 1994, two suspected cases of Ebola and Lassa fevers in Lausanne in 2000, and in the same year, six suspected cases of Lassa fever in Geneva. Given the considerable diversity in the management of patients with suspected or confirmed VHF, national guidelines are needed, as well as the establishment of a national reference centre.

A study was performed to estimate the prevalence of nosocomial infections (NI) and assess differences between medical care settings in one hospital complex. A seven-day period-prevalence survey was conducted in May 1998 in a large primary and tertiary healthcare centre in Geneva, Switzerland, that included all patients in acute, sub-acute and chronic care settings. Variables included demography, exposure to invasive devices and antibiotics, surgical history, and patients' localization. Overall prevalence of NI was 11.3% (acute, 8.4%; sub-acute, 11.4%; chronic care setting, 16.4%) in the 1928 patients studied, and ranged from 0% in ophthalmology to 23% in critical care units. Odds of infection in sub-acute and chronic care settings were significantly higher than in the acute care setting even after adjustment for case-mix [OR, 2.59; 95% confidence interval (CI(95)) 1.53-4.41; and OR, 2.34; Cl(95)1.38-3.95, respectively]. As a distinct group, patients in the geriatric location (belonging to the sub-acute care setting) showed a significant proportion of urinary (39%) and respiratory (21%) tract infections, contrasting with a relatively low exposure to urinary catheters (6.1%) and orotracheal intubation (0%). In conclusion, sub-acute and chronic care settings are associated with high infection prevalence even after case-mix adjustment. Prevalence studies are an easy surveillance tool that can be exploited further by analysing data according to hospital care settings to identify high-risk areas., (Copyright 2001 The Hospital Infection Society.)

Background: Hand hygiene prevents cross infection in hospitals, but compliance with recommended instructions is commonly poor. We attempted to promote hand hygiene by implementing a hospital-wide programme, with special emphasis on bedside, alcohol-based hand disinfection. We measured nosocomial infections in parallel., Methods: We monitored the overall compliance with hand hygiene during routine patient care in a teaching hospital in Geneva, Switzerland, before and during implementation of a hand-hygiene campaign. Seven hospital-wide observational surveys were done twice yearly from December, 1994, to December, 1997. Secondary outcome measures were nosocomial infection rates, attack rates of methicillin-resistant Staphylococcus aureus (MRSA), and consumption of handrub disinfectant., Findings: We observed more than 20,000 opportunities for hand hygiene. Compliance improved progressively from 48% in 1994, to 66% in 1997 (p<0.001). Although recourse to handwashing with soap and water remained stable, frequency of hand disinfection substantially increased during the study period (p<0.001). This result was unchanged after adjustment for known risk factors of poor adherence. Hand hygiene improved significantly among nurses and nursing assistants, but remained poor among doctors. During the same period, overall nosocomial infection decreased (prevalence of 16.9% in 1994 to 9.9% in 1998; p=0.04), MRSA transmission rates decreased (2.16 to 0.93 episodes per 10,000 patient-days; p<0.001), and the consumption of alcohol-based handrub solution increased from 3.5 to 15.4 L per 1000 patient-days between 1993 and 1998 (p<0.001)., Interpretation: The campaign produced a sustained improvement in compliance with hand hygiene, coinciding with a reduction of nosocomial infections and MRSA transmission. The promotion of bedside, antiseptic handrubs largely contributed to the increase in compliance.