German Nosocomial Infection Surveillance System Research Articles

Surveillance of Clostridium difficile-associated diarrhoea with the German nosocomial infection surveillance system KISS (CDAD-KISS)

A study of 2856 Clostridium difficile -associated diarrhoea (CDAD) patients from 34 hospitals in Germany was carried out over a period of 12 months in 2007. The overall incidence of CDAD cases was 46.5 per 10,000 admitted patients, or 6.6 cases per 10,000 patient-days. Seventy-three percent of cases were considered to be nosocomial and 8.4% were classified as severe. There was a wide range in the incidence of CDAD between the hospitals (interquartile range [IQR] 3.2–9.2 cases per 10,000 patient-days), and the incidence of nosocomial cases (IQR 1.7–6.7 per 10,000 patient-days). The differences between the hospitals were in line with the differences in local diagnostic and infection control procedures. The overall incidence in the hospitals participating in the surveillance system was much higher than that in the discharge data from the whole of Germany in 2006. This may be due to more diligent ICD9 coding by the clinicians during an active surveillance strategy. However, the group of hospitals participating in the study was small and may not be representative of the situation in the country as a whole.

The national nosocomial surveillance network in Hungary: results of two years of surgical site infection surveillance

In 2004, a secure web-based national nosocomial infection surveillance system was established in Hungary. The system, named NNSR (Nemzeti Nosocomiális Surveillance Rendszer), is based on the US National Nosocomial Infection Surveillance System (NNIS). Surgical procedures, definitions, surveillance methodology and patient risk indices are those established by NNIS. In this paper, we present the results of the first two years of the surgical patient component of our system. During this period, 41 hospitals participated and selected 11 surgical procedures for surveillance. Altogether 15812 procedures were surveyed and 360 resulting surgical site infections (SSI) were recorded. The overall SSI rate was 2.27%. The most commonly selected procedures and corresponding SSI rates were caesarean section (1.31%), herniorrhaphy (2.09%), cholecystectomy (1.52%) and hip replacement (2.91%). Standardised infection ratios (SIR) were calculated for chosen surgical procedures in order to compare against NNIS published rates. SSI rates for colonic surgery, caesarean section and mastectomy were lower than expected according to the NNIS data but higher for cholecystectomy, herniorrhaphy and hip prosthesis infection rates. We intend to recruit more participating hospitals, leading to a robust national database that can be used to target infection control interventions for patients in Hungary.

Time-trends for Gram-negative and multidrug-resistant Gram-positive bacteria associated with nosocomial infections in German intensive care units between 2000 and 2005

This study analysed the time-trends for bacteria associated with nosocomial lower respiratory tract infections (LRTIs), bloodstream infections (BSIs) and urinary tract infections (UTIs) that were reported to the German Nosocomial Infection Surveillance System for intensive care units (ICUs). Data concerning 19 822 nosocomial infections were submitted by 139 ICUs between 2000 and 2005. There was a significant increase in the proportion of Gram-negative bacteria causing LRTIs (from 63.9% to 68.4%) and UTIs (from 65.3% to 68.6%). The proportion of BSIs caused by Gram-negative bacteria declined significantly, from 36.4% to 22.7%. The frequency of methicillin-resistant Staphylococcus aureus among all S. aureus isolates increased from 19.8% to 37.2%.

Trends in Ventilator-Associated Pneumonia Rates Within the German Nosocomial Infection Surveillance System (KISS)

To investigate trends in ventilator-associated pneumonia (VAP) rates during participation in the German nosocomial infection surveillance system (Krankenhaus-Infektions-Surveillance-System [KISS]). A total of 71 ICUs that began participating in KISS in 1999 or later and continued participation for at least 36 months were selected. Beginning with the first month of participation, the pooled mean rate of VAP in the ICUs was calculated for each year of participation. The incidence densities for the 3 years of participation were compared using the Pearson chi (2) test. Relative risks (RRs) and 95% confidence intervals (CIs) were calculated. VAP rates were calculated for each ICU and year of participation, and rates for years 1 and 3 were compared using the Wilcoxon test for paired samples. Twenty-nine medical-surgical, 18 medical, 20 surgical, 2 neurosurgical, and 2 pediatric ICUs met the selection criteria. Surveillance data were available on 181,275 patients, for whom there were 613,098 patient-days and 224,138 ventilator-days. A total of 2,043 cases of VAP were reported. The ICUs had a pooled VAP rate of 10.5 cases per 1,000 ventilator-days during year 1 of KISS surveillance. In year 2, the rate decreased by 19%, to 8.7 cases per 1,000 ventilator-days (RR, 0.81 [95% CI, 0.73-0.90]). In year 3, the rate decreased by 24% from year 1, to 8.0 cases per 1,000 ventilator-days (RR, 0.76; 95% CI, 0.68-0.85). Both results were significant (P<.001 by the Pearson chi (2) test). Comparison of the VAP rates of the ICUs did not show a significant difference between years 1 and 3 of KISS participation. Surveillance was associated with a significant reduction in the pooled rate of VAP during years 1-3 of KISS participation.

Device-Associated Infection Rates for Non–Intensive Care Unit Patients

Reference data from intensive care units (ICUs) are not applicable to non-ICU patients because of the differences in device use rates, length of stay, and severity of underlying diseases among the patient populations. In contrast to the huge amount of data available for ICU patients, appropriate surveillance data for non-ICU patients have been missing in Germany. To establish a new module ("DEVICE-KISS") of the German Nosocomial Infection Surveillance System for generating stratified reference data for non-ICU wards. Non-ICU patients from 42 German hospitals. Monthly patient-days, device-days and nosocomial infections (NIs) (using Centers for Disease Control and Prevention definitions) were counted. Device use rates were calculated, and NI rates were stratified by different medical specialities. From July 2002 through June 2004, among the 77 wards, there were a total of 536,955 patient-days and 74,188 device-days (for CVC-associated primary bloodstream infections, there were 181,401 patient-days and 8,317 central vascular catheter [CVC]-days in 29 wards; for urinary catheter-associated urinary tract infections, there were 445,536 patient-days and 65,871 urinary catheter-days in 65 wards) and 483 NIs (36 bloodstream infections and 447 urinary tract infections). The mean device use rates were 4.6 device-days per 100 patient-days for CVCs (29 wards) and 14.8 device-days per 100 patient-days for urinary catheters (65 wards), respectively. Mean device-associated NI rates were 4.3 infections per 1,000 CVC-days for CVC-associated bloodstream infections and 6.8 infections per 1,000 urinary catheter-days for catheter-associated urinary tract infections. DEVICE-KISS allows non-ICUs to recognize an outlier position with regard to NIs by providing well-founded reference data for non-ICU patients.

Are KISS Data Representative of German Intensive Care Units?

Data collected within the German nosocomial infection surveillance system KISS are recommended as reference data for judging nosocomial infection rates in German intensive care units (ICUs). It is unknown whether the KISS data tend to under- or overestimate the true infection incidence rates. In this article, methodological aspects of the SIR1 study on the incidence of nosocomial infections are discussed, with the aim of estimating unbiased incidence rates of nosocomial infections in interdisciplinary German ICUs and examining whether the KISS data are representative. We discuss the following methodological issues: 1) Sample size estimation. 2) Stratified random sampling of German ICUs. 3) Investigation of seasonal effects. 4) Statistical modeling of incidence rates using a negative binomial regression model. 5) Comparison of weighted incidence rates with the standardized rate ratio (SRR). Random sampling proved difficult to realize in practice since many ICUs refused to participate, particularly those in small hospitals. Analysis was adjusted for hospital size. No seasonal trends were found in the KISS data. Due to marked differences between ICUs, the number of infections is over-dispersed compared to a Poisson model, so negative binomial regression was used. Fifty ICUs were observed for two consecutive months each, corresponding to 21,832 patient days, during which 262 infections occurred. Infections were more frequent in large hospitals. The incidence rates provided by the SIR study are on average (SRR) 1.89 (1.63-2.20) times as large as those estimated by the KISS system. For estimating nosocomial infection incidence rates, random sampling and statistical modeling of over-dispersion were successfully performed. The study provides evidence that the KISS surveillance system tends to underestimate the true incidence rates of nosocomial infections in German ICUs.

Mortality Risk Factors with Nosocomial Staphylococcus aureus Infections in Intensive Care Units: Results from the German Nosocomial Infection Surveillance System (KISS)

As the number of nosocomial methicillin-resistant Staphylococcus aureus (MRSA) infections in German intensive care units increases, the problem of MRSA infection as such is becoming ever more serious. The aim of this study was to investigate whether mortality rates from nosocomial MRSA pneumonia and primary bloodstream infections (BSI) differ significantly from those of nosocomial pneumonia and primary BSI caused by methicillin-susceptible S. aureus (MSSA). For the analysis data from the ICU component of the German nosocomial infection surveillance system (KISS) were used (January 1997 to June 2002). To identify mortality risk factors a logistic regression analysis with step-wise variable selection was conducted including all cases of nosocomial S. aureus pneumonia and primary BSI. The possible risk factors that were evaluated were age > median, male gender, time in the ICU before infection > median, type of ICU, type and size of hospital, intubation, CVC use, total parenteral nutrition, year of investigation, infection caused by MRSA. Data from 274 ICUs and 505,487 ICU patients were recorded and a total of 6,888 cases of nosocomial pneumonia and 2,357 cases of primary BSI identified, of which 1,851 cases of S. aureus pneumonia and 378 cases of S. aureus primary BSI were considered for analysis. 59 of the 349 patients with MRSA pneumonia (16.9%) and 105 of the 1,502 patients with MSSA pneumonia (7.0%) died. 16 of the 95 patients with primary MRSA BSI (16.8%) and 17 of the 283 patients with primary MSSA BSI died (6.0%). Four factors were significantly associated with mortality from S. aureus pneumonia, one of them being pneumonia caused by MRSA (OR = 2.62; CI95 1.69-4.02). Only MRSA was significantly associated with death from S. aureus primary BSI (OR = 3.84; CI95 1.51-10.2). Nosocomial pneumonia and primary BSI from MRSA may be associated with death, but the cause-effect relationship of severity of illness and MRSA remains to be determined due to the limitations of surveillance data.

Finding a method for optimizing risk adjustment when comparing surgical-site infection rates.

To investigate whether stratification of the risk of developing a surgical-site infection (SSI) is improved when a logistic regression model is used to weight the risk factors for each procedure category individually instead of the modified NNIS System risk index. The German Nosocomial Infection Surveillance System, based on NNIS System methodology, has 273 acute care surgical departments participating voluntarily. Data on 9 procedure categories were included (214,271 operations). For each of the procedure categories, the significant risk factors from the available data (NNIS System risk index variables of ASA score, wound class, duration of operation, and endoscope use, as well as gender and age) were identified by multiple logistic regression analyses with stepwise variable selection. The area under the receiver operating characteristic (ROC) curve resulting from these analyses was used to evaluate the predictive power of logistic regression models. For most procedures, at least two of the three variables contributing to the NNIS System risk index were shown to be independent risk factors (appendectomy, knee arthroscopy, cholecystectomy, colon surgery, herniorrhaphy, hip prosthesis, knee prosthesis, and vascular surgery). The predictive power of logistic regression models (including age and gender, when appropriate) was low (between 0.55 and 0.71) and for most procedures only slightly better than that of the NNIS System risk index. Without the inclusion of additional procedure-specific variables, logistic regression models do not improve the comparison of SSI rates from various hospitals.

To isolate or not to isolate? Analysis of data from the German Nosocomial Infection Surveillance System regarding the placement of patients with methicillin-resistant Staphylococcus aureus in private rooms in intensive care units.

To investigate whether isolating patients with MRSA in private rooms in ICUs (or cohorting) is a protective factor for nosocomial MRSA infection. Association between nosocomial MRSA infection rates and ICU structure and process parameters in the German Nosocomial Infection Surveillance System (KISS). Two hundred twelve ICUs participating in KISS in 2001. In June 2001, a structured questionnaire was sent to the participating ICUs regarding their preventive measures, their type and size, their patient-to-personnel ratios, and routine cultures. Univariate and multivariate analyses were conducted to identify risk factors for nosocomial MRSA infection. The questionnaire was completed by 164 (77.4%) of the ICUs. These ICUs had 325 nosocomial MRSA infections in a 5-year period (1997 to 2001). The mean incidence density of nosocomial MRSA infections was 0.3/1,000 patient-days. Ninety-one ICUs (55.5%) did not register any nosocomial MRSA infections during the observation period. Forty-two ICUs had an incidence density of at least 0.3/1,000 patient-days (75th percentile). Surgical ICUs were found to be a risk factor for a nosocomial MRSA infection rate above this threshold. Multivariate analysis found surgical ICUs to be an independent predictor and isolation in private rooms (or cohorts) to be a protective factor (OR, 0.36; CI95, 0.17-0.79). Many (34.4%) of the German ICUs have not isolated MRSA patients in private rooms or cohorts, a procedure associated with lower MRSA infection rates in this study.

Reducing central venous catheter-associated primary bloodstream infections in intensive care units is possible: data from the German nosocomial infection surveillance system.

The German Nosocomial Infection Surveillance System (KISS) began in 1997 as a nationwide surveillance project for voluntary registration of nosocomial infections in intensive care units (ICUs). This study investigates trends in the rates of central venous catheter (CVC)-associated primary bloodstream infections (BSIs) in ICUs since participation in KISS. Eighty-four ICUs that had participated in KISS for at least 24 months were considered for more detailed analysis. Monthly rates of primary BSI for the 84 ICUs were pooled for the 24 months. The best model for describing the curve of reduction was sought. Additionally, incidence densities were compared using the z test. For the 212 ICUs participating, a relative 25.7% decrease (from 2.1 to 1.6 primary BSIs per 1,000 CVC-days) was observed from January 1997 to June 2001. The 84 ICUs that participated in KISS for a minimum of 24 months accumulated 552,359 patient-days and 404,897 CVC-days during their 24 months. A linear regression model was selected to explain the curve of primary BSI reduction in the 84 ICUs. It showed a decrease from 2.1 to 1.5 primary BSIs per 1,000 CVC-days, meaning an overall relative reduction of 28.6% during the 2-year observation period. These results were significant (Student's t test for the monthly reduction coefficient; P = .04). The reduction of primary BSIs was shown for both clinical sepsis and laboratory-confirmed, CVC-associated primary BSIs. Performing surveillance with KISS was associated with a reduction of the rates of CVC-associated primary BSIs in ICU patients.