Christine Geffers

How many infections are caused by patient-to-patient transmission in intensive care units?*

Objective:The proportion of intensive care unit (ICU)-acquired infections that are a consequence of nosocomial cross-transmission between patients in tertiary ICUs is unknown. Such information would be useful for the implementation of appropriate infection control measures. Design:A prospective cohort study during 18 months. Setting:Five ICUs from two university hospitals. Patients:All patients admitted for ≥48 hrs. Measurement:ICU-acquired infections were ascertained during daily bedside patient and chart reviews. Episodes of potential cross-transmission were identified by highly discriminating genetic typing of all clinical and surveillance isolates of the ten bacterial species most frequently associated with nosocomial infections in ICUs. Isolation of indistinguishable isolates in two or more patients defined potential transmission episodes. Main Results:During 28,498 patient days, 431 ICU-acquired infections and 141 episodes of nosocomial transmissions were identified. A total of 278 infections were caused by the ten species that were genotyped, and 41 of these (14.5%) could be associated with transmissions between patients. Conclusion:Infections acquired during treatment in modern tertiary ICUs are common, but a causative role of direct patient-to-patient transmission can only be ascertained for a minority of these infections on the basis of routine microbiological investigations.

Use of multistate models to assess prolongation of intensive care unit stay due to nosocomial infection

BACKGROUND Reliable data on the costs attributable to nosocomial infection (NI) are crucial to demonstrating the real cost-effectiveness of infection control measures. Several studies investigating this issue with regard to intensive care unit (ICU) patients have probably overestimated, as a result of inappropriate study methods, the part played by NIs in prolonging the length of stay. METHODS Data from a prospective study of the incidence of NI in 5 ICUs over a period of 18 months formed the basis of this analysis. For describing the temporal dynamics of the data, a multistate model was used. Thus, ICU patients were counted as case patients as soon as an NI was ascertained on any particular day. All patients were then regarded as control subjects as long as they remained free of NI (time-to-event data analysis technique). RESULTS Admitted patients (n=1,876) were observed for the development of NI over a period of 28,498 patient-days. In total, 431 NIs were ascertained during the study period (incidence density, 15.1 NIs per 1,000 patient-days). The influence of NI as a time-dependent covariate in a proportional hazards model was highly significant (P< .0001, Wald test). NI significantly reduced the discharge hazard (hazard ratio, 0.72 [95% confidence interval, 0.63-0.82])--that is, it prolonged the ICU stay. The mean prolongation of ICU length of stay due to NI (+/- standard error) was estimated to be 5.3+/-1.6 days. CONCLUSIONS Further studies are required to enable comparison of data on prolongation of ICU length of stay with the results of various study methods.

Ten years of KISS: The most important requirements for success

Ten years ago, in January 1997, data collection for the German national nosocomial infection surveillance system was established, which is known by the acronym KISS (Krankenhaus-Infektions-Surveillance-System). Meanwhile KISS was able to demonstrate a beneficial effect from ongoing surveillance activities and appropriate feedback to the users in combination with reference data for ventilator associated pneumonia, primary bloodstream infections and surgical site infections. Significant reductions of infection rates between 20-30% over 3 years periods in the components for intensive care units, operative departments and neonatal intensive care units were demonstrated. Due to our experience the following requirements have to be fulfilled to keep a surveillance system successful over longer periods: close contact between the participating institutions, consideration of new developments, timely regular data feedback and constant reevaluation of the way of data presentation, data validity and demonstration of its contribution to the reduction of healthcare associated infections (HAI). The article describes in more detail how KISS tries to fulfill these requirements.

Nosocomial infections and multidrug-resistant organisms in Germany: epidemiological data from KISS (the Hospital Infection Surveillance System).

BACKGROUND More than 800 hospitals and 586 intensive care units (ICUs) in Germany currently participate in a nationwide surveillance system for nosocomial infections (Krankenhaus-Infektions-Surveillance-System, KISS), which collects data on the frequency of nosocomial infections and pathogens and on the appearance of pathogens of special epidemiological importance. METHODS Data were collected from ICUs regarding lower respiratory tract infections, primary sepsis, and urinary tract infections and on the temporal relation of these types of infection to the use of specific medical devices (invasive ventilation, central venous catheters, and urinary catheters). On the basis of these data, device-associated infection rates (number of infection per 1000 device days) were calculated for different types of ICUs. KISS also collected data on all ICU patients colonized or infected with selected multidrug-resistant organisms (MDRO) and on all hospitalized patients with methicillin-resistant Staphylococcus aureus (MRSA) and Clostridium difficile-associated diarrhea (CDAD). RESULTS Device-associated infection rates ranged from 0.9 to 9.6 per 1000 device-days, depending on the type of infection and the type of ICU. An extrapolation from these figures yields an estimate of 57 900 ICU-acquired infections occurring in Germany each year. The most common MDRO in ICU patients is MRSA. The frequency of MRSA has remained stable in recent years, but that of other MDROs among ICU patients is rising. Hospitalized patients are twice as likely to acquire CDAD as they are to acquire MRSA. CONCLUSION Nosocomial infections are common in the ICU. The percentage of ICU patients with MDRO is low, but rising. Future preventive strategies must address this development.

Incidence of healthcare-associated infections in high-risk neonates: results from the German surveillance system for very-low-birthweight infants

Infants with birthweight <1500g (VLBW) are at high risk of healthcare-associated infection (HAI). We present surveillance data from the NEO-KISS surveillance system, collected between 2000 and 2005 by 52 neonatology departments in Germany. Infants were stratified into two birthweight categories (<1000 and 1000-1499 g), and rates of nosocomial bloodstream infection (BSI), nosocomial pneumonia and necrotising enterocolitis (NEC) were calculated. The data presented comprise 8677 VLBW and 339,972 patient-days. The incidence of bloodstream infection was 6.5 per 1000 patient-days (8.5 and 4.0 according to birthweight category). The incidence of central venous catheter (CVC)-associated BSI was 11.1 per 1000 CVC-days and the incidence of peripheral venous catheter (PVC)-associated BSI was 7.8 per 1000 PVC-days. The incidence of pneumonia was 0.9 per 1000 patient-days (1.3 and 0.4 according to birthweight category). The incidence of pneumonia among intubated patients was 2.7 per 1000 ventilator-days, while the incidence of pneumonia among patients receiving continuous nasel positive airway pressure (CPAP) was 1.0 per 1000 CPAP-days. The incidence of NEC was 0.9 per 1000 patient-days (1.1 and 0.6 according to birthweight category). HAI is frequent among VLBW and shows wide variation between neonatology departments. Preventive strategies to reduce infections in these infants should be prioritised.

Risk factors for the development of nosocomial pneumonia and mortality on intensive care units: application of competing risks models

IntroductionPneumonia is a very common nosocomial infection in intensive care units (ICUs). Many studies have investigated risk factors for the development of infection and its consequences. However, the evaluation in most of theses studies disregards the fact that there are additional competing events, such as discharge or death.MethodsA prospective cohort study was conducted over 18 months in five intensive care units at one university hospital. All patients that were admitted for at least 2 days were included, and surveillance of nosocomial pneumonia was conducted. Various potential risk factors (baseline- and time-dependent) were evaluated in two competing risks models: the acquisition of nosocomial pneumonia and discharge (dead or alive; model 1) and for the risk of death in the ICU and discharge alive (model 2).ResultsPatients from 1,876 admissions were included. A total of 158 patients developed nosocomial pneumonia. The main risk factors for nosocomial pneumonia in the multivariate analysis in model 1 were: elective surgery (cause-specific hazard ratio = 1.95; 95% CI 1.33 to 2.85) or emergency surgery (1.59; 95% CI 1.10 to 2.28) prior to ICU admission, usage of a nasogastric tube (3.04; 95% CI 1.25 to 7.37) and mechanical ventilation (5.90; 95% CI 2.47 to 14.09). Nosocomial pneumonia prolonged the length of ICU stay but was not directly associated with a fatal outcome (p = 0.55).ConclusionMore studies using competing risk models, which provide more accurate data compared to naive survival curves or logistic models, should be carried out to verify the impact of risk factors and patient characteristics for the acquisition of nosocomial infections and infection-associated mortality.

Mortality risk factors with nosocomial Staphylococcus aureus infections in intensive care units: results from the German Nosocomial Infection Surveillance System (KISS).

Introduction: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).Methods: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.Results: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).Conclusion: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.

Reducing central venous catheter-associated primary bloodstream infections in intensive care units is possible: Data from the German Nosocomial Infection Surveillance System

BACKGROUND AND OBJECTIVE 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. METHODS 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. RESULTS 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 (Students 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. CONCLUSION Performing surveillance with KISS was associated with a reduction of the rates of CVC-associated primary BSIs in ICU patients.

Dramatic increase in vancomycin-resistant enterococci in Germany

OBJECTIVES Among European countries, Germany has one of the highest proportions of vancomycin-resistant Enterococcus faecium bloodstream infections. The aim of this study was to investigate the development of vancomycin-resistant enterococci (VRE) in German hospitals and to consider the regional distribution of VRE in Germany. METHODS Data from three components of the German national nosocomial surveillance system (KISS) from the period 2007-12 were used for analysis: ICU-KISS data on nosocomial primary bloodstream infections and urinary tract infections from intensive care units (ICUs); OP-KISS data on surgical site infections from surgical departments; and Pathogen-KISS data concentrating on VRE cases (infections and colonizations) in ICUs. Trends over time were calculated and a map according to German federal states was prepared. RESULTS Data from up to 645 ICUs and 681 surgical departments for 2 year periods from 2007 to 2012 were analysed. The proportion of VRE increased significantly for surgical site infections (526%; P < 0.01) and bloodstream infections (265%; P < 0.01) and non-significantly for urinary tract infections (278%; P = 0.07). A large subgroup of ICUs also reported VRE cases in the same period, with a significant increase of 282%. The mapping of federal states showed large variation in VRE proportions and incidence rates in a belt of states with significantly higher VRE proportions from west (North Rhine-Westphalia) to east (Saxony). CONCLUSIONS The high overall VRE proportion in Germany is mainly due to the situation in four states. There is an urgent need to analyse the epidemiology of VRE in detail to develop appropriate infection control strategies.

Early- and Late-Onset Pneumonia: Is This Still a Useful Classification?

ABSTRACT The choice of empirical treatment of nosocomial pneumonia in the intensive-care unit (ICU) used to rely on the interval after the start of mechanical ventilation. Nowadays, however, the question of whether in fact there is a difference in the distribution of causative pathogens is under debate. Data from 308 ICUs from the German National Nosocomial Infection Surveillance System, including information on relevant pathogens isolated in 11,285 cases of nosocomial pneumonia from 1997 to 2004, were used for our evaluation. Each individual pneumonia case was allocated either to early- or to late-onset pneumonia, with three differentiation criteria: onset on the 4th day, the 5th day, or the 7th day in the ICU. The frequency of pathogens was evaluated according to these categories. A total of 5,066 additional cases of pneumonia were reported from 2005 to 2006, after the CDC criteria had been modified. From 1997 to 2004, the most frequent microorganisms were Staphylococcus aureus (2,718 cases, including 720 with methicillin [meticillin]-resistant S. aureus), followed by Pseudomonas aeruginosa (1,837 cases), Klebsiella pneumoniae (1,305 cases), Escherichia coli (1,137 cases), Enterobacter spp. (937 cases), streptococci (671 cases), Haemophilus influenzae (509 cases), Acinetobacter spp. (493 cases), and Stenotrophomonas maltophilia (308 cases). The order of the four most frequent pathogens (accounting for 53.7% of all pathogens) was the same in both groups and was independent of the cutoff categories applied: S. aureus was first, followed by P. aeruginosa, K. pneumoniae, and E. coli. Thus, the predictabilities of the occurrence of pathogens were similar for the earlier (1997-to-2004) and later (2005-to-2006) time frames. This classification is no longer helpful for empirical antibiotic therapy, since the pathogens are the same for both groups.