D. Sohr

Risk Factors for Death Due to Nosocomial Infection in Intensive Care Unit Patients: Findings From the Krankenhaus Infektions Surveillance System

OBJECTIVE To determine risk factors for death among patients with nosocomial pneumonia and patients with primary bloodstream infections (BSI) in intensive care units (ICUs). DESIGN Prospective cohort study. SETTING Data collected from January 1997 through June 2003 from ICUs registered with the Krankenhaus Infektions Surveillance System in Germany. PATIENTS A total of 8,432 patients with nosocomial pneumonia from 202 ICUs and 2,759 patients with nosocomial primary BSI from 190 ICUs. METHODS The following risk factors were considered in the analysis: age, sex, time in the ICU before onset of infection, type of ICU, type and size of hospital, intubation, central venous catheter use, total parenteral nutrition, and type of pathogen. RESULTS A total of 750 patients (8.9%) with nosocomial pneumonia and 302 patients (10.9%) with nosocomial primary BSI died. Multiple logistic regression analysis identified treatment in a medical or surgical ICU (odds ratio [OR], 1.55 [95% confidence interval {CI}, 1.32-1.82]) or a hospital with more than 1,000 beds (OR, 2.14 [95% CI, 1.81-2.56]), age older than 65 years (OR, 1.54 [95% CI, 1.31-1.81]), and infection with methicillin-resistant Staphylococcus aureus (OR, 2.39 [95% CI, 1.81-3.12]) or multidrug-resistant Pseudomonas aeruginosa (OR, 3.00 [95% CI, 1.90-4.63]) as independent determinants of death from nosocomial pneumonia. Age older than the median of 63 years (OR, 1.44 [95% CI, 1.12-1.86]) and methicillin-resistant S. aureus as the causative agent (OR, 2.98 [95% CI, 1.81-5.82]) were both associated with increased mortality from primary BSI. The types of infecting pathogens, particularly those resistant to multiple drugs, were also strong outcome predictors among ICU patients. CONCLUSIONS The study results underline the need for further investigations of the role of antimicrobial resistance in the outcome of patients with nosocomial pneumonia and patients with primary BSI.

Reproducibility of the Surveillance Effect to Decrease Nosocomial Infection Rates

OBJECTIVE To investigate whether the reduction effect due to participation in a nosocomial infection surveillance system for laboratory-confirmed central venous catheter (CVC)-associated primary bloodstream infection (BSI), ventilator-associated pneumonia (VAP), and surgical site infection (SSI) is reproducible for different time periods, independent of confounding factors that might occur during a specific time period. METHODS Data from the German national nosocomial infection surveillance system from the period January 1997 through June 2008 were used. CVC-associated BSI data and SSI data were analyzed for 3 starting periods, and VAP data were analyzed for 2 starting periods. Monthly infection rates were calculated for the following 36 months, and relative risks comparing the first and third surveillance years of each period were calculated. RESULTS A total of 2,399 CVC-associated BSI cases from 267 intensive care units, 3,637 VAP cases from 150 intensive care units, and 829 SSIs following 3 different procedures from 113 departments were analyzed. A significant reduction in VAP was shown for both starting periods investigated (overall relative risk [RR], 0.80 [95% CI, 0.74-0.86]). A significant reduction in CVC-associated BSI was demonstrated for 2 of 3 starting periods (overall RR, 0.83 [95% CI, 0.75-0.91]). A significant reduction in SSI was found for 2 starting periods for knee prosthesis insertion (overall RR, 0.56 [95% CI, 0.38-0.82]), for all of the 3 starting periods for cesarean delivery (overall RR, 0.75 [95% CI, 0.61-0.93]), and for none of the 3 starting periods for endoscopically performed cholecystectomy (overall RR, 0.89 [95% CI, 0.62-1.27]). CONCLUSIONS The surveillance effect, manifest as a significant reduction of nosocomial infection rates between the first and third years of participation in a surveillance system, was observed independently from the calendar year in which the surveillance activities started.

Outbreak of carbapenem-resistant Pseudomonas aeruginosa infection in a surgical intensive care unit.

Infection control personnel performing surveillance activities noticed a cluster of patients with isolates of carbapenem-resistant Pseudomonas aeruginosa (CRPA) in the surgical intensive care unit (SICU) of a German University Hospital. An outbreak investigation including a descriptive analysis, a case-control study comparing 15 CRPA case patients with 18 patients with carbapenem-susceptible P. aeruginosa, environmental sampling and pulsed-field gel electrophoresis (PFGE) typing of P. aeruginosa isolates was carried out. Fifteen patients acquired CRPA in the SICU during the outbreak period between 1 July 2006 and 31 October 2006 and PFGE typing of 11 available patient isolates revealed two outbreak strains as well as sporadic CRPA isolates. Both outbreak strains were resistant to penicillins, cephalosporins, carbapenems, aminoglycosides and quinolones, and remained susceptible only to colistin. The most likely mode of transmission was cross-transmission between patients during postoperative wound care with abdominal and/or thoracic drains (odds ratio: 64.33; 95% confidence interval: 5.32-999) and therapy with quinolones (48.37; 3.71-999) being independent risk factors for acquisition of CRPA. No further clusters of CRPA cases were observed after implementation of contact isolation precautions and after healthcare workers were made aware of the likely mode of transmission. This study shows the complex epidemiology of CRPA in a SICU including cross-transmission of two CRPA strains related to postoperative wound care.

Validation of surveillance in the intensive care unit component of the German nosocomial infections surveillance system.

A validation study was performed for the intensive care unit component of the German nosocomial infections surveillance system (Krankenhaus Infektions Surveillance System [KISS]). A total of 286 reported infections and 1,195 medical records with no reported infection from 20 randomly selected KISS intensive care units were reviewed by trained physicians. The mean sensitivity was 66% (median, 81%), and the mean specificity was 99.4% (median, 99.6%).

A Point-prevalence Study for MRSA in a German University Hospital to Identify Patients at Risk and to Evaluate an Established Admission Screening Procedure

Background:Due to the enormous increase in the number of MRSA-patients, in July 2004, an extended admission screening protocol was implemented in ICUs and surgical wards at Hannover Medical School.Patients and Methods:In 2005, a point-prevalence study (also known as a cross-sectional study) was conducted to determine the prevalence of MRSA and Panton-Valentine leukocidin (PVL) among inpatients, to identify patients at risk for MRSA colonization and to evaluate compliance with admission screening. Inpatients were screened by taking cultures from nose, throat and skin lesions. S. aureus isolates were tested for antimicrobial susceptibility and PVL. MRSA was analyzed by staphylococcal protein A (spa) typing.Results:Of 509 inpatients, 145 (28%) were S. aureus carriers. 27 (19%) inpatients were MRSA positive, i.e., the MRSA point-prevalence was 5.3% (95% CI, 3.49; 7.70). spa type t032 was predominant in 67% of the MRSA inpatients. The PVL gene was present in one (0.2%) methicillin-susceptible strain. Comparison with data retrieved from the local hospital MRSA database showed that, the status of 37% of the MRSA had previously remained undetected (10/27). Consequently, MRSA colonization was newly identified in 2.0% (10/509) of the patients. Compliance with admission screening failed in three cases. Nosocomial acquisition was identified in three patients. Four other patients harbouring MRSA were newly identified on wards without routine screening (three neurological, one internal medicine ward).Conclusion:Despite extended admission screening, 37% of all MRSA-positive inpatients were missed. The neurological patients were identified as a further risk group and were included in the admission screening procedure established.

New identification of outliers and ventilator-associated pneumonia rates from 2005 to 2007 within the German Nosocomial Infection Surveillance System.

This study presents data for ventilator use and ventilator-associated pneumonia (VAP) rates from the German hospital surveillance system for nosocomial infections (KISS: Krankenhaus Infektions Surveillance System). New Centers for Disease Control and Prevention (CDC) definitions became effective during 2005 and we describe the new method used by KISS to determine individual units with data at extreme ranges. The number of VAP cases per 1000 device-days was calculated and a new visual method, specifically funnel plots, was introduced to identify outliers. The VAP rate will be highly influenced by chance variability if only a few VAP cases are observed during a low number of ventilator-days. Funnel plots take this relationship between event rate and volume of cases into account. A total of 391 intensive care units (ICUs) reported surveillance data from 8 86 816 patients and included 6896 VAPs and 3 113 983 patient-days for the period January 2005 to December 2007. The mean VAP rate according to the new CDC definitions was 5.5 cases per 1000 ventilator-days (median: 4.4). The mean ventilator use in all ICUs was 35.7 (median: 29.3). Funnel plots identified 14.3% as outliers; 34 of them as high, and 22 as low, outliers. Since 2008, visual feedback to the KISS ICUs has been supplied by funnel plots. These are less prone to misinterpretation than histograms and they indicate when investigation is required for increasing VAP.

Concordance between European and US case definitions of healthcare-associated infections

BackgroundSurveillance of healthcare-associated infections (HAI) is a valuable measure to decrease infection rates. Across Europe, inter-country comparisons of HAI rates seem limited because some countries use US definitions from the US Centers for Disease Control and Prevention (CDC/NHSN) while other countries use European definitions from the Hospitals in Europe Link for Infection Control through Surveillance (HELICS/IPSE) project. In this study, we analyzed the concordance between US and European definitions of HAI.MethodsAn international working group of experts from seven European countries was set up to identify differences between US and European definitions and then conduct surveillance using both sets of definitions during a three-month period (March 1st -May 31st, 2010). Concordance between case definitions was estimated with Cohen’s kappa statistic (κ).ResultsDifferences in HAI definitions were found for bloodstream infection (BSI), pneumonia (PN), urinary tract infection (UTI) and the two key terms “intensive care unit (ICU)-acquired infection” and “mechanical ventilation”. Concordance was analyzed for these definitions and key terms with the exception of UTI. Surveillance was performed in 47 ICUs and 6,506 patients were assessed. One hundred and eighty PN and 123 BSI cases were identified. When all PN cases were considered, concordance for PN was κ = 0.99 [CI 95%: 0.98-1.00]. When PN cases were divided into subgroups, concordance was κ = 0.90 (CI 95%: 0.86-0.94) for clinically defined PN and κ = 0.72 (CI 95%: 0.63-0.82) for microbiologically defined PN. Concordance for BSI was κ = 0.73 [CI 95%: 0.66-0.80]. However, BSI cases secondary to another infection site (42% of all BSI cases) are excluded when using US definitions and concordance for BSI was κ = 1.00 when only primary BSI cases, i.e. Europe-defined BSI with ”catheter” or “unknown” origin and US-defined laboratory-confirmed BSI (LCBI), were considered.ConclusionsOur study showed an excellent concordance between US and European definitions of PN and primary BSI. PN and primary BSI rates of countries using either US or European definitions can be compared if the points highlighted in this study are taken into account.

Prolonged duration of operation: an indicator of complicated surgery or of surgical (mis)management?

PurposeThe aim of this study was to investigate whether a prolonged operative time should be regarded as an indicator of quality problems in operating rooms or as patient-specific risk factors when analyzing surgical site infection (SSI) rates.MethodData from the SSI component of the German national nosocomial infection surveillance system (KISS) were used to address this question. Eight procedure categories tracked by at least 30 departments participating in KISS were included in the analysis, namely, hip (2 types) and knee prosthesis, breast surgery, hernia repair, C-section, cholecystectomy and colon operations. Various multiple logistic regression analyses were performed for each procedure category to predict duration of operation. Patient factors (sex, age, American Society of Anesthesiologists score, wound contamination class) and hospital factors (hospital status, size, annual volume) were considered. The area under the receiver operating characteristic (ROC) curve was used to evaluate predictive power including patient- and hospital-based factors.ResultsA total of 253,454 operations were included in the analysis. In general, the predictive power of the model including all variables for the different procedure types was relatively low (C-index range: 0.57–0.63) and not much higher than that of the models including only patient-based or only hospital-based variables, respectively. The predictive power for the duration of operative time based on the model including only hospital-based variables was as good as or better than that of the model including only patient-based factors.ConclusionDuration of operation is at least partially determined by hospital factors and, consequently, should be used as a quality indicator to compare SSI infections between hospitals, rather than being used as a patient factor to adjust comparisons between hospitals.

Risk factors associated with surgical site infections following vascular surgery at a German university hospital.

Surgical site infection (SSI) after vascular surgery is a serious complication increasing morbidity, mortality, and costs for healthcare systems. A 4-year retrospective cohort study was performed in a university hospital with patients who had undergone arterial vascular surgery below the aortic arch. Investigated variables included demographics and clinical data. Forty-four of 756 patients experienced SSI, 29 of which were superficial, five were deep, and 10 had organ/space infections. Coagulase-negative staphylococci (22%), enterococci (20%), and Staphylococcus aureus (18%) were the most common pathogens. Independent risk factors for SSIs were femoral grafting [odds ratio (OR) 6·7], peripheral atherosclerotic disease, Fontaine stages III-IV (OR 4·1), postoperative drainage >5 days (OR 3·6), immunosuppression (OR 2·8), duration of operation >214 min (OR 2·8), and body mass index >29 (OR 2·6). The application of perioperative antibiotic prophylaxis was an independent protective factor (OR 0·2). Patients with certain risk factors for SSIs warrant special attention for infection prevention.

An outbreak of Clostridium difficile -associated disease (CDAD) in a German university hospital

We investigated an outbreak of Clostridium difficile (CD)associated disease (CDAD) in a cardiac surgical department that took place between January 25th and April 28th 2007 at Hannover Medical School, Germany. Immediate infection control measures such as changing the surface disinfectant from an alcohol-based glucoprotamine to an oxygen-active disinfectant cleaner and the primary education of staff were proved to be insufficient to control the outbreak. Therefore, a “CD infection control bundle” was created consisting of: (a) implementation of a CDAD outbreak team; (b) education on hand hygiene; (c) the aim of early case finding as soon as clinical symptoms of CDAD were noticed; (d) daily control of microbiological results; (e) suggesting proper antimicrobial therapy of patients on the ward avoiding high-risk substances; (f) reinforcement of currently existing infection control measures, such as including the isolation of CDAD cases in single rooms; (g) and, finally, interim closure of the unit for any new admissions. For the treatment of CDAD, initially, metronidazole and, in the case of failure of initial therapy, oral vancomycin were used. A case–control study was performed. Cases were defined as proposed by the ECDC: (a) onset of diarrhoea ≥48 h after admission or ≥4 weeks after the most recent discharge and (b) positive enzyme-immunoassay (EIA) for CD toxins A or B in stool samples (RIDASCREEN® Clostridium difficile Toxin A/B test, R-Biopharm, Glasgow, United Kingdom) or the culturing of toxin-producing CD (Clostridium difficile-selective media, Oxoid, Hampshire, United Kingdom). The results of Gram strain, colony morphology and biochemical testing with the RapID II ANA System® (Remel, Lenexa, USA) were used for species determination. Cultured strains were examined by pulsed field gel electrophoresis (PFGE) using GelCompar II® software (Applied Maths NV, Sint-Martens-Latern, Belgium) and by polymerase chain reaction (PCR) ribotyping, as described by others [1]. Antimicrobial susceptibility testing was performed by E-test® (AB Biodisk, Solna, Sweden) on agar plates containing vitamin K1, haemin and 5% defibrinated sheep red blood cells (Inverness Medical Deutschland, Cologne, Germany). Breakpoint minimal inhibitory concentrations (MICs) were ≥8 μg/mL for fluoroquinolones (FQ) [2] and ≥4 μg/mL for erythromycin [3]. Severe CDAD was defined as readmission because of relapse, necessity of intensive care because of CDAD, surgical procedure due to CDAD or CDAD contributing to the patient’s death within 30 days after diagnosis [4–6]. Controls were diarrhoeal patients admitted to the same unit during the same time period but were negative for CD toxin EIA, including CD culture (= confirmed CD negative) and negative for other gastrointestinal infectious agents. Age, gender, co-morbidities, underlying diseases, endoscopic procedures, history of antimicrobial exposure, readmission and relapse of CDAD in both groups were Eur J Clin Microbiol Infect Dis (2009) 28:543–545 DOI 10.1007/s10096-008-0655-7