Methicillin-resistant Staphylococcus aureus central line-associated bloodstream infections in US intensive care units, 1997-2007.

CONTEXT: Concerns about rates of methicillin-resistant Staphylococcus aureus (MRSA) health care-associated infections have prompted calls for mandatory screening or reporting in efforts to reduce MRSA infections. OBJECTIVE: To examine trends in the incidence of MRSA central line-associated bloodstream infections (BSIs) in US intensive care units (ICUs). DESIGN, SETTING, AND PARTICIPANTS: Data reported by hospitals to the Centers for Disease Control and Prevention (CDC) from 1997-2007 were used to calculate pooled mean annual central line-associated BSI incidence rates for 7 types of adult and non-neonatal pediatric ICUs. Percent MRSA was defined as the proportion of S aureus central line-associated BSIs that were MRSA. We used regression modeling to estimate percent changes in central line-associated BSI metrics over the analysis period. MAIN OUTCOME MEASURES: Incidence rate of central line-associated BSIs per 1000 central line days; percent MRSA among S. aureus central line-associated BSIs. RESULTS: Overall, 33,587 central line-associated BSIs were reported from 1684 ICUs representing 16,225,498 patient-days of surveillance; 2498 reported central line-associated BSIs (7.4%) were MRSA and 1590 (4.7%) were methicillin-susceptible S. aureus (MSSA). Of evaluated ICU types, surgical, nonteaching-affiliated medical-surgical, cardiothoracic, and coronary units experienced increases in MRSA central line-associated BSI incidence in the 1997-2001 period; however, medical, teaching-affiliated medical-surgical, and pediatric units experienced no significant changes. From 2001 through 2007, MRSA central line-associated BSI incidence declined significantly in all ICU types except in pediatric units, for which incidence rates remained static. Declines in MRSA central line-associated BSI incidence ranged from -51.5% (95% CI, -33.7% to -64.6%; P < .001) in nonteaching-affiliated medical-surgical ICUs (0.31 vs 0.15 per 1000 central line days) to -69.2% (95% CI, -57.9% to -77.7%; P < .001) in surgical ICUs (0.58 vs 0.18 per 1000 central line days). In all ICU types, MSSA central line-associated BSI incidence declined from 1997 through 2007, with changes in incidence ranging from -60.1% (95% CI, -41.2% to -73.1%; P < .001) in surgical ICUs (0.24 vs 0.10 per 1000 central line days) to -77.7% (95% CI, -68.2% to -84.4%; P < .001) in medical ICUs (0.40 vs 0.09 per 1000 central line days). Although the overall proportion of S. aureus central line-associated BSIs due to MRSA increased 25.8% (P = .02) in the 1997-2007 period, overall MRSA central line-associated BSI incidence decreased 49.6% (P < .001) over this period. CONCLUSIONS: The incidence of MRSA central line-associated BSI has been decreasing in recent years in most ICU types reporting to the CDC. These trends are not apparent when only percent MRSA is monitored.

Measurement of the impact of risk adjustment for central line-days on interpretation of central line-associated bloodstream infection rates.

OBJECTIVE: To describe methods to assess the practical impact of risk adjustment for central line-days on the interpretation of central line-associated bloodstream infection (BSI) rates, because collecting these data is often burdensome. METHODS: We analyzed data from 247 hospitals that reported to the adult and pediatric intensive care unit component of the National Nosocomial Infections Surveillance System from 1995 through 2003. For each unit each year, we calculated the percentile error as the absolute value of the difference between the percentile based on a risk-adjusted or more-sophisticated measure (eg, the central line-day rate) and the percentile based on a crude or less-sophisticated measure (eg, the patient-day rate). Using rate per central line-day as the "gold standard," we calculated performance characteristics (eg, sensitivity and predictive values) of rate per patient-day for finding central line-associated BSI rates higher or lower than the mean. Greater impact of risk adjustment is indicated by higher values for percentile error and lower values for performance characteristics. RESULTS: The median percentile error was +/-7 (i.e., the percentile based on central line-days could be 7% higher or lower than the percentile based on patient-days). This error was less than 10 percentile points for 62% of the unit-years, was between 10 and 19 percentile points for 22% of the unit-years, and was 20 percentile points or more for 15% of the unit-years. Use of the rate based on patient-days had a sensitivity of 76% and a positive predictive value of 61% for detecting a significantly high or low central line-associated BSI rate. CONCLUSIONS: We found that risk adjustment for central line-days has an important impact on the calculated central line-associated BSI percentile for some units. Similar methods can be used to evaluate the impact of other risk adjustment methods. Our results support current recommendations to use central line-days for surveillance of central line-associated BSI when comparisons are made among facilities.

Comparisons of health care-associated infections identification using two mechanisms for public reporting.

BACKGROUND: Many states have or are in process of legislating hospitals to report health care-associated infections (HAI). The purpose of this article is to compare two methods currently in use by different states: 1) selected infections due to medical care Patient Safety Indicator (PSI-7); and 2) Centers for Disease and Prevention Control (CDC) protocols for central line-associated bloodstream infections (CLA-BSI). METHODS: Data came from a multihospital study. Site coordinators provided lists of elderly Medicare patients admitted in an enrolled intensive care unit in 2002 cross referenced with patient specific data on CLA-BSI following CDC protocols. PSI-7 was identified using Medicare data and the Agency for Healthcare Research and Quality PSI software version 2.1. RESULTS: The full sample comprised records from 14,637 patients from 41 intensive care units in 24 hospitals. Patients were excluded if they did not meet the PSI-7 denominator criteria. In a sample of 9,948 patients, both methods identified infections in 89 (0.89%) patients. The methods had little concordance with only 8 patients identified using both methods. CONCLUSIONS: Inconsistencies that we identified in this study are concerning given the fact that reports of HAI generated by different methods vary widely. Mandatory reporting mechanisms should be standardized and their accuracy confirmed.

Estimating health care-associated infections and deaths in U.S. hospitals, 2002.

OBJECTIVE: The purpose of this study was to provide a national estimate of the number of healthcare-associated infections (HAI) and deaths in United States hospitals. METHODS: No single source of nationally representative data on HAIs is currently available. The authors used a multi-step approach and three data sources. The main source of data was the National Nosocomial Infections Surveillance (NNIS) system, data from 1990-2002, conducted by the Centers for Disease Control and Prevention. Data from the National Hospital Discharge Survey (for 2002) and the American Hospital Association Survey (for 2000) were used to supplement NNIS data. The percentage of patients with an HAI whose death was determined to be caused or associated with the HAI from NNIS data was used to estimate the number of deaths. RESULTS: In 2002, the estimated number of HAIs in U.S. hospitals, adjusted to include federal facilities, was approximately 1.7 million: 33,269 HAIs among newborns in high-risk nurseries, 19,059 among newborns in well-baby nurseries, 417,946 among adults and children in ICUs, and 1,266,851 among adults and children outside of ICUs. The estimated deaths associated with HAIs in U.S. hospitals were 98,987: of these, 35,967 were for pneumonia, 30,665 for bloodstream infections, 13,088 for urinary tract infections, 8,205 for surgical site infections, and 11,062 for infections of other sites. CONCLUSION: HAIs in hospitals are a significant cause of morbidity and mortality in the United States. The method described for estimating the number of HAIs makes the best use of existing data at the national level.

Detection of postoperative surgical-site infections: comparison of health plan-based surveillance with hospital-based programs.

BACKGROUND: Review of health plan administrative data has been shown to be more sensitive than other methods for identifying postdischarge surgical-site infections (SSIs), but there has not been a direct comparison between this method and hospital-based surveillance for all infections, including those diagnosed before discharge. We compared these two methods for identifying SSIs following coronary artery bypass graft (CABG) procedures. METHODS: We studied 1,352 CABG procedures performed among members of one health plan from March 1993 through June 1997. Health plan administrative records were reviewed based on claims containing diagnoses or procedures suggestive of infection or outpatient dispensing of antibiotics appropriate for SSI. Hospital-based surveillance information was also reviewed. SSI rates were calculated based on the total events identified by either mechanism. RESULTS: Postdischarge information was reviewed for 328 (85%) of 388 procedures. SSIs were confirmed in 167 patients (13% overall risk of confirmed SSI; range, 3% to 14% in the 5 hospitals). The overall sensitivity of hospital-based surveillance was 49.7% (83 of 167), and that of health plan data was 71.8% (120 of 167). There was no significant difference among hospitals in the sensitivity of either surveillance mechanism. CONCLUSIONS: Surveillance based on health plan data identified more postoperative infections, including those occurring before discharge, than did hospital-based surveillance. Screening administrative data and pharmacy activity may be an important adjunct to SSI surveillance, allowing efficient comparison of hospital-specific rates. Interpretation of differences among hospitals' infection rates requires case mix adjustment and understanding of variations in hospitals' discharge diagnosis coding practices.

Device-associated infections among neonatal intensive care unit patients: incidence and associated pathogens reported to the National Healthcare Safety Network, 2006-2008.

OBJECTIVE: To describe rates and pathogen distribution of device-associated infections (DAIs) in neonatal intensive care unit (NICU) patients and compare differences in infection rates by hospital type (children's vs general hospitals). PATIENTS AND SETTING: Neonates in NICUs participating in the National Healthcare Safety Network from 2006 through 2008. METHODS: We analyzed central line-associated bloodstream infections (CLABSIs), umbilical catheter-associated bloodstream infections (UCABs), and ventilator-associated pneumonia (VAP) among 304 NICUs. Differences in pooled mean incidence rates were examined using Poisson regression; nonparametric tests for comparing medians and rate distributions were used. RESULTS: Pooled mean incidence rates by birth weight category (750 g or less, 751-1,000 g, 1,001-1,500 g, 1,501-2,500 g, and more than 2,500 g, respectively) were 3.94, 3.09, 2.25, 1.90, and 1.60 for CLABSI; 4.52, 2.77, 1.70, 0.91, and 0.92 for UCAB; and 2.36, 2.08, 1.28, 0.86, and 0.72 for VAP. When rates of infection between hospital types were compared, only pooled mean VAP rates were significantly lower in children's hospitals than in general hospitals among neonates weighing 1,000 g or less; no significant differences in medians or rate distributions were noted. Pathogen frequencies were coagulase-negative staphylococci (28%), Staphylococcus aureus (19%), and Candida species (13%) for bloodstream infections and Pseudomonas species (16%), S. aureus (15%), and Klebsiella species (14%) for VAP. Of 673 S. aureus isolates with susceptibility results, 33% were methicillin resistant. CONCLUSIONS: Neonates weighing 750 g or less had the highest DAI incidence. With the exception of VAP, pooled mean NICU incidence rates did not differ between children's and general hospitals. Pathogens associated with these infections can pose treatment challenges; continued efforts at prevention need to be applied to all NICU settings.

An American Journal of Infection Control and National Healthcare Safety Network data quality collaboration: a supplement of new case studies.

The rationale for the case study series is presented, along with results of the first 5 American Journal of Infection Control-National Healthcare Safety Network case studies. Although the respondents were correct in their assessments more often than not, opportunities for improvement remain. Ten new case studies with questions are provided. Participants are provided with instructions on how to submit responses for continuing education credit through the Centers for Disease Control and Prevention. Answers with referenced explanations will be provided immediately to those who seek continuing education credit and at a later date via the online journal for those who do not.

Improved risk adjustment in public reporting: coronary artery bypass graft surgical site infections.

OBJECTIVE: The objective was to develop a new National Healthcare Safety Network (NHSN) risk model for sternal, deep incisional, and organ/space (complex) surgical site infections (SSIs) following coronary artery bypass graft (CABG) procedures, detected on admission and readmission, consistent with public reporting requirements. PATIENTS AND SETTING: A total of 133,503 CABG procedures with 4,008 associated complex SSIs reported by 293 NHSN hospitals in the United States. METHODS: CABG procedures performed from January 1, 2006, through December 31, 2008, were analyzed. Potential SSI risk factors were identified by univariate analysis. Multivariate analysis with forward stepwise logistic regression modeling was used to develop the new model. The c-index was used to compare the predictive power of the new and NHSN risk index models. RESULTS: Multivariate analysis independent risk factors included ASA score, procedure duration, female gender, age, and medical school affiliation. The new risk model has significantly improved predictive performance over the NHSN risk index (c-index, 0.62 and 0.56, respectively). CONCLUSIONS: Traditionally, the NHSN surveillance system has used a risk index to provide procedure-specific risk-stratified SSI rates to hospitals. A new CABG sternal, complex SSI risk model developed by multivariate analysis has improved predictive performance over the traditional NHSN risk index and is being considered for endorsement as a measure for public reporting.

Improving risk-adjusted measures of surgical site infection for the national healthcare safety network.

BACKGROUND: The National Healthcare Safety Network (NHSN) has provided simple risk adjustment of surgical site infection (SSI) rates to participating hospitals to facilitate quality improvement activities; improved risk models were developed and evaluated. METHODS: Data reported to the NHSN for all operative procedures performed from January 1, 2006, through December 31, 2008, were analyzed. Only SSIs related to the primary incision site were included. A common set of patient- and hospital-specific variables were evaluated as potential SSI risk factors by univariate analysis. Some ific variables were available for inclusion. Stepwise logistic regression was used to develop the specific risk models by procedure category. Bootstrap resampling was used to validate the models, and the c-index was used to compare the predictive power of new procedure-specific risk models with that of the models with the NHSN risk index as the only variable (NHSN risk index model). RESULTS: From January 1, 2006, through December 31, 2008, 847 hospitals in 43 states reported a total of 849,659 procedures and 16,147 primary incisional SSIs (risk, 1.90%) among 39 operative procedure categories. Overall, the median c-index of the new procedure-specific risk was greater (0.67 [range, 0.59-0.85]) than the median c-index of the NHSN risk index models (0.60 [range, 0.51-0.77]); for 33 of 39 procedures, the new procedure-specific models yielded a higher c-index than did the NHSN risk index models. CONCLUSIONS: A set of new risk models developed using existing data elements collected through the NHSN improves predictive performance, compared with the traditional NHSN risk index stratification.

Staffing and structure of infection prevention and control programs.

BACKGROUND: The nature of infection prevention and control is changing; however, little is known about current staffing and structure of infection prevention and control programs. METHODS: Our objectives were to provide a snapshot of the staffing and structure of hospital-based infection prevention and control programs in the United States. A Web-based survey was sent to 441 hospitals that participate in the National Healthcare Safety Network. RESULTS: The response rate was 66% (n = 289); data were examined on 821 professionals. Infection preventionist (IP) staffing was significantly negatively related to bed size, with higher staffing in smaller hospitals (P < .001). Median staffing was 1 IP per 167 beds. Forty-seven percent of IPs were certified, and 24 percent had less than 2 years of experience. Most directors or hospital epidemiologists were reported to have authority to close beds for outbreaks always or most of the time (n = 225, 78%). Only 32% (n = 92) reported using an electronic surveillance system to track infections. CONCLUSION: This study is the first to provide a comprehensive description of current infection prevention and control staffing, organization, and support in a select group of hospitals across the nation. Further research is needed to identify effective staffing levels for various hospital types as well as examine how the IP role is changing over time.

Trends in incidence of late-onset methicillin-resistant Staphylococcus aureus infection in neonatal intensive care units: data from the National Nosocomial Infections Surveillance System, 1995-2004.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is increasingly being reported to cause outbreaks in neonatal intensive care units (NICUs). We assessed the scope and magnitude of MRSA infections with disease onset after 3 days of age (late-onset MRSA infections) in NICUs. METHODS: We analyzed data reported by NICUs participating in the National Nosocomial Infections Surveillance system from 1995 through 2004. For each surveillance month, all healthcare-associated infections as defined by National Nosocomial Infections Surveillance criteria were reported, along with antimicrobial susceptibility patterns of the isolates. We pooled the data from all NICUs by birth weight category and calendar year. Poisson regression was used to assess changes in incidence of late-onset MRSA infections per 10,000 patient-days. RESULTS: Overall, 149 NICUs reported 4831 S. aureus infections and 5,878,139 patient-days. Methicillin testing data were available for 4302 S. aureus isolates, of which 975 (23%) were MRSA. Incidence of late-onset MRSA infection per 10,000 patient-days, combining all birthweight categories, increased 308% from 0.7 in 1995 to 3.1 in 2004 (P < 0.001). A significant increase in incidence of MRSA infections was observed among all 4 birthweight categories analyzed separately (2500 g). The distribution of MRSA infection by type of infection did not vary during the study period; 299 (31%) of MRSA infections were bloodstream infections, 174 (18%) were pneumonia, and 161 (17%) were conjunctivitis. CONCLUSION: The incidence of late-onset MRSA infections increased substantially between 1995 and 2004, indicating a need to reinforce infection control recommendations and to explore potential sources and routes of transmission.

Dialysis Surveillance Report: National Healthcare Safety Network (NHSN)-data summary for 2006.

Thirty-two outpatient hemodialysis providers in the United States voluntarily reported 3699 adverse events to the Centers for Disease Control and Prevention (CDC) National Healthcare Safety Network (NHSN) during 2006. These providers were previously enrolled in the Dialysis Surveillance Network. The pooled mean rates of hospitalization among patients with arteriovenous fistulas, grafts, permanent and temporary central venous catheters were 7.7, 9.2, 15.7, and 34.7 per 100 patient-months, respectively. For bloodstream infection the pooled mean rates were 0.5, 0.9, 4.2, and 27.1 per 100 patient-months in these groups. Among the 599 isolates reported, 461 (77%) represented access-associated blood stream infections in patients with central lines, and 138 (23%) were in patients with fistulas or grafts. The microorganisms most frequently identified were common skin contaminants (e.g., coagulase-negative staphylococci). In 2007, enrollment in NHSN opened to all providers of outpatient hemodialysis. Specific information is available at http://www.cdc.gov/ncidod/dhqp/nhsn_FAQenrollment.html.

Making use of electronic data: the National Healthcare Safety Network eSurveillance Initiative.

Efforts are underway at the Centers for Disease Control and Prevention to foster greater use of electronic data stored in health care application databases for surveillance of health care-associated infections and antimicrobial use and resistance. These efforts, referred to as the National Healthcare Safety Network (NHSN) eSurveillance Initiative, focus on standards-based solutions for conveying health care data and validation processes to confirm that the data received at the Centers for Disease Control and Prevention accurately reflect the data transmitted by health care facilities. Standard vehicles for data transmission, specifically Health Level Seven standards for electronic messages and structured documents, and standard vocabularies for representing microorganisms and other information needed for surveillance, are central features of the eSurveillance Initiative. Progress to date in this initiative is reviewed, and future project plans are outlined. Enhanced interoperability between health care and public health information systems is achievable for surveillance purposes, but major challenges must be overcome to realize the full benefits sought by the eSurveillance Initiative.

NHSN annual update: antimicrobial-resistant pathogens associated with healthcare-associated infections: annual summary of data reported to the National Healthcare Safety Network at the Centers for Disease Control and Prevention, 2006-2007.

OBJECTIVE: To describe the frequency of selected antimicrobial resistance patterns among pathogens causing device-associated and procedure-associated healthcare-associated infections (HAIs) reported by hospitals in the National Healthcare Safety Network (NHSN). METHODS: Data are included on HAIs (ie, central line-associated bloodstream infections, catheter-associated urinary tract infections, ventilator-associated pneumonia, and surgical site infections) reported to the Patient Safety Component of the NHSN between January 2006 and October 2007. The results of antimicrobial susceptibility testing of up to 3 pathogenic isolates per HAI by a hospital were evaluated to define antimicrobial-resistance in the pathogenic isolates. The pooled mean proportions of pathogenic isolates interpreted as resistant to selected antimicrobial agents were calculated by type of HAI and overall. The incidence rates of specific device-associated infections were calculated for selected antimicrobial-resistant pathogens according to type of patient care area; the variability in the reported rates is described. RESULTS: Overall, 463 hospitals reported 1 or more HAIs: 412 (89%) were general acute care hospitals, and 309 (67%) had 200-1,000 beds. There were 28,502 HAIs reported among 25,384 patients. The 10 most common pathogens (accounting for 84% of any HAIs) were coagulase-negative staphylococci (15%), Staphylococcus aureus (15%), Enterococcus species (12%), Candida species (11%), Escherichia coli (10%), Pseudomonas aeruginosa (8%), Klebsiella pneumoniae (6%), Enterobacter species (5%), Acinetobacter baumannii (3%), and Klebsiella oxytoca (2%). The pooled mean proportion of pathogenic isolates resistant to antimicrobial agents varied significantly across types of HAI for some pathogen-antimicrobial combinations. As many as 16% of all HAIs were associated with the following multidrug-resistant pathogens: methicillin-resistant S. aureus (8% of HAIs), vancomycin-resistant Enterococcus faecium (4%), carbapenem-resistant P. aeruginosa (2%), extended-spectrum cephalosporin-resistant K. pneumoniae (1%), extended-spectrum cephalosporin-resistant E. coli (0.5%), and carbapenem-resistant A. baumannii, K. pneumoniae, K. oxytoca, and E. coli (0.5%). Nationwide, the majority of units reported no HAIs due to these antimicrobial-resistant pathogens.