Wendy Bamberg

Multistate Point-Prevalence Survey of Health Care–Associated Infections

BACKGROUND Currently, no single U.S. surveillance system can provide estimates of the burden of all types of health care-associated infections across acute care patient populations. We conducted a prevalence survey in 10 geographically diverse states to determine the prevalence of health care-associated infections in acute care hospitals and generate updated estimates of the national burden of such infections. METHODS We defined health care-associated infections with the use of National Healthcare Safety Network criteria. One-day surveys of randomly selected inpatients were performed in participating hospitals. Hospital personnel collected demographic and limited clinical data. Trained data collectors reviewed medical records retrospectively to identify health care-associated infections active at the time of the survey. Survey data and 2010 Nationwide Inpatient Sample data, stratified according to patient age and length of hospital stay, were used to estimate the total numbers of health care-associated infections and of inpatients with such infections in U.S. acute care hospitals in 2011. RESULTS Surveys were conducted in 183 hospitals. Of 11,282 patients, 452 had 1 or more health care-associated infections (4.0%; 95% confidence interval, 3.7 to 4.4). Of 504 such infections, the most common types were pneumonia (21.8%), surgical-site infections (21.8%), and gastrointestinal infections (17.1%). Clostridium difficile was the most commonly reported pathogen (causing 12.1% of health care-associated infections). Device-associated infections (i.e., central-catheter-associated bloodstream infection, catheter-associated urinary tract infection, and ventilator-associated pneumonia), which have traditionally been the focus of programs to prevent health care-associated infections, accounted for 25.6% of such infections. We estimated that there were 648,000 patients with 721,800 health care-associated infections in U.S. acute care hospitals in 2011. CONCLUSIONS Results of this multistate prevalence survey of health care-associated infections indicate that public health surveillance and prevention activities should continue to address C. difficile infections. As device- and procedure-associated infections decrease, consideration should be given to expanding surveillance and prevention activities to include other health care-associated infections.

Burden of Clostridium difficile Infection in the United States

BACKGROUND The magnitude and scope of Clostridium difficile infection in the United States continue to evolve. METHODS In 2011, we performed active population- and laboratory-based surveillance across 10 geographic areas in the United States to identify cases of C. difficile infection (stool specimens positive for C. difficile on either toxin or molecular assay in residents ≥ 1 year of age). Cases were classified as community-associated or health care-associated. In a sample of cases of C. difficile infection, specimens were cultured and isolates underwent molecular typing. We used regression models to calculate estimates of national incidence and total number of infections, first recurrences, and deaths within 30 days after the diagnosis of C. difficile infection. RESULTS A total of 15,461 cases of C. difficile infection were identified in the 10 geographic areas; 65.8% were health care-associated, but only 24.2% had onset during hospitalization. After adjustment for predictors of disease incidence, the estimated number of incident C. difficile infections in the United States was 453,000 (95% confidence interval [CI], 397,100 to 508,500). The incidence was estimated to be higher among females (rate ratio, 1.26; 95% CI, 1.25 to 1.27), whites (rate ratio, 1.72; 95% CI, 1.56 to 2.0), and persons 65 years of age or older (rate ratio, 8.65; 95% CI, 8.16 to 9.31). The estimated number of first recurrences of C. difficile infection was 83,000 (95% CI, 57,000 to 108,900), and the estimated number of deaths was 29,300 (95% CI, 16,500 to 42,100). The North American pulsed-field gel electrophoresis type 1 (NAP1) strain was more prevalent among health care-associated infections than among community-associated infections (30.7% vs. 18.8%, P<0.001). CONCLUSIONS C. difficile was responsible for almost half a million infections and was associated with approximately 29,000 deaths in 2011. (Funded by the Centers for Disease Control and Prevention.).

Epidemiology of Community-Associated Clostridium difficile Infection, 2009 Through 2011

IMPORTANCE Clostridium difficile infection (CDI) has been increasingly reported among healthy individuals in the community. Recent data suggest that community-associated CDI represents one-third of all C difficile cases. The epidemiology and potential sources of C difficile in the community are not fully understood. OBJECTIVES To determine epidemiological and clinical characteristics of community-associated CDI and to explore potential sources of C difficile acquisition in the community. DESIGN AND SETTING Active population-based and laboratory-based CDI surveillance in 8 US states. PARTICIPANTS Medical records were reviewed and interviews performed to assess outpatient, household, and food exposures among patients with community-associated CDI (ie, toxin or molecular assay positive for C difficile and no overnight stay in a health care facility within 12 weeks). Molecular characterization of C difficile isolates was performed. Outpatient health care exposure in the prior 12 weeks among patients with community-associated CDI was a priori categorized into the following 3 levels: no exposure, low-level exposure (ie, outpatient visit with physician or dentist), or high-level exposure (ie, surgery, dialysis, emergency or urgent care visit, inpatient care with no overnight stay, or health care personnel with direct patient care). MAIN OUTCOMES AND MEASURES Prevalence of outpatient health care exposure among patients with community-associated CDI and identification of potential sources of C difficile by level of outpatient health care exposure. RESULTS Of 984 patients with community-associated CDI, 353 (35.9%) did not receive antibiotics, 177 (18.0%) had no outpatient health care exposure, and 400 (40.7%) had low-level outpatient health care exposure. Thirty-one percent of patients without antibiotic exposure received proton pump inhibitors. Patients having CDI with no or low-level outpatient health care exposure were more likely to be exposed to infants younger than 1 year (P = .04) and to household members with active CDI (P = .05) compared with those having high-level outpatient health care exposure. No association between food exposure or animal exposure and level of outpatient health care exposure was observed. North American pulsed-field gel electrophoresis (NAP) 1 was the most common (21.7%) strain isolated; NAP7 and NAP8 were uncommon (6.7%). CONCLUSIONS AND RELEVANCE Most patients with community-associated CDI had recent outpatient health care exposure, and up to 36% would not be prevented by reduction of antibiotic use only. Our data support evaluation of additional strategies, including further examination of C difficile transmission in outpatient and household settings and reduction of proton pump inhibitor use.

Epidemiology of Carbapenem-Resistant Enterobacteriaceae in 7 US Communities, 2012-2013

IMPORTANCE Carbapenem-resistant Enterobacteriaceae (CRE) are increasingly reported worldwide as a cause of infections with high-mortality rates. Assessment of the US epidemiology of CRE is needed to inform national prevention efforts. OBJECTIVE To determine the population-based CRE incidence and describe the characteristics and resistance mechanism associated with isolates from 7 US geographical areas. DESIGN, SETTING, AND PARTICIPANTS Population- and laboratory-based active surveillance of CRE conducted among individuals living in 1 of 7 US metropolitan areas in Colorado, Georgia, Maryland, Minnesota, New Mexico, New York, and Oregon. Cases of CRE were defined as carbapenem-nonsusceptible (excluding ertapenem) and extended-spectrum cephalosporin-resistant Escherichia coli, Enterobacter aerogenes, Enterobacter cloacae complex, Klebsiella pneumoniae, or Klebsiella oxytoca that were recovered from sterile-site or urine cultures during 2012-2013. Case records were reviewed and molecular typing for common carbapenemases was performed. EXPOSURES Demographics, comorbidities, health care exposures, and culture source and location. MAIN OUTCOMES AND MEASURES Population-based CRE incidence, site-specific standardized incidence ratios (adjusted for age and race), and clinical and microbiological characteristics. RESULTS Among 599 CRE cases in 481 individuals, 520 (86.8%; 95% CI, 84.1%-89.5%) were isolated from urine and 68 (11.4%; 95% CI, 8.8%-13.9%) from blood. The median age was 66 years (95% CI, 62.1-65.4 years) and 284 (59.0%; 95% CI, 54.6%-63.5%) were female. The overall annual CRE incidence rate per 100<000 population was 2.93 (95% CI, 2.65-3.23). The CRE standardized incidence ratio was significantly higher than predicted for the sites in Georgia (1.65 [95% CI, 1.20-2.25]; P < .001), Maryland (1.44 [95% CI, 1.06-1.96]; P = .001), and New York (1.42 [95% CI, 1.05-1.92]; P = .048), and significantly lower than predicted for the sites in Colorado (0.53 [95% CI, 0.39-0.71]; P < .001), New Mexico (0.41 [95% CI, 0.30-0.55]; P = .01), and Oregon (0.28 [95% CI, 0.21-0.38]; P < .001). Most cases occurred in individuals with prior hospitalizations (399/531 [75.1%; 95% CI, 71.4%-78.8%]) or indwelling devices (382/525 [72.8%; 95% CI, 68.9%-76.6%]); 180 of 322 (55.9%; 95% CI, 50.0%-60.8%) admitted cases resulted in a discharge to a long-term care setting. Death occurred in 51 (9.0%; 95% CI, 6.6%-11.4%) cases, including in 25 of 91 cases (27.5%; 95% CI, 18.1%-36.8%) with CRE isolated from normally sterile sites. Of 188 isolates tested, 90 (47.9%; 95% CI, 40.6%-55.1%) produced a carbapenemase. CONCLUSIONS AND RELEVANCE In this population- and laboratory-based active surveillance system in 7 states, the incidence of CRE was 2.93 per 100<000 population. Most CRE cases were isolated from a urine source, and were associated with high prevalence of prior hospitalizations or indwelling devices, and discharge to long-term care settings.

Effect of Nucleic Acid Amplification Testing on Population-based Incidence Rates of Clostridium difficile Infection

Nucleic acid amplification testing (NAAT) is increasingly being adopted for diagnosis of Clostridium difficile infection (CDI). Data from 3 states conducting population-based CDI surveillance showed increases ranging from 43% to 67% in CDI incidence attributable to changing from toxin enzyme immunoassays to NAAT. CDI surveillance requires adjustment for testing methods.

Invasive Methicillin-Resistant Staphylococcus aureus Infections Among Patients on Chronic Dialysis in the United States, 2005–2011

BACKGROUND Approximately 15 700 invasive methicillin-resistant Staphylococcus aureus (MRSA) infections occurred in US dialysis patients in 2010. Frequent hospital visits and prolonged bloodstream access, especially via central venous catheters (CVCs), are risk factors among hemodialysis patients. We describe the epidemiology of and recent trends in invasive MRSA infections among dialysis patients. METHODS We analyzed population-based data from 9 US metropolitan areas from 2005 to 2011. Cases were defined as MRSA isolated from a normally sterile body site in a surveillance area resident who received dialysis, and were classified as hospital-onset (HO; culture collected >3 days after hospital admission) or healthcare-associated community-onset (HACO; all others). Incidence was calculated using denominators from the US Renal Data System. Temporal trends in incidence and national estimates were calculated controlling for age, sex, and race. RESULTS From 2005 to 2011, 7489 cases were identified; 85.7% were HACO infections, and 93.2% were bloodstream infections. Incidence of invasive MRSA infections decreased from 6.5 to 4.2 per 100 dialysis patients (annual decrease, 7.3%) with annual decreases of 6.7% for HACO and 10.5% for HO cases. Among cases identified during 2009-2011, 70% of patients were hospitalized in the year prior to infection. Among hemodialysis cases, 60.4% of patients were dialyzed through a CVC. The 2011 national estimated number of MRSA infections was 15 169. CONCLUSIONS There has been a substantial decrease in invasive MRSA infection incidence among dialysis patients. Most cases had previous hospitalizations, suggesting that efforts to control MRSA in hospitals might have contributed to the declines. Infection prevention measures should include improved vascular access and CVC care.

Carbapenem-resistant Klebsiella pneumoniae producing New Delhi metallo-β-lactamase at an acute care hospital, Colorado, 2012.

OBJECTIVE To investigate an outbreak of New Delhi metallo-β-lactamase (NDM)-producing carbapenem-resistant Enterobacteriaceae (CRE) and determine interventions to interrupt transmission. DESIGN, SETTING, AND PATIENTS Epidemiologic investigation of an outbreak of NDM-producing CRE among patients at a Colorado acute care hospital. METHODS Case patients had NDM-producing CRE isolated from clinical or rectal surveillance cultures (SCs) collected during the period January 1, 2012, through October 20, 2012. Case patients were identified through microbiology records and 6 rounds of SCs in hospital units where they had resided. CRE isolates were tested by real-time polymerase chain reaction for blaNDM. Medical records were reviewed for epidemiologic links; relatedness of isolates was evaluated by pulsed-field gel electrophoresis (PFGE) and whole genome sequencing (WGS). Infection control (IC) was assessed through staff interviews and direct observations. RESULTS Two patients were initially identified with NDM-producing CRE during July-August 2012. A third case patient, admitted in May, was identified through microbiology records review. SC identified 5 additional case patients. Patients had resided in 11 different units before identification. All isolates were highly related by PFGE. WGS suggested 3 clusters of CRE. Combining WGS with epidemiology identified 4 units as likely transmission sites. NDM-producing CRE positivity in certain patients was not explained by direct epidemiologic overlap, which suggests that undetected colonized patients were involved in transmission. CONCLUSIONS A 4-month outbreak of NDM-producing CRE occurred at a single hospital, highlighting the risk for spread of these organisms. Combined WGS and epidemiologic data suggested transmission primarily occurred on 4 units. Timely SC, combined with targeted IC measures, were likely responsible for controlling transmission.

Improved Phenotype-Based Definition for Identifying Carbapenemase Producers among Carbapenem-Resistant Enterobacteriaceae

A new, less restrictive definition increases detection of Klebsiella pneumoniae carbapenemase producers.

Association between Outpatient Antibiotic Prescribing Practices and Community- Associated Clostridium difficile Infection

A modest, 10% reduction in outpatient antibiotic prescribing among U.S. adults could result in a substantial 17% reduction in Clostridium difficile infections that originate in the community.

Evaluating the accuracy of sampling to estimate central line-days: simplification of the National Healthcare Safety Network surveillance methods.

OBJECTIVE To evaluate the accuracy of weekly sampling of central line-associated bloodstream infection (CLABSI) denominator data to estimate central line-days (CLDs). DESIGN Obtained CLABSI denominator logs showing daily counts of patient-days and CLD for 6-12 consecutive months from participants and CLABSI numerators and facility and location characteristics from the National Healthcare Safety Network (NHSN). SETTING AND PARTICIPANTS Convenience sample of 119 inpatient locations in 63 acute care facilities within 9 states participating in the Emerging Infections Program. METHODS Actual CLD and estimated CLD obtained from sampling denominator data on all single-day and 2-day (day-pair) samples were compared by assessing the distributions of the CLD percentage error. Facility and location characteristics associated with increased precision of estimated CLD were assessed. The impact of using estimated CLD to calculate CLABSI rates was evaluated by measuring the change in CLABSI decile ranking. RESULTS The distribution of CLD percentage error varied by the day and number of days sampled. On average, day-pair samples provided more accurate estimates than did single-day samples. For several day-pair samples, approximately 90% of locations had CLD percentage error of less than or equal to ±5%. A lower number of CLD per month was most significantly associated with poor precision in estimated CLD. Most locations experienced no change in CLABSI decile ranking, and no locations CLABSI ranking changed by more than 2 deciles. CONCLUSIONS Sampling to obtain estimated CLD is a valid alternative to daily data collection for a large proportion of locations. Development of a sampling guideline for NHSN users is underway.