Infection Control & Hospital Epidemiology
mid-1980s to control an outbreak of ESBL-producing Klebsiella pneumoniae infection. Although active surveillance was originally conducted for infection control purposes, the data collected have been increasingly utilized to assist in the selection of empirical antibiotic therapy in the setting of possible infection.18 At the Children’s National Health System (CNHS), active surveillance for ESBL-E colonization has been conducted in the NICU since the early 1990s, when ESBL-E was emerging and a point-prevalence study revealed colonization rate of nearly 30% in the unit. The primary purpose for initiating active surveillance was to reduce the risk for ESBL-E transmission. Since then, other changes have been implemented on the unit including but not limited to physical environment design, infection control prac- tices, and improved safety culture. The aims of this study were to evaluate the efficacy and financial impact of active surveillance on ESBL colonization and infection in our level IV NICU and to assess the need for continuing this practice by reviewing 19 years of data.
Methods Study setting
The NICU is a level IV unit offering care for premature infants transferred from hospitals throughout the Washington, DC, metropolitan region. Before 2009, the unit was an open ward with 6 bays and 1 swing area with 2 shared rooms, for a maximum capacity of 48 patients. In 2009, the unit moved to a newly designed 54-bed space with 46 primary rooms and 2 shared bays that could accommodate 4 patients each. In 2017, the unit expanded to 60 beds through the addition of several private rooms in the adjacent space. A NICU-specific ESBL-E protocol requires patients to be
screened for ESBL-E colonization by testing rectal swab speci- mens collected upon admission and weekly thereafter, until the patient tested positive or was discharged from the hospital, whichever occurs first. Patients are placed on contact precautions for the entire hospital stay if ESBL-E is detected in a specimen collected for either active surveillance or clinical diagnosis. Healthcare providers are required to wear a single-use gown and gloves upon entry to a patient room or bay for those patients assigned to contact precautions. As reported previously, the unit has had additional
active surveillance for the detection of vancomycin-resistant Enterococcus (VRE)19 and methicillin-resistant Staphylococcus aureus (MRSA),20 respectively. The VRE surveillance was undertaken from 2003 to March 2017, while MRSA surveillance was implemented in 2015 and is ongoing. The VRE active sur- veillance was conducted only once by testing rectal swabs col- lected upon patient admission, whereas MRSA surveillance is conducted by testing nasal swabs collected upon patient admis- sion and weekly thereafter until the patient becomes MRSA positive or is discharged, whichever occurs first.
Study patients and data sources
In this study, we included patients admitted to the CNHS NICU between January 1999 and March 2018. Active surveillance for ESBL-E colonization was conducted between January 1999 and March 2017 among all patients admitted to the unit. An electronic microbiology data repository was searched to identify NICU patients that had ESBL-E isolated from specimens
Statistical analysis
Data were managed using Microsoft Excel (Microsoft, Redmond, WA). Descriptive analyses computing percentages for categorical variables and averages for continued variables were performed using STATA software (StataCorp, College Station, TX). A U-chart was constructed to describe changes in the hospital
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collected for active surveillance or for clinical diagnosis. Patients were considered to have a subsequent infection if an infection due to the same ESBL-E pathogen detected by active surveillance occurred after colonization was detected and before discharge. In September 2005, the institution implemented an electronic
medical record system, which made data extraction feasible. Thus, for this study, the medical charts for patients admitted after September 2005 were reviewed to extract additional information related to patient characteristics (ie, demographics, gestational age, and birthweight), clinical diagnosis, prognosis, and to determine factors that could distinguish infection versus coloni- zation. Administrative databases were queried to obtain the annual number of patient admissions as well as patient days.
Microbiology testing methods
Identification of Enterobacteriaceae species was conducted using the Centers for Disease Control and Prevention MacConkey Agar (MAC) protocol. The detection and confirmation of ESBL–E was performed using the MicroScan Walkaway System (Beckman Coulter, Brea, California). Enterobacteriaceae isolates with an elevated minimum inhibitory concentration (MIC) for cefotaxime (CEFO) (>2µg/mL) or ceftazidime (CEFT) (>1 µg/mL) were suspected for ESBL-E. An isolate was considered positive for ESBL production if there was a ≥8-fold difference between MICs of CEFO or CEFT when tested alone compared to the MICs of these antibiotics when tested in the presence of clavulanic acid, as determined automatically by the MicroScan Walkaway System.
Definitions
Hospital-acquired ESBL-E colonization or infection was defined as ESBL-E detected for the first time from a specimen collected for either active surveillance or clinical diagnosis after a patient had been admitted for at least 2 days, with the day of admission considered as day zero. The overall incidence rate of ESBL-E colonization or infection was defined as the number of ESBL-E colonizations or infections per 100 patient admissions. The hospital-acquired incidence rate was defined as the number of hospital-acquired ESBL-E infections per 1,000 patient days. To estimate the cost associated with ESBL-E active surveil-
lance, published data were used to calculate the direct costs associated with both the required supplies and laboratory tech- nician time to process specimens collected for Klebsiella pneumoniae carbapenemase (KPC)–producing Enterobacter- iaceae active surveillance in the University of Virginia Health System, Charlottesville, Virginia, in 2012.21 Although this cost analysis was specifically for KPC-producing Enterobacteriaceae, it provided itemized direct costs for supplies that our laboratory uses to process specimens collected for ESBL-E active surveil- lance. This study estimated that active surveillance cost $11.37 and $2.47 (2012 US$ value) if a specimen was confirmed to be positive or negative, respectively.
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