Active Surveillance Cultures for Multidrug Resistant Gram-Negative Organisms at an Acute Care Hospital

Overview

Active Surveillance Culture programs (ASC) have been initiated in health-care systems in recent years as a mechanism for tracking multi-drug resistant organisms (MDRO), with a goal to reduce the transfer of those organisms to other patients. Consequently, the Center for Disease Prevention and Control (CDC) charged infection control personnel to develop institutional guidelines for the prevention of transmission of multidrug-resistant organisms, within health care settings. The CDC guidelines include performance of active surveillance cultures for patients after admission to health care facilities or to high-risk-patient care units, to detect colonization with target multidrug-resistant organisms. The most commonly tracked antimicrobial resistance organisms in hospital surveillance programs are methicillin resistant Staphylococcus aureus (MRSA), vancomycin resistant enterococcus (VRE), Clostridium difficile, extended-spectrum beta-lactamase (ESBL) producing gram-negative bacilli (e.g. Escherichia coli, Klebsiella pneumoniae), and carbapenem resistant Enterobacteriaceae (CRE). Patients who are colonized with these potential pathogens are placed under contact precautions to prevent transmission to other patients. While clinical outcomes studies exist for MDR gram-positive organisms \[particularly methicillin resistant Staphylococcus aureus (MRSA)\] ASC, data is limited for MDR gram-negative organisms. The study is retrospective cohort study to evaluate if isolation of an MDR gram-negative pathogen on ASC predicts subsequent infection with the same pathogen. Patients \>18 years of age, admitted to MHS with ASC for MDR gram-negative pathogens, will be included if criteria met. Outcomes of interest will be evaluated with appropriate statistical tests, and multivariate analyses will be used to control for predictors of interest. All analysis will be considered significant at an alpha of \<0.05. The investigators anticipate that increased screening with isolation will result in decreased subsequent MDRO gram-negative infection. Furthermore, the investigators hope that this will also result in improved patient's outcomes, mortality, and decreased cost, including excessive use of anti-infectives and its unintended consequences such as microbial resistance.

This is a retrospective cross-sectional study of patients with ASC at MHS. Patients \>18 years of age, admitted to MHS during the study specified period, will be included if there is documented ASC. Patients will be identified through the clinical microbiology laboratory records. Figure 1 is a flow diagram of ASC stratification. Study populations All patients with documented laboratory surveillance culture from January 1, 2006 to December 31, 2012 will be included. Eligible cultures (see definitions below) will be identified based on positive surveillance cultures from MHS. Patients identified with select criteria per objective will be further analyzed in subsequent phases to complete all outcomes of interest. Patients will be excluded if they are ≤18 years, expired before initial surveillance culture is positive, were not admitted, or were transferred to another institution. Patients will be excluded if they underwent amputation or surgical revision for wound infections. Patients with polymicrobial MDR gram-negative pathogen on ASC will be included; however, the main focus of this study is the subset of patients with monomicrobial ASC. Lastly, only the index culture will be considered, for patients with multiple wounds ASC. Data Collection Initial phase will focus on review of surveillance cultures within the past year (calendar year 2012) to determine objective number one. Prior years are included to evaluate earlier documentation of colonization and whether number of patients/cultures per year has significant variation. Subsequent phases will collect specific data identified as significant or varied based on previous analysis. Data will be collected via extraction and chart review from MHS's electronic medical record (EMR) on identified patients. Patient demographics (weight, sex, race, age, allergy), co-morbid conditions (diabetes, immunosuppressed, HIV/AIDS, organ transplant, malignancy, chronic lung disease, chronic kidney disease, liver disease, surgery in past 30 days), location in the hospital, type of residence (i.e., home, long-term care facility, etc), source of infection, treatment data (antibiotics administered and duration), length of stay in survivors, hospital cost, antibiotic cost, severity of illness by mean Simplified Acute Physiologic Score (SAPS) II score (based on clinical data present during the 24 hours preceding the index blood culture), hospital mortality, and DRG. Previous hospitalizations, antimicrobial usage and surveillance culture results will be recorded. Surveillance cultures from nares, rectum, endotracheal aspirates, urine, and wound swab will be included. Microbiology data (organism, culture source, and number of classes of antibiotics with resistance) will be documented. Patients with positive ASC for MDR gram-negative pathogens will be evaluated for antimicrobial use for 1) ASC only and 2) Subsequent positive cultures due to suspected or proven active infection. Cost for each of the following classifications will be determined and compared: microbiological cultures including antimicrobial susceptibility test, length of stay, cost of antimicrobial and associated diagnosis related groups (DRG) per infection type.