The rate at which pathogens resist antimicrobial treatment is significantly higher in the hospital setting than in the outpatient setting, report researchers from Centers for Disease Control and Prevention (CDC) and Emory University's Rollins School of Public Health in Clinical Infectious Diseases.
The team found that pathogens isolated from patients in hospital intensive care units (ICUs) are most resistant to antibiotics, organisms infecting patients in other areas of the hospital were less resistant and organisms isolated from outpatients were least resistant to treatment.
'As the rate of antimicrobial resistance increases, more resources should be allocated to stem this problem within the ICU, including more surveillance activities, scrupulous and stricter infection control in hospitals, and improved use of antibiotics,' conclude first author Lennox K. Archibald, of the Hospital Infections Program, National Center for Infectious Diseases, CDC; Emory's John McGowan Jr., M.D., professor of epidemiology; and other CDC and Emory co-authors.
Data come from the National Nosocomial Infections Surveillance System (NNIS; www.cdc.gov/ncidod/diseases/hip/nnis.htm), the nation's most extensive system for tracking hospital-acquired (nosocomial) infections and for gauging how resistant nosocomial pathogens are to antimicrobials. Researchers from the Hospital Infections Program, CDC and Emory are using NNIS data for Project ICARE (Intensive Care Antimicrobial Resistance Epidemiology). Their current paper summarizes Phase 1 of Project ICARE and includes data from eight NNIS hospitals.
Specimens isolated from inpatients and outpatients were analyzed to assess resistance levels of eight organisms to eight common antimicrobials (13 organism/antimicrobial combinations).
The group reports that pathogens from inpatients with the following organism/antimicrobial combinations resisted treatment more steadfastly than the same pathogens isolated from outpatients:
- 49 percent of coagulase-negative Staphylococcus isolated from inpatients resisted treatment with methicillin vs. 36 percent resistance among outpatients;
- 33 percent of Staphylococcus aureus isolated from inpatients resisted treatment with methicillin vs. 14.5 percent resistance among outpatients;
- 26 percent of Enterobacter cloacae isolated from inpatients resisted treatment with ceftazidime vs. 12 percent resistance among outpatients;
- 12 percent of Pseudomonas aeruginosa isolated from inpatients resisted treatment with imipenem vs. 6.5 percent resistance among outpatients;
- 7.8 percent of P. aeruginosa isolated from inpatients resisted treatment with ceftazidime vs. 4 percent resistance among outpatients;
- 6.3 percent of Enterococcus species isolated from inpatients resisted treatment with vancomycin vs. 1.4 percent resistance among outpatients.
'Patients admitted to ICUs are at greatest risk of acquiring nosocomial infections, partly because of their serious underlying disease but also because of exposure to life-saving invasive procedures, prolonged use of in situ invasive devices, therapy with multiple antimicrobials, and extended hospital stays,' the authors explain. 'Moreover, antimicrobial resistance in pathogens is more likely encountered in the ICU because of the selection effect of treatment with multiple antimicrobials for a single patient, which may result in amplification of antimicrobial resistance in organisms. The increasing number of ICU beds in hospitals is an important development regarding both antimicrobial resistance and nosocomial infections. The relative magnitude of antimicrobial resistance in ICUs will increase as hospitals devote more beds and resources to those units.'
Project ICARE is sponsored by the National Foundation for Infectious Diseases; Zeneca Pharmaceuticals; American Society for Health-System Pharmacists; Bayer Corporation, Pharmaceutical Division; Rhone-Poulenc-Rorer; Roche Laboratories; and Kimberly-Clark Corporation.
Scope of the Problem
The following excerpt comes verbatim from the introduction to 'Antimicrobial
Resistance in Isolates from Inpatients and Outpatients in the United States:
Increasing Importance of the Intensive Care Unit' published in the journal
Clinical Infectious Diseases
(Feb. 1997;24:211-5, L. Archibald et al).
'Antimicrobial-resistant pathogens are challenges to progress in controlling emerging infections, especially hospital-acquired infections'.
Increases in the rate of antimicrobial resistance are resulting in the use of much more expensive drugs, more prolonged hospitalizations, higher death-rates, and higher health care costs.
Yearly expenditures incurred from drug resistance in the United States are estimated to approach $4 billion and are rising.
Most, but not all, studies have found a higher prevalence of antimicrobial resistance in hospitals in general and in intensive care units (ICUs) in particular than in the community. Such resistance presents a serious challenge for physicians.
For example, data from the National Nosocomial Infections Surveillance (NNIS) system, currently the only national source of information in infections due to hospital-acquired pathogens and their associated antimicrobial susceptibility profiles, indicate that the rate of resistance to vancomycin in hospital-acquired Enterococcus species is increasing. As of December 1993, 14.2% of all enterococci associated with nosocomial infections in ICU patients were vancomycin-resistant. Most of these pathogens were resistant to all currently available antimicrobials.
Among certain gram-negative bacilli, the resistance rate is also increasing.
In hospitals participating in the NNIS system, NNIS data indicate that the percentage of Klebsiella pneumoniae resistant to extended-spectrum B-lactam agents increased from 1.5% in 1986 to 12.8% in 1993. NNIS data also suggest that in one region these resistant Klebsiella strains first appeared in an ICU in one hospital and then spread to other hospitals in the surrounding area.
Unfortunately, antimicrobial resistance is not limited to the hospital setting. Streptococcus pneumoniae infections are a leading cause of morbidity and
mortality in young children, persons with underlying debilitating medical conditions, and elderly persons. Multidrug-resistant strains of this organism are emerging throughout the United States. Methicillin-resistant Staphylococcus aureus, traditionally thought to be hospital-acquired but infrequently recognized in the community for over a decade, is now found outside hospitals in relatively large numbers.
Defining appropriate control measures for antimicrobial-resistant pathogens has been of particular concern for acute care hospitals. With a changing emphasis on integrated health care systems that provide care for patients in acute care, extended care, and ambulatory care settings, dwindling resources will need to be prioritized and appropriately focused on infection control in hospitals and prevention of antimicrobial resistance. This task has been complicated by the fact that the magnitude of antimicrobial resistance in the hospital compared with that in the community setting is not clear. In addition, the contribution of the ICU to overall resistance in the hospital needs clarification.
Therefore, to evaluate and compare resistance in these two settings, in 1994 the Hospital Infections Program and the Centers for Disease Control and Prevention (CDC), in cooperation with the Rollins School of Public Health at Emory University, began Project ICARE (Intensive Care Antimicrobial Resistance Epidemiology). This project began with phase 1 in April 1994; a second phase started early in 1996.
Lennox Archibald -- Hospital Infections Program, National Center for Infectious Diseases, Centers for Disease Control and Prevention (CDC).
Lisa Phillips -- doctoral student in epidemiology, Rollins School of Public Health, Emory University.
Dominique Monnet -- formerly visiting scientist at CDC, current affiliation: Statens Seruminstitut, Copenhagen, Denmark
John E. McGowan, Jr.-- professor of epidemiology, Rollins School of Public Health, and professor of pathology and laboratory medicine, School of Medicine, Emory University, Emory University.
Fred Tenover -- chief, Nosocomial Pathogens Laboratory Branch, CDC, and adjunct professor of epidemiology, Rollins School of Public Health, Emory University.
Robert Gaynes -- director, National Nosocomial Infections Surveillance System, CDC, and adjunct associate professor of epidemiology, Rollins School of Public Health, Emory University.