ICUs likely realm of billion-dollar bugs
Look to your intensive care unit (ICU) for a front-line attack on antibiotic resistance. Emerging data indicate that the fight against resistant bacteria might best start there where a rise in resistant pathogens is most pronounced.Initial data from a study called ICARE (Intensive Care Antimicrobial Resistance Epidemiology) reveal a step-wise decrease in resistant pathogens across the spectrum of care. Researchers found the greatest percentages of antibiotic-resistant isolates in ICU patients, followed by non-ICU hospital patients and outpatients, respectively.1 Increases in the rate of antimicrobial resistance are resulting in the use of more expensive drugs, more prolonged hospitalizations, higher death rates, and higher health care costs — an estimated $4 billion annually in the United States, ICARE researchers report.
"In this day of cuts and limited resources, where do you focus your efforts? The answer is the ICU," says the study’s lead author, Lennox Archibald, MD, medical epidemiologist in the hospital infections program of the Centers for Disease Control and Prevention (CDC) in Atlanta.
ICARE includes data from eight geographically dispersed sentinel hospitals in the CDC’s National Nosocomial Infections Surveillance (NNIS) system. Statistics were reported in terms of percentage of resistant isolates of the total number of isolates tested for inpatients (ICU and non-ICU) and outpatients. For example, 6.3% of enterococci isolated from inpatients were vancomycin-resistant (VRE), compared with 1.4% VRE among outpatients. (See table, below.)
Most of these pathogens are resistant to all currently available antibiotics, the authors noted. Likewise, overall NNIS data for gram-negative bacilli indicate that the percentage of Klebsiella pneumoniae resistant to extended-spectrum beta-lactam agents increased from 1.5% in 1986 to 12.8% by 1993. In at least one case, the resistant Klebsiella strains first "appeared in an ICU in one hospital and then spread to other hospitals in the surrounding area," the authors pointed out.
As the rate of antimicrobial resistance increases, more resources should be allocated to attack the problem in ICUs, including heightened surveillance and improved use of antibiotics, the researchers concluded. While the need for more "scrupulous and stricter infection control" was cited in the study, the researchers say no new infection control measures are being advised. It appears the primary answer to the problem will be in the form of surveillance for infections, identifying specific drug resistance patterns, and implementing antibiotic controls. That means, for example, that infection control professionals and others working in critical care settings should begin focusing infection surveillance and antibiotic control efforts on ICU patients, rather than trying to attack the problem globally.
Focusing surveillance in ICUs may allow early detection of outbreaks. In a Canadian study, clinicians comparing isolates from ICU patients with other hospital isolates effectively curtailed an outbreak of multidrug-resistant Pseudomonas aeruginosa in an ICU.2 Without the targeted effort, the outbreak might have gone undetected and spread throughout the hospital, they concluded.
Patients admitted to ICUs are at greater risk of acquiring nosocomial infections because of their serious underlying disease, prolonged use of invasive devices, and extended hospital stays. "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," ICARE researchers concluded.
An emerging trend that may skew the data is the rise in ICU bed censuses even as overall hospital census is falling due to the transition to outpatient care. The trend is occurring in the NNIS system hospitals and is starting to appear in other surveys. The perceived impact of emerging antimicrobial resistance in ICUs may increase as hospitals devote more beds and resources to those units.
"The chief risk factor for acquisition of a nosocomial infection is [invasive] device use," Archibald explains. The more critical the condition of the patient, the higher the probability a device will be used. If you have a high rate of nosocomial infections, there is going to be a parallel increase in antimicrobial use.
As these infections are treated with increasing amounts of antibiotics in the ICU, certain "bug-drug" combinations are appearing in the initial ICARE data that show a direct relationship between the level of use of the antibiotic and an attendant rise of resistant pathogens. "As usage increases, resistance increases," Archibald says.
References
1. Archibald L, Phillips L, Monnet D, et al. Antimicrobial resistance in isolates from inpatients and outpatients in the United States: Increasing importance of the intensive care unit. Clin Infect Dis 1997; 24:211-215.
2. Bryce EA, Smith JA. Focused microbiological surveillance and gram-negative beta-lactamase-mediated resistance in an intensive care unit. Infect Control Hosp Epidemiol 1995; 16:331-334.
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