ICUs could become new front line in the battle against antibiotic overuse
ICARE project tracing increasing drug resistance to ICU
A new front line in the battle against infections is being drawn, and it’s right outside your ICU. Data from ongoing studies indicate that rising patient counts in ICUs are resulting in the growth of antibiotic resistant bacteria found there.Initial data from a continuing study called ICARE (Intensive Care Antimicrobial Resistance Epidemiology) reveal that the danger of resistant pathogens increases as care moves toward the ICU. In general, researchers found the greatest percentages of antibiotic resistant isolates in ICU patients, followed by non-ICU hospital patients and outpatients, respectively.1
The focus on antibiotic resistance in infections also takes on new meaning because of concerns expressed by epidemiologists about the emergence in the United States of a vancomycin-resistant Staphylococcus aureus. Last month, the Centers for Disease Control and Prevention (CDC) in Atlanta issued stringent infection control guidelines following the finding of an intermediate resistant strain in Japan. Most experts say it is only a matter of time before a similar strain shows up in the United States.
Results are costly for patients and institutions
Increases in the rate of antimicrobial resistance are resulting in the use of much more expensive drugs, prolonged hospitalizations, higher death rates, and higher health care costs — an estimated $4 billion annually in this country, the ICARE researchers report."In this day of cuts and limited resources, where do you focus your efforts? The answer is the ICU," says lead author Lennox Archibald, MD, MRCP (UK), medical epidemiologist for the CDC’s hospital infections program in Atlanta.
The ICARE study included data from eight geographically dispersed hospitals in the CDC’s National Nosocomial Infections Surveillance (NNIS) system, and was conducted in cooperation with the Rollins School of Public Health at Emory University in Atlanta. The data were reported in terms of percentage of resistant isolates of the total number of isolates tested for inpatients (ICU and non-ICU patients) and outpatients. For example, 6.3% of enterococci isolated from inpatients were vancomycin resistant (VRE) compared with 1.4% VRE among outpatients. (For study results, see table, above.)
As the rate of antimicrobial resistance increases, more resources should be allocated to attack the problem in ICUs, including heightened surveillance activities and improved use of antibiotics, the researchers concluded. (For guidelines to combat antimicrobial resistance, see story, p. XXX.)
Surveillance, controls needed
In any case, it appears the primary answer to the problem is going to come in the form of surveillance for infections, identifying specific drug resistance patterns, and then implementing antibiotic controls. That means, for example, that ICUs should be the focus of infection surveillance and antibiotic control efforts rather than looking hospitalwide.Indeed, focusing surveillance on ICUs may allow early detection of outbreaks of resistant infections. For example, in a Canadian study, clinicians comparing isolates from ICU patients to other hospital isolates detected and effectively curtailed an outbreak of multidrug-resistant Pseudomonas aeruginosa in an ICU. 2 Without the targeted effort, the P. Aeruginosa ICU outbreak may have gone undetected and spread out within 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.
Another important emerging trend that may compound the problem is that ICU bed census is on the rise even as overall hospital census is falling due to the transition to outpatient care, Archibald says. The 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 probability you will have a device. If you have a high rate of nosocomial infections, there is going to be a parallel increase in antimicrobial use."
As ICUs treat such infections with increasing amounts of antibiotics, 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, he adds..
"What it means is a directly proportional relationship in mathematical terms — as usage increases, resistance increases," Archibald says. "A good example is ceftazidime use and ceftazidime-resistant Enterobacter cloacae. Also ceftazidime use and ceftazidime-resistant Pseudomonas aeruginosa. The third one is anti-staphylococcal agents — penicillin and first generation cephalasporins — and percentage of methicillin-resistant Staphylococcus aureus."
Can thresholds be detected?
That raises the question of whether it might be possible, as some researchers have suggested, to detect "thresholds" of antibiotic use that begin to create such resistance, decreasing the drug in question as resistant microorganisms begin to appear.3A recent position paper on antibiotic resistance by the Society for Healthcare Epidemiolgy of America (SHEA), referred to the theory, noting that the threshold for selection of resistant organisms may differ by individual and by patient population.4"This may explain why, in ICUs, where there is usually a small population undergoing intensive antibiotic therapy or prophylaxis, resistance tends to be more common, pathogens are more often multiply resistant, and spread within the population is more likely," SHEA stated.
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.
3. Levy SB. Balancing the drug-resistance equation. Trends Microbiol 1994; 2:341-342.
4. Shales, DM, Gerding DN, John Jr, JF, et al. SHEA position paper: Society for Healthcare Epidemiolgy of America and Infectious Disease Society of America Joint Committee on the Prevention of Antimicrobial Resistance: Guidelines for the prevention of antimicrobial resistance in hospitals. Infect Control Hosp Epidemiol 1997; 18:275-291. I
5. Maki, DG. "Nosocomial Infection in the Intensive Care Unit." In:Parrillo JE, Bone RC, eds. Critical Care Medicine:Principles of Diagnosis and Management. St. Louis: Mosby Year Book Inc.; 1995, pp. 893-954.
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