Invasive Methicillin-Resistant Staphylococcus aureus Infections Among Dialysis Patients --- United States, 2005

Staphylococcus aureus is a leading cause of bloodstream and other invasive infections in the United States. S. aureus has become increasingly resistant to first-line antimicrobial agents in health-care settings (1). Dialysis patients are especially vulnerable to infections, frequently those caused by antimicrobial-resistant organisms, including methicillin-resistant Staphylococcus aureus (MRSA). To assess the incidence of invasive MRSA infection among dialysis patients in the United States during 2005, surveillance data were analyzed from the Active Bacterial Core surveillance (ABCs) system. This report summarizes the results of that analysis, which estimated that, in 2005, the incidence of invasive MRSA infection among dialysis patients was 45.2 cases per 1,000 population. Persons receiving dialysis are at high risk for infection with invasive MRSA compared with the general population, in which rates of invasive MRSA have ranged from 0.2 to 0.4 infections per 1,000 population (2). The findings in this report underscore the need for continued surveillance and infection-control strategies aimed at reducing infection rates and preventing additional antimicrobial resistance among persons receiving dialysis.

ABCs, part of CDC's Emerging Infections Program, conducts ongoing, active, population-based surveillance for invasive pathogens, including MRSA, in selected areas of the United States. In 2005, the entire state of Connecticut and 23 counties in eight other states (California, Colorado, Georgia, Maryland, Minnesota, New York, Oregon, and Tennessee) monitored MRSA infections. A case was defined as a positive MRSA culture from normally sterile sites (e.g., blood, cerebrospinal fluid, joint fluid, or pleural fluid) occurring in a patient residing in the ABCs surveillance area. Surveillance staff collected demographic and clinical data from patient records and reported the data to CDC. All cases of invasive MRSA reported during 2005 were used to calculate incidence rates. Demographic and outcome data were analyzed from case reports obtained during July 2004--June 2006. The analysis was limited to cases occurring in patients with a history of peritoneal dialysis or hemodialysis during the preceding 12 months; recurrent cases were excluded. The number of dialysis patients was obtained for Connecticut and the 23 counties from the United States Renal Data System dialysis population count (as of December 31, 2004) for use as denominators; 2005 denominators were not yet available (3).

Laboratories voluntarily submitted isolates from cases, and a subset of isolates was collected for microbiologic characterization at CDC. A total of 126 isolates were obtained from dialysis patients. Isolates were tested by pulsed-field gel electrophoresis (PFGE) and were grouped into types using Dice coefficients with 80% relatedness. Isolates with pulsed-field types USA300, USA400, USA1000, or USA1100 are obtained primarily from community infections and are considered to be of community origin; those with types USA100, USA200, and USA500 are predominantly from health-care--associated infections and are considered to be of health-care origin (4).

Of the 5,287 cases of invasive MRSA reported from ABCs sites during 2005, a total of 813 (15.4%) occurred in dialysis patients. Overall incidence of invasive MRSA infection among dialysis patients was 45.2 cases per 1,000 dialysis population, indicating a 100-fold higher risk than for the general population (Table). The rate varied by ABCs site, from 27.2 in California to 92.0 in Maryland. During July 2004--June 2006, approximately 70% of invasive MRSA infections among dialysis patients occurred in persons aged >50 years. Males and blacks accounted for 57% and 56%, respectively, of the total population of dialysis patients with these infections. The majority (86%) of the infections were bloodstream infections, identified via positive blood culture. Approximately 85% of dialysis patients had an invasive device or catheter in place at the time of infection, and approximately 90% required hospitalization. The in-hospital mortality rate for MRSA-related hospitalization was 17%.

Of the 126 MRSA isolates obtained from dialysis patients, 80% of the strains were of health-care origin, with USA100 representing 92% of the health-care strains and 74% of all isolates obtained. Community strains accounted for approximately 14% of the strains detected in dialysis patients, with USA300 accounting for 89% of the community strains and nearly 13% of all dialysis isolates. Six percent of the isolates either did not match existing USA strains within 80% or were classified as other non-USA strains. Antibiotic susceptibility results were reported for 113 MRSA isolates from dialysis patients. None of the isolates were resistant to vancomycin, daptomycin, or linezolid.

Reported by: A Collins, MD, B Forrest, United States Renal Data System Coordinating Center, Minneapolis, Minnesota. RM Klevens, DDS, P Patel, MD, MJ Arduino, DrPH, G Fosheim, MPH, M Morrison, MPH, Div of Healthcare Quality Promotion, National Center for Preparedness, Detection, and Control of Infectious Diseases (proposed); CA Lucero, MD, EIS Officer, CDC.

Editorial Note:

Since the first renal dialysis was performed in 1943, substantial improvements have been made in dialysis technology and in the care of persons with end-stage renal disease (ESRD). At the same time, the number of dialysis patients has increased substantially. The dialysis population reached 335,963 at the end of 2004, triple the number from 1988 and up 16% since 2000 (3). Repeated hospitalizations and surgeries and administration of prolonged courses of antimicrobial agents increase exposure to potential pathogens and create opportunities for antimicrobial resistance in this population. The rate of invasive MRSA infection described in this report (45.2 infections per 1,000 dialysis population) is higher than for any other known patient population and is 100 times higher than for the general population. Overall incidence of invasive MRSA in the general population ranges from 0.2 to 0.4 infections per 1,000 population (2).

Infections are the second most common cause of death in ESRD patients, accounting for nearly 14% of deaths (3). Approximately 70% of ESRD patients receive long-term dialysis treatment. Infections associated with vascular access are among the most serious complications of chronic dialysis. Data from the Dialysis Surveillance Network, reported through March 2005, indicate that the organisms most frequently associated with catheter-access--related bacteremias were coagulase-negative staphylococci (38%), S. aureus (29%), gram-negative bacilli (21%), and nonstaphylococcal gram-positive cocci, including enterococci (10%) (5). Dialysis patients with S. aureus bloodstream infections have costly and lengthy hospitalizations, frequently with substantial complications and hospital readmission (6).

Persons receiving hemodialysis are especially vulnerable to vascular-access infections because they require vascular access for prolonged periods and undergo frequent puncture of their vascular-access site. Furthermore, patients colonized with MRSA can serve as a reservoir for transmission in health-care settings. The primary risk factor for bacterial infections among dialysis patients is vascular-access type. Risk is highest for catheters, intermediate for grafts, and lowest for native arteriovenous fistulas (5). Despite higher rates of bacteremia among patients with catheters, the percentage of U.S. dialysis patients with an indwelling hemodialysis catheter increased substantially from 1995 to 2002 (7). The most basic strategy to prevent catheter-related bacteremias, including invasive MRSA infections among hemodialysis patients, is minimizing the use of catheters for long-term vascular access (1).

Antimicrobial therapy for hemodialysis-associated infections is one of the factors increasing the prevalence of antimicrobial resistance. MRSA strains of health-care origin, such as USA100, are typically multidrug resistant. During 1995--2002, the percentage of dialysis centers treating one or more patients with MRSA increased from 40% to 76% (7). In addition, in the United States, during 1997--2000, five of the first six patients reported with vancomycin-intermediate S. aureus had received dialysis (8), and the first patient reported to be infected with vancomycin-resistant S. aureus was a hemodialysis patient (9).

Health-care providers should follow published guidelines for judicious use of antimicrobials, particularly vancomycin, to reduce selection for antimicrobial-resistant pathogens (1). Recommendations for the prevention of antimicrobial resistance are available from CDC's 12-step Campaign to Prevent Antimicrobial Resistance Among Dialysis Patients (10). In addition, a resource on the prevention of infections and patient-to-patient transmission of infections in dialysis settings is CDC's Recommendations for Preventing Transmission of Infections Among Chronic Hemodialysis Patients (1).

Acknowledgment

This report is based, in part, on contributions by J Nadle, MPH, California Emerging Infections Program, Oakland, California; K Gershman, MD, Colorado Emerging Infections Program, Denver, Colorado; S Petit, MPH, Connecticut Dept of Health, Hartford, Connecticut; S Ray, MD, Grady Memorial Hospital, Atlanta, Georgia; LH Harrison, MD, Maryland Emerging Infections Program and Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland; J Buck, MPH, Minnesota Dept of Health, Minneapolis, Minnesota; G Dumyati, MD, Univ of Rochester, Rochester General Hospital, Rochester, New York; M Emerson, PhD, Oregon Emerging Infections Program, Portland, Oregon; B Barnes, Tennessee Emerging Infections Program, Nashville, Tennessee; and the United States Renal Data System, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health.

References

1. CDC. Recommendations for preventing transmission of infections among chronic hemodialysis patients. MMWR 2001;50(No. RR-05).
2. Fridkin SK, Hageman JC, Morrison M, et al. Methicillin-resistant Staphylococcus aureus disease in three communities. N Engl J Med 2005;352:1436--44.
3. United States Renal Data System. United States Renal Data System 2006 annual data report: atlas of end-stage renal disease in the United States. Bethesda, MD: US Department of Health and Human Services, National Institutes of Health; 2006.
4. McDougal LK, Steward CD, Killgore GE, Chaitram JM, McAllister SK, Tenover FC. Pulsed-field gel electrophoresis typing of oxacillin-resistant Staphylococcus aureus isolates from the United States: establishing a national database. J Clin Microbiol 2003;41:5113--20.
5. Klevens RM, Tokars JI, Andrus M. Electronic reporting of infections associated with hemodialysis. Nephrol News Issues 2005;19:37--43.
6. Nissenson AR, Dylan ML, Griffiths RI, et al. Clinical and economic outcomes of Staphylococcus aureus septicemia in ESRD patients receiving hemodialysis. Am J Kidney Dis 2005;46:301--8.
7. Finelli L, Miller JT, Tokars JI, Alter MJ, Arduino MJ. National surveillance of dialysis-associated diseases in the United States, 2002. Semin Dial 2005;18:52--61.
8. Fridkin SK. Vancomycin-intermediate and -resistant Staphylococcus aureus: what the infectious disease specialist needs to know. Clin Infect Dis 2001;32:108--15.
9. CDC. Staphylococcus aureus resistant to vancomycin---United States, 2002. MMWR 2002;51:565--7.
10. CDC. Campaign to prevent antimicrobial resistance in healthcare settings. 12 steps to prevent antimicrobial resistance among dialysis patients. Available at http://www.cdc.gov/drugresistance/healthcare/patients.htm#dialysis.

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Date last reviewed: 3/8/2007