Staph aureus Blood Stream Infection in End-Stage Renal Disease Associated With Substantial Illness and Increased Healthcare Costs

CHICAGO -- Substantial treatment costs and illness are suffered by end-stage renal disease (ESRD) patients who develop Staph aureus blood stream infections (bacteremias), according to new pharmacoeconomic studies presented this week at the 43rd annual Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) in Chicago.

Moreover, ESRD patients with Staph aureus bacteremia that are caused by bacteria that are resistant to the antibiotic methicillin (MRSA) are at a higher risk of dying and incur higher treatment costs than patients with bacteremias caused by methicillin sensitive Staph aureus (MSSA). The two studies, sponsored by Nabi Biopharmaceuticals, Inc. and executed by Duke University Medical Center, were presented by investigators from Duke University Medical Center and Duke Clinical Research Institute, Durham, NC.

"Staph aureus is the most common cause of serious hospital-acquired infections, including bloodstream infections, and their increased resistance to many different antibiotics is a growing source of concern in the medical community," said Henrik S. Rasmussen, MD, PhD, Nabi Biopharmaceuticals senior vice president, clinical, medical and regulatory affairs. "Despite its clinical significance, the economic impact of Staph aureus bacteremia has not been fully appreciated. The two studies presented at ICAAC clearly describe the clinical outcomes, associated with health care resource utilization and infection-associated costs of Staph aureus bacteremia among a large group of prospectively identified, hemodialysis-dependent patients. The full data from these studies have been submitted for publication."

"Clearly, these studies point out the tremendous challenges that continue to face healthcare professionals trying to manage Staph aureus bacteremias in ESRD patients," continued Rasmussen. "These results underscore the need for a new approach such as Nabi Biopharmaceuticals' StaphVAX (Staphylococcus aureus Polysaccharide Conjugate Vaccine) vaccine for preventing these infections with the potential to significantly reduce the tremendous costs associated with them."

The first study reported on 210 hemodialysis-dependent patients with Staph aureus bacteremia treated at Duke University Hospital. These patients experienced significant complications due to their infections. The mean initial hospitalization costs almost doubled for patients with complicated Staph aureus bacteremias such as endocarditis and osteomyelitis versus bacteremias without these complications ($32,462 compared to $17,011, p=0.002). The mean cost of treating Staph aureus bacteremia, including readmissions and outpatient costs, was $24,034 per episode.

The second study reported on the resources, costs and mortality among 143 dialysis-dependent patients hospitalized with Staph aureus bacteremia. In this study, ESRD patients with bacteremia caused by MRSA proved to be at a higher risk of dying within 12 weeks and incurred higher costs than patients with bacteremia caused by MSSA. MRSA infections are responsible for up to 60 percent of Staph aureus infections in the U.S. today.

Patients with ESRD are at high-risk of developing Staph aureus bacteremias partly because they are immune-compromised due to their debilitating underlying disease and also because the need for access to the vascular system for dialysis puts them at increased risk of infection. This patient population is projected to continue to grow due to the increasing number of patients suffering from the complications of diabetes, which can often result in the loss of kidney function.

Nabi Biopharmaceuticals is planning to initiate a confirmatory Phase III clinical trial with StaphVAX in the United States in approximately 3,000 ESRD patients during the fourth quarter of 2003. The primary endpoint of the trial will be the incidence of bacteremia caused by types 5 and 8 Staph aureus through 8 months post-vaccination. This endpoint correlates with the peak efficacy point in the first StaphVAX Phase III trial, which was published in the Feb. 14, 2002 issue of The New England Journal of Medicine. In an attempt to sustain efficacy beyond 8 months in these patients at chronic risk for Staph aureus infections, the confirmatory Phase III trial will also include a booster vaccination at 8 months. The vaccine's ability to generate antibodies, efficacy and safety will continue to be followed for up to six months following the booster dose. Secondary endpoints for this trial will also include the cost of Staph aureus bacteremia infections that occur during the study.

Staph aureus is the most common cause of serious hospital-acquired infections, including bloodstream infections. Community-acquired staph infections are also of growing concern as they continue to increase in prevalence. Hospitals and other healthcare settings worldwide face unprecedented crises from the rapid emergence and dissemination of antibiotic- resistant bacteria, according to the National Institutes of Health and the Centers for Disease Control and Prevention (CDC). Strains of drug-resistant staph are found in most hospitals, often leaving vancomycin as the antibiotic of last resort for treating patients with these infections. With vancomycin-resistant strains of Staph aureus now appearing globally, many experts believe that a vaccine to prevent these infections may offer the best long-term solution.

According to the CDC, more than 2 million patients in the U.S. each year contract an infection as a result of exposure while receiving healthcare in a hospital. Staph aureus is among the most common causes of these hospital-acquired infections and is reportedly associated with a death rate of 10 percent to 30 percent because of its capacity to cause serious complications and its resistance to many different antibiotics. Staph aureus can spread from the blood (bacteremia), to the bones (osteomyelitis), or the inner lining of the heart and its valves (endocarditis), or cause abscesses in internal organs such as the lungs, liver and kidneys. People most at risk for these infections are surgical patients, trauma or burn victims, newborns whose immune systems are not yet developed, and patients with chronic illnesses such as diabetes, cancer, or lung or kidney diseases. People whose immune systems are suppressed due to disease, chemotherapy, or radiation therapy are generally more susceptible to these bacterial infections. ESRD patients on hemodialysis represent a particular high-risk group due to a combination of their compromised immune system and the need for repeated access to their blood system several times a week.

Source: Nabi Biopharmaceuticals