In confronting the issue of healthcare-associated infections (HAIs), hospitals are soon to be squeezed from two new directions. First, they will be facing a new reimbursement environment in which they will no longer receive reimbursement for infections deemed to be healthcare associated, whether or not the patient is a carrier at admission (carriers of MRSA are at higher risk of infection from their own strain of MRSA). Secondly, by virtue of mandatory reporting laws in many states, hospitals’ rates of HAIs will increasingly be subject to public scrutiny.
An increasing number of patients carry methicillin-resistant Staphylococcus aureus (MRSA), especially if they have had prior hospital admissions or are residents of long-term care facilities. These patients not only have an increased risk of infection, but they may also transmit infection to others. In this new healthcare environment, economic considerations will drive the implementation of the most effective infection prevention strategies.
Limiting the opportunity for transmission time by using the fastest test for MRSA and S. aureus colonization has been shown to dramatically reduce transmission events and infection rates. Last year, one hospital saved an estimated $576,000 per year by performing MRSA testing once a day, using a molecular test for patients in the ICU, followed by strict isolation for colonized patients.1 The cost reduction was a result of decreased transmission and infections, even without invoking decolonization. Similar dramatic declines in MRSA infection rates have been observed in the ICUs of the VA hospitals nationwide; rapid testing, followed by barrier precautions has resulted in a 76% reduction in ICU infections.
Decolonization: From the Early Days to Today's Greater Challenge
Although patients carrying MRSA in their noses are even more likely to develop an infection with their own strain of Staphylococcus than those harboring the more benign methicillin-susceptible S. aureus (MSSA), both pathogens are significant causes of surgical site infections.
In one study, researchers found that critically ill S. aureus-colonized patients had a 27-fold higher risk of developing a S. aureus infection within 16-19 days after hospital admission than did non-colonized patients.
In another study, researchers reported that either MRSA colonization detected at hospital admission or acquisition in the healthcare institution resulted in a ten times higher incidence of MRSA infection than for patients colonized with MSSA or not colonized. A follow up study of colonized patients after they leave the hospital revealed a 20-30% risk of serious infection following soft tissue or respiratory tract acquisition and a 40-50% risk of serious infection if the initial isolate came from bone, joint fluid, or nares (as detected on a surveillance test). Clearly, being a carrier of SA or MRSA is a significant risk factor-a sort of "horizontally acquired" genetic risk factor for developing an infection.
Preventing Infections in MSSA and MRSA-colonized Patients
With the advent of molecular methods for detection of MRSA, we are now armed with the optimal diagnostic tools for recognition of nasal carriers. We can now isolate patients quickly to prevent patient-to-patient transmission. But for individual patients who are carriers, can anything be done to prevent infections in MSSA and MRSA-colonized patients?
Testing and Decolonization Works
Newer studies are showing that indeed, case recognition followed by selective decolonization is highly beneficial to patients who are carriers. In a study published in the NEJM earlier this year, the authors found "The results of our trial provide solid evidence of the preventive effect of S. aureus decolonization and a good estimate of the size of this effect: the risk of hospital-associated S. aureus infections was reduced by nearly 60%".2
In a study published in the Journal of Bone & Joint Surgery, authors from New England Baptist Hospital noted "Our study demonstrates the feasibility of implementing a hospital-wide prescreening program for detecting previously unidentified methicillin-resistant Staphylococcus arueus and methicillin-sensitive Staphylococcus arueus carriers with use of rapid polymerase chain reaction-based assay. Practically, such a program allows early identification of methicillin-resistant Staphylococcus arueus-colonized patients, treatment, adjustment of preoperative antibiotic prophylaxis, and early isolation and contact precautions for those who continue to remain colonized with methicillin-resistant Staphylococcus arueus."
Clearly, there is a strong and growing body of evidence demonstrating the effectiveness of rapid identification and intervention strategies for MRSA and Staphylococcus aureus colonization. There are also pressures encouraging the adoption of these strategies. In this demanding healthcare environment, on-demand molecular testing is proving essential, with economic considerations and patient outcomes driving the implementation of the most effective tests and interventions.
1. Espinoza C, et al. A Pilot Study of Active Surveillance for MRSA by PCR on Admission to ICUs at a Tertiary Care Center. Abstr. K-3367. Abstracts of the 48th annual Interscience Conference on Antimicrobial Agents and Chemotherapy and the Infectious Diseases Society of America 46th Annual Meeting. ASM & IDSA, Washington, D.C. 2008:518.
2. Bode LG, et al. Preventing Surgical-Site Infections in Nasal Carriers of Staphylococcus aureus. N Engl J Med. 2010 Jan 7;362(1):75-7.
3. Kim et al. Institutional Prescreening for Detection and Eradication of Methicillin-Resistant Staphylococcus aureus in Patients Undergoing Elective Orthopaedic Surgery. Journal of Bone & Joint Surgery