Nasal MRSA Carriage: A Study of Current Prevalence with Commentary
Creech CB, Kernodle DS, Alsectzer M, et al. Increasing rates of nasal carriage of methicillin-resistant Staphylococcus aureus in healthy children. Pediatr Infect Dis J. 2005;24:617-621.
Review by Laura Ortman, MD
The incidence of methicillin-resistant Staphylococcus aureus (MRSA) infections seen in outpatient clinics and emergency rooms appears to be on the rise. In 2001 a study done at Vanderbilt University Medical Center found the prevalence of MRSA in its pediatric community to be 0.8%1. Creech, et al., devised a study to describe the current prevalence of MRSA colonization in the same population.
The study population was children between the ages of two weeks and 21 years of age presenting for a health maintenance visit at two outpatient clinics. Nasal swabs were obtained and cultures preformed on plates with and without oxacillin containing media. Possible MRSA isolates were confirmed with PCR for the mecA gene, which codes for the protein responsible for beta-lactam resistance.
Of the 500 children enrolled 182 (36.4%) were found to be colonized with S. aureus. 46 (9.2%) isolates were positive for the mecA gene and considered MRSA. The only risk factor found to increase risk for MRSA colonization was having a family member who works in a hospital (odds ratio, 2.0; 95% confidence interval, 1.03-4.1). Fifty-four percent of MRSA isolates were resistant to erythromycin, and 32% of these had inducible clindamycin resistance.
Commentary: This study shows a greater than tenfold increase in MRSA colonization in a three-year time period in a healthy outpatient population. This finding is consistent with other studies that have shown increasing rates of colonization.2-3 This increase has led some institutions to attempt decolonization of MRSA, most often using nasal mupirocin. To determine if current evidence supports attempts to eradicate MRSA nasal colonization, the following literature search was performed: Cochrane DSR, ACP Journal Club, PubMed, and PubMed Clinical Queries were searched using the search terms “MRSA,” “colonization,” and “staphylococcus.”
One Cochrane review summarizes the evidence for use of antimicrobial agents on MRSA colonized patients4. Of six randomized controlled trials, only one compares rates of infection during follow-up between the study and control groups. The difference in infections was not statistically significant. Five other studies of inconsistent quality followed eradication rates of MRSA and varied widely in their results. The Cochrane review concluded that there was insufficient evidence to recommend nasal decolonization of MRSA.
One article reviewed the evidence for intranasal mupirocin for S. aureus.5 This review did not differentiate between MRSA and MSSA. The authors appraised clinical trials that evaluated the effect of mupirocin on MRSA colonization and infection. In a trial of patients undergoing dialysis there was no overall difference in the rate of infection between groups. In trials using mupirocin for preoperative prophylaxis there was no difference in number of surgical site infections. The authors concluded that mupirocin did not result in long-term clearance of S. aureus and that the available evidence does not support its use for prevention of infection. With the current evidence routine decolonization of patients colonized with MRSA cannot be recommended.
References
- Nakamura MM, Rohling KL, Shashaty M, et al. Prevalence of methicillin-resistant Staphylococcus aureus nasal carriage in the community pediatric population. Pediatr Infect Dis J. 2002;21:917-922.
- Herold BC, Immergluck LC, Maranan MC, et al. Community-acquired methicillin-resistant Staphylococcus aureus in children with no identified predisposing risk. JAMA. 1998;279:593-598.
- Fergie JE, Purcell K. Community-acquired methicillin-resistant Staphylococcus aureus infections in south Texas children. Pediatr Infect Dis J. 2001;20:860-863.
- Loeb M, Main C, Walker-Dilks C. Antimicrobial drugs for treating methicillin-resistant Staphylococcus aureus colonization. Cochrane Database Syst Rev. 2003;(4):CD003340.
- Laupland KB, Conly JM. Treatment of Staphylococcus aureus colonization and prophylaxis for infection with topical intranasal mupirocin: an evidence-based review. Clin Infect Dis. 2003;37:933-938.