Staphylococcus aureus nasal colonization and association with infections in liver transplant recipients

Abstract

Background: Staphylococcus aureus has emerged as a leading cause of bacterial infections after liver transplantation. However, the role of nasal colonization in the development of S aureus infections has never been explored in liver transplant recipients. The objectives of this study were to determine whether nasal carriage of S aureus was a risk factor for S aureus infections in liver transplant recipients.

Methods: Over a 2-year period, 30 consecutive liver transplant recipients were studied. Beginning when the recipients were transplant candidates, nasal cultures were performed at each admission and monthly thereafter until discharge or death.

Results: Overall, 67% (20/30) of the patients were nasal carriers, 70% of the carriers had methicillin-resistant S aureus (MRSA), 15% had methicillin-sensitive S aureus, and 15% had both MRSA and methicillin-sensitive S aureus. Infections were significantly associated with the carrier state; 100% (9/9) of the infected patients were carriers as compared with 50% (11/21) of the noninfected patients (P=0.01). All infections were a result of MRSA, and 56% (5/9) of the infections were bacteremia. Median time to the onset of S aureus infections was 16 days after transplant. Pulse field gel electrophoresis (with digestion of S aureus with SmaI restriction enzyme) in seven infected patients demonstrated that the isolates from the anterior nares matched the invasive isolates in all cases. A total of 43% (3/7) of these infected patients shared the same restriction pattern.

Conclusion: MRSA colonization of the anterior nares was a significant predictor of MRSA infections in liver transplant recipients. Infections occurred only in those colonized with MRSA and were a result of the endogenously colonizing S aureus strains in all cases.