Association between antimicrobial locks for hemodialysis central venous catheters and antibiotic resistance

Antimicrobial locks (AMLs) are effective in preventing catheter-associated bloodstream infections (CABSI) in hemodialysis (HD) patients, but may increase antibiotic resistance. In our center, gentamicin-heparin locks have been used for all HD central venous catheters since July 1, 2004. We previously reported a significant reduction in CABSI rates, but a short-term trend to increased gentamicin resistance among coagulase-negative staphylococci (CNS). We present a further 3-year follow-up study of bacterial resistance in our dialysis center. We examined the susceptibility of bacterial isolates from CABSI from July 1, 2006 to July 31, 2009, restricting analyses to CNS, gram-negative bacilli, and Staphylococcus aureus. We compared the frequency of gentamicin resistance in these isolates between four groups: CABSI in HD patients, non-CABSI in HD patients, peritonitis in peritoneal dialysis (PD) patients, and bloodstream infection in the nonend-stage kidney failure general population. For CNS isolates, the frequency of gentamicin resistance was similar between the CABSI and PD peritonitis groups, but higher in both groups than the general population. The pattern was similar for S.?aureus although the differences were of borderline statistical significance. The frequency of gentamicin resistance among gram-negative bacilli isolates did not differ between groups. Gentamicin resistance was more common than expected in CNS and possibly S.?aureus isolates from CABSI, although this resistance may be part of a generally higher frequency of antibiotic resistance in the dialysis population, rather than a direct result of AML use. AMLs remain a valuable clinical tool although surveillance is needed to ensure that benefits continue to outweigh risks.