Molecular epidemiology of coagulase-negative Staphylococcus blood isolates from neonates with persistent bacteremia and children with central venous catheter infections.

Multilocus enzyme electrophoresis was used to genetically characterize sequential isolates of coagulase-negative staphylococci (CONS) from 3 neonates with persistent bacteremia and organisms cultured from several sites in 23 children with presumed catheter-related sepsis (CRS). For 2 of 3 neonates and 21 (91%) of 23 of the patients with presumed CRS, the same CONS clone was isolated from multiple consecutive blood cultures (mean, 7.3 isolates; range, 3-19). For the 23 children with presumed CRS, 7 (30%) had catheter hub (CH) and 7 (30%) had catheter exist site (CES) cultures positive for CONS; cultures from 3 of these patients (from both CH and CES) grew CONS. Genetic analysis of isolates recovered from the CH and peripheral and central venous catheter blood cultures of all 7 patients revealed clonal identity of the strain grown from all sites. In contrast, only 4 (57%) of 7 of the CONS isolates from the CES were the same clone as that isolated from the blood. These data suggest that repetitive isolation of CONS during the course of CRS is due to ongoing bacteremia, not culture contamination with distinct CONS isolates. The results also are consistent with the hypothesis that the CH is a more likely site of initial colonization by CONS than the exist site in patients with CRS.