Semiquantitative cultures of intravascular catheters from cancer patients

Three-hundred seventy-nine catheter tips were prospectively cultured by both a semiquantitative method and by broth culture, over a 2-month period. One hundred eleven of the catheters were culture-positive in broth, and 47 of these were also culture-positive by the semiquantitative method. Clinical signs of infection were reviewed for the 111 culture-positive catheters and for 50 of the 268 culture-negative catheters. Both culture-positive and culture-negative catheters were infrequently associated with local signs of infection (10% and 12%, respectively). Culture-positive catheters, however, were more likely to be associated with systemic signs of infection than were culture-negative catheters (15% and 2%, respectively). Among the culture-positive catheters, those that yielded ≥15 colonies on semiquantitative culture were more likely to be associated with septicemias than were those with <15 colonies (22% and 6%, respectively). Nevertheless, there were five catheter-related bacteremias that were associated with catheters which were culture-negative on semiquantitative culture but culture-positive in broth. The proportion of patients with culture-positive and culture-negative catheters who were febrile was similar (30% and 42%, respectively). Semiquantitative cultures of catheters from cancer patients are useful, but the result should be interpreted with some caution.