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 greater than or equal to 15 colonies on semiquantitative culture were more likely to be associated with septicemias than were those with less than 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.