Bloodstream infection in neutropenic cancer patients related to short-term nontunnelled catheters determined by quantitative blood cultures, differential time to positivity, and molecular epidemiological typing with pulsed-field gel electrophoresis

Abstract

To determine the rate of catheter-related bloodstream infection (CRBSI) among cases of primary bloodstream infection (BSI) in febrile neutropenic cancer patients with short-term nontunnelled catheters, quantitative paired blood cultures (Isolator) from the central venous catheter (CVC) and peripheral vein were obtained between November 1999 and January 2001. Bactec blood culture bottles were obtained to determine the differential time to positivity (DTP). CRBSI was defined as a quantitative blood culture ratio of >5:1 (CVC versus peripheral) with proven identity of isolates from positive peripheral and CVC blood cultures as confirmed by pulsed-field gel electrophoresis. Forty-nine episodes of primary BSI were detected among 235 cancer patients with febrile neutropenia. Of these, 18 episodes (37%) were CRBSI and 31 (63%) were BSI with an unknown portal of entry. Coagulase-negative staphylococci were present in nine cases of CRBSI (50%). The identity of isolates from peripheral and CVC blood cultures was confirmed in all cases. Earlier positivity (>2 h) of CVC-drawn versus peripheral blood cultures was observed in 18 of 22 CRBSI-associated blood cultures (sensitivity, 82%; specificity, 88%; positive predictive value, 75%; negative predictive value, 92%). In summary, CRBSI accounted for 37% of cases of primary BSI in this population of neutropenic cancer patients. DTP compares favourably with quantitative blood cultures for the diagnosis of CRBSI and may be particularly useful for patients in whom catheter salvage is highly desirable.

FIG. 1.

QBC ratio (CVC versus peripheral) and DPT of blood cultures from neutropenic patients with and without CRBSI.

FIG. 2.

Fingerprint patterns of CoNS genomic DNA obtained by PFGE after restriction with SmaI. Lanes: 1 and 20: molecular size marker; 2 to 17, corresponding S. epidermidis blood isolates obtained from the catheter hub and from peripheral sites in seven patients; 18 and 19, S. haemolyticus blood isolates.