Prospective Study of the Value of Quantitative Culture of Organisms from Blood Collected through Central Venous Catheters in Differentiating between Contamination and Bloodstream Infection

Abstract

Collection of blood through a central venous catheter for the diagnosis of bacteremia is a debated topic. Quantitative cultures of organisms from blood collected through central venous catheters were found to be highly sensitive, specific, and predictive of bacteremia, especially when a cutoff point of 15 colonies of skin organisms was used.Drawing of blood through a central venous catheter (CVC) for the diagnosis of bacteremia is highly debated (2,4,(11)(12)(13)15) due to the possibility of culturing blood contaminated by organisms adhering to CVC lumen. Although quantitative blood cultures (QBC) collected simultaneously through a CVC and peripheral venipuncture (PV) have been used for the diagnosis of catheter-related bloodstream infections (3,6,14), the usefulness of QBC collected through CVC for the diagnosis of bacteremia from any source has not been thoroughly investigated.Between September 1999 and May 2002, we followed up adult cancer patients who required new insertions of a peripherally inserted or subclavian silicone CVC at the M. D. Anderson Cancer Center in order to evaluate the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of QBC collected through CVC for the diagnosis of bacteremia. Maximal sterile barrier precautions were followed during catheter insertions (9). Patients were followed up until catheter removal or up to 100 days, whichever occurred first. At the onset of fever or the suspicion of catheter-related bloodstream infections, simultaneous QBC collected through CVC and PV were obtained. When the CVC remained in place beyond 100 days, blood cultures were performed, even in the absence of signs and symptoms of infection (SSI). Microorganisms were identified according to standard methods (8). An initial 10 ml of CVC-collected blood was discarded to avoid contact with previously infused drugs with antimicrobial activity. Subsequently, two 20-ml blood samples were drawn for QBC, one through the CVC and the other through PV, and a 10-ml portion of each was cultured aerobically (Bactec 9240, Bactec Plus Aerobic/F; BD Diagnostic Systems, Sparks, MD).At our institution, anaerobes constitute less than 0.1% of positive cultures; most of these are found to be possible contaminants. The remaining 10 ml was placed into isolator tubes (Isolator 10; Wampole, Cranbury, NJ) to be cultured quantitatively (lysis centrifugation method) (5). We defined bacteremia according to guidelines from the Centers for Disease Control and Prevention (CDC) (7). Possible contaminating microorganisms included skin microorganisms such as coagulase-negative staphylococci (CNS), diphtheroids, and Bacillus spp., whereas pathogenic microorganisms included Staphylococcus aureus, alpha-hemolytic Streptococcus spp., gram-negative bacilli, and Candida spp. A QBC collected through CVC was considered a true positive if (i) a pathogen was isolated in the presence of SSI such as fever, hypotension, and rigors or when the same pathogen was isolated from a peripheral blood culture within 48...

Differentiating Culture Samples Representing Coagulase-Negative Staphylococcal Bacteremia from Those Representing Contamination by Use of Time-to-Positivity and Quantitative Blood Culture Methods

“…Diagnosis of true CoNS bloodstream infection becomes particularly difficult when only a single blood culture sample is obtained (4)(5)(6)(7)(8)(9)(10)(11). We previously reported that a cutoff point of Ͼ15 CFU/ml and positive clinical findings were useful for differentiating culture samples representing true bacteremia from contaminated blood culture samples (2). Furthermore, QBCs are not widely performed in all hospitals and may not be routinely available to clinicians.…”

Coagulase-negative staphylococcal bacteremia: risk factors for mortality and impact of initial appropriate antimicrobial therapy on outcome

“…In patients with central venous catheter (CVC) lines, catheterrelated bloodstream infections (CRBSIs) were defined as follows: (1) the culture of a specimen of purulent drainage from the insertion site grew CoNS that had the same resistance pattern as the culture strain from the peripheral blood; (2) the semiquantitative culture of the removed CVC tip revealed ≥15 colony-forming units by the roll plate technique [14]; (3) indicative differential time to positivity (i.e., the blood culture obtained through an intravascular catheter became positive at least 2 h earlier than a positive simultaneous blood culture obtained from a peripheral vein [15]). Surgical wound infection was defined according to the definitions of the Centers for Disease Control and Prevention (CDC) [16].…”

Management of the Catheter in Documented Catheter‐Related Coagulase‐Negative Staphylococcal Bacteremia: Remove or Retain?

“…Febrile high-risk patients, such as the critically ill patients or patients with cancer, may often have blood cultures contaminated with CoNS from the hands of medical personnel or the catheter hub, particularly if the blood specimens are drawn from the CVC [26,27]. Use of strict criteria for the definition of CoNS bacteremia that include 2 blood cultures positive for CoNS as well as high quantitative blood cultures (115 CFU/ mL) has been shown to be important for distinguishing true CoNS bacteremia from contaminated blood cultures [2,[20][21][22][23]. Furthermore, use of strict criteria for CRBSI, as per the IDSA guidelines, is necessary to attribute true CoNS bacteremia to the catheter rather than other sources that could exist in patients with cancer who have long-term catheters in place [17].…”

“…In addition to the clinical signs and symptoms of infection (fever, chills, rigors, or hypotension), true CoNS CRBSI was defined on the basis of the following 3 criteria, which are predictive of true bacteremia: (1) at least 2 blood cultures, from any source, should be available for all patients [2,[20][21][22]; (2) at least 1 blood culture should yield a quantitative blood count of у15 CFU/mL [23]; and (3) the blood samples that yielded positive culture results should have been collected within a 72-h period [24]. Bacteremia also had to fulfill the definition criteria of the IDSA for probable or definite CRBSI [17].…”