Differential Quantitative Blood Cultures Research Articles

Diagnosis and Management of Central Venous Catheter-Related Infections

Use of central venous catheters (CVCs) can lead to catheter-related bloodstream infections (CRBSIs) and such infections are associated with serious morbidity and mortality and with increased health care costs. The diagnosis of CRBSI needs to be accurate for adequate management. Semiquantitative catheter tip culture has been established as standard in most laboratories, but this method requires catheter removal. Catheter-sparing diagnostic methods, such as differential quantitative blood cultures and differential time to positivity have emerged as reliable diagnostic techniques. Management of CRBSIs involves deciding on catheter removal and the type and duration of systemic antimicrobial therapy. Such decisions depend on the identity of the organism causing the bloodstream infection and the clinical and radiographic manifestations suggesting a complicated course.

Diagnosis of central venous catheter-related bloodstream infection without catheter removal: A prospective observational study

BackgroundCatheter-related bloodstream infections (CRBSI) resulting from bacterial colonisation of an intravascular catheter are the leading cause of nosocomially acquired sepsis contributing significantly towards in-hospital morbidity and mortality. Suspicion of central venous CRBSI leads frequently to catheter withdrawal but not all infection requires the catheter to be withdrawn; therefore, diagnosis of central venous CRBSI without catheter withdrawal is a necessity. MethodsThe study was prospectively performed in a cohort of adult patients who had short term central venous catheter use. The samples collected from each patients included, skin swab from insertion site, swab from catheter hub, paired blood samples from catheter and from the peripheral vein for quantitative blood culture collected within 15 min of each other and catheter-tip sample by cutting off the tip (distal 5-cm segment). All samples were processed immediately. Results50 episodes of clinical sepsis involving 100 patients occurred in the study population. 28 of the episodes were confirmed as CR-BSI (56%). Blood culture from the central venous catheter had the highest sensitivity (71.43%) and the greatest negative predictive value (86.67%). However, the peripheral blood culture was most specific and had the highest positive predictive value (specificity75%; positive predictive value 50%). The most accurate technique was differential quantitative blood cultures (accuracy 72%), followed by semiquantitative superficial cultures (accuracy 68%), although there were no statistically significant differences between values. ConclusionWe recommend combining semiquantitative cultures and peripheral blood cultures to screen for CR-BSI, leaving differential quantitative blood cultures as a confirmatory and more specific technique.

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

Studies and guidelines recommending the retention of the central venous catheter (CVC) in patients with coagulase-negative staphylococcal bacteremia were based on loose definitions of bacteremia and/or did not evaluate the risk of recurrence. In this study, we used strict definitions of coagulase-negative staphylococcal bacteremia to determine the impact of CVC retention on response to and recurrence of infection. During the period from July 2005 through December 2007, we retrospectively evaluated 188 patients with coagulase-negative staphylococcal bacteremia. Bacteremia was defined using the strict Centers for Disease Control and Prevention criteria of 2 positive blood culture results. Catheter-related bacteremia was confirmed by differential quantitative blood cultures (>or=3:1) or time to positivity (>2 h). Resolution of infection within 48 h after commencement of antimicrobial therapy was not influenced by CVC removal or exchange versus retention and occurred in 175 patients (93%). Multiple logistic regression analysis showed that infection was 7.0 times (95% confidence interval [CI], 1.5-32.6 times) more likely to fail to resolve in patients with an intensive care unit stay prior to infection ( P = .013 ) and 3.8 times (95% CI, 1.1-13.3 times) more likely to fail to resolve in patients who had other concurrent sites of infection (P = .041 ). Duration of therapy did not affect recurrence. Multiple logistic regression analysis revealed that patients with catheter retention were 6.6 times (95% CI, 1.8-23.9 times) more likely to have a recurrence than were those whose catheter was removed or exchanged (P = .004). CVC retention does not have an impact on the resolution of coagulase-negative staphylococcal bacteremia but is a significant risk factor of recurrence.

Infecciones asociadas a dispositivos intravasculares utilizados para la terapia de infusión

Catheter-related bloodstream infections are associated with recognized morbidity and mortality, especially in critically ill patients. Skin insertion site, the catheter hub, hematogenous seeding of the catheter tip from a distant site of infection, and infusate contamination are the sources of catheter colonization and infections. Coagulase-negative staphylococci, Staphylococcus aureus, aerobic gram-negative bacilli, and Candida spp most commonly cause catheter-related bloodstream infection. Catheter-sparing diagnostic methods, such as differential quantitative blood cultures and time to positivity have emerged as reliable diagnostic techniques. Management of catheter-related infection varies according to the type of catheter involved. In most cases of nontunneled catheter-related bacteremia and fungemia, the catheter should be removed. For management of bacteremia and fungemia from a tunneled catheter or implantable device, such as a port, the decision to remove the catheter or device should be based on the severity of the patient's illness, documentation that the vascular-access device is infected, assessment of the specific pathogen involved, and presence of complications, such as endocarditis, septic thrombosis, tunnel infection, or metastatic seeding. When a catheter-related infection is documented and a specific pathogen is identified, systemic antimicrobial therapy should be narrowed and consideration given for antibiotic lock therapy, if the catheter or implantable device is not removed. Novel preventive strategies include cutaneous antisepsis, maximum sterile barrier, use of antimicrobial catheters, and antimicrobial catheter lock solution.

Correlation between early clinical response after catheter removal and diagnosis of catheter-related bloodstream infection

We conducted a retrospective post hoc analysis of prospectively collected data of cancer patients with central venous catheters (CVCs) who developed bacteremia with positive quantitative blood cultures (QBCs) drawn simultaneously through peripheral vein and CVC and which grew the same microorganisms from both blood cultures. We investigated whether clinical response of bacteremia, within 24, 48, or 72 h post-CVC removal, could be diagnostic of catheter-related bloodstream infection (CRBSI) when compared with microbiologic methods. Clinical response to antimicrobial therapy within 24 h of CVC removal in a patient with bacteremia was found to be highly suggestive of CRBSI, a finding that correlated well with semiquantitative catheter cultures and differential QBCs. However, response to antimicrobial therapy at ≥48 h after CVC removal was less likely to be diagnostic of CRBSI and could reflect a response to antimicrobial therapy irrespective of the source of the bloodstream infections.

A Randomized and Prospective Study of 3 Procedures for the Diagnosis of Catheter-Related Bloodstream Infection without Catheter Withdrawal

Suspicion of catheter-related bloodstream infection (CR-BSI) leads frequently to unnecessary catheter withdrawals, and many catheter-tip cultures yield negative results. The objective of this study was to compare the yield of 3 microbiological procedures to assess CR-BSI without catheter withdrawal. The study was prospectively performed in a group of patients without neutropenia or blood disorders who were admitted to the intensive care unit during a 37-month period with sepsis suspected on clinical grounds and who had central venous catheters inserted for >48 h. The microbiological procedures compared were semiquantitative cultures from hub and skin (superficial), differential quantitative blood cultures, and differential time to positivity between cultures of blood obtained from catheter hubs and peripheral blood. Of the 204 episodes of suspected CR-BSI included in the study, 28 were confirmed to be CR-BSI. We obtained the following results for sensitivity, specificity, positive and negative predictive values, and accuracy: superficial cultures, 78.6%, 92.0%, 61.1%, 96.4%, and 90.2%, respectively; differential quantitative blood cultures, 71.4%, 97.7%, 83.3%, 95.6%, and 94.1%, respectively; and differential time to positivity, 96.4%, 90.3%, 61.4%, 99.4%, and 91.2%, respectively. CR-BSI can be assessed without catheter withdrawal in patients without neutropenia or blood disorders who have catheters inserted for a short time and are hospitalized in the intensive care unit. Convenience, use of resources, and expertise should determine the technique of choice in different medical contexts. Because of ease of performance, low cost, and wide availability, we recommend combining semiquantitative superficial cultures and peripheral vein blood cultures to screen for CR-BSI, leaving differential quantitative blood cultures as a confirmatory and more specific technique.

Differential quantitative blood cultures for the diagnosis of catheter-related bloodstream infections associated with short- and long-term catheters: A prospective study

We prospectively evaluated the value of two levels of differential quantitative blood culture (DQBC) ratio (≥2:1 or ≥5:1) in diagnosing catheter-related bloodstream infections (CRBSIs) in patients with malignancy that have short-term and long-term central venous catheters (CVCs) (<30 and ≥30 days of placement). Diagnosis of CRBSIs was based on results of semiquantitative cultures of removed catheters. For short-term CVCs a 5:1 or greater DQBC ratio had an 18% sensitivity, 67% specificity, 18% positive predictive value (PPV) and 67% negative predictive value (NPV), whereas a 2:1 or greater cut-off point for the DQBC was associated with a 45% sensitivity, 48% specificity, 26% PPV, and 68% NPV for the diagnosis of CRBSIs. For long-term CVCs, a cut-off point of 5:1 or greater of the DQBC had an 81% sensitivity, 40% specificity, 36% PPV, and 83% NPV for the diagnosis of CRBSIa, whereas a 2:1 or greater cut-off point had a 90% sensitivity, 30% specificity, 35% PPV, and 88% NPV for the diagnosis of CRBSIs. In conclusion, DQBCs are not diagnostic of CRBSIs for short-term CVCs. In long-term CVCs, DQBCs at 2:1 or greater or 5:1 or greater are sensitive but associated with low specificity and positive predictive value.

New tools in diagnosing catheter-related infections.

Clinical criteria alone are insufficient to allow a diagnosis of intravascular catheter-related sepsis (CRS). A definite diagnosis of CRS usually requires removal of the catheter for quantitative catheter tip culture. However, only about 15-25% of central venous catheters (CVC) removed because infection is suspected actually prove to be infected, and the diagnosis is always retrospective. Other diagnostic tests, such as differential quantitative blood cultures from samples taken simultaneously from the catheter and a peripheral vein, have been proposed to avoid unjustified removal of the catheter and the potential risks associated with the placement of a new catheter at a new site: a central-to-peripheral blood culture colony count ratio of 5:1 to 10:1 is considered indicative of CRS. Despite its high specificity, the latter diagnostic technique is not routinely used in clinical practice because of its complexity and cost. The measurement of the differential time to positivity between hub blood (taken from the catheter port) and peripheral blood cultures might be a reliable tool facilitating the diagnosis of CRS in situ. In an in vitro study, we found a strong relationship between the inoculum size of various microorganisms and the time to positivity of cultures. When the times to positivity of cultures of blood taken simultaneously from central and peripheral veins in patients with and without CRS were examined, we found that earlier positivity of central vs peripheral vein blood cultures was highly correlated with CRS. Using a cut-off value of +120 min, the "differential time to positivity" of the paired blood samples, defined as time to positivity of the peripheral blood minus that of the hub blood culture, had 91% specificity and 94% sensitivity for the diagnosis of CRS. This method may be coupled with other techniques that have high negative predictive value, such as skin cultures at the catheter exit site. This diagnostic test can be proposed for routine clinical practice in most hospitals using automatic devices for blood cultures positivity detection. Endoluminal brushing of the catheter is considered sensitive and specific for the diagnosis of CRS, but the risk of embolisation or subsequent bacteraemia should be considered. Gram staining and the acridine-orange leucocyte cytospin test on through-catheter blood culture have been proposed for rapid diagnosis of CRS without catheter removal. The technique, which requires 100 microl catheter blood and the use of light and ultraviolet microscopy, is considered simple, rapid (30 min) and inexpensive. In conclusion, diagnostic tools such as paired blood cultures or Gram staining and the acridine-orange leucocyte cytospin test should allow a diagnosis of CRS without catheter removal in cancer patients.

Differential quantitative blood cultures in the diagnosis of catheter-related sepsis in intensive care units.

The aim of this prospective study was to compare differential blood cultures and quantitative catheter tip cultures for the diagnosis of catheter-related sepsis. Over a period of 2 years, 283 central venous catheters were inserted in 190 adult patients. Catheters were removed when they were no longer needed or when infection was suspected. Immediately before removal of the central venous catheters, blood cultures were performed, with blood drawn simultaneously from the catheter and the peripheral vein. After removal, quantitative catheter culture was performed according to the Brun-Buisson modified Cleri technique. Fifty-five quantitative catheter cultures were positive. They were classified as contaminated (n = 18), colonized (n = 23), or infected (n = 14). Differential blood cultures correctly identified 13 infections. With a catheter/peripheral cfu ratio of 8, differential blood cultures had a sensitivity of 92.8% and a specificity of 98.8%. When the catheters were removed because of suspected infection, differential blood cultures had a sensitivity of 92.8% and a specificity of 100%. Differential blood culture, a technique that does not necessitate catheter removal, seems effective in the diagnosis of catheter-related sepsis in patients in the intensive care unit.

Bacterial colonization and peripheral bacteraemia associated with central venous haemodialysis catheters: A cross‐sectional study

Summary: Septicaemia related to internal luminal colonization of central venous catheters has been described in many clinical settings including haemodialysis. the prevalence and consequence of intraluminal colonization of central venous haemodialysis catheters is unknown. A cross‐sectional study of asymptomatic patients receiving haemodialysis through central venous catheters was performed. Differential (central line and peripheral) quantitative blood cultures were taken on three occasions. Twenty‐one patients were studied and 20 had colonized central venous catheters. the organisms isolated were Coagulase negative Staphylococci (16 cases), Bacillus species (three), Corynebacterium (three), Pseudomonas species (three), and others (three). Fifteen patients also had significant peripheral bacteraemia associated with the same organism that was cultured from their central line. Seven patients had septic episodes associated with these same organisms. Swabs taken of the internal catheter surfaces also cultured these organisms. the vast majority (95%) of central venous haemodialysis catheters are colonized by bacteria. Seventy‐six per cent have associated peripheral bacteraemia, which can lead to systemic infection.

Value of differential quantitative blood cultures in the diagnosis of catheter-related sepsis.

A prospective study was performed to assess the value of differential quantitative blood cultures in the diagnosis of catheter-related sepsis when this condition is suspected on clinical grounds and to establish a reliable discriminative value for application without removal of the inserted catheter. A total of 107 central venous catheters from 64 patients were used for the study. Blood was obtained simultaneously through the suspected infected device and from a peripheral venipuncture. The catheter was removed and its tip cultured semiquantitatively. Catheter-related sepsis occurred in 17 patients. Using as cut-off value a colony count fourfold higher in blood drawn through the catheter than in simultaneously drawn peripheral blood, a sensitivity of 94%, specificity of 100% and positive predictive value of 100% were obtained. A single bacterial count greater than 100 cfu/ml in the quantitative culture of the catheter blood specimen in the presence of a positive qualitative peripheral blood culture of the same organism was also highly suggestive of catheter-related sepsis. Differential quantitative blood culture is a reliable method for the diagnosis of catheter-associated sepsis without catheter removal.