Validity of earlier positivity of central venous blood cultures in comparison with peripheral blood cultures for diagnosing catheter-related bacteremia in cancer patients

[Guideline-conform treatment of sepsis]

The time to administration of broad-spectrum antibiotics and (secondarily) to the initiation of hemodynamic stabilization are the most important factors influencing survival of patients with sepsis and septic shock; however, the basic prerequisite for the initiation of an adequate treatment is that a suspected diagnosis of sepsis is made first. Therefore, the treatment of sepsis, even before it has begun, is an interdisciplinary and interprofessional task. This article provides an overview of the current state of the art in sepsis treatment and points towards new evidence that has the potential to change guideline recommendations in the coming years. In summary, the following points are critical: (1) sepsis must be diagnosed as soon as possible and the implementation of a source control intervention (in case of a controllable source) has to be implemented as soon as (logistically) possible. (2) In general, intravenous broad-spectrum antibiotics should be given within the first hour after diagnosis if sepsis or septic shock is suspected. In organ dysfunction without shock, where sepsis is a possible but unlikely cause, the results of focused advanced diagnostics should be awaited before a decision to give broad-spectrum antibiotics is made. If it is not clear within 3 h whether sepsis is the cause, broad-spectrum antibiotics should be given when in doubt. Administer beta-lactam antibiotics as a prolonged (or if therapeutic drug monitoring is available, continuous) infusion after an initial loading dose. (3) Combination treatment with two agents for one pathogen group should remain the exception (e.g. multidrug-resistant gram-negative pathogens). (4) In the case of doubt, the duration of anti-infective treatment should rather be shorter than longer. Procalcitonin can support the clinical decision to stop (not to start!) antibiotic treatment! (5) For fluid treatment, if hypoperfusion is present, the first (approximately) 2L (30 ml/kg BW) of crystalloid solution is usually safe and indicated. After that, the rule is: less is more! Any further fluid administration should be carefully weighed up with the help of dynamic parameters, the patient's clinical condition and echo(cardio)graphy.

Utility of Differential Time to Positivity in Diagnosing Central Line-Associated Bloodstream Infections: A Systematic Review and Meta-Analysis

BACKGROUND

Differential time to positivity (DTP), defined as pathogen growth at least 2 hours earlier from catheter versus paired peripheral blood cultures, is sometimes used to diagnose central line-associated bloodstream infections (CLABSIs). Previous studies assessing DTP, however, have been small, provided conflicting results, and did not assess heterogeneity across important subgroups.

METHODS

We systematically reviewed the diagnostic characteristics of DTP for CLABSI using MEDLINE, Embase, WoS, CINAHL, LILACS, AMED, and the Cochrane database. Studies were included if they reported sensitivities, specificities, predictive values, likelihood ratios, or 2 × 2 tables of DTP for diagnosing CLABSI. Extracted data were analyzed by using forest plots, bivariate model meta-analysis, and QUADAS-2 quality assessment.

RESULTS

We identified 274 records, of which 23 met the criteria for meta-analysis. Among 2526 suspected CLABSIs, DTP demonstrated a summary sensitivity of 81.3% (95% confidence interval [CI]: 72.8%-87.7%), specificity of 91.8% (95% CI: 84.5%-95.8%), positive likelihood ratio of 9.89 (95% CI: 5.14-19.00), and negative likelihood ratio of 0.20 (95% CI: .14-.30). Covariate analysis based on catheter duration, study design, and patient immune status demonstrated no significant differences. However, DTP performed worse for Staphylococcus aureus (low sensitivity but high specificity) and Candida (high sensitivity but low specificity) compared to other organisms.

CONCLUSIONS

DTP performs well in ruling CLABSIs in or out. Obtaining paired catheter and peripheral blood cultures for DTP when the infectious source is unclear may prevent unnecessary line removal and diagnostic tests. However, this must be balanced against higher contamination rates from catheter cultures.

Usefulness of differential time to positivity between catheter and peripheral blood cultures for diagnosing catheter-related bloodstream infection: Data analysis from routine clinical practice in the intensive care unit

PURPOSE

To assess the accuracy of differential time to positivity (DTP) method for the diagnosis of catheter-related bloodstream infections (CRBSI) in the routine practice of our intensive care unit (ICU).

MATERIALS AND METHODS

Over a five-year study period, ICU patients with a central venous catheter in place for ≥48 h and undergoing DTP test with catheter tip culture were analyzed. We investigated: the accuracy of DTP test with the usual threshold of 120 min in confirming the clinical suspicion of CRBSI; the most accurate threshold value of DTP to detect CRBSI; the diagnostic accuracy of the ratio (rather than the difference) between times to positivity.

RESULTS

Among 278 episodes of paired blood cultures, 13% were CRBSIs. DTP value ≥120 min used for the diagnosis of CRBSI yielded 41% sensitivity and 74% specificity. Performance of DTP values in predicting CRBSI was low (AUC = 0.60 [95%CI: 0.48-0.72]). Cutoff value of the ratio between times to positivity was 0.80, with 46% sensitivity and 79% specificity.

CONCLUSIONS

The routine use of the DTP method at any cutoff point has inadequate accuracy in detecting CRBSI in the real every day clinical practice. Not even the ratio between times to positivity seems to be clinically useful.

Time to positivity in bloodstream infection is not a prognostic marker for mortality: analysis of a prospective multicentre randomized control trial

OBJECTIVES

Time to positivity (TTP), calculated automatically in modern blood culture systems, is considered a proxy for microbial load and has been suggested as a potential prognostic marker in bloodstream infections. In this large, multicentre, prospectively collected cohort, our primary analysis aimed to quantify the relationship between the TTP of monomicrobial blood cultures and mortality.

METHODS

Data from a multicentre randomized controlled trial (RAPIDO) in bloodstream infection were analysed. Bloodstream infections were classified into 13 groups/subgroups. The relationship between mortality and TTP was assessed by logistic regression, adjusted for site, organism, and clinical variables, and linear regression was applied to examine the association between clinical variables and TTP. Robustness was assessed by sensitivity analysis.

RESULTS

In total 4468 participants were included in the RAPIDO. After exclusions, 3462 were analysed, with the most common organisms being coagulase-negative staphylococci (1072 patients) and Escherichia coli (861 patients); 785 patients (22.7%) died within 28 days. We found no relationship between TTP and mortality for any groups except for streptococci (odds ratio (OR) with each hour 0.98, 95%CI 0.96-1.00) and Candida (OR 1.03, 95%CI 1.00-1.05). There was large variability between organisms and sites in TTP. Fever (geometric mean ratio (GMR) 0.95, 95%CI 0.92-0.99), age (GMR per 10 years 1.01, 95%CI 1.00-1.02), and neutrophilia were associated with TTP (GMR 1.03, 95%CI 1.02-1.04).

CONCLUSIONS

Time to positivity is not associated with mortality, except in the case of Candida spp. (longer times associated with worse outcomes) and possibly streptococci (shorter times associated with worse outcomes). There was a large variation between median times across centres, limiting external validity.

Intestinal parasitism in pediatric oncology children receiving chemotherapy: unexpected low prevalence

Background

Children with underlying malignancies and those on chemotherapy are at risk for having intestinal parasitic infections, which can lead to a severe course and death. This cross-sectional study was done to assess the copro-parasitological and copro-molecular prevalence of entero-parasites in children with malignancies and those on chemotherapy.

Procedure

Stool samples were collected from 137 Egyptian hospitalized cancerous children with different malignancies in the National Cancer Institute, and receiving chemotherapy.

Faecal samples were examined microscopically. Genomic copro-DNA was extracted from fecal samples and amplified by 3 separate nPCR assays targeting Cryptosporidium, G. intestinalis and Entamoeba histolytica complex.

Result

The overall prevalence of enteroparasites was 6.6 % (9 cases). Only Giardia copro-DNA was encountered in 2 (1.4%) faecal samples of patients. Coproscopy detected parasites in 7 cases: Blastocystis spp. in 5 cases (3.6%), Hymenolepis nana in 1 case (0.7%) and Ascaris lumbericoides in 1 case (0.7%).

Conclusion

Low prevalence may be due to patient's use of prophylactic anti-parasitic and anti-fungal drugs, a standard protocol, basic hygienic practices and good nursing all of which are preventive against enteroparasites transmission. Among studied variables only diarrhoeic individuals who had a solid tumor, and soft/liquid stool with mucus and blood were predictors of intestinal parasitism.

Differential time to positivity of central and peripheral blood cultures is inaccurate for the diagnosis of Staphylococcus aureus long-term catheter-related sepsis

OBJECTIVES

Differential time to positivity of cultures of blood drawn simultaneously from central venous catheter and peripheral sites is widely used to diagnose catheter-related bloodstream infections without removing the catheter. However, the accuracy of this technique for some pathogens, such as Staphylococcus aureus, is debated in routine practice.

METHODS

In a 320-bed reference cancer centre, the charts of patients with at least one blood culture positive for S. aureus among paired blood cultures drawn over a six-year period were studied retrospectively. Microbiological data were extracted from the prospectively compiled database of the microbiology unit. Data concerning the 149 patients included were reviewed retrospectively by independent physicians blinded to the absolute and differential times to positivity, in order to establish or refute the diagnosis of catheter-related sepsis. Due to missing data, 48 charts were excluded, so 101 cases were actually analysed. The diagnosis was established in 62 cases, refuted in 15 cases and inconclusive in the remaining 24 cases.

RESULTS

For the 64 patients with both central and peripheral positive blood cultures, the differential positivity time was significantly greater for patients with catheter-related bloodstream infections due to S. aureus (P<0.02). However, because of the high number of false-negative cases, the classic cut-off limit of 120 min showed 100% specificity but only 42% sensitivity for the diagnosis of catheter-related bloodstream infection due to S. aureus.

CONCLUSIONS

These results strongly suggest that despite its high specificity, the differential time to positivity may not be reliable to rule out catheter-related bloodstream infection due to S. aureus.

Surviving Sepsis Campaign: International Guidelines for Management of Sepsis and Septic Shock: 2016

OBJECTIVE

To provide an update to "Surviving Sepsis Campaign Guidelines for Management of Sepsis and Septic Shock: 2012."

DESIGN

A consensus committee of 55 international experts representing 25 international organizations was convened. Nominal groups were assembled at key international meetings (for those committee members attending the conference). A formal conflict-of-interest (COI) policy was developed at the onset of the process and enforced throughout. A stand-alone meeting was held for all panel members in December 2015. Teleconferences and electronic-based discussion among subgroups and among the entire committee served as an integral part of the development.

METHODS

The panel consisted of five sections: hemodynamics, infection, adjunctive therapies, metabolic, and ventilation. Population, intervention, comparison, and outcomes (PICO) questions were reviewed and updated as needed, and evidence profiles were generated. Each subgroup generated a list of questions, searched for best available evidence, and then followed the principles of the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system to assess the quality of evidence from high to very low, and to formulate recommendations as strong or weak, or best practice statement when applicable.

RESULTS

The Surviving Sepsis Guideline panel provided 93 statements on early management and resuscitation of patients with sepsis or septic shock. Overall, 32 were strong recommendations, 39 were weak recommendations, and 18 were best-practice statements. No recommendation was provided for four questions.

CONCLUSIONS

Substantial agreement exists among a large cohort of international experts regarding many strong recommendations for the best care of patients with sepsis. Although a significant number of aspects of care have relatively weak support, evidence-based recommendations regarding the acute management of sepsis and septic shock are the foundation of improved outcomes for these critically ill patients with high mortality.

Surviving Sepsis Campaign: International Guidelines for Management of Sepsis and Septic Shock: 2016

OBJECTIVE

To provide an update to "Surviving Sepsis Campaign Guidelines for Management of Sepsis and Septic Shock: 2012".

DESIGN

A consensus committee of 55 international experts representing 25 international organizations was convened. Nominal groups were assembled at key international meetings (for those committee members attending the conference). A formal conflict-of-interest (COI) policy was developed at the onset of the process and enforced throughout. A stand-alone meeting was held for all panel members in December 2015. Teleconferences and electronic-based discussion among subgroups and among the entire committee served as an integral part of the development.

METHODS

The panel consisted of five sections: hemodynamics, infection, adjunctive therapies, metabolic, and ventilation. Population, intervention, comparison, and outcomes (PICO) questions were reviewed and updated as needed, and evidence profiles were generated. Each subgroup generated a list of questions, searched for best available evidence, and then followed the principles of the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system to assess the quality of evidence from high to very low, and to formulate recommendations as strong or weak, or best practice statement when applicable.

RESULTS

The Surviving Sepsis Guideline panel provided 93 statements on early management and resuscitation of patients with sepsis or septic shock. Overall, 32 were strong recommendations, 39 were weak recommendations, and 18 were best-practice statements. No recommendation was provided for four questions.

CONCLUSIONS

Substantial agreement exists among a large cohort of international experts regarding many strong recommendations for the best care of patients with sepsis. Although a significant number of aspects of care have relatively weak support, evidence-based recommendations regarding the acute management of sepsis and septic shock are the foundation of improved outcomes for these critically ill patients with high mortality.

Blood culture differential time to positivity enables safe catheter retention in suspected catheter-related bloodstream infection: a randomized controlled trial

OBJECTIVE

To evaluate the clinical usefulness and safety of the differential-time-to-positivity (DTP) method for managing the suspicion of catheter-related bloodstream infection (CR-BSI) in comparison with a standard method that includes catheter removal in critically ill patients.

METHODS-DESIGN

A prospective randomized study was carried out.

SETTING

A 16-bed clinical-surgical ICU (July 2007-February 2009).

INTERVENTIONS

Patients were randomly assigned to one of two groups at the time CR-BSI was suspected. In the standard group, a standard strategy requiring catheter withdrawal was used to confirm or rule out CR-BSI. In the DTP group, DTP without catheter withdrawal was used to confirm or rule out CR-BSI.

MEASUREMENTS

clinical and microbiological data, CR-BSI rates, unnecessary catheter removals, and complications due to new puncture or to delays in catheter removal.

RESULTS

Twenty-six patients were analyzed in each group. In the standard group, 6 of 37 suspected episodes of CR-BSI were confirmed and 5 colonizations were diagnosed. In the DTP group, 5 of 26 suspected episodes of CR-BSI were confirmed and four colonizations were diagnosed. In the standard group, all catheters (58/58, 100%) were removed at the time CR-BSA was suspected, whereas in the DTP group, only 13 catheters (13/41, 32%) were removed at diagnosis, and 10 due to persistent septic signs (10/41, 24%). In cases of confirmed CR-BSI, there were no differences between the two groups in the evolution of inflammatory parameters during the 48hours following the suspicion of CR-BSI.

CONCLUSIONS

In critically ill patients with suspected CR-BSI, the DTP method makes it possible to keep the central venous catheter in place safely.

Central line-associated bloodstream infections: prevention and management

Approximately 80,000 central venous line-associated bloodstream infections (CLA-BSI) occur in the United States each year. CLA-BSI is most commonly caused by coagulase-negative staphylococci, Staphylococcus aureus, Candida spp, and aerobic gram-negative bacilli. These organisms commonly gain entrance in into the bloodstream via the catheter-skin interface (insertion site) or via the catheter hub. Use of strict aseptic technique for insertion is the key method for the prevention of CLA-BSI. Various methods can be used to reduce unacceptably high rates of CLA-BSI, including use of an antiseptic- or antibiotic-impregnated catheter, daily chlorhexidine baths/washes, and placement of a chlorhexidine-impregnated sponge over the insertion site.

Differential time to positivity and quantitative cultures for noninvasive diagnosis of catheter-related blood stream infection in children

BACKGROUND

Accurate diagnosis of catheter-related blood stream infection (CRBSI) is necessary to make a decision about removal of the catheter. Differential time to positivity (DTP) and the ratio of quantitative cultures (RQC) between central and peripheral blood cultures have not been evaluated against a strict standard in children, namely catheter tip culture.

OBJECTIVE

Our aim is to compare DTP and RQC in the diagnosis of catheter tip-confirmed catheter-related infection in children.

METHOD

Prospective study performed in 2 large hospitals in Santiago, Chile. Children with clinically suspected CRBSI had 2 peripheral and central vein blood samples obtained for automated culture in Bact/Alert and for quantitative cultures in 5% sheep blood agar plate. The catheter tip was cultured. Sensitivity, specificity, positive predictive value, negative predictive value, likelihood ratios (LR), and accuracy of DTP and RQC were compared against catheter tip-confirmed CRBSI.

RESULTS

During a 3-year period, 344 clinically suspected CRBSIs were diagnosed in children of which 124 episodes met study criteria. Catheter tip culture-confirmed CRBSI in 25 (20%) of 124 episodes. A total of 34 microorganisms were cultured from 25 CRBSI; 8 of 25 (32%) episodes were polymicrobial. Staphylococcus aureus followed by coagulase-negative Staphylococcus were the most common microorganisms. For CRBSI, DTP and RQC reached a sensitivity of 75% versus 24% (P < 0.001), specificity of 86 versus 94%, positive predictive value of 58% versus 50%, negative predictive value of 93% versus 82%, LR of 5.48 versus 4.50, and accuracy of 0.84 versus 0.79.

CONCLUSIONS

In children, DTP was better than RQC for diagnosis of catheter tip-confirmed CRBSI.

Intravascular catheter-related infections: advances in diagnosis, prevention, and management

Indwelling vascular catheters are a leading source of bloodstream infections in critically ill patients and cancer patients. Because clinical diagnostic criteria are either insensitive or non-specific, such infections are often overdiagnosed, resulting in unnecessary and wasteful removal of the catheter. Catheter-sparing diagnostic methods, such as differential quantitative blood cultures and time to positivity have emerged as reliable diagnostic techniques. Novel preventive strategies include cutaneous antisepsis, maximum sterile barrier, use of antimicrobial catheters, and antimicrobial catheter lock solution. Management of catheter-related bloodstream infections involves deciding on catheter removal, antimicrobial catheter lock solution, and the type and duration of systemic antimicrobial therapy. Such decisions depend on the identity of the organism causing the bloodstream infection, the clinical and radiographical manifestations suggesting a complicated course, the underlying condition of the host (neutropenia, thrombocytopenia), and the availability of other vascular access sites.

Diagnosis of catheter-related bloodstream infection in neonates: a study on the value of differential time to positivity of paired blood cultures

OBJECTIVE

Diagnosis of neonatal catheter-related bloodstream infection (CRBSI) is currently based on isolation of identical bacterial species from bloodstream and catheter tip cultures. This requires removal of the catheter followed by the insertion of a new catheter. The objective of this study was to investigate whether differential time to positivity (DTP) of blood cultures drawn from paired peripheral vein and central vascular catheter is useful for diagnosing neonatal CRBSI, avoiding removal of the catheter.

DESIGN

Retrospective observational study.

SETTING

Neonatal intensive care unit, University Hospital of Antwerp, Belgium.

PATIENTS

Neonates with probable and definite nosocomial bloodstream infection.

INTERVENTIONS

All episodes of nosocomial bloodstream infection (NBSI) in an approximately 7.5-yr period were identified retrospectively. Definite NBSI episodes in which paired blood cultures were obtained were retained to calculate DTP, to determine the optimal DTP cutoff for the diagnosis of CRBSI, and to assess the validity of DTP for the diagnosis of CRBSI.

MEASUREMENTS AND MAIN RESULTS

Of 32 NBSI episodes included in the study, 16 were CRBSI, seven were non-CRBSI, and nine were classified as "diagnosis uncertain." In CRBSI, blood cultures drawn from a central vascular catheter were positive earlier than those drawn from a peripheral vein (median 9.67 hrs vs. 21.58 hrs, p < .01). Median DTP was 10.42 hrs in CRBSI and -0.33 hrs in non-CRBSI (p = .01). The optimal DTP cutoff for the diagnosis of CRBSI was > or =1 hr (area under the receiver operating characteristic curve = 0.84 +/- 0.11), with a sensitivity of 94%, a specificity of 71%, a positive predictive value of 88%, and a negative predictive value of 83%.

CONCLUSIONS

Differential time to positivity of paired blood cultures may have some potential in the diagnosis of catheter-related infections in neonatal intensive care unit patients and should be subjected to a prospective study.

Time-to-positivity in patients with Escherichia coli bacteraemia

The time from the start of incubation to a positive reading of blood cultures (time-to-positivity; TTP) is related to the concentration of bacteria in blood. Information concerning the correlation of TTP with clinical parameters, and its usefulness as a prognostic factor in patients with Escherichia coli bacteraemia, is limited. To investigate the relationship of TTP to clinical parameters, 459 cases of monomicrobial E. coli bloodstream infections from a single institution between 1997 and 2005 were reviewed. All cases involved patients who were not undergoing antibiotic treatment at the time of blood sampling. The in-hospital mortality rate was 6.3%. Median TTP was significantly shorter for patients who died than for those who survived (9.7 h, inter-quartile range 7.85-11.05 h vs. 11.2 h, inter-quartile range 10.1-11.4 h; p <0.001). Patients with TTP in the lowest quartile were more likely to be female, to have a non-urinary tract or an unknown origin of bacteraemia, to have severe sepsis or shock, and to subsequently die. In a multivariable Cox regression model, the hazard ratio for death from any cause for patients with a short TTP was 3.13 (95% CI 1.28-7.64; p 0.01). TTP in patients with E. coli bacteraemia provides prognostic information beyond that provided by the presence of haematological illness, a Charlson score > or =3, a non-urinary tract origin of bacteraemia, and the presence of severe sepsis or shock.

Time to positivity in blood cultures of adults with Streptococcus pneumoniae bacteremia

BACKGROUND

previous studies have established that bacterial blood concentration is related with clinical outcome. Time to positivity of blood cultures (TTP) has relationship with bacterial blood concentration and could be related with prognosis. As there is scarce information about the usefulness of TTP, we study the relationship of TTP with clinical parameters in patients with Streptococcus pneumoniae bacteremia.

METHODS

TTP of all cases of Streptococcus pneumoniae bacteremia, detected between January 1995 and December 2004 using the BacT/Alert automated blood culture system in a teaching community hospital was analyzed. When multiple cultures were positive only the shortest TTP was selected for the analysis.

RESULTS

in the study period 105 patients with Streptococcus pneumoniae bacteremia were detected. Median TTP was 14.1 hours (range 1.2 h to 127 h). Immunosuppressed patients (n = 5), patients with confusion (n = 19), severe sepsis or shock at the time of blood culture extraction (n = 12), those with a diagnosis of meningitis (n = 7) and those admitted to the ICU (n = 14) had lower TTP. Patients with TTP in the first quartile were more frequently hospitalized, admitted to the ICU, had meningitis, a non-pneumonic origin of the bacteremia, and a higher number of positive blood cultures than patients with TTP in the fourth quartile. None of the patients with TTP in the 90th decile had any of these factors associated with shorter TTP, and eight out of ten patients with TTP in the 10th decile had at least one of these factors. The number of positive blood cultures had an inverse correlation with TTP, suggesting a relationship of TTP with bacterial blood concentration.

CONCLUSION

Our data support the relationship of TTP with several clinical parameters in patients with Streptococcus pneumoniae bacteremia, and its potential usefulness as a surrogate marker of outcome.

Detection of catheter-related bloodstream infections by the Gram stain–acridine orange leukocyte cytospin test in hematopoietic stem cell transplant recipients

In patients with central venous catheters (CVCs), catheter-related bloodstream infections (CRBI) are a prominent cause of morbidity, excess hospital costs, and in some cases mortality. The aim of this prospective study was to assess the validity of the Gram stain-acridine orange leukocyte cytospin (AOLC) test for the diagnosis of CRBI in hematopoietic stem cell transplant (HSCT) recipients with nontunnelled CVCs, using the differential-time-to-positivity (DTP)/clinical criteria as the criterion standard to define CRBIs. CVCs were externalized, nontunnelled, polyurethane double lumen catheters (Arrows, Readings, USA). All CVCs were placed in the subclavian vein by the infraclavicular approach, in the operating room. Catheters were inserted percutaneously, using the Seldinger technique. Study catheters were not exchanged over guidewires. Between May 2002 and December 2004, a total of 245 consecutive patients were included. Twenty-six of the 245 patients (10.6%) had CRBI as determined by the DTP method. The Gram stain-AOLC was positive in only two patients (7.6%) with a CRBI. Our results suggest that the Gram stain-AOLC test is not useful for the diagnosis of catheter-related bloodstream infection in HSCT recipients.2006.

Qualitative versus quantitative blood cultures in the diagnosis of catheter-related bloodstream infections in children with malignancy

BACKGROUND

Paired quantitative and qualitative blood cultures have been introduced for the diagnosis of catheter-related bloodstream infections (CRBI) with the catheter in situ. The aim of the study was to compare the diagnostic performance and the prognostic value of the two methods in the evaluation of febrile episodes without an apparent source in children with cancer.

PROCEDURE

During a 4-year period, in every febrile episode without an apparent focus, blood was drawn simultaneously from the catheter lumen and a peripheral vein in order to perform paired quantitative (Isolator) as well as qualitative (BacT/Alert) blood cultures. The diagnosis of a CRBI was defined as either a case of greater (at least 10 fold) or earlier (differential time to positivity >2 h) bacterial growth from the catheter compared to the peripheral blood sample, respectively.

RESULTS

Nineteen febrile episodes manifested in 16 children (total period of observation 11,150 catheter-days) were evaluated with both methods. A concordant diagnosis of CRBI was stated with both methods in six episodes; one episode was diagnosed as CRBI only with qualitative culture criteria. Treatment failure resulted in catheter removal in five out of the seven episodes defined as CRBI with either method. Episodes where a CRBI was ruled out with both methods had a favorable outcome.

CONCLUSIONS

In this study the two methods showed comparable results in the diagnosis of CRBI and both were of prognostic significance, regarding the outcome of the treatment. However, large scale studies are required in order to evaluate the clinical relevance and the cost effectiveness of performing routinely paired blood cultures with either method.

Time to positivity in Staphylococcus aureus bacteremia: possible correlation with the source and outcome of infection

BACKGROUND

Staphylococcus aureus bacteremia often persists and causes metastatic infections. It is unknown whether the time between blood culture incubation and growth detection (i.e., the time to positivity) in a continuously monitored system--a probable surrogate marker of bacteremia severity--correlates with outcome.

METHODS

We performed a prospective, observational study involving adult inpatients who had S. aureus bacteremia between 1 January 2002 and 30 June 2003 at a 600-bed teaching hospital. Measurements included time to positivity in initial blood culture series, duration of bacteremia, rate of metastatic infection, and outcome.

RESULTS

A total of 376 S. aureus bacteremias (> or = 1 positive blood culture result) were reported for 357 patients aged 18-103 years (median age, 59 years); 64 bacteremias were excluded because blood was drawn after antibiotic therapy was started (n = 59) or through an intravascular catheter (n = 5). The source of infection was identified in 244 series (78.2%). Metastatic infection was detected in 25 bacteremias (8.0%). The mortality rate was 25.6%. The duration of bacteremia (determined in 251 series) was 1-59 days (median duration, 1 day; 70th percentile, 3 days). The time to positivity ranged from 4.2 to 98.2 h (median time to positivity, 15.5 h) and was significantly shorter for patients with an endovascular source of infection (14.9+/-5.4 vs. 19.5+/-10.6 h; P < .0005), extended duration (i.e., > or = 3 days) of bacteremia (14.1+/-4.2 vs. 18.6+/-9.2 h; P < .0005), and metastatic infection (12.9+/-5.9 vs 18.0+/-9.3 h; P = .007). Analysis of a range of cutoff values demonstrated that a time to positivity of < or = 14 h yielded the best sensitivity and specificity for predicting the source and outcome of infection. Logistic regression analyses revealed that a time to positivity of < or = 14 h was an independent predictor of an endovascular source of infection (P < .0005), extended bacteremia (P < .0005), metastatic infection (P < .0005), and attributable mortality (P = .017).

CONCLUSIONS

Time to positivity in S. aureus bacteremia may provide useful diagnostic and prognostic information. Growth of S. aureus within 14 h after the initiation of incubation may identify patients with a high likelihood of endovascular infection sources, delayed clearance, and complications.

Comparison of contamination rates of catheter-drawn and peripheral blood cultures

The aim of this study was to assess the sensitivity and specificity of catheter-drawn and peripheral blood cultures. Paired blood culture samples collected over a 44-month period from a 280 bed Brisbane metropolitan hospital were analysed, using standard clinical and microbiological criteria, to determine whether blood culture isolates represented true bacteraemias or contamination. Catheter-collected cultures had a specificity of 85% compared with 97% for peripheral cultures. In only two instances (0.2%) was the diagnosis of clinically significant bacteraemia made on the basis of catheter culture alone. This study concluded that catheter-collected samples are not a good test for true bacteraemia, and that peripheral cultures are more reliable when the results of the paired cultures are discordant.

In situ diagnosis of intravascular catheter-related bloodstream infection: A comparison of quantitative culture, differential time to positivity, and endoluminal brushing

OBJECTIVE

To compare the accuracy of three techniques that do not require central venous catheter removal to diagnose catheter-related bloodstream infection.

DESIGN

Prospective cohort study of central venous catheters from suspected cases of catheter-related bloodstream infection.

SETTING

University teaching hospital.

PATIENTS

One hundred and twenty-five central venous catheters from patients with suspected catheter-related bloodstream infection (a raised peripheral white blood cell count, temperature >37 degrees C, and/or local signs of infection at the catheter skin entry site) in intensive care and surgical patients in a large teaching hospital were assessed.

INTERVENTIONS

None.

MEASUREMENTS

Three techniques were compared: the differential time to positivity of central venous catheter vs. peripheral-blood cultures, quantitative culture of central venous catheter vs. peripheral blood, and the endoluminal brush with peripheral blood culture.

MAIN RESULTS

Central venous catheters with a median dwell time of 11 days were examined. There were 36 episodes of catheter-related bloodstream infection, defined as a positive result from at least two of the three tests in the presence of a peripheral blood culture growing the same microorganism and without an identifiable alternative source of sepsis. The sensitivities of the endoluminal brush, quantitative culture, and differential time to positivity techniques were 100%, 89%, and 72%, respectively, with corresponding specificities of 89%, 97%, and 95%. Blood could be directly aspirated from only 231 of 312 (74%) lumens. In the 20 cases of catheter-related bloodstream infection associated with multiple-lumen central venous catheters, endoluminal brushing was positive for one, two, and three lumens in nine (45%), six (30%), and five (25%) cases, respectively.

CONCLUSIONS

All three techniques had relatively high sensitivity. However, inability to obtain samples via central venous catheters is a major drawback of the differential time to positivity and quantitative blood culture approaches. Differential time to positivity is simple to perform and has high specificity and therefore could be used as a first line approach, with the endoluminal brush reserved for cases where blood cannot be obtained. All lumens of multiple-lumen central venous catheters must be sampled to ensure maximal sensitivity.

Difference in time to positivity is useful for the diagnosis of catheter-related bloodstream infection in hematopoietic stem cell transplant recipients

Catheter-related bloodstream infections are associated with recognized morbidity and mortality. Accurate diagnosis of such infections results in proper management of patients and in reducing unnecessary removal of catheters. We carried out a prospective study in a bone marrow transplant unit to assess the validity of a test based on the earlier positivity of central venous blood cultures in comparison with peripheral blood cultures for predicting catheter-related bacteremia. Between May 2002 and June 2004, 38 bloodstream infections with positive simultaneous central venous catheter and peripheral vein blood cultures were included. A total of 22 patients had catheter-related bacteremias and 16 had noncatheter-related bacteremias, using the catheter-tip culture/clinical criteria as the criterion standard to define catheter-related bacteremia. Differential time to positivity of 120 min or more was associated with 86% sensitivity and 87% specificity. In conclusion, differential time to positivity of 120 min or more is sensitive and specific for catheter-related bacteremia in hematopoietic stem cell transplant recipients who have nontunnelled short-term catheters.

Detection of catheter-related bloodstream infections by the differential-time-to-positivity method and gram stain-acridine orange leukocyte cytospin test in neutropenic patients after hematopoietic stem cell transplantation

For febrile neutropenic patients who received hematopoietic stem cell transplantation, the Gram stain-acridine orange leukocyte cytospin (AOLC) test and the differential-time-to-positivity method (DTP) were performed. As a diagnostic tool for catheter-related bloodstream infections in these patients, the Gram stain-AOLC test has a lower sensitivity than does the DTP method but acceptable positive and negative predictive values.

Diagnosis and Management of Long-term Central Venous Catheter Infections

The pathogenesis, diagnosis, and management of central venous catheter infections differ between short-term and long-term catheters. This review summarizes available data regarding the diagnosis and management of catheter-related bloodstream infections (CRBSIs) associated with long-term catheters. A review of various diagnostic modalities is provided, including methods of CRBSI diagnosis for catheters that are retained. Management of CRBSIs for long-term catheters is also addressed, with an emphasis on differentiating infections that require catheter removal from those that may allow catheter salvage. Data regarding catheter salvage with use of antibiotic lock therapy are also reviewed.

Difference in time to detection: a simple method to differentiate catheter-related from non-catheter-related bloodstream infection in immunocompromised pediatric patients

Current methods for diagnosis of catheter-related infection (CRI) are cumbersome and may require removal of the central venous catheter (CVC). A prospective study was conducted to validate the difference in time to detection (DTD) of cultures of blood samples obtained simultaneously from a peripheral vein (PV) and from the CVC for differentiation of CRI and non-CRI. During a 15-month period, 9 episodes were categorized as CRI and 24 as non-CRI. The median DTD for patients with CRI was significantly higher than that for patients with non-CRI (457 vs. -4 min; P<.001). The optimum cutoff point for diagnosis of CRI was a DTD of > or =120 min (sensitivity, 88.9%; specificity, 100%). With pretest probability of CRI ranging from 28% to 54%, the positive predictive value of a DTD of > or =120 min for the diagnosis of CRI was 100%; the negative predictive value was 89%-96%. On the basis of findings from this study, which is the largest, to date, to involve pediatric patients with tunneled CVCs and the first to use paired quantitative blood cultures as a "criterion standard," DTD was found to be a simple, reliable tool for diagnosis of CRI in hospitals that use continuously read blood culture systems.

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

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.

Catheter-related bloodstream infections in HIV-infected patients

Bloodstream infections (BSI) constitute a significant public health problem and represent an important cause of morbidity and mortality in hospitalized patients, with an approximate incidence of one episode per hundred hospital admissions. Studies on BSI in HIV+ patients have identified central venous catheters (CVC) as a risk factor, with an attributable mortality rate of 10-20%. The long-term CVC-related infection risk appeared to be 5 to 10-fold higher with respect to the infection rates among HIV- patients. CVC associated infection rate ranges from 1.3 to 12 infections per 1,000 catheter-days. Staphylococcus aureus is the most common etiologic agent causative of CVC-related BSI, likely the result of the high skin and nasal carriage of this organism among HIV+ patients, mostly intravenous drug users. Coagulase-negative staphylococci are also frequently identified as cause of CVC-related BSI, likely the result of breaches in infection control measures and in antiseptic technique during CVC management. Treating bacteremia without catheter removal would be optimal, but the reported efficacy of systemic antibiotic therapy alone is only 25-32%. Conversely, recent studies have shown that, using an antibiotic-lock procedure, up to 90% of HIV-infected and uninfected patients achieved complete eradication of catheter-related BSIs without catheter removal. Clinical trials using new materials such as covalently linked heparin on the CVC surface, electrically charged CVC, novel topical agents that interfere with bacterial colonization, antiadhesin molecules and agents that block the gene expression involved in the biofilm formation, are all needed to reduce the high catheter-related infection risk among HIV+ patients.