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

Acute Oncology Care: A narrative review of the acute management of neutropenic sepsis and immune-related toxicities of checkpoint inhibitors

Cancer care has become increasingly specialized and advances in therapy have resulted in a larger number of patients receiving care. There has been a significant increase in the number of patients presenting with cancer related emergencies including treatment toxicities and those directly related to the malignancy. Suspected neutropenic sepsis is an acute medical emergency and empirical antibiotic therapy should be administered immediately. The goal of empirical therapy is to cover the most likely pathogens that will cause life-threatening infections in neutropenic patients. Patients with febrile neutropenia are a heterogeneous group with only a minority of treated patients developing significant medical complications. Outpatient management of low risk febrile neutropenia patients identified by the MASCC score is a safe and effective strategy. Immunotherapy with "checkpoint inhibitors" has significantly improved outcomes for patients with metastatic melanoma and evidence of benefit in a wide range of malignancies is developing. Despite these clinical benefits a number of immune related adverse events have been recognised which can affect virtually all organ systems and are potentially fatal. The timing of the onset of the adverse events is dependent on the organ system affected and unlike anti-neoplastic therapy can be delayed significantly after initiation or completion of therapy. The field of Acute Oncology is changing rapidly. Alongside, the traditional challenge of neutropenic sepsis there are many emerging toxicities. Further research into the optimal management, strategies and pathways of acutely unwell patients with cancer is required.

Prosthetic Device Infections

The immunocompromised host is a particularly vulnerable population in whom routine and unusual infections can easily and frequently occur. Prosthetic devices are commonly used in these patients and the infections associated with those devices present a number of challenges for both the microbiologist and the clinician. Biofilms play a major role in device-related infections, which may contribute to failed attempts to recover organisms from routine culture methods. Moreover, device-related microorganisms can be difficult to eradicate by antibiotic therapy alone. Changes in clinical practice and advances in laboratory diagnostics have provided significant improvements in the detection and accurate diagnosis of device-related infections. Disruption of the bacterial biofilm plays an essential role in recovering the causative agent in culture. Various culture and nucleic acid amplification techniques are more accurate to guide directed treatment regimens. This chapter reviews the performance characteristics of currently available diagnostic assays and summarizes published guidelines, where available, for addressing suspected infected prosthetic devices.

Microbiological screening for earlier detection of central venous catheter-related bloodstream infections

BACKGROUND

Catheter-related bloodstream infections (CRBSIs) are currently detected with a reactive diagnostic policy, that is, application of tests to patients with clinically suspected CRBSI. The aim of our study was to evaluate whether CRBSIs could be anticipated in an earlier stage by microbiological screening using peptide nucleic acid fluorescence in situ hybridization (PNA FISH) with universal hybridization probes or acridine-orange leucocyte cytospin (AOLC) tests in haemodialysis and haematological patients with CVCs in situ compared with routine test.

MATERIALS AND METHODS

Peptide nucleic acid fluorescence in situ hybridization (PNA FISH) and AOLC tests using blood samples from both CVC lines in patients undergoing haemodialysis were performed three times a week and from one CVC line in haematological patients were performed daily. Results were compared with those obtained from routinely performed CRBSI diagnostic tests.

RESULTS

One hundred fifteen patients with 139 catheter periods were investigated. The mean observation time per catheter period was 25 days (IQR 13.5-43.5), resulting in 5615 CVC days with a total of 4839 tested blood samples. Five CRBSI cases were detected by routine measures resulting in a CRBSI rate of 0.9/1000 catheter days. Four of five CRBSIs could be anticipated by positive PNA FISH and AOLC tests 2-8 days before the diagnosis was established with routine measures.

CONCLUSIONS

The proactive anticipative strategy using microscopic examination of CVC blood samples to anticipate CRBSI in an earlier stage compared with routine measures is a new diagnostic approach in patients with CVCs and a high risk of developing CRBSI.

Optimization of microbial screening for cord blood

BACKGROUND

Collection and processing of cord blood (CB) is associated with significant risk of contamination; hence standards mandate microbial screening of the final product. The sensitivity of current methods to evaluate the microbial content of CB is unknown, given the small volume tested and reduced sensitivity of pediatric bottles. Hence, this study was undertaken to evaluate an optimal microbial screening method.

STUDY DESIGN AND METHODS

CB was collected using a closed system then spiked with organisms at 1 or 10 colony-forming units (CFUs)/mL. Samples were screened using culture bottles (BacT/ALERT, bioMérieux; and BACTEC, Becton Dickinson). Several methods were evaluated with different combinations of inoculated bottles (adult vs. pediatric), sample types (plasma discard, red blood cell [RBC] discard, or final product), and sample volumes.

RESULTS

Of 94 cord blood units (CBUs) spiked with organisms before screening, 81% tested positive for contamination overall. Screening of CB in pediatric bottles resulted in equivalent detection rates on the BacT/ALERT and BACTEC systems (33% at 1 CFU/mL and 73% at 10 CFUs/mL, respectively). However, the pediatric bottle screen only detected 15% of obligate anaerobes. A combined fraction method showed superior detection (71%) compared to the plasma fraction (27%) and resulted in optimal anaerobic detection.

CONCLUSIONS

This study demonstrates that the optimal microbial screening method for CB includes testing a combination of discard fractions (plasma and RBCs) in addition to final product using an automated culture system. Inoculating a small sample of final product in a pediatric bottle is suboptimal for microbial detection and may lead to distribution of contaminated CB for transplantation.

Antimicrobial therapy of febrile complications after high-dose chemotherapy and autologous hematopoietic stem cell transplantation--guidelines of the Infectious Diseases Working Party (AGIHO) of the German Society of Hematology and Oncology (DGHO)

More than 18,000 autolgous transplantation were performed in Europe in the year 2009. It as a routine procedure in experienced centres. Even if there is a low mortality rate, infections are a major issue after transplantation, occurring in more than 60 % of the patients. In this review we discuss all aspects of infections after autologous stem transplantation, including epidemiology, diagnostics, therapeutic algorithms, prophylaxis and supportive therapy.

Evidence-based guidelines for empirical therapy of neutropenic fever in Korea

Neutrophils play an important role in immunological function. Neutropenic patients are vulnerable to infection, and except fever is present, inflammatory reactions are scarce in many cases. Additionally, because infections can worsen rapidly, early evaluation and treatments are especially important in febrile neutropenic patients. In cases in which febrile neutropenia is anticipated due to anticancer chemotherapy, antibiotic prophylaxis can be used, based on the risk of infection. Antifungal prophylaxis may also be considered if long-term neutropenia or mucosal damage is expected. When fever is observed in patients suspected to have neutropenia, an adequate physical examination and blood and sputum cultures should be performed. Initial antibiotics should be chosen by considering the risk of complications following the infection; if the risk is low, oral antibiotics can be used. For initial intravenous antibiotics, monotherapy with a broad-spectrum antibiotic or combination therapy with two antibiotics is recommended. At 3-5 days after beginning the initial antibiotic therapy, the condition of the patient is assessed again to determine whether the fever has subsided or symptoms have worsened. If the patient's condition has improved, intravenous antibiotics can be replaced with oral antibiotics; if the condition has deteriorated, a change of antibiotics or addition of antifungal agents should be considered. If the causative microorganism is identified, initial antimicrobial or antifungal agents should be changed accordingly. When the cause is not detected, the initial agents should continue to be used until the neutrophil count recovers.

Sources and outcome of bloodstream infections in cancer patients: the role of central venous catheters

Simultaneously drawn quantitative blood cultures are used to diagnose catheter-related bloodstream infections. We conducted this study to determine the frequency with which central venous catheters were the source of bloodstream infections detected through paired positive blood cultures drawn from cancer patients and the potential for quantitative blood cultures to help predict outcome in neutropenic and non-neutropenic patients. From September 1999 to November 2000, we identified 169 patients with bloodstream infections. Of all bloodstream infections, 56% were catheter-related bloodstream infections. Gram-positive bacteremia was found to be catheter-related in 55% and 69% of patients with hematologic malignancy and solid tumors, respectively, whereas gram-negative bacteremia was catheter-related in only 19% of patients with underlying hematologic malignancy and in 60% of patients with solid tumor (P = 0.01). By multivariate analysis, poor response was associated with critical illness and persistent neutropenia (P < 0.01). In neutropenic patients with catheter-related bloodstream infections, peripheral quantitative blood cultures of >or=100 CFU/mL was also associated with poor response (P = 0.05). Central venous catheters were the major source of bloodstream infection, particularly in patients with solid tumors. In addition to critical illness and persistent neutropenia, quantitative blood cultures might be useful in predicting outcomes for neutropenic patients with catheter-related bloodstream infections.

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.