Evolution, incidence, and susceptibility of bacterial bloodstream isolates from 519 bone marrow transplant patients

Immune deficits in allogeneic hematopoietic stem cell transplant (HSCT) recipients

Immune deficits account for the high frequency of life threatening bacterial, viral, and fungal opportunistic infections seen in allogeneic HSCT recipients. Despite advances in infectious disease management, the integrity of host defenses remains the mainstay of defense. The intensity of the preparative regimen, degree of HLA matching, source of stem cells (marrow, blood, or cord), extent of T-cell depletion, and immunosuppressive therapy are some of the factors that impact the kinetics, characteristics, and quality of immune reconstitution. Graft-versus-host disease and its prophylaxis or treatment produce a host environment that is particularly vulnerable to infections. Mucosal disruption and prolonged severe neutropenia usually confine their impact to the early course of transplant. After initial engraftment, HSCT recipients remain at great risk for opportunistic infections and this is related to prolonged and severe T-lymphocyte dysfunction of a complex multifactorial nature. B cell dysfunction is less problematic clinically, but includes deficiencies of immunoglobulin subclasses and impaired ability to mount a vaccine response. Advances in understanding of these immune deficits have resulted in successful strategies including revaccination, growth factors, thymic protection, and adoptive cellular therapy with antigen-specific cells.

Antibiotic Resistance of Non-Pneumococcal Streptococci and Its Clinical Impact

Viridans streptococci (VGS) form a phylogenetically heterogeneous group of species belonging to the genus Streptococcus (1). However, they have some common phenotypic properties. They are alfa- or non-haemolytic. They can be differentiated from S. pneumoniae by resistance to optochin and the lack of bile solubility (2). They can be differentiated from the Enterococcus species by their inability to grow in a medium containing 6.5% sodium chloride (2). Earlier, so-called nutritionally variant streptococci were included in the VGS but based on the molecular data they have now been removed to a new genus Abiotrophia (3) and are not included in the discussion below. VGS belong to the normal microbiota of the oral cavities and upper respiratory tracts of humans and animals. They can also be isolated from the female genital tract and all regions of the gastrointestinal tract (2, 3). Several species are included in VGS and are listed elsewhere (2, 3). Clinically the most important species belonging to the VGS are S. mitis, S. sanguis and S. oralis.

Predictors of mortality in patients undergoing autologous hematopoietic cell transplantation admitted to the intensive care unit

Between January 2001 and July 2006, 1013 patients received autologous hematopoietic cell transplants (AHCT) at Canada's largest transplant center. In this retrospective cohort study of AHCT patients admitted to the intensive care unit (ICU), we describe the outcomes following ICU admission and the variables measured in the first 24 h of ICU admission associated with overall ICU mortality. Results indicate a 3.3% ICU admission rate (n=34) with 13 deaths (1% overall mortality rate, 38% in ICU mortality rate). The worst outcome was in AL amyloid patients of whom 28% were admitted to the ICU, with an ICU mortality rate of 55%. The Sequential Organ Failure Assessment (SOFA) score and Acute Physiology and Chronic Health Evaluation (APACHE II) score in the first 24 h were statistically associated with mortality by univariate analysis. Other variables measured at 24 h and associated with ICU mortality included multiorgan failure, mechanical ventilation, inotropic support >4 h and Gram-negative sepsis. Our data indicate that ICU admission in the autotransplant population is rare and that it is influenced by underlying diagnosis, with AL amyloid patients having the highest risk. Our observations may assist clinical decision-making regarding the continuation of intensive care delivered 24 h after ICU admission.

Bone marrow transplant cure for beta-thalassaemia major: initial experience from a developing country

Between July 2001 and June 2007, 48 consecutive patients with beta-thalassaemia major received allogeneic haematopoietic stem cell transplants (allo HSCT) from human-leukocyte-antigen-matched siblings at the Armed Forces Bone Marrow Transplant Centre, Rawalpindi, Pakistan, using standard conditioning regimens. The median age of the patient cohort was 4 years (range, 1-14 years). Thirty-one patients were in risk class I, 11 in class II and six patients were in class III. Engraftment was achieved in all patients. Survival was calculated from the date of transplant to death or last follow-up. Major post-transplant complications encountered were acute graft versus host disease (Ac GvHD) (grades II-IV), 35.4%; chronic GvHD, 8.3%; haemorrhagic cystitis, 12.5%; veno-occlusive disease (VOD) of the liver, 6.2%; bacterial infections, 37.5%; fungal infections, 19%; cytomegalovirus (CMV) infection, 6.2%; herpes infection, 6.2%; and tuberculosis in 2% of patients. Graft rejection was observed in five patients. Three patients received second transplants. Mortality was observed in 20.8% of patients. Major fatal complications included GvHD, VOD, intracranial haemorrhage, septicaema, CMV disease and disseminated tuberculosis. Overall survival and disease-free survival were 79% and 75%, respectively, at 6 years post-HSCT.

Umbilical cord blood transplantation: basic biology and clinical challenges to immune reconstitution

Allogeneic stem cell transplantation has continued to evolve as a common procedure for the treatment of hematological malignancies and bone marrow failure. Donor bone marrow and mobilized peripheral stem cells are routinely employed for the reconstitution of immune function in leukemia and lymphoma patients following radiation and/or chemotherapy. Unfortunately, only 30% of patients have an HLA-identical sibling donor and the identification of matched unrelated donors, particularly for minorities, can present an exceptional challenge. The transplantation of umbilical cord blood (UCB) represents the most recent strategy to expand the potential donor pool while maintaining an acceptable level of treatment-related complications. First utilized in children, UCB transplantation permits a higher degree of HLA disparity while demonstrating a reduction in the incidence and severity of graft-versus-host disease (GvHD) compared to previous transplantation modalities. Despite the apparent decrease in GvHD, relapse rates remain comparable to transplantation with bone marrow or mobilized peripheral blood suggesting a strong graft-versus-leukemia/lymphoma (GvL) effect. However, several issues complicate the use of UCB transplantation and its extension to the treatment of adults. Many infections that afflict transplant patients are particularly frequent and more severe in the context of UCB transplantation. UCB T-cells are naive and therefore display less proliferation and IFN-gamma production in response to cognate antigen and also appear to demonstrate defects in signal transduction mechanisms. In addition, UCB contains T regulatory cells (Treg) with more potent suppressor function than adult Treg. Furthermore, adult patients often require more total cells and CD34+ progenitors for transplantation than a single UCB unit can provide. Thus, strategies to expand selected subpopulations from UCB and the use of multi-unit transplantation are areas of active research. This review will provide a condensed summary of the clinical history of UCB transplantation and emphasize the advantages and disadvantages of this approach to hematological malignancies in comparison to other methods of hematopoietic stem cell transplantation. Subsequently, it will mainly focus on the current challenges to immune reconstitution presented by UCB transplantation, recent research into their cellular and molecular mechanisms, and experimental approaches to overcome them.

In vitro activity of daptomycin and tigecycline against coagulase-negative staphylococcus blood isolates from bone marrow transplant recipients

BACKGROUND AND OBJECTIVE

Multi-resistant coagulase-negative staphylococci (CNS) may cause systemic infections in patients undergoing bone marrow transplantation. Daptomycin, a new lipopeptide, and tigecycline, a new glycylcycline, have excellent activity against Gram-positive bacteria including methicillin-resistant staphylococci. This study presents the in vitro activity of daptomycin and tigecycline compared to vancomycin and fosfomycin against 105 CNS isolated from 76 bone marrow transplant patients with symptomatic bacteremia.

MATERIAL AND METHODS

Blood stream isolates of Staphylococcus epidermidis (n = 102) and Staphylococcus haemolyticus (n = 3) from bone marrow transplant patients were collected from 2000 to 2006. The susceptibility of all isolates was tested using methods of the Clinical Laboratory Standards Institute.

RESULTS

The minimal inhibitory concentrations MIC(50) and MIC(90) were 0.125 microg/mL and 0.25 microg/mL for daptomycin, 0.25 and 0.5 microg/mL for tigecycline, 1 microg/mL and 2 microg/mL for vancomycin, and 8 microg/mL and >256 microg/mL for fosfomycin, respectively. MIC values of tested agents were similar for both methicillin-sensitive and methicillin-resistant S. epidermidis strains.

CONCLUSIONS

All CNS isolates were susceptible to the new antistaphylococcal agents daptomycin and tigecycline. Although vancomycin had been used over the past 30 yr at our bone marrow transplant unit all CNS were still susceptible to vancomycin.

Infectious complication in 314 patients after high-dose therapy and autologous hematopoietic stem cell transplantation: risk factors analysis and outcome

BACKGROUND

Infectious complications occur in most of the patients receiving high-dose therapy (HDT) and autologous hematopoietic stem cell transplantation (HSCT). The objective of the study was to analyze of the type and incidence of infectious complications during neutropenia after HDT and autologous HSCT with respect to risk factors related to stem cell transplant setting in patients treated for hematological malignancies in a single center.

PATIENTS AND METHODS

A total number of 314 patients diagnosed for Hodgkin's disease (HD), non-Hodgkin's lymphoma (NHL), acute myeloid leukemia (AML), multiple myeloma (MM) or acute lymphoblastic leukemia (ALL) were included in the study. Analysis of risk factors and outcome of infections after HDT and autologous HSCT was performed.

RESULTS

Infectious complications during neutropenia after HDT occurred in 92.3% patients. Microbiologically documented infections (MDI) accounted for 38.9% of febrile episodes, clinically documented infections (CDI) for 9.3%, and fever of unknown origin (FUO) for 51.7% cases. Median time to defervescence with antibiotic therapy was seven days for FUO and nine days for documented infections (p < 0.001). Duration of infection correlated with the length of very severe neutropenia (p < 0.001). Response to first-line antibiotic therapy was seen in 34% patients. Infections were fatal in 12 (3.8%) patients. The highest probability of infection was observed for ALL and AML patients, especially these conditioned with total body irradiation (TBI).

CONCLUSION

Patients at high risk of infection after autologous HSCT were identified as those with acute leukemia and those after conditioning with TBI, all with prolonged neutropenia. We suggest that newer prophylactic strategies should be administered to these groups of patients.

High-performance liquid chromatography with ultraviolet detection for real-time therapeutic drug monitoring of meropenem in plasma

A simple, rapid, and precise high-performance liquid chromatography (HPLC) method using ultrafiltration to remove plasma protein was developed to determine meropenem concentrations in human plasma in a clinical setting. Plasma was separated by centrifugation at 4 degrees C from blood collected in heparinized vacuum tubes, and meropenem was stabilized by immediately mixing the plasma with 1M 3-morpholinopropanesulfonic acid buffer (pH 7.0) (1:1). Ultrafiltration was used for plasma deproteinization. Meropenem was detected by ultraviolet absorbance at 300 nm with no interfering plasma peak. The calibration curve of meropenem in human plasma was linear from 0.05 to 100 microg/mL. Intraday and interday precision was less than 7.17% (CV), and accuracy was between 97.7% and 106.3% over 0.05 microg/mL. The limit of detection was 0.01 microg/mL. The assay has been clinically applied to a real-time therapeutic drug monitoring in pediatric patients and pharmacokinetic studies.

Eicosanoid regulation of pulmonary innate immunity post-hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation (HSCT) is a therapeutic option for a number of malignant and inherited disorders. However, the efficacy of this therapy is limited by a number of serious infectious and noninfectious complications. Pulmonary infections represent a significant cause of morbidity and mortality post-HSCT and can occur both pre- and post-hematopoietic reconstitution. Susceptibility to Gram-negative bacterial infections despite full hematopoietic engraftment suggests that innate immunity remains impaired months to years post-HSCT. This review will describe the process and complications of HSCT and will summarize what is known about innate immune reconstitution post-HSCT. Data from the literature as well as our own laboratory will be presented to suggest that an eicosanoid imbalance characterized by over-production of prostaglandins and under-production of leukotrienes leads to impaired lung phagocyte function post-HSCT. Of therapeutic interest, strategies which limit production of prostaglandins can improve pulmonary host defense in animal HSCT models, which suggests that this may also be beneficial for human HSCT recipients.

Comparison of automated strategies for surveillance of nosocomial bacteremia

OBJECTIVE

Surveillance of nosocomial bloodstream infection (BSI) is recommended, but time-consuming. We explored strategies for automated surveillance.

METHODS

Cohort study. We prospectively processed microbiological and administrative patient data with computerized algorithms to identify contaminated blood cultures, community-acquired BSI, and hospital-acquired BSI and used algorithms to classify the latter on the basis of whether it was a catheter-associated infection. We compared the automatic classification with an assessment (71% prospective) of clinical data.

SETTING

An 850-bed university hospital.

PARTICIPANTS

All adult patients admitted to general surgery, internal medicine, a medical intensive care unit, or a surgical intensive care unit over 3 years.

RESULTS

The results of the automated surveillance were 95% concordant with those of classical surveillance based on the assessment of clinical data in distinguishing contamination, community-acquired BSI, and hospital-acquired BSI in a random sample of 100 cases of bacteremia. The two methods were 74% concordant in classifying 351 consecutive episodes of nosocomial BSI with respect to whether the BSI was catheter-associated. Prolonged episodes of BSI, mostly fungemia, that were counted multiple times and incorrect classification of BSI clinically imputable to catheter infection accounted for 81% of the misclassifications in automated surveillance. By counting episodes of fungemia only once per hospital stay and by considering all cases of coagulase-negative staphylococcal BSI to be catheter-related, we improved concordance with clinical assessment to 82%. With these adjustments, automated surveillance for detection of catheter-related BSI had a sensitivity of 78% and a specificity of 93%; for detection of other types of nosocomial BSI, the sensitivity was 98% and the specificity was 69%.

CONCLUSION

Automated strategies are convenient alternatives to manual surveillance of nosocomial BSI.

Bacterial bloodstream infection in neutropenic adult patients after myeloablative cord blood transplantation: experience of a single institution in Japan

Bacterial infection is one of the most important causes of morbidity and mortality after unrelated cord blood transplantation (CBT). In the present study, we studied 101 adult patients with respect to the incidence, outcome, and risk factors for bacterial bloodstream infection (BSI) within 30 days after CBT using a myeloablative conditioning regimen. Bacterial BSI occurred in 12 patients within 30 days after CBT. The cumulative incidence of bacterial BSI was 12%. The median time of onset was day +6 (range, day -1 to day +13) after CBT. In all patients, the neutrophil count was 0/microL at the onset of bacterial BSI. Eight (67%) and 4 (33%) of the isolates were Gram-positive and Gram-negative bacteria, respectively. Only 2 (17%) of the 12 patients who had bacterial BSI died within 100 days after CBT. No risk factors for the occurrence of bacterial BSI within 30 days after CBT were identified. The low mortality rate for bacterial BSI in the neutropenic period appeared to be associated with the low incidence (6%) of transplantation-related death at day +100 in our study patients. Early diagnosis of bacterial BSI and prompt treatment with effective antibiotics are necessary for neutropenic adult patients after myeloablative CBT.

[Guidelines for the diagnosis and treatment of patients with bacteriemia. Guidelines of the Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica]

Bacteremia is a complex clinical syndrome in constant transformation that is an important, growing cause of morbidity and mortality. Even though there is a great deal of specific information about bacteremia, few comprehensive reviews integrate this information with a practical AIM. The main objective of these Guidelines, which target hospital physicians, is to improve the clinical care provided to patients with bacteremia by integrating blood culture results with clinical data, and optimizing the use of diagnostic procedures and antimicrobial testing. The document is structured into sections that cover the epidemiology and etiology of bacteremia, stratified according to the various patient populations, and the diagnostic work-up, therapy, and follow-up of patients with bacteremia. Diagnostic and therapeutic decisions are presented as recommendations based on the grade of available scientific evidence.

Blood stream infection after hematopoietic stem cell transplantation is associated with increased mortality

Blood stream infection (BSI) is a serious complication of hematopoietic stem cell transplantation (HSCT). The aim of this retrospective cohort analysis was to describe BSI after HSCT, and to assess the predictors and outcomes of BSI after HSCT using multivariable modeling. Of the 243 subjects transplanted, 56% received allogeneic HSCT and 106 (43.6%) developed BSI. Of the 185 isolates, 68% were Gram-positive cocci, 21% were Gram-negative bacilli (GNR) and 11% were fungi. Type of allogeneic HSCT was an independent risk factor for BSI (hazard ratio (HR) 3.26, 95% confidence interval (CI) 1.50, 7.07, P = 0.01), as was the degree of HLA matching (HR 1.84, 95% CI 1.00, 3.37, P = 0.05). BSI was a significant independent predictor of mortality after HSCT (HR 1.79, 95% CI 1.18, 2.73, P = 0.007), after adjusting for acute graft-versus-host disease (GVHD) and allogeneic HSCT (both predicting death < or = 3 months after HSCT). In contrast to the effects of acute GVHD and allogeneic HSCT, the effect of BSI was evident throughout the post-HSCT period. GNR BSI and vancomycin-resistant enterococcal BSI also were significantly associated with death. We concluded that BSI is a common complication of HSCT associated with increased mortality throughout the post-HSCT period.

Pseudomonas aeruginosa lipopolysaccharide: a major virulence factor, initiator of inflammation and target for effective immunity

Pseudomonas aeruginosa is one of the most important bacterial pathogens encountered by immunocompromised hosts and patients with cystic fibrosis (CF), and the lipopolysaccharide (LPS) elaborated by this organism is a key factor in virulence as well as both innate and acquired host responses to infection. The molecule has a fair degree of heterogeneity in its lipid A and O-antigen structure, and elaborates two different outer-core glycoforms, of which only one is ligated to the O-antigen. A close relatedness between the chemical structures and genes encoding biosynthetic enzymes has been established, with 11 major O-antigen groups identified. The lipid A can be variably penta-, hexa- or hepta-acylated, and these isoforms have differing potencies when activating host innate immunity via binding to Toll-like receptor 4 (TLR4). The O-antigen is a major target for protective immunity as evidenced by numerous animal studies, but attempts, to date, to produce a human vaccine targeting these epitopes have not been successful. Newer strategies employing live attenuated P. aeruginosa, or heterologous attenuated bacteria expressing P. aeruginosa O-antigens are potential means to solve some of the existing problems related to making a P. aeruginosa LPS-specific vaccine. Overall, there is now a large amount of information available about the genes and enzymes needed to produce the P. aeruginosa LPS, detailed chemical structures have been determined for the major O-antigens, and significant biologic and immunologic studies have been conducted to define the role of this molecule in virulence and immunity to P. aeruginosa infection.

Epidemiology of bacteremia and factors associated with multi-drug-resistant gram-negative bacteremia in hematopoietic stem cell transplant recipients

The incidence of Gram-negative bacteremia has increased in hematopoietic stem cell transplant (HSCT) recipients. We prospectively collected data from 13 Brazilian HSCT centers to characterize the epidemiology of bacteremia occurring early post transplant, and to identify factors associated with infection due to multi-drug-resistant (MDR) Gram-negative isolates. MDR was defined as an isolate with resistance to at least two of the following: third- or fourth-generation cephalosporins, carbapenems or piperacillin-tazobactam. Among 411 HSCT, fever occurred in 333, and 91 developed bacteremia (118 isolates): 47% owing to Gram-positive, 37% owing to Gram-negative, and 16% caused by Gram-positive and Gram-negative bacteria. Pseudomonas aeruginosa (22%), Klebsiella pneumoniae (19%) and Escherichia coli (17%) accounted for the majority of Gram-negative isolates, and 37% were MDR. These isolates were recovered from 20 patients, representing 5% of all 411 HSCT and 22% of the episodes with bacteremia. By multivariate analysis, treatment with third-generation cephalosporins (odds ratio (OR) 10.65, 95% confidence interval (CI) 3.75-30.27) and being at one of the hospitals (OR 9.47, 95% CI 2.60-34.40) were associated with infection due to MDR Gram-negative isolates. These findings may have important clinical implications in the decision of giving prophylaxis and selecting the empiric antibiotic regimen.

Invasive Pseudomonas aeruginosa infections: high rate of recurrence and mortality after hematopoietic cell transplantation

Limited data exist regarding the incidence and factors associated with outcome of invasive Pseudomonal infections in hematopoietic cell transplant (HCT). A retrospective analysis of cases of invasive Pseudomonas aeruginosa infection and factors associated with outcome was performed. P. aeruginosa invasive infection occurred in 95 of 5772 patients (1.65%) a median of 63 days after HCT (range 5-1435). Only 28% of infections occurred during periods of neutropenia (absolute neutrophil count<500 cells/mm(3)). Infection-attributable mortality during the initial episode of infection was 35.8%. Factors associated with initial mortality included the presence of a copathogen and high-dose steroid use. Ten (16.4%) of those who survived the initial infection experienced a recurrence of P. aeruginosa infection at a median of 9 days (range 3-17) after stopping antibiotics and 60% of those died as a result of recurrent infection a median of 1 day (range 1-7) after onset of recurrence. Grade 3-4 graft-versus-host disease was associated with a higher risk of recurrent infection. The risk of recurrence was not influenced by the presence of copathogens. Thus, invasive P. aeruginosa infections are associated with high recurrence rates and mortality in this immunocompromised population. Aggressive attempts to reduce immunosuppression and to treat copathogens may help during the initial infection.

Pulmonary complications of haematopoietic cell transplantation in children

Paediatric haematopoietic cell transplantation has experienced significant advances in the last few decades. However, pulmonary complications are an important limitation to the efficacy of this intervention, contributing to post-transplantation morbidity and mortality. Such complications persist even in experienced centres and occur in adult and paediatric recipients. This review identifies the paediatric pulmonary complications that are commonly seen following haematopoietic cell transplantation and addresses both infectious and non-infectious aetiologies and their clinical manifestations, evaluation, and potential therapy. Ultimately, improvement in outcomes will require attention to immunosuppression as well as traditional diagnostic procedures and treatment. This article aims to review the current state of pulmonary complications post-transplantation, to examine the impact of our recent advances and changes in treatment, and to identify potential future therapies and hypothesise what role these might have on long-term survival.

Critical Role of Prostaglandin E2Overproduction in Impaired Pulmonary Host Response following Bone Marrow Transplantation

The success of bone marrow transplantation (BMT) as a therapy for malignant and inherited disorders is limited by infectious complications. We previously demonstrated syngeneic BMT mice are more susceptible to Pseudomonas aeruginosa pneumonia due to defects in the ability of donor-derived alveolar macrophages (AMs), but not polymorphonuclear leukocytes (PMNs), to phagocytose bacteria. We now demonstrate that both donor-derived AMs and PMNs display bacterial killing defects post-BMT. PGE2 is a lipid mediator with potent immunosuppressive effects against antimicrobial functions. We hypothesize that enhanced PGE2 production post-BMT impairs host defense. We demonstrate that lung homogenates from BMT mice contain 2.8-fold more PGE2 than control mice, and alveolar epithelial cells (2.7-fold), AMs (125-fold), and PMNs (10-fold) from BMT animals all overproduce PGE2. AMs also produce increased prostacyclin (PGI2) post-BMT. Interestingly, the E prostanoid (EP) receptors EP2 and EP4 are elevated on donor-derived phagocytes post-BMT. Blocking PGE2 synthesis with indomethacin overcame the phagocytic and killing defects of BMT AMs and the killing defects of BMT PMNs in vitro. The effect of indomethacin on AM phagocytosis could be mimicked by an EP2 antagonist, AH-6809, and exogenous addition of PGE2 reversed the beneficial effects of indomethacin in vitro. Importantly, in vivo treatment with indomethacin reduced PGE2 levels in lung homogenates and restored in vivo bacterial clearance from the lung and blood in BMT mice. Genetic reduction of cyclooxygenase-2 in BMT mice also had similar effects. These data clearly demonstrate that overproduction of PGE2 post-BMT is a critical factor determining impaired host defense against pathogens.

Coincidental outbreak of methicillin-resistant Staphylococcus aureus in a hematopoietic stem cell transplantation unit

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most common nosocomial pathogens among hospital-acquired infections, and immunocompromised patients are highly susceptive to infection. The molecular typing of isolated strains is a common method for tracing an outbreak of MRSA, but experience with this approach is still limited in the hematopoietic stem cell transplantation (HSCT) ward.

METHODS

We experienced 6 cases of MRSA infection/colonization in our 26-bed HSCT ward during a 4-week period. This unusual outbreak strongly suggested that the same MRSA strain was involved despite strict isolation and aseptic patient care. Clarification of the transmission pattern was critical, and we applied pulsed-field gel electrophoresis (PFGE) and amplified fragment length polymorphism (AFLP) assays for evaluation.

RESULTS AND CONCLUSION

In four of the six cases, the pattern of bands examined by PFGE and AFLP analyses supported the idea that direct person-to-person transmission was very unlikely and the outbreak was coincidental. This experience highlights the clinical value of molecular typing methods for the clinical epidemiological assessment of MRSA outbreak.

Bacteria commonly isolated from keratitis specimens retain antibiotic susceptibility to fluoroquinolones and gentamicin plus cephalothin

PURPOSE

Patients presenting with presumed infective keratitis were studied to determine predisposing factors, the current susceptibilities of the bacterial isolates to a range of relevant antibiotics, the success rate of topical antibiotic treatment of keratitis and predictors of failure of topical therapy.

METHODS

Corneal scrapings taken from patients who presented between January 2002 and December 2003 to the Sydney Eye Hospital Emergency Department with keratitis were cultured. The minimum inhibitory concentration of selected antibiotics was determined for each bacterial isolate using an agar dilution technique.

RESULTS

One hundred and twelve consecutive patients presented with corneal ulcers. Forty-seven of the 112 (42%) patients had a growth from the corneal scraping. Potential predisposing factors were identified in 64% of patients, most frequently contact lens wear (36% of patients). Coagulase-negative staphylococci were the most common species isolated. Other common organisms isolated include Pseudomonas aeruginosa, Corynebacterium spp., Staphylococcus aureus and Streptococcus spp.

CONCLUSIONS

Most microorganisms isolated from patients with bacterial keratitis showed susceptibility to ciprofloxacin and aminoglycosides. Cephalothin plus aminoglycoside constituted an effective initial broad-spectrum antibiotic combination. The success rate of topical antibiotic treatment of corneal abscess is 89%. Predictors of failure include older age group, medium or large ulcer, culture-negative keratitis, hypopyon and poor visual acuity.

Current trends of infectious complications following hematopoietic stem cell transplantation in a single center

This study was to analyze the infectious complications after hematopoietic stem cell transplantation (HSCT) according to the recent changes of HSCT. Medical records of 379 adult patients who underwent HSCT consecutively at Catholic HSCT Center from January 2001 to December 2002 were reviewed retrospectively. Allogeneic HSCT accounted for 75.7% (287/379) and autologous HSCT for 24.3% (92/379). During pre-engraftment period, bacterial infection was predominant, and E. coli was still the most common organism. After engraftment, viral infection was predominant. The incidence of invasive fungal infection showed bimodal distribution with peak correlated with neutropenia and graft-versus-host disease (GVHD). The overall mortality and infection-related mortality rates according to 3 periods were as follows; during pre-engraftment, 3.16% (12/379) and 1.8% (7/379); during midrecovery period, 7.9% (29/367) and 4.1% (15/367); during late-recovery period, 26.9% (91/338), and 15.9% (54/338). Risk factors for infection-related mortality were as follows; during pre-engraftment period, fungal infection and septic shock; during the mid-recovery period, hemorrhagic cystitis and delayed engraftment; during the late-recovery period, fungal infection, chronic GVHD, and relapse. In conclusion, infection was still one of the main complications after HSCT and highly contributes to mortality. The early diagnosis and the effective vaccination strategy are needed for control of infections.

Bacteremias: a leading cause of death

Bloodstream infections (BSIs), recognized to be a major cause of morbidity and mortality globally, are increasing in incidence. The reported rates of crude and attributable mortality vary, possibly due to heterogeneity in patient populations and methodology. Few studies, however, have focused on pathogen-specific attributable mortality. These studies include S. aureus, coagulase-negative staphylococci and enterococcus. Other studies of attributable mortality have been conducted in select populations such as nosocomial and community-acquired cohorts, intensive care units, neutropenic patients, and HIV-positive patients. Regrettably, despite advances in treatment and intensive care facilities, mortality remains high.

Bloodstream Infections among Heart Transplant Recipients

BACKGROUND

Heart transplant (HT) recipients are prone to life-threatening infections, including bloodstream infection (BSI), but information on this topic is particularly scarce.

METHODS

We studied 309 consecutive HT performed at our institution between 1988 and 2003. We assessed the characteristics of each episode of BSI, prophylaxis and immunosuppression used, and possible related factors.

RESULTS

Sixty episodes of BSI occurred in 15.8% of all HT recipients. Rates of BSI/transplanted patient decreased progressively throughout the study period: 21.2%, 14.3%, and 7.5% in each 5-year period (P=0.03). BSI episodes occurred a median of 51 days after transplantation. The main BSI origins were: lower respiratory tract (23%), urinary tract (20%), and catheter-related-BSI (16%). Gram-negative organisms predominated (55.3%), followed by Gram-positive (44.6%). Mortality was 59.2%, with 12.2% directly attributable to BSI. Independent risk factors for BSI after HT were: hemodialysis (OR 6.5; 95% CI 3.2-13), prolonged intensive care unit stay (OR 3.6; 95% CI 1.6-8.1), and viral infection (OR 2.1; 95% CI 1.1-4). BSI was a risk factor for mortality (OR 1.8; 95% CI 1.2-2.8).

CONCLUSION

BSIs have decreased in HT recipients, but still contribute to mortality, mainly if related to pneumonia or polymicrobial infections. Reduction of early postoperative complications and viral infections are amenable goals that may further reduce BSI in this population.

Vancomycin tolerance, a potential mechanism for refractory gram-positive bacteremia observational study in patients with cancer

BACKGROUND

The clinical significance of infections caused by vancomycin-tolerant (Vt) gram-positive organisms in patients with cancer remains unclear.

METHODS

Twenty-five patients with nonenterococcal gram-positive bloodstream infection, which was refractory to vancomycin therapy, were identified by reviewing the Infectious Diseases consultation database at the tertiary care cancer center. Among these, 8 patients in whom vancomycin-tolerance was documented are described. Antibiotic tolerance was defined as a > 32 times increase in minimum bactericidal concentration compared with minimum inhibitory concentration.

RESULTS

Eight patients with persistent fever and bacteremia of > 72 hours' duration after the initiation of vancomycin therapy were treated. The median age of these patients, which included 3 men and 5 women, was 44 years +/- 11 years. Solid tumors were more common (6 patients) and 2 patients had acute leukemia. Six patients (75%) were neutropenic (absolute neutrophil count < 500/mm3), including 2 breast cancer patients who had undergone autologous stem cell transplantation. The causative organisms were Staphylococcus aureus (n = 3 patients), group G streptococci (n = 2 patients), and Staphylococcus epidermidis, Streptococcus mitis, and Streptococcus sanguis (1 patient each). All isolates demonstrated a minimum bactericidal concentration for vancomycin that was at least 32 times greater than the minimum inhibitory concentration. Rapid defervescence (< or = 24 h) and resolution of bacteremia occurred with the addition of gentamicin (4 patients) or gentamicin plus rifampin (4 patients). None of these infections recurred after discontinuation of therapy.

CONCLUSIONS

Lack of clinical and/or microbiologic response to vancomycin should raise the suspicion of possible infection due to Vt gram-positive bacteria, and alternative bactericidal therapy should be instituted early, especially in patients with underlying immune suppression.

Treatment and control of severe infections caused by multiresistant Pseudomonas aeruginosa

Pseudomonas aeruginosa is one of the leading causes of nosocomial infections. Severe infections, such as pneumonia or bacteraemia, are associated with high mortality rates and are often difficult to treat, as the repertoire of useful anti-pseudomonal agents is limited (some beta-lactams, fluoroquinolones and aminoglycosides, and the polymyxins as last-resort drugs); moreover, P. aeruginosa exhibits remarkable ability to acquire resistance to these agents. Acquired resistance arises by mutation or acquisition of exogenous resistance determinants and can be mediated by several mechanisms (degrading enzymes, reduced permeability, active efflux and target modification). Overall, resistance rates are on the increase, and may be different in different settings, so that surveillance of P. aeruginosa susceptibility is essential for the definition of empirical regimens. Multidrug resistance is frequent, and clinical isolates resistant to virtually all anti-pseudomonal agents are increasingly being reported. Monotherapy is usually recommended for uncomplicated urinary tract infections, while combination therapy is normally recommended for severe infections, such as bacteraemia and pneumonia, although, at least in some cases, the advantage of combination therapy remains a matter of debate. Antimicrobial use is a risk factor for P. aeruginosa resistance, especially with some agents (fluoroquinolones and carbapenems), and interventions based on antimicrobial rotation and restriction of certain agents can be useful to control the spread of resistance. Similar measures, together with the prudent use of antibiotics and compliance with infection control measures, are essential to preserve the efficacy of the currently available anti-pseudomonal agents, in view of the dearth, in the near future, of new options against multidrug-resistant P. aeruginosa strains.

Bloodstream infection after umbilical cord blood transplantation using reduced-intensity stem cell transplantation for adult patients

Bloodstream infection (BSI) is a significant problem after cord blood transplantation (CBT). However, little information has been reported on BSI after reduced-intensity CBT (RI-CBT). We retrospectively reviewed the medical records of 102 patients. The median age of the patients was 55 years (range, 17-79 years). Preparative regimens comprised fludarabine 125 to 150 mg/m 2 , melphalan 80 to 140 mg/m 2 , or busulfan 8 mg/kg and total body irradiation 2 to 8 Gy. Prophylaxis against graft-versus-host disease comprised cyclosporin or tacrolimus. BSI developed within 100 days of RI-CBT in 32 patients. The cumulative incidence of BSI was 25% at day 30 and 32% at day 100. The median onset was day 15 (range, 1-98 days). Causative organisms included Pseudomonas aeruginosa (n = 12), Staphylococcus epidermidis (n = 11), Staphylococcus aureus (n = 6), Enterococcus faecium (n = 4), Enterococcus faecalis (n = 4), Stenotrophomonas maltophilia (n = 4), and others (n = 7). Of the 32 patients with BSI, 25 (84%) died within 100 days after RI-CBT. BSI was the direct cause of death in 8 patients (25%). Univariate analysis failed to identify any significant risk factors. BSI clearly represents a significant and fatal complication after RI-CBT. Further studies are warranted to determine clinical characteristics, identify patients at high risk of BSI, and establish therapeutic strategies.

Pre- and post-engraftment bloodstream infection rates and associated mortality in allogeneic hematopoietic stem cell transplant recipients

We report on bloodstream infection (BSI) rates, risk factors, and outcome in a cohort of 298 adult and pediatric hematopoietic stem cell transplantation (HSCT) recipients at Memorial Sloan-Kettering Hospital from September 1999 through June 2003. Methods. Prospective surveillance study. BSI rates are reported per 10,000 HSCT days. Date of engraftment is defined as the first of at least 3 consecutive dates of absolute neutrophil count >500/mm(3) after stem cell infusion. BSI severity grades: severe (intravenous antibiotics), life threatening (sepsis), or fatal (caused or contributed to death). Results. The incidence of pre- and post-engraftment BSI was 22% and 19.5%, respectively. Pre-engraftment highest rates were observed for viridans streptococci (58), Enterobacteriaceae (39), and Enterococcus faecium (34). Post-engraftment rates ranged from 0.2 to 2.9 without any predominant pathogen. In multivariate analyses, pre-engraftment BSI was associated with diagnosis of chronic myelogenous leukemia, age >18 years and peripheral blood stem cell graft; post-engraftment BSI was associated with acute graft-versus-host disease, neutropenia, and liver or kidney dysfunction. Attributable mortality was 12.5% and 1.7% for pre- and post-engraftment BSI, respectively. BSI fatality rates were 24% for viridans streptococci, 8% for E. faecium, 11% for Staphylococcus aureus, and 67% for Candida. Conclusions. Pre-engraftment BSI, especially by viridans streptococci and E. faecium, was associated with substantial attributable mortality. Post-engraftment BSI was a marker of post-transplant complications and rarely the primary cause of death.

A safety evaluation of drotrecogin alfa (activated) in hematopoietic stem cell transplant patients with severe sepsis: lessons in clinical research

We conducted an open-label, multicenter, single-arm clinical trial to investigate the safety and efficacy of drotrecogin alfa (activated) (Drot AA) in hematopoietic stem cell transplant (HSCT) patients with severe sepsis. Drot AA was administered as a continuous i.v. infusion of 24 microg/kg/h for 96 h. The target enrollment was 250 patients in 15-20 transplant centers over a 2-year period (March 2003-March 2005). However, after only 10 months, in December 2003, the trial was stopped due to a low enrollment of seven patients at three of the 15 sites that were open for accrual. Six of the seven patients completed the drug infusion. Two patients experienced serious bleeding events. The first patient developed a nonfatal diffuse alveolar hemorrhage 2 days after study-drug completion. The second patient had severe coagulopathy and developed a fatal intracranial hemorrhage on the third day of drug infusion. Three of the seven patients were alive 100 days after the HSCT. The slow enrollment rate was attributed to changes in transplant preparatory regimens, enhancements in antimicrobial prophylactic protocols and the use of antimicrobial-coated catheters. The small number of patients in this report precludes a definitive assessment of the safety and efficacy of Drot AA in HSCT patients.

Early bacteremia in pediatric hematopoietic stem cell transplant patients on oral antibiotic prophylaxis

BACKGROUND

Bacteremia occurs during hematopoietic stem cell transplant (HSCT) in 20%-25% of patients and the use of gut decontamination (GD) to decrease this risk is controversial. Our purpose was to determine the incidence of bacteremia and antimicrobial resistance post-HSCT in pediatric patients receiving GD, and to identify risk factors associated with infection.

PROCEDURES

This was a retrospective cohort study of 182 pediatric patients undergoing first HSCT for malignant disease at The Children's Hospital of Philadelphia from January, 1999 to December, 2002. We examined the impact of age, sex, race, diagnosis, disease status, conditioning regimen, recent bacteremia, stem cell source, donor, graft versus host disease prophylaxis agents, and mucositis severity using Cox proportional hazard models. GD consisted of amoxicillin (azithromycin, if penicillin allergic) and oral gentamicin. Outcome was first episode of bacteremia prior to absolute neutrophil count (ANC) 500/mm(3). Antibiotic susceptibilities were performed on all isolates.

RESULTS

Seventy-four patients (41%) developed bacteremia. The majority were Gram-positive cocci, with Staphylococcal (50%) and Streptococcal species (28%) the most common. Gram-negative organisms were identified in 22% with Pseudomonas (5.7%) and Klebsiella species (3.4%) the most common. Of the Streptococcal infections, 72% were resistant to ampicillin; only 25% of the Gram-negative bacteria were resistant to gentamicin. Race was the only factor associated with early bacteremia (hazard ratio 2.3 for non-Caucasian, non-African-American patients, CI 1.3-4.3, P = 0.007).

CONCLUSIONS

Early bacteremia is common after HSCT, despite the use of GD. Resistant Gram-positive organisms predominate, consistent with recent trends in immunocompromised patients. Although used in practice, there is no clear evidence for the efficacy of GD and this study provides the basis upon which to develop a randomized clinical trial evaluating the current GD regimen with placebo.

Long-term follow-up of patients treated at home during the pancytopenic phase after allogeneic haematopoietic stem cell transplantation

To prevent neutropenic infections, patients are kept in isolation rooms after allogeneic haematopoietic stem cell transplantation (ASCT). Patients living within one hours' driving distance from our unit were given the opportunity of treatment at home after ASCT during the pancytopenic phase. We compared 36 patients treated at home during March 1998 until December 2000, with 54 controls treated in the hospital during September 1995 and September 2001. The incidence of grades II-IV acute graft-versus-host disease (GVHD) was lower in the home care group compared to the controls, that is, 17 vs 44% (P < 0.01). The cumulative incidence of chronic GVHD was 52% in the home care group, compared to 57% in the controls. Transplant-related mortality (TRM) was 13% in the home care patients vs 44% in the controls (P = 0.002). The probability of relapse was similar in the two groups. The 4-year survival was 63% in the home care patients compared to 44% in the controls (P = 0.04). Home care after ASCT is a novel approach that resulted in less TRM, similar incidence of chronic GVHD and relapse, and improved long-term survival compared to controls treated in the hospital.

Value of surveillance blood culture for early diagnosis of occult bacteremia in patients on corticosteroid therapy following allogeneic hematopoietic stem cell transplantation

Bloodstream infection (BSI) is a significant complication following allogeneic hematopoietic stem cell transplantation (allo-SCT). Corticosteroids mask inflammatory responses, delaying the initiation of antibiotics. We reviewed medical records of 69 allo-SCT patients who had been on >0.5 mg/kg prednisolone to investigate the efficacy of weekly surveillance blood cultures. A total of 36 patients (52%) had positive cultures, 25 definitive BSI and 11 probable BSI. Pathogens in definitive BSI were Staphylococcus epidermidis (n=7), S. aureus (n=4), Entrococcus faecalis (n=3), Pseudomonas aeruginosa (n=5), Acenitobacter lwoffii (n=4), and others (n=10). The median interval from the initiation of corticosteroids to the first positive cultures was 24 days (range, 1-70). At the first positive cultures, 15 patients with definitive BSI were afebrile. Four of them remained afebrile throughout the period of positive surveillance cultures. Patients with afebrile BSI tended to be older (P=0.063), and had in-dwelling central venous catheters less frequently than febrile patients (P<0.0001). Bloodstream pathogens were directly responsible for death in two patients with afebrile BSI. This study demonstrates that cortisosteroid frequently masks inflammatory reactions in allo-SCT recipients given conrticosteroids, and that surveillance blood culture is only diagnostic clue for 'occult' BSI.

Perspectives for the management of febrile neutropenic patients with cancer in the 21st century

Over the past several decades, there has been substantial progress in the management of patients with febrile neutropenia. However, the ever-changing patterns of infection, ecology, and antibiotic-resistance trends do not allow the development of treatment guidelines that could be applied universally. Hence, the institution's predominant pathogens and resistance patterns should guide the empirical choice of antimicrobials. Prompt initiation of antimicrobial therapy remains the gold standard. Monotherapy with the newer broad-spectrum antimicrobials has tended to replace the classic combination therapy. Empirical administration of glycopeptides, such as vancomycin, without documentation of a gram-positive infection is not favored. The development of risk-stratification models has allowed for identification of low-risk patients with additional treatment options, such as early discharge and exclusively outpatient treatment with oral antimicrobials. The initiation of empirical antifungal therapy in persistently febrile neutropenic patients has become common practice, especially recently, since the introduction of new, effective, less toxic antifungal drugs. It is hoped that the development of new nonculture-based diagnostic methods will allow for the early detection of invasive fungal infections and, thus, the replacement of empirical antifungal therapy with pathogen-specific, preemptive therapy.

Infections in Patients with Febrile Neutropenia: Epidemiology, Microbiology, and Risk Stratification

Determinations of the type and setting of empirical therapy for immunocompromised patients with fever are complicated by the characteristics of the underlying illness and the effects of treatments already received, as well as by changing microbiological patterns and trends in drug resistance at national and institutional levels. Several systems have been proposed to distinguish patients who could benefit from outpatient antibiotic therapy from patients who require hospitalization. Practical considerations may decide whether the necessary monitoring during the period of neutropenia can be achieved.

Cord blood transplantation in adult patients

Early clinical reports outlining outcomes for primarily pediatric patients undergoing UCB transplantation point to delayed time to hematopoietic recovery and favorable incidence and severity of GvHD. Recently, clinical reports in adult patients identified the feasibility of UCB transplantation for those patients lacking an available histocompatible-related or unrelated adult donor Intensive clinical and laboratory research is ongoing focused on strategies to foster UCB allogeneic donor engraftment thereby allowing wider application of this stem cell source for patients requiring allogeneic transplantation.

Bacterial infections in low-risk, febrile neutropenic patients

BACKGROUND

Accurate identification of low-risk, febrile neutropenic patients has become possible only recently. Many such patients are treated with oral antibiotics without hospitalization. To the authors' knowledge, data concerning the spectrum of bacterial infections in these patients are scarce, and collecting such data may have an impact on the choice of empiric oral regimen(s).

METHODS

Using the same risk-prediction and eligibility criteria, four studies of empiric therapy in low-risk, febrile neutropenic patients were conducted at the authors' institution. Based on that experience, patients also were entered on clinical pathways for outpatient therapy. For the current study, microbiologic data were pooled from those trials and clinical pathways (757 episodes) to describe the nature and spectrum of infections seen in this setting.

RESULTS

Unexplained fever occurred most often (58% of episodes), and both clinically documented and microbiologically documented infections were seen with equal frequency (21% of episodes, respectively). The most common clinical sites of infection were the upper respiratory tract, skin, and skin structure. Among microbiologically documented infections, monomicrobial, gram-positive infections accounted for 49% (with coagulase-negative staphylococci the most frequent); monomicrobial, gram-negative infections accounted for 36% (with Escherichia coli the most frequent); and 15% of infections were polymicrobial.

CONCLUSIONS

In this description of the spectrum of infections in the largest cohort of low-risk febrile neutropenic patients to date, episodes of unexplained fever were predominant, but gram-positive, gram-negative, and polymicrobial infections also were documented. Although these patients were at low risk for complications, they required broad-spectrum antibiotic therapy when they developed neutropenic fever.

Occurrence and antimicrobial resistance pattern comparisons among bloodstream infection isolates from the SENTRY Antimicrobial Surveillance Program (1997-2002)

The empiric treatment of patients with bloodstream infections (BSI) has become more complicated in an era of increasing antimicrobial resistance. The SENTRY Antimicrobial Surveillance Program has monitored BSI from patients in medical centers worldwide since 1997. During 1997-2002, a total of 81,213 BSI pathogens from North America, Latin America, and Europe were tested for antimicrobial susceptibility. S. aureus, E. coli, and coagulase-negative staphylococci were the three most common BSI pathogens in all three regions each year. Prevalence variability was noted in regions for some species, including higher rates of isolation of E. coli in Europe, Enterococcus spp. in North America, and Gram-negative enteric and nonenteric species in Latin America. Patient age analysis showed the most common BSI pathogen among neonates was coagulase-negative staphylococci and among elderly patients, E. coli. Resistance among BSI pathogens was much more prevalent in nosocomial infections and in patients in intensive care units (ICUs); age differences were also noted. Geographically, oxacillin-resistant S. aureus (39.1%, 2002) and vancomycin-resistant enterococci (17.7%, 2002) were highest in North America, and extended-spectrum beta-lactamase-producing Klebsiella spp. (35.8-46.7%) and multidrug-resistant P. aeruginosa (18.7%, 2002) were highest in Latin America. Activity of commonly used antimicrobial agents remained relatively stable in North America, except in the case of vancomycin-resistant enterococci (20% decline between 1997 and 2002). An epidemiologic investigation of oxacillin-resistant S. aureus in North America identified 10 significant clones (ribotypes) and the common resistance patterns associated with them. Surveillance of BSI pathogens is needed to determine trends of resistance and provide useful information regarding patient risk factors and geographic differences.

Predictive value of isolating Pseudomonas aeruginosa from aerobic and anaerobic blood culture bottles

Pseudomonas aeruginosa is a particularly virulent pathogen when it causes bacteraemia and early diagnosis is essential to reduce morbidity and mortality. It is an aerobe and is thought by many to be almost exclusively isolated from the aerobic blood culture bottle in cases of bacteraemia. This study analysed 277 Gram-negative bacteraemic episodes over 1 year at a single institution in order to assess the predictive value of this finding. In 39 of 44 episodes of P. aeruginosa bacteraemia, the organism was isolated from the aerobic bottle only, which gave a sensitivity of 88.6 % for this 'test' and a specificity of 73.8 %. However, for all episodes of Gram-negative bacteraemia, the likelihood of a Gram-negative bacillus occurring in the aerobic bottle first being P. aeruginosa was only 39 %. The converse finding of a Gram-negative bacillus isolated first in the anaerobic bottle or from both bottles together was clinically helpful, having a negative predictive value of 97.2 % (i.e. that the organism was not P. aeruginosa).

Bacterial and fungal bloodstream isolates from 796 hematopoietic stem cell transplant recipients between 1991 and 2000

To examine shifts in the etiology, incidence, evolution, susceptibility, and patient mortality of bacterial and fungal bloodstream isolates (BSIs) from hematopoietic stem cell transplantation (HSCT) recipients, we reviewed the BSIs of 796 patients who underwent an HSCT in our institution during a 10-year period. Four hundred eighty-nine episodes of bacterial and fungal BSI were detected in 330 patients (41%). Three hundred ten isolates (63%) were gram-positive bacteria, 142 (29%) were gram-negative, and 18 and 19 isolates were different species of anaerobic organism and Candida spp. (both 4%). Coagulase-negative staphylococci (CoNS), with 210 isolates, were the organism most frequently isolated in each year of study and during the three phases of immune recovery after HSCT. The ratio of gram-positive to gram-negative has declined from 3.3 (1991-1992) to 1.8 (1999-2000). Crude mortality occurred in 47 cases of 489 BSI episodes (10%). Mortality according to groups was gram-negative, 7%; gram-positive, 9%; and anaerobic bacteria, 11%. Candida spp. was the group that accounted for the highest crude mortality, with 42%. Gram-positive microorganisms were isolated more often than gram-negative organisms, but the trend is reversing. CoNS were the leading pathogen during the 10 years of study and during the three phases of immune recovery after HSCT. Crude mortality of HSCT patients with BSI was low except for infections caused by Candida spp.

Infections among allogeneic bone marrow transplant recipients in India

SUMMARY

Infections are a major cause of morbidity and mortality in patients undergoing high-dose therapy and allogeneic bone marrow transplantation (BMT) despite prophylaxis, use of growth factors and newer antimicrobial drugs. We report the clinical profile of infections among 297 patients who underwent 304 allogeneic transplants between 1986 and December 2001. All patients developed febrile neutropenia. There were 415 documented infections among 304 transplants. This included bacterial (34.9%), viral (42.9%), fungal (15.9%) and other infections (6.3%) including tuberculosis. Bacterial pathogens were mainly Gram-negative bacteria (80%) as compared to Gram-positive (20%) bacteria. The common Gram-negative bacteria were nonfermenting Gram-negative bacteria (NFGNB) (24.9%), Pseudomonas (17.9%), Escherichia coli (17.9%) and Klebsiella (9.7%). The major source of positive cultures was blood (53.7%) followed by urine (25.5%) and sputum (8.9%). In all, 133/304 (43.7%) transplants had 178 documented viral infections. The common viral infections were due to cytomegalovirus, herpes group of viruses and transfusion-related hepatitis; and 60/304 (19.7%) transplants had 66 documented fungal infections. Common fungi included Aspergillus species (69.7%), Candida (22.2%) and Zygomycetes (8.1%). Tuberculosis was documented in 2.3% of the transplants. Catheter infections were suspected or documented in 7.8% of the transplants (24/304). The incidence of infections in this series from developing countries is not significantly different from reports from the West. Bone Marrow Transplantation (2004) 33, 311-315. doi:10.1038/sj.bmt.1704347 Published online 1 December 2003

Changes in the etiology of bacteremia in febrile neutropenic patients and the susceptibilities of the currently isolated pathogens

The etiology of bacteremia in febrile neutropenic patients in the past few decades has shifted from gram-negative to gram-positive organisms. Potential reasons include the use of indwelling catheters, local environmental conditions, and the administration of specific antibiotic agents, especially as prophylaxis. Other factors may emerge from new studies, such as the categorization of febrile neutropenic patients into groups at low risk and at high risk of developing serious complications, continuing changes in resistance in the community, the use of antibiotic-coated catheters, and future changes in cytotoxic chemotherapy or antineoplastic therapy. In addition, there has been a drift in susceptibility patterns, with resistance issues seen in the general population of hospitalized patients now emerging in febrile neutropenic patients, as well as some issues specific to these patients. These changes affect empirical therapy as it was practiced a decade ago. Among the most commonly used agents, cefepime and carbapenems continue to show the highest rates of in vitro susceptibility, providing coverage against most gram-positive and gram-negative organisms and reducing the need for glycopeptides. Older agents continue to show degradation of their effectiveness. Among Pseudomonas aeruginosa strains, susceptibility to all agents continues to decline.

Influence of Selective Bowel Decontamination on the Organisms Recovered During Bacteremia in Neutropenic Patients

Objective:

To assess the influence of prophylactic selective bowel decontamination (SBD) on the spectrum of microbes causing bloodstream infection (BSI).

Design:

The microbes causing BSI in neutropenic patients of a hematologic ward (HW) and a bone marrow transplantation unit (BMTU), respectively, were compared by retrospective analysis of blood culture results from January 1996 to June 2003.

Setting:

A 30-bed HW (no SBD) and a BMTU including a 7-bed normal care ward and an 8-bed intensive care unit (SBD used) of a 2,200-bed university teaching hospital.

Results:

The overall incidences of bacteremia in the HW and the BMTU were similar (72.6 vs 70.6 episodes per 1,000 admissions; P = .8). Two hundred twenty episodes of BSI were recorded in 164 neutropenic patients of the HW and 153 episodes in 127 neutropenic patients of the BMTU. Enterobacteriaceae (OR, 3.14; CI95, 1.67–5.97; P = .0002) and Streptococcus species (OR, 2.04; CI95, 1.14–3.70; P = .015) were observed more frequently in HW patients and coagulase-negative staphylococci more frequently in BMTU patients (OR, 0.15; CI95, 0.09–0.26; P< .00001). No statistically significant differences were found for gram-negative nonfermentative bacilli (P = .53), Staphylococcus aureus (P = .21), Enterococcus species (P = .48), anaerobic bacteria (P = .1), or fungi (P = .50).

Conclusions:

SBD did not lead to a significant reduction in the incidence of bacteremia, but significant changes in microbes recovered from blood cultures were observed. SBD should be considered when empiric antimicrobial therapy is prescribed for suspected BSI.

Teicoplanin in patients with acute leukaemia and febrile neutropenia: a special population benefiting from higher dosages

OBJECTIVE

To define the optimal dosage regimen of teicoplanin that ensures early therapeutically relevant trough concentrations (C(min)) [>10 mg/L at 24 hours and possibly close to 20 mg/L at 48 hours] in patients with acute leukaemia who develop febrile neutropenia after chemotherapy.

DESIGN

Prospective observational pharmacokinetic study.

PARTICIPANTS

Adult patients (n = 33) with normal renal function previously treated with antineoplastic chemotherapy because of acute lymphocytic or acute nonlymphocytic leukaemia, and subsequently developing febrile neutropenia treated with empirical antimicrobial therapy.

DESIGN

First, the standard dosage group (n = 11) was administered standard loading and maintenance doses of teicoplanin (400 mg every 12 hours for three doses followed by 400 mg once daily). Blood samples were collected at defined times as part of routine monitoring and assessed for teicoplanin plasma concentration by fluorescence polarisation immunoassay. Secondly, the high dosage group (n = 22) received a high loading regimen (800 + 400 mg 12 hours apart on day 1, 600 + 400mg 12 hours apart on day 2) followed by a high maintenance regimen (400 mg every 12 hours) from day 3 on.

RESULTS

In the standard dosage group, no patient had the recommended teicoplanin C(min) of >or=10 mg/L within the first 72 hours, and only five of the 11 patients (45%) had a C(min) of >or=10 mg/L after 120 hours. No patient had a C(min) of >or=20 mg/L. In the high dosage group, teicoplanin C(min) averaged >or=10 mg/L within 24 hours, and this value was achieved within 48 hours in all but one patient. Of note, C(min) at 72 hours exceeded 20 mg/L in ten of the 22 patients (45%). No patient experienced significant impairment of renal function.

CONCLUSIONS

In this patient group, therapeutically relevant C(min) may be achieved very early in the treatment period with loading doses of 12 mg/kg and 6 mg/kg 12 hours apart on day 1, and 9 mg/kg and 6 mg/kg 12 hours apart on day 2, regardless of renal function. Subsequently, in patients with normal renal function a maintenance dosage of 6 mg/kg every 12 hours may be helpful in ensuring C(min) close to 20 mg/L. Assessment of C(min) after 48-72 hours may be useful to individualise teicoplanin therapy. Factors increasing volume of distribution and/or renal clearance of teicoplanin (fluid load, hypoalbuminaemia, leukaemic status) may explain the need for higher dosages.

Nosocomial bloodstream infections in US hospitals: analysis of 24,179 cases from a prospective nationwide surveillance study

BACKGROUND

Nosocomial bloodstream infections (BSIs) are important causes of morbidity and mortality in the United States.

METHODS

Data from a nationwide, concurrent surveillance study (Surveillance and Control of Pathogens of Epidemiological Importance [SCOPE]) were used to examine the secular trends in the epidemiology and microbiology of nosocomial BSIs.

RESULTS

Our study detected 24,179 cases of nosocomial BSI in 49 US hospitals over a 7-year period from March 1995 through September 2002 (60 cases per 10,000 hospital admissions). Eighty-seven percent of BSIs were monomicrobial. Gram-positive organisms caused 65% of these BSIs, gram-negative organisms caused 25%, and fungi caused 9.5%. The crude mortality rate was 27%. The most-common organisms causing BSIs were coagulase-negative staphylococci (CoNS) (31% of isolates), Staphylococcus aureus (20%), enterococci (9%), and Candida species (9%). The mean interval between admission and infection was 13 days for infection with Escherichia coli, 16 days for S. aureus, 22 days for Candida species and Klebsiella species, 23 days for enterococci, and 26 days for Acinetobacter species. CoNS, Pseudomonas species, Enterobacter species, Serratia species, and Acinetobacter species were more likely to cause infections in patients in intensive care units (P<.001). In neutropenic patients, infections with Candida species, enterococci, and viridans group streptococci were significantly more common. The proportion of S. aureus isolates with methicillin resistance increased from 22% in 1995 to 57% in 2001 (P<.001, trend analysis). Vancomycin resistance was seen in 2% of Enterococcus faecalis isolates and in 60% of Enterococcus faecium isolates.

CONCLUSION

In this study, one of the largest multicenter studies performed to date, we found that the proportion of nosocomial BSIs due to antibiotic-resistant organisms is increasing in US hospitals.

Kinetics of myeloid and lymphocyte recovery and infectious complications after unrelated umbilical cord blood versus HLA-matched unrelated donor allogeneic transplantation in adults

Sources for allogeneic stem cells for patients with haematological disorders lacking a histocompatible sibling donor include matched unrelated donor (MUD) and umbilical cord blood (UCB). A total of 51 patients with haematological disorders, treated with myeloablation and transplantation with either unrelated human leucocyte antigen (HLA) partially matched UCB (28 patients) or HLA-matched MUD grafts (23 patients) during 1997-2003, were evaluated for life-threatening infections, haematological reconstitution, graft versus host disease, relapse and event-free survival (EFS). The median duration of neutropenia after transplantation was longer (29 d vs. 14 d) in the UCB group. The probability of donor-derived neutrophil engraftment by day 42 was 0.86 [95% confidence interval (CI) 0.71-1.0] in UCB recipients versus 0.96 (95% CI 0.87-1.0) in MUD recipients surviving >28 d. Overall infection rates were higher in UCB recipients, particularly at the early time points (before day +50) after transplantation. Graft failure occurred in five UCB recipients and two MUD recipients and was associated with the occurrence of bacteraemia during neutropenia. The EFS at 3-year follow-up was 0.25 in UCB and 0.35 in MUD recipients. UCB transplantation in adults is associated with delayed neutrophil and lymphocyte recovery compared with MUD grafting, and higher rates of bacteraemia at early time points after transplantation.