Epidemiology of bloodstream infections and the impact of antimicrobial resistance in pediatric hematopoietic cell transplant

Bloodstream infections (BSI) pose a substantial threat to the well-being and survival of patients undergoing hematopoietic stem cell transplantation (HSCT). Risk factors for these infections vary across the different post-HSCT phases. In the pre-engraftment period, patients are particularly susceptible to infection due to prolonged neutropenia, mucosal damage, and extensive use of central venous line (CVL). In the post-engraftment phase, the emergence of graft versus host diseases further compounds the risk. The epidemiology of these infections has undergone notable changes over the years due to multifactorial reasons, including the evolution of protocols that intensify immunosuppression. In this context, the emergence of multi-drug resistance (MDR) microorganisms can be a challenge due to the elevated risk of mortality in these vulnerable patients. Unfortunately, there is a lack of comprehensive data on this topic, particularly in pediatrics. This article aims to provide a summary of the epidemiology of BSI in the different post-transplant phases and the impact of MDR pathogens. Having knowledge about the local epidemiology of BSI can be instrumental in tailoring targeted therapies, leading to improved survival rates in HSCT recipients.

Rapid Administration of Antibiotics for Reducing Fever Days in Patients Receiving Hematopoietic Stem Cell Transplantation

Background and Objectives: Neutropenic fever (NF) is a major cause of mortality and morbidity in patients undergoing hematopoietic stem cell transplantation (HSCT). To date, no study has discussed the relationship of fever days in HSCT with the time between recording the fever and administering antibiotics. This study aimed to examine the association between fever days in HSCT and the time interval between recording the fever and intravenous (IV) antibiotics to the febrile neutropenia patient. Materials and Methods: A total of 22 patients who developed NF after HSCT in one hospital were analyzed. Patients who received IV antibiotics injection within 30 min were categorized in group A and those who received the injection after 30 min were categorized in group B. Fever was defined by an attack with an oral temperature of 38.3 °C. Patients’ characteristics and possible risk factors were recorded and analyzed. Results: Groups A and B had 14 and 8 patients, respectively. Patient characteristics, including age, diagnosis, sex, and antibiotics level, were similar between the two groups. The median duration of fever days was 1.5 (range, 1−5) in group A and 6.5 (range, 1−14) in group B (p = 0.003). Multivariant analysis of possible independent impact factors of “fever days in HSCT” was performed. The odds ratio of “antibiotics given time” was 4.00 (95% confidence interval [CI] = 2.26 to 7.22, p = 0.001). The “antibiotics level” did not affect the NF period (odds ratio = −0.80, 95% CI = −2.40 to 1.07, p = 0.453). Conclusions: Rapid IV administration of antibiotics (<30 min after fever attack) can reduce the fever days in patients undergoing HSCT.

Bacteremia in Hematopoietic Stem Cell Recipients Receiving Fluoroquinolone Prophylaxis: Incidence, Resistance, and Risk Factors

Background

Bacteremia is a common complication in hematopoietic stem cell transplant (HSCT) recipients. Prophylactic fluoroquinolone is recommended and used in these individuals. Breakthrough infections can occur with fluoroquinolone-resistant strains. We aimed to identify the incidence, resistance, and risk factors for bacteremia in HSCT recipients receiving fluoroquinolone prophylaxis.

Materials and Methods

This retrospective study was performed on patients who received fluoroquinolone prophylaxis and underwent autologous and allogeneic HSCT between 2015 and 2019. The incidence of bacteremia, comorbidity, treatment, and invasive procedures was compared in these patients with and without bacteremia.

Results

There were 553 patients included in the study, 68 (12.3%) had bacteremia. The incidence of bacteremia is 8.2% of autologous HSCT recipients and 18.4% of allogeneic HSCT recipients. The significant risk factors associated with bacteremia were steroid-using (odds ratio [OR]:13.83, 95% confidence interval [CI]: 2.88 - 66.40), higher Charlson Comorbidity Index (CCI)-mean (OR: 1.57, 95% CI: 1.15 - 2.16), diabetes mellitus (OR: 4.29, 95% CI: 1.11 - 16.48) in autologous HSCT, steroid-using (OR: 6.84, 95% CI: 1.44 - 32.33), longer duration of neutropenia (OR: 1.05, 95% CI: 1.01 - 1.09) using central venous catheter (OR: 7.81, 95% CI: 1.00 - 61.23) in allogeneic HSCT. Seventy-three pathogens were isolated from a total of 68 bacteremia episodes. The most commonly occurring agents were Escherichia coli, Klebsiella pneumoniae and Enterococcus spp. Resistance to fluoroquinolones was 87.2%, 70.0% and 60.0% among these strains, respectively.

Conclusion

High CCI, diabetes mellitus, use of steroids and long-term neutropenia and use of central venous catheters were significantly associated with the breakthrough bacteremia in HSCT recipients receiving fluoroquinolone prophylaxis. Fluoroquinolone prophylaxis may reduce the incidence of bacteremia but may select strains resistant to fluoroquinolone.

Bacteremia in pediatric patients with hematopoietic stem cell transplantation

BACKGROUND

This study aimed to describe the incidence, microbiological profile, and risk factors associated with bacteremia in pediatric patients with hematopoietic stem cell transplantation (HSCT).

METHODS

A retrospective cohort study was performed on patients under 18 years old who underwent HSCT due to any indication, between January 2012 and January 2017. The patient data were collected from the first 100 days post-HSCT. Bacteremia was defined as the isolation of bacteria from at least one blood culture. The relation between bacteremia and associated risk factors was evaluated using univariate and multivariate analysis.

RESULTS

We enrolled a total of 111 pediatric patients who received HSCT during the period of study. The total number of patients who developed at least one episode of bacteremia was 46 (41.4%), and the total number of bacteremia episodes was 62. Rectal swabs were performed in 44 patients to detect prior colonization and this showed that 25% of them were positive, the main pathogen isolated being carbapenem-resistant enterobacteriaceae. The Gram-negative bacteria cases accounted for 60% of 62 events. The main Gram-negative bacteria isolated were Klebsiella pneumoniae and Escherichia coli and the majority were resistant strains. The mortality rate on day +100 for the whole cohort was 18% (n=20). Regarding the patients with bacteremia, the mortality rate on day +100 was 30% (n=14), and the cause of death was related to infection in 10 of them. We did not find any statistically significant risk factor for the development of bacteremia.

CONCLUSION

Bacteremia is common after HSCT, and there is a high frequency of resistant Gram-negative infections which is related to high mortality.

Características clínicas y microbiológicas de pacientes con neutropenia febril en un hospital universitario

Objetivo: Describir las características clínicas, demográficas, frecuencia, tipo de aislamientos microbiológicos y resistencia a los antimicrobianos de pacientes con neoplasias hematológicas que presentaron como complicación neutropenia febril en el Hospital Universitario de San IgnacioMétodos: Estudio descriptivo observacional, se tomaron datos de historias clínicas de los pacientes adultos hospitalizados en la Unidad de Hematología y Trasplante de Médula Ósea, que cumplieron criterios de neutropenia febril entre enero de 2013 y diciembre de 2014Resultados: se recolectaron 345 episodios de neutropenia febril, correspondientes a 193 pacientes. Se documentó foco infeccioso en el 68,1% de los episodios, con aislamiento microbiológico en el 62.9% de los episodios, con predominio de bacilos gram negativos, en 63,7% de los casos, seguido por los cocos gram positivos en 27,9% y hongos en 4,9%. En cuanto a los mecanismos de resistencia, en los aislamientos Escherichia coli y Klebsiella peumoniae se encontró producción de Beta Lactamasas de Espectro Extendido (BLEEs) en 17,5 y 13,8%; Carbapenemasas tipo KPC en 1,25 y 2,8% respectivamente. En cuanto a Staphylococcus aureus, se encontró resistencia a meticilina en 6,8% de los aislamientos. Mortalidad asociada a infección en 16,5% de los casos.Conclusión: En pacientes con Neoplasias Hematológicas con neutropenia febril post quimioterapia en el Hospital Universitario de San Ignacio encontramos alta probabilidad de documentación de foco infeccioso, con predominio de microorganismos gram negativos, especialmente enterobacterias; con comportamiento similar en pacientes post trasplante de precursores hematopoyéticos.

Pharmacokinetics and pharmacodynamics of continuous-infusion meropenem in pediatric hematopoietic stem cell transplant patients

This study explored the pharmacokinetics and the pharmacodynamics of continuous-infusion meropenem in a population of pediatric hematopoietic stem cell transplant (HSCT) patients who underwent therapeutic drug monitoring. The relationship between meropenem clearance (CLM) and estimated creatinine clearance (CLCR) was assessed by nonlinear regression. A Monte Carlo simulation was performed to investigate the predictive performance of five dosing regimens (15 to 90 mg/kg of body weight/day) for the empirical treatment of severe Gram-negative-related infections in relation to four different categories of renal function. The optimal target was defined as a probability of target attainment (PTA) of ≥90% at steady-state concentration-to-MIC ratios (C SS/MIC) of ≥1 and ≥4 for MICs of up to 8 mg/liter. A total of 21 patients with 44 meropenem C SS were included. A good relationship between CLM and estimated CLCR was observed (r (2) = 0.733). Simulations showed that at an MIC of 2 mg/liter, the administration of continuous-infusion meropenem at doses of 15, 30, 45, and 60 mg/kg/day may achieve a PTA of ≥90% at a C SS/MIC ratio of ≥4 in the CLCR categories of 40 to <80, 80 to <120, 120 to <200, and 200 to <300 ml/min/1.73 m(2), respectively. At an MIC of 8 mg/liter, doses of up to 90 mg/kg/day by continuous infusion may achieve optimal PTA only in the CLCR categories of 40 to <80 and 80 to <120 ml/min/1.73 m(2). Continuous-infusion meropenem at dosages up to 90 mg/kg/day might be effective for optimal treatment of severe Gram-negative-related infections in pediatric HSCT patients, even when caused by carbapenem-resistant pathogens with an MIC of up to 8 mg/liter.

Potential impact of a microarray-based nucleic acid assay for rapid detection of Gram-negative bacteria and resistance markers in positive blood cultures

We evaluated the Verigene Gram-negative blood culture (BC-GN) test, a microarray that detects Gram-negative bacteria and several resistance genes. A total of 102 positive blood cultures were tested, and the BC-GN test correctly identified 97.9% of the isolates within its panel. Resistance genes (CTX-M, KPC, VIM, and OXA genes) were detected in 29.8% of the isolates, with positive predictive values of 95.8% (95% confidence interval [CI], 87.7% to 98.9%) in Enterobacteriaceae and 100% (95% CI, 75.9% to 100%) in Pseudomonas aeruginosa and negative predictive values of 100% (95% CI, 93.9% to 100%) and 78.6% (95% CI, 51.0% to 93.6%), respectively.

Identification of single nucleotide polymorphisms in hematopoietic cell transplant patients affecting early recognition of, and response to, endotoxin

Hematopoietic cell transplant (HCT) is a life-saving therapy for many malignant and non-malignant bone marrow diseases. Associated morbidities are often due to transplant-related toxicities and infections, exacerbated by regimen-induced immune suppression and systemic incursion of bacterial products. Patients undergoing myeloablative conditioning for HCT become endotoxemic and display blood/plasma changes consistent with lipopolysaccharide (LPS)-induced systemic innate immune activation. Herein, we addressed whether patients scheduled for HCT display differences in recognition/response to LPS ex vivo traceable to specific single nucleotide polymorphisms (SNPs). Two SNPs of LPS binding protein (LBP) were associated with changes in plasma LBP levels, with one LBP SNP also associating with differences in efficiency of extraction and transfer of endotoxin to myeloid differentiation factor-2 (MD-2), a step needed for activation of TLR4. None of the examined SNPs of CD14, bactericidal/permeability-increasing protein (BPI), TLR4 or MD-2 were associated with corresponding protein plasma levels or endotoxin delivery to MD-2, but CD14 and BPI SNPs significantly associated with differences in LPS-induced TNF-α release ex vivo and infection frequency, respectively. These findings suggest that specific LBP, CD14 and BPI SNPs might be contributory assessments in studies where clinical outcome may be affected by host response to endotoxin and bacterial infection.

Prevention of bacterial infection in pediatric oncology: what do we know, what can we learn?

Bacterial sepsis continues to be a leading cause of morbidity and toxic death in children receiving intensive therapy for cancer. Empiric therapy for suspected infections and treatment of documented infections are well-established standards of care. The routine use of prophylactic strategies is much less common in pediatric oncology. This paper will review the current literature on the use and risks of antimicrobial prophylaxis as well as non-pharmacological methods for infection prevention and will address areas in need of further research.

CD4(+) CD28(+) lymphocytes on day 5 after high-dose melphalan for multiple myeloma predict a low risk of infections during severe neutropenia and are associated with the number of reinfused T lymphocytes of the autologous stem cell graft

BACKGROUND AIMS

Neutropenia following high-dose chemotherapy is associated with a substantial risk of infectious complications. The aim of this study was to identify variables in residual leukocyte subsets during neutropenia that are predictive for neutropenic fever.

METHODS

Residual leukocytes in the peripheral blood on day 5 after autologous blood stem cell transplantation were analyzed by three-color flow cytometry in 55 consecutive patients with multiple myeloma. Furthermore, the number of T cells transfused with the autografts was determined.

RESULTS

Neutrophil counts at day 5 and neutrophil engraftment were similar in patients with and without neutropenic fever. Low absolute lymphocyte, CD4(+) CD28(+) and CD45RO(+) CD28(+) counts at day 5 were associated with neutropenic fever. T-cell counts at day 5 correlated with the CD3(+) cell number in the graft.

CONCLUSIONS

Our data show that the absolute lymphocyte, CD4(+) CD28(+) and CD45RO(+) CD28(+) counts play a role in host defense during severe neutropenia. The T-cell number in the graft may help to identify patients at high risk of neutropenic infections.

How I manage haematology patients with septic shock

Patients with a variety of haematological conditions are at risk of infection and its most serious complication: septic shock. Mortality for septic shock remains high and especially so in patients with haematological malignancy and following bone marrow transplantation. However, advances in the treatment of severe sepsis have improved mortality rates even though evidence for the management of severe sepsis in haematology patients is limited. Wherever possible this review will concentrate on evidence directly applicable to haematology patients but inevitably will have to extrapolate evidence from other patient groups. The Surviving Sepsis Guidelines 2008 provide information on best practice in the management of patients with severe sepsis and septic shock and are broadly applicable though not specific to haematology patients. This review summarizes a practical approach to the management of severe sepsis in haematology patients and highlights areas of research which may bring new treatments in the future. The review is limited to the management and initial resuscitation of septic shock in adult haematology patients and will not address the detailed intensive care management of these patients or the management of severe sepsis in children.

Impact of bloodstream infections on outcome and the influence of prophylactic oral antibiotic regimens in allogeneic hematopoietic SCT recipients

This study aimed to determine the impact of blood stream infections (BSIs) on outcome of allogeneic hematopoietic SCT (HSCT), and to examine the influence of old (non-levofloxacin-containing) and new (levofloxacin-based) prophylactic antibiotic protocols on the pattern of BSIs. We retrospectively enrolled 246 allogeneic HSCT recipients between January 1999 and June 2006, dividing patients into BSI (within 6 months post-HSCT, n=61) and non-BSI groups (n=185). We found that Gram-negative bacteria (GNB) predominated BSI pathogens (54%). Multivariate analyses showed that patients with a BSI, compared with those without, had a significantly greater 6-month mortality (hazard ratio, 1.75; 95% confidence interval, 1.09-2.82; P=0.021) and a significantly increased length of hospital (LOH) stay (70.8 vs 55.2 days, P=0.014). Moreover, recipients of old and new protocols did not have a significantly different 6-month mortality and time-to-occurrence of BSIs. However, there were significantly more resistant GNB to third-generation cephalosporins and carbapenem in recipients of levofloxacin-based prophylaxis. Our data suggest that BSIs occur substantially and impact negatively on the outcome and LOH stay after allogeneic HSCT despite antibiotic prophylaxis. Levofloxacin-based prophylaxis, albeit providing similar efficacy to non-levofloxacin-containing regimens, may be associated with increased antimicrobial resistance.

Prophylactic antibiotics for the prevention of neutropenic fever in patients undergoing autologous stem-cell transplantation: results of a single institution, randomized phase 2 trial

One hundred and fifty-seven patients undergoing high-dose chemotherapy (HDT) and autologous stem-cell transplantation (ASCT) for hematopoietic malignancies and solid tumors were randomly assigned to receive (Group A) or not (Group B) prophylaxis with ciprofloxacin, orally, and vancomycin, intravenously. Prophylactic antibiotics were given from day 0 until resolution of neutropenia or the appearance of a febrile event. Furthermore, patients in both groups received once a day fluconazole, orally. The primary end-point of our study was the incidence of neutropenic febrile episodes attributed to infection. One hundred and twelve (71.3%) patients developed neutropenic fever, 50 (56.2%) in Group A and 62 (91.2%) in Group B (P < 0.001) with the majority (82%) of patients developing fever of unknown origin. Patients on prophylactic antibiotics had a significantly lower rate of bacteremias (5.6%) than did those randomized to no prophylaxis (29.4%) (P = 0.005) and, when developing neutropenic fever, they had a lower probability of response to first-line empirical antibiotics (P = 0.025). Prophylactic administration of ciprofloxacin and vancomycin reduced the incidence of neutropenic fever in patients receiving HDT with ASCT, however, without affecting the total interval of hospitalization, time to engraftment, or all-cause mortality. Therefore, our results do not support the use of antibiotic prophylaxis for patients undergoing HDT and ASCT.