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

Role of silicon in alleviating boron toxicity and enhancing growth and physiological traits in hydroponically cultivated Zea mays var. Merit

BACKGROUND

Boron (B) is a micronutrient, but excessive levels can cause phytotoxicity, impaired growth, and reduced photosynthesis. B toxicity arises from over-fertilization, high soil B levels, or irrigation with B-rich water. Conversely, silicon (Si) is recognized as an element that mitigates stress and alleviates the toxic effects of certain nutrients. In this study, to evaluate the effect of different concentrations of Si on maize under boron stress conditions, a factorial experiment based on a randomized complete block design was conducted with three replications in a hydroponic system. The experiment utilized a nutrient solution for maize var. Merit that contained three different boron (B) concentrations (0.5, 2, and 4 mg L-1) and three Si concentrations (0, 28, and 56 mg L-1).

RESULTS

Our findings unveiled that exogenous application of B resulted in a substantial escalation of B concentration in maize leaves. Furthermore, B exposure elicited a significant diminution in fresh and dry plant biomass, chlorophyll index, chlorophyll a (Chl a), chlorophyll b (Chl b), carotenoids, and membrane stability index (MSI). As the B concentration augmented, malondialdehyde (MDA) content and catalase (CAT) enzyme activity exhibited a concomitant increment. Conversely, the supplementation of Si facilitated an amelioration in plant fresh and dry weight, total carbohydrate, and total soluble protein. Moreover, the elevated activity of antioxidant enzymes culminated in a decrement in hydrogen peroxide (H2O2) and MDA content. In addition, the combined influence of Si and B had a statistically significant impact on the leaf chlorophyll index, total chlorophyll (a + b) content, Si and B accumulation levels, as well as the enzymatic activities of guaiacol peroxidase (GPX), ascorbate peroxidase (APX), and H2O2 levels. These unique findings indicated the detrimental impact of B toxicity on various physiological and biochemical attributes of maize, while highlighting the potential of Si supplementation in mitigating the deleterious effects through modulation of antioxidant machinery and biomolecule synthesis.

CONCLUSIONS

This study highlights the potential of Si supplementation in alleviating the deleterious effects of B toxicity in maize. Increased Si consumption mitigated chlorophyll degradation under B toxicity, but it also caused a significant reduction in the concentrations of essential micronutrients iron (Fe), copper (Cu), and zinc (Zn). While Si supplementation shows promise in counteracting B toxicity, the observed decrease in Fe, Cu, and Zn concentrations warrants further investigation to optimize this approach and maintain overall plant nutritional status.

Corticosteroid Dosing Level, Incidence and Profile of Bacterial Blood Stream Infections in Hospitalized COVID-19 Patients

COVID-19 patients with severe or critical symptoms are often treated with corticosteroids, per contemporary guidelines. Due to their immunosuppressive and immunomodulatory properties, corticosteroids are associated with the development of superinfections. We aimed to retrospectively assess patterns of corticosteroid use and the profiles of bacterial blood stream infections associated with exposure to different dosing levels, in a cohort of 1558 real-life adult COVID-19 patients. A total of 1391 (89.3%) patients were treated with corticosteroids, with 710 (45.6%) patients receiving low, 539 (34.6%) high and 142 (9.1%) very high corticosteroid doses. Bacteremia developed in a total of 178 (11.4%) patients. The risk of bacteremia was of similar magnitude between the no and low-dose corticosteroid treatments (p = 0.352), whereas it progressively increased with high (OR 6.18, 95% CI (2.66-14.38), p < 0.001) and very high corticosteroid doses (OR 8.12, 95% CI (3.29-20.05), p < 0.001), compared to no corticosteroid treatment. These associations persisted after multivariate adjustments and were present independently of sex, comorbidity burden, and mechanical ventilation. The profiles of individual bacterial pathogens differed depending on the used corticosteroid doses. High and very high corticosteroid doses are frequently used for real-life COVID-19 patients with severe and critical clinical presentations and are associated with a higher risk of bacteremia independently of sex, comorbidity burden, and mechanical ventilation use.

Changes in the expression of mexB, mexY, and oprD in clinical Pseudomonas aeruginosa isolates

Changes in expression levels of drug efflux pump genes, mexB and mexY, and porin gene oprD in Pseudomonas aeruginosa were investigated in this study. Fifty-five multidrug-resistant P. aeruginosa (MDRP) strains were compared with 26 drug-sensitive strains and 21 strains resistant to a single antibiotic. The effect of the efflux inhibitor Phe-Arg-β-naphthylamide on drug susceptibility was determined, and gene expression was quantified using real-time quantitative real-time reverse transcription polymerase chain reaction. In addition, the levels of metallo-β-lactamase (MBL) and 6'-N-aminoglycoside acetyltransferase [AAC(6')-Iae] were investigated. Efflux pump inhibitor treatment increased the sensitivity to ciprofloxacin, aztreonam, and imipenem in 71%, 73%, and 29% of MDRPs, respectively. MBL and AAC(6')-Iae were detected in 38 (69%) and 34 (62%) MDRP strains, respectively. Meanwhile, 76% of MDRP strains exhibited more than 8-fold higher mexY expression than the reference strain PAO1. Furthermore, 69% of MDRP strains expressed oprD at levels less than 0.01-fold of those in PAO1. These findings indicated that efflux pump inhibitors in combination with ciprofloxacin or aztreonam might aid in treating MDRP infections.

Prevalence of Pseudomonas aeruginosa and its antibiotic resistance in patients who have received Hematopoietic Stem-Cell Transplantation; A globally Systematic Review

Gram-negative bacteria are infectious and life-threatening agents after hematopoietic stem cell transplantation (HSCT). So, this study aimed to investigate the prevalence of Pseudomonas aeruginosa and its antibiotic resistance in patients who have received Hematopoietic Stem-Cell Transplantation through a systematic review. The systematic search was done with key words; Pseudomonas aeruginosa, hematopoietic stem cell transplantation from 2000 to the end of July 2023 in Google Scholar and PubMed/Medline, Scopus, and Web of Science. Twelve studies were able to include our study. Quality assessment of studies was done by Appraisal tool for Cross-Sectional Studies. The most of the included studies were conducted as allo-HSCT. Infections such as respiratory infection, urinary infection and bacteremia have occurred. The rate of prevalence with P. aeruginosa has varied between 3 and 100%. The average age of the participants was between 1 and 74 years. The rate of prevalence of P. aeruginosa resistant to several drugs has been reported to be variable, ranging from 20 to 100%. The highest antibiotic resistance was reported against cefotetan (100%), and the lowest was related to tobramycin (1.8%) followed by amikacin, levofloxacin and ciprofloxacin with the prevalence of 16.6%. Our findings showed a high prevalence and antibiotic resistance rate of P. aeruginosa in Hematopoietic stem cell transplantation. Therefore, more serious health measures should be taken in patients after transplantation.

Clinical impact and early prediction of carbapenem-resistant Pseudomonas aeruginosa bacteraemia in allogeneic hematopoietic stem cell transplantation recipients

OBJECTIVE

Although antipseudomonal agents are administered in high-risk patients, no reports have focused on the risk of carbapenem-resistant (CR) Pseudomonas aeruginosa bacteraemia in allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients.

METHODS

We retrospectively studied a cohort of adult allo-HSCT recipients with P. aeruginosa bacteraemia, focusing on a comparison between carbapenem-sensitive (CS) and CR P. aeruginosa after initiating conditioning chemotherapy at our institute between January 2005 and December 2020. The incidence, all-cause 30-d mortality of P. aeruginosa bacteraemia, and risk factors for carbapenem resistance among patients with P. aeruginosa bacteraemia in allo-HSCT recipients were evaluated.

RESULTS

Forty-eight patients with P. aeruginosa bacteraemia were included, with an incidence of 3.84/100 recipients (CS = 1.92 vs. CR = 1.92). The all-cause 30-d mortality was significantly higher in CR P. aeruginosa bacteraemia (CS = 4.2% vs. CR = 39.1%; P = 0.003). The factor significantly associated with CR P. aeruginosa bacteraemia was carbapenem use for at least 3 d within 30 d before the onset of bacteraemia (odds ratio = 8.92; 95% confidence interval: 1.35-58.90). Inappropriate antimicrobial selection was significantly more frequent in CR P. aeruginosa bacteraemia (CS = 0% vs. CR = 29.2%; P ˂ 0.009).

CONCLUSION

Empirical combination therapy with reference to antimicrobial susceptibility profiles in each institution should be considered when CR P. aeruginosa bacteraemia is suspected in allo-HSCT recipients based on the risk of carbapenem exposure.

Carbapenem-Resistant Enterobacteriaceae (CRE) among Children with Cancer: Predictors of Mortality and Treatment Outcome

Carbapenem-resistant Enterobacteriaceae (CRE) is an important emerging threat among pediatric cancer patients, with a high mortality rate. This retrospective study included all pediatric cancer patients with (CRE) bloodstream infections (BSIs) at a children's cancer hospital in Egypt (2013-2017). Two hundred and fifty-four pediatric cancer patients with CRE BSI were identified; 74% had hematological malignancies, and 26% had solid tumors. Acute myeloid leukemia was the most common hematological malignancy (50%). The main clinical features for acquiring CRE-BSI were previous antibiotics exposure (90%), profound neutropenia (84%), prolonged steroid use (45%), previous colonization with a resistant pathogen (35%), ICU admission within 90 days (28%), and central venous catheter use (24%). E. coli was the most common isolated pathogen (56%), followed by Klebsiella pneumoniae (37%). All isolates were resistant to carbapenem with an MIC < 4-8 μg/mL in 100 (45%) and >8 μg/mL in 153 (55%). The overall mortality rate was 57%, and 30 day mortality was reported in 30%. Upon multivariate analysis, for the patients with Klebsiella pneumoniae BSI, carbapenem resistance with an MIC > 8 μg/mL and associated typhlitis or pneumonia were predictors of poor outcome. In conclusion, CRE-BSI is a major threat among pediatric cancer patients in limited resource countries with limited options for treatment. Antimicrobial stewardship for early detection through routine screening, adequate empirical treatment, and timely adequate therapy may impact the outcome for such high-risk patient groups.

Effect of Combination Antibiotic Empirical Therapy on Mortality in Neutropenic Cancer Patients with Pseudomonas aeruginosa Pneumonia

To assess the effect of combination antibiotic empirical therapy on 30-day case-fatality rate in neutropenic cancer patients with Pseudomonas aeruginosa (PA) bacteremic pneumonia. This was a multinational, retrospective cohort study of neutropenic onco-hematological patients with PA bloodstream infection (BSI) (2006−2018). The effect of appropriate empirical combination therapy, appropriate monotherapy and inappropriate empirical antibiotic therapy [IEAT] on 30-day case-fatality was assessed only in patients with PA bacteremic pneumonia. Among 1017 PA BSI episodes, pneumonia was the source of BSI in 294 (28.9%). Among those, 52 (17.7%) were caused by a multidrug-resistant (MDR) strain and 68 (23.1%) received IEAT, mainly when the infection was caused by an MDR strain [38/52 (73.1%) vs. 30/242 (12.4%); p < 0.001]. The 30-day case-fatality rate was higher in patients with PA bacteremic pneumonia than in those with PA BSI from other sources (55.1% vs. 31.4%; p < 0.001). IEAT was associated with increased 30-day case-fatality (aHR 1.44 [95%CI 1.01−2.03]; p = 0.042), whereas the use of appropriate combination empirical treatment was independently associated with improved survival (aHR 0.46 [95%CI 0.27−0.78]; p = 0.004). Appropriate empirical monotherapy was not associated with improved overall survival (aHR 1.25 [95%CI 0.76−2.05]; p = 0.39). Combination antibiotic empirical therapy should be administered promptly in febrile neutropenic patients with suspected pneumonia as the source of infection.

Emergence of non-susceptibility during persistent Pseudomonas aeruginosa bacteraemia in haematopoietic cell transplant recipients and haematological malignancy patients

Background

Systematic studies pertaining to the emergence of resistance during therapy of Pseudomonas aeruginosa bloodstream infections (BSIs) in haematopoietic cell transplant (HCT) recipients and haematological malignancy (HM) patients are lacking.

Objectives

To determine how frequently non-susceptibility emerges during therapy of P. aeruginosa BSIs and to compare these findings with non-HCT/HM patients.

Patients and methods

P. aeruginosa BSIs that occurred at our institution between 1 July 2012 and 31 October 2019 in HCT/HM patients and non-HCT/HM patients were identified. Episodes in which bacteraemia persisted while on appropriate therapy (‘persistent BSI’) were evaluated for emergence of non-susceptibility during therapy.

Results

In total, 96 BSI episodes among 86 HCT/HM patients were analysed. Eight persistent BSI episodes (8.3%) occurred in eight patients (9.3%). Repeat susceptibility testing was performed in seven (87.5%) of these episodes. Non-susceptibility to the treatment agent emerged in five (71.4%) episodes and to any antipseudomonal agent in seven (100%) episodes. The 21 day mortality rate associated with persistent BSI was 87.5% (seven of eight), and it was 80% (four of five) among persistent BSI episodes in which non-susceptibility to the treatment agent emerged on therapy. Non-susceptibility to any antipseudomonal agent during persistent BSI emerged significantly more frequently in HCT/HM patients compared with non-HCT/HM patients.

Conclusions

Non-susceptibility emerges frequently during persistent P. aeruginosa BSIs in HCT/HM patients, and this is associated with a high mortality rate. Our findings have implications for the management of persistent P. aeruginosa BSIs in these patients. Larger studies are needed to confirm and expand on our findings.

Experimental Models of Infectious Pulmonary Complications Following Hematopoietic Cell Transplantation

Pulmonary infections remain a major cause of morbidity and mortality in hematopoietic cell transplantation (HCT) recipients. The prevalence and type of infection changes over time and is influenced by the course of immune reconstitution post-transplant. The interaction between pathogens and host immune responses is complex in HCT settings, since the conditioning regimens create periods of neutropenia and immunosuppressive drugs are often needed to prevent graft rejection and limit graft-versus-host disease (GVHD). Experimental murine models of transplantation are valuable tools for dissecting the procedure-related alterations to innate and adaptive immunity. Here we review mouse models of post-HCT infectious pulmonary complications, primarily focused on three groups of pathogens that frequently infect HCT recipients: bacteria (often P. aeruginosa), fungus (primarily Aspergillus fumigatus), and viruses (primarily herpesviruses). These mouse models have advanced our knowledge regarding how the conditioning and HCT process negatively impacts innate immunity and have provided new potential strategies of managing the infections. Studies using mouse models have also validated clinical observations suggesting that prior or occult infections are a potential etiology of noninfectious pulmonary complications post-HCT as well.

Invasive pulmonary aspergillosis/pseudomonas

A 47-year-old Caucasian man on long-standing antifungal therapy for chronic necrotising aspergillosis and a history of recurrent pseudomonas pneumonias presented to the outpatient pulmonary clinic with dyspnoea and chest discomfort for 3 days. A CT angiography of the chest demonstrated angioinvasion from the previously noted left upper lobe cavitary lesion into the left main pulmonary artery, along with new consolidating lesions. Due to the high risk for massive haemoptysis, he was evaluated by thoracic surgery and underwent a successful left pneumonectomy. As invasive pulmonary aspergillosis is associated with high mortality, surgical intervention should always be considered, especially in those who develop extensive disease, despite being on aggressive antifungal therapy. Though minimally described in literature, invasive pulmonary pseudomonas also carries a high mortality risk. In our patient, cultures from the resected lung only demonstrated Pseudomonas aeruginosa.

Infection-Related Mortality in Adults and Children Undergoing Allogeneic Hematopoietic Cell Transplantation: An Australian Registry Report

Infection-related mortality (IRM) is the most common non-relapse-related cause of death reported after allogeneic hematopoietic cell transplantation (HCT). Information on the incidence and timing of specific infective organisms and the risk factors for IRM is essential to developing prevention strategies. This report provides the first account of IRM in adults and children undergoing HCT in Australia. Between 2013 and 2018, 2705 adult and 689 pediatric first HCTs were identified from the Australasian Bone Marrow Transplant Recipient Registry database, associated with 1075 (39.7%) total overall deaths in adults and 134 (19.4%) in children. Demographics and causes of death, including infectious etiology and causative organisms, were extracted from the database for adults and children for analysis. At day +100 and 1 year post-HCT, IRM was the leading cause of early post-HCT mortality in adults, accounting for 6.2% and 9.8%, respectively; in children, IRM was the leading cause of post-HCT mortality at day +100 at 2.5% and the second highest cause of post-HCT mortality at 1 year post-HCT at 4.9%, following relapse at 5.8%. In adults, older age, transplantation not in a first complete remission (non-CR1), the use of antithymocyte globulin (ATG) or alemtuzumab, donor-positive/recipient-negative cytomegalovirus (CMV) serostatus, and acute graft-versus-host disease were significant risk factors for IRM. However, in children, age >5 years, acute lymphocytic leukemia as the primary disease, and mismatched unrelated or haploidentical donor source were predictive of IRM. Of the deaths in which an infectious etiology was reported in adults (52.4%), 49.3% were attributed to bacteria, 25.3% to fungus, 21.7% to viruses, and 3.6% to post-transplantation lymphoproliferative disorder (PTLD). The most common organisms were Pseudomonas spp, Enterococcus spp, Candida spp, Aspergillus spp, and CMV. In children where an infectious etiology was reported (64%), 13% were attributed to bacteria, 26% to fungus, 45% to viruses, and 16% to PTLD. This report highlights that IRM was the leading cause of death early post-HCT in Australia. Strategies to reduce IRM, such as individualized pre-transplantation infection risk assessment, rapid diagnostics, and prevention management strategies should be explored to determine whether these outcomes can be improved. In addition, improving the completeness and accuracy of reported data, particularly for infectious pathogens, could assist in directing management strategies to reduce IRM in HCT.

Emergent Plasmapheresis for Hyperammonemia in a Re-do Double Lung Transplant Patient

Hyperammonemia after lung transplant is a severe complication that can result in cerebral herniation. It is associated with up to 70% mortality in patients who have had solid organ transplantation. We describe a rare case in which hyperammonemia was emergently and successfully treated with plasmapheresis in a re-do double lung transplant patient who developed shocked liver.

Clinical Significance of Carbapenem-Tolerant Pseudomonas aeruginosa Isolated in the Respiratory Tract

We often come across difficult to treat infections—even after administering appropriate antibiotics according to the minimal inhibitory concentration of the causative bacteria. Antibiotic tolerance has recently started to garner attention as a crucial mechanism of refractory infections. However, few studies have reported the correlation between clinical outcomes and antibiotic tolerance. This study aims to clarify the effect of antibiotic tolerance on clinical outcomes of respiratory tract infection caused by Pseudomonas aeuginosa (P. aeruginosa). We examined a total of 63 strains isolated from sputum samples of different patients and conducted a retrospective survey with the medical records of 37 patients with imipenem-sensitive P. aeruginosa infections. Among them, we selected 15 patients with respiratory infections, and they were divided into high-tolerance minimal bactericidal concentration for adherent bacteria (MBC^AD)/minimal inhibitory concentration for adherent bacteria (MIC^AD) ≥ 32 (n = 9) group and low-tolerance MBC^AD/MIC^AD ≤ 16 (n = 6) group for further investigations. The findings indicated that the high-tolerance group consisted of many cases requiring hospitalization. Chest computed tomography findings showed that the disease was more extensive in the high-tolerance group compared to the low-tolerance group. Regarding the bacterial phenotypic characterization, the high-tolerance group significantly upregulated the production of the virulence factors compared to the low-tolerance group. Our study provided evidence that carbapenem tolerance level is a potent prognostic marker of P. aeruginosa infections, and carbapenem tolerance could be a potential target for new antimicrobial agents to inhibit the progression of persistent P. aeruginosa infections.

Optimal Treatment Duration of Pseudomonas aeruginosa Infections in Allogeneic Hematopoietic Cell Transplant Recipients

In a large, multicenter, contemporary, 8-year, cohort study, one third of allogeneic-hematopoietic cell transplant (HCT) recipients with Pseudomonas aeruginosa (PSA) infection developed a recurrent infection within 3 months. Antibiotic treatment duration of ≥14 days was the only significantly associated variable with reduced recurrence rates of PSA infections in allogeneic-HCT recipients.

Loquat-Inspired Janus Drug Delivery System for Flexible and Robust Tumor Targeting Therapy

With the inspiration of the shape of the loquat fruit, here, we developed a similarly shaped Janus carrier. This peculiar gold rod-partially exposed structure not only significantly increased the drug loading capability but also improved its infrared response efficiency. A better effect of drug-photothermal treatment thus could be realized. With the aid of an external 3D printed drug guiding device, this carrier could accurately reach different affected areas. The subsequent infrared triggered multiple tumor therapy, thus, could be conducted in the designated location. The corresponding experimental results demonstrated the reliability, flexibility, and biocompatibility of the proposed drug delivery system for two different tumor targeting treatments.

Febrile Neutropenia in Transplant Recipients

Febrile neutropenic patients are at increased risk of developing infections. During the initial stages of neutropenia, most of these infections are bacterial. The spectrum of bacterial infections depends to some extent on whether or not patients receive antimicrobial prophylaxis when neutropenic. Since most transplant recipients do, Gram-positive organisms predominate, due to the fact prophylaxis is directed primarily against Gram-negative organisms. Staphylococcus species (often methicillin-resistant), Streptococcus species (viridans group streptococci, beta-hemolytic streptococci), and Enterococcus species (including vancomycin-resistant strains) are isolated most often. Therefore, potent empiric Gram-positive coverage is recommended by many in this setting. Escherichia coli, Pseudomonas aeruginosa, and Klebsiella species are the most common Gram-negative pathogens isolated. Non-fermentative Gram-negative bacilli (Stenotrophomonas maltophilia, Acinetobacter species) are emerging as important pathogens. Many of these organisms acquire multiple mechanisms of resistance that render them multidrug resistant. The administration of prompt, broad-spectrum, empiric, antimicrobial therapy is essential and is generally based on local epidemiology and susceptibility/resistance patterns. Response rate to the initial regimen is generally in the range of 75–85%. Fungal infections develop in patients with prolonged neutropenia (greater than 7–10 days). Candida species and Aspergillus species are the predominant fungal pathogens, although many other fungi are opportunistic pathogens in this setting. Fungal infections are seldom documented microbiologically or on histopathology, and the administration of empiric antifungal therapy, when such infections are suspected, is the norm. Therapy is often prolonged, and outcomes are still suboptimal. The importance of infection control and antimicrobial stewardship cannot be overemphasized.

Multiple bloodstream infections in pediatric stem cell transplant recipients: A case series

Bacterial bloodstream infections (BSIs) are associated with poor outcomes following stem cell transplantation (SCT). We describe the demographics, treatment, complications, and outcome of 23 pediatric SCT recipients who developed three or more BSIs in the first year after SCT at our center from 2011 through 2016. The majority underwent allogeneic SCT (n = 22/23;96%), mainly from an unrelated donor (n = 19/22,86%); developed grade 2-4 graft versus host disease (GVHD; n = 14/23, 61%), all steroid refractory; and were diagnosed with thrombotic microangiopathy (n = 21/23, 91%). One-year overall survival was 56% (n = 13/23). We observed a high rate of transplant-associated thrombotic microangiopathy and steroid-refractory acute GVHD in patients with three or more BSIs.

Ceftolozane-tazobactam therapy for multidrug-resistant Pseudomonas aeruginosa infections in patients with hematologic malignancies and hematopoietic-cell transplant recipients

Multidrug-resistant (MDR) Pseudomonas aeruginosa infection causes significant mortality among patients with hematologic malignancies and hematopoietic-cell transplant recipients. Ceftolozane-tazobactam (C-T) is a novel therapeutic option for MDR-P. aeruginosa infections but clinical experience in these patients is limited. We report favorable clinical outcomes and lack of limiting toxicities using C-T monotherapy to treat invasive MDR-P. aeruginosa infections in these patient populations.

Thrombospondin-1 protects against pathogen-induced lung injury by limiting extracellular matrix proteolysis

Acute lung injury is characterized by excessive extracellular matrix proteolysis and neutrophilic inflammation. A major risk factor for lung injury is bacterial pneumonia. However, host factors that protect against pathogen-induced and host-sustained proteolytic injury following infection are poorly understood. Pseudomonas aeruginosa (PA) is a major cause of nosocomial pneumonia and secretes proteases to amplify tissue injury. We show that thrombospondin-1 (TSP-1), a matricellular glycoprotein released during inflammation, dose-dependently inhibits PA metalloendoprotease LasB, a virulence factor. TSP-1-deficient (Thbs1-/-) mice show reduced survival, impaired host defense, and increased lung permeability with exaggerated neutrophil activation following acute intrapulmonary PA infection. Administration of TSP-1 from platelets corrects the impaired host defense and aberrant injury in Thbs1-/- mice. Although TSP-1 is cleaved into 2 fragments by PA, TSP-1 substantially inhibits Pseudomonas elastolytic activity. Administration of LasB inhibitor, genetic disabling of the PA type II secretion system, or functional deletion of LasB improves host defense and neutrophilic inflammation in mice. Moreover, TSP-1 provides an additional line of defense by directly subduing host-derived proteolysis, with dose-dependent inhibition of neutrophil elastase from airway neutrophils of mechanically ventilated critically ill patients. Thus, a host matricellular protein provides dual levels of protection against pathogen-initiated and host-sustained proteolytic injury following microbial trigger.

High mortality of bloodstream infection outbreak caused by carbapenem-resistant P. aeruginosa producing SPM-1 in a bone marrow transplant unit

PURPOSE

Carbapenem resistance in P. aeruginosa is increasing worldwide. In Brazil, SPM-1 is the main P. aeruginosa carbapenemase identified. Little is known about the virulence factor in SPM-1 clones.Methodolgy. We describe a carbapenem-resistant P. aeruginosa bloodstream infection (CRPa-BSI) outbreak in a bone marrow transplant Unit (BMT). Twenty-nine CRPa-BSI cases were compared to 58 controls. Microbiological characteristics of isolates, such as sensitivity, carbapenemase gene PCR for P. aeruginosa, and PFGE are described, as well as the whole-genome sequence (WGS) of three strains.Results/Key findings. The cultures from environmental and healthcare workers were negative. Some isolates harboured KPC and SPM. The WGS showed that the 03 strains belonged to ST277, presented the same mutations in outer membrane protein, efflux pump, and virulence genes such as those involved in adhesion, biofilm, quorum-sensing and the type III secretion system, but differ regarding the carbapenemase profile. A predominant clone-producing SPM harbouring Tn 4371 was identified and showed cross-transmission; no common source was found. Overall mortality rate among cases was 79 %. The first multivariate analysis model showed that neutropenia (P=0.018), GVHD prophylaxis (P=0.016) and prior use of carbapenems (P=0.0089) were associated with CRPa-BSI. However, when MASCC>21 points and platelets were added in the final multivariate analysis, only prior use of carbapenems remained as an independent risk factor for CRPa-BSI (P=0.043).

CONCLUSIONS

The predominant clone belonging to ST277 showed high mortality. Carbapenem use was the only risk factor associated with CRPa-BSI. This finding is a wake-up call for the need to improve management in BMT units.

Syk inhibitor R406 downregulates inflammation in an in vitro model of Pseudomonas aeruginosa infection

As Pseudomonas aeruginosa infections are characterized by strong inflammation of infected tissues, anti-inflammatory therapies in combination with antibiotics have been considered for the treatment of associated diseases. Syk tyrosine kinase is an important regulator of inflammatory responses, and its specific inhibition was explored as a therapeutic option in several inflammatory conditions; however, this has not been studied in bacterial infections. We used a model of in vitro infection of human monocytic cell line THP-1 and lung epithelial cell line H292 with both wild-type and flagella-deficient mutant of P. aeruginosa strain K, as well as with clinical isolates from cystic fibrosis patients, to study the effect of a small molecule Syk inhibitor R406 on inflammatory responses induced by this pathogen. One-hour pretreatment of THP-1 cells with 10 μmol/L R406 resulted in a significant downregulation of the expression of the adhesion molecule ICAM-1, pro-inflammatory cytokines TNF-α and IL-1β, and phosphorylated signaling proteins ERK2, JNK, p-38, and IκBα, as well as significantly decreased TNF-α release by infected H292 cells. The results suggest that Syk is involved in the regulation of inflammatory responses to P. aeruginosa, and R406 may potentially be useful in dampening the damage caused by severe inflammation associated with this infection.

Pseudomonas aeruginosa blood stream infection isolates from patients with recurrent blood stream infection: Is it the same genotype?

The type identity of strains of Pseudomonas aeruginosa from primary and recurrent blood stream infection (BSI) has not been widely studied. Twenty-eight patients were identified retrospectively from 2008 to 2013 from five different laboratories; available epidemiological, clinical and microbiological data were obtained for each patient. Isolates were genotyped by iPLEX MassARRAY MALDI-TOF MS and rep-PCR. This showed that recurrent P. aeruginosa BSI was more commonly due to the same genotypically related strain as that from the primary episode. Relapse due to a genotypically related strain occurred earlier in time than a relapsing infection from an unrelated strain (median time: 26 vs. 91 days, respectively). Line related infections were the most common source of suspected BSI and almost half of all BSI episodes were associated with neutropenia, possibly indicating translocation of the organism from the patient's gut in this setting. Development of meropenem resistance occurred in two relapse isolates, which may suggest that prior antibiotic therapy for the primary BSI was a driver for the subsequent development of resistance in the recurrent isolate.

Infections in Hematopoietic Cell Transplant Recipients: Results From the Organ Transplant Infection Project, a Multicenter, Prospective, Cohort Study

Background

Infection is a major cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT). Our object was to better define the epidemiology and outcomes of infections after HCT.

Methods

This was a prospective, multicenter cohort study of HCT recipients and conducted from 2006 to 2011.

The study included 4 US transplant centers and 444 HCT recipients. Data were prospectively collected for up to 30 months after HCT using a standardized data collection tool.

Results

The median age was 53 years, and median follow up was 413 (range, 5–980) days. The most common reason for HCT was hematologic malignancy (87%). The overall crude mortality was 52%. Death was due to underlying disease in 44% cases and infection in 21%. Bacteremia occurred in 231 (52%) cases and occurred early posttransplant (median day 48). Gram-negative bloodstream infections were less frequent than Gram-positive, but it was associated with higher mortality (45% vs 13%, P = .02). Clostridium difficile infection developed in 148 patients (33%) at a median of 27 days post-HCT. There were 53 invasive fungal infections (IFIs) among 48 patients (11%). The median time to IFI was 142 days. Of 155 patients with cytomegalovirus (CMV) infection, 4% had CMV organ involvement. Varicella zoster infection (VZV) occurred in 13 (4%) cases and was disseminated in 2. Infection with respiratory viruses was seen in 49 patients. Pneumocystis jirovecii pneumonia was rare (1%), and there were no documented cases of nocardiosis, toxoplasmosis, endemic mycoses, or mycobacterial infection. This study lacked standardized antifungal and antiviral prophylactic strategies.

Conclusions

Infection remains a significant cause of morbidity and mortality after HCT. Bacteremias and C difficile infection are frequent, particularly in the early posttransplant period. The rate of IFI is approximately 10%. Organ involvement with CMV is infrequent, as are serious infections with VZV and herpes simplex virus, likely reflecting improved prevention strategies.

Explorative gene analysis of antibiotic tolerance-related genes in adherent and biofilm cells of Pseudomonas aeruginosa

BACKGROUND

Antibiotic tolerance has attracted worldwide attention, as it leads to chronic, refractory, and persistent infections that are difficult to control. Bacterial biofilms are well known to be more tolerant to antibiotics compared to planktonic bacteria. We previously revealed that adherent bacteria on a solid surface also exhibited tolerance to antibiotics before forming a biofilm. However, little is known about the mechanisms of antibiotic tolerance for adherent or biofilm cells.

OBJECTIVES

We investigated the mechanisms of antibiotic tolerance in the biofilm life cycle using adherent and biofilm cells, and evaluated the possibility that common mechanisms operate at each stage.

METHODS

We constructed transposon mutants of Pseudomonas aeruginosa PAO1 and screened for low-tolerant mutants with two different methods, using adherent cells and biofilm cells.

RESULTS

Fourteen and nine mutants exhibiting low antibiotic tolerance were detected in the adherent cells and biofilm cells, and 14 and 7 candidate genes linked to this tolerance were identified by sequencing, respectively. Eight of the 14 genes related to the antibiotic tolerance of the adherent cells were involved in biofilm formation. Two of the seven genes related to the antibiotic tolerance of biofilm cells participated in the antibiotic tolerance of adherent cells.

CONCLUSIONS

The antibiotic tolerance of adherent cells and biofilm formation appear to be under the same regulation mechanism to promote survival in the presence of antibiotics. Antibiotic tolerance shows a complex regulation mechanism at each stage of biofilm formation.

Antibacterial Resistance in Patients with Hematopoietic Stem Cell Transplantation

Recipients of hematopoietic stem cell transplantation (HSCT) are at substantial risk of bacterial, fungal, viral, and parasitic infections depending on the time elapsed since transplantation, presence of graft-versus-host disease (GVHD), and the degree of immunosuppression. Infectious complications in HSCT recipients are associated with high morbidity and mortality. Bacterial infections constitute the major cause of infectious complications, especially in the early post-transplant period. The emergence of antibacterial resistance complicates the management of bacterial infections in this patient group. Multidrug-resistant bacterial infections in this group of patients have attracted considerable interest and may lead to significant morbidity and mortality. Empirical antibacterial therapy in patients with HSCT and febrile neutropenia has a critical role for survival and should be based on local epidemiology. This review attempts to provide an overview of risk factors and epidemiology of emerging resistant bacterial infections and their management in HSCT recipients.

Antibiotic duration and timing of the switch from intravenous to oral route for bacterial infections in children: systematic review and guidelines

Few studies are available to inform duration of intravenous antibiotics for children and when it is safe and appropriate to switch to oral antibiotics. We have systematically reviewed antibiotic duration and timing of intravenous to oral switch for 36 paediatric infectious diseases and developed evidence-graded recommendations on the basis of the review, guidelines, and expert consensus. We searched databases and obtained information from references identified and relevant guidelines. All eligible studies were assessed for quality. 4090 articles were identified and 170 studies were included. Evidence relating antibiotic duration to outcomes in children for some infections was supported by meta-analyses or randomised controlled trials; in other infections data were from retrospective series only. Criteria for intravenous to oral switch commonly included defervescence and clinical improvement with or without improvement in laboratory markers. Evidence suggests that intravenous to oral switch can occur earlier than previously recommended for some infections. We have synthesised recommendations for antibiotic duration and intravenous to oral switch to support clinical decision making and prospective research.

A Microfluidic Channel Method for Rapid Drug-Susceptibility Testing of Pseudomonas aeruginosa

The recent global increase in the prevalence of antibiotic-resistant bacteria and lack of development of new therapeutic agents emphasize the importance of selecting appropriate antimicrobials for the treatment of infections. However, to date, the development of completely accelerated drug susceptibility testing methods has not been achieved despite the availability of a rapid identification method. We proposed an innovative rapid method for drug susceptibility testing for Pseudomonas aeruginosa that provides results within 3 h. The drug susceptibility testing microfluidic (DSTM) device was prepared using soft lithography. It consisted of five sets of four microfluidic channels sharing one inlet slot, and the four channels are gathered in a small area, permitting simultaneous microscopic observation. Antimicrobials were pre-introduced into each channel and dried before use. Bacterial suspensions in cation-adjusted Mueller-Hinton broth were introduced from the inlet slot and incubated for 3 h. Susceptibilities were microscopically evaluated on the basis of differences in cell numbers and shapes between drug-treated and control cells, using dedicated software. The results of 101 clinically isolated strains of P. aeruginosa obtained using the DSTM method strongly correlated with results obtained using the ordinary microbroth dilution method. Ciprofloxacin, meropenem, ceftazidime, and piperacillin caused elongation in susceptible cells, while meropenem also induced spheroplast and bulge formation. Morphological observation could alternatively be used to determine the susceptibility of P. aeruginosa to these drugs, although amikacin had little effect on cell shape. The rapid determination of bacterial drug susceptibility using the DSTM method could also be applicable to other pathogenic species, and it could easily be introduced into clinical laboratories without the need for expensive instrumentation.

Pseudomonas aeruginosa exoenzymes U and Y induce a transmissible endothelial proteinopathy

We tested the hypothesis that Pseudomonas aeruginosa type 3 secretion system effectors exoenzymes Y and U (ExoY and ExoU) induce release of a high-molecular-weight endothelial tau, causing transmissible cell injury characteristic of an infectious proteinopathy. Both the bacterial delivery of ExoY and ExoU and the conditional expression of an activity-attenuated ExoU induced time-dependent pulmonary microvascular endothelial cell gap formation that was paralleled by the loss of intracellular tau and the concomitant appearance of high-molecular-weight extracellular tau. Transfer of the high-molecular-weight tau in filtered supernatant to naïve endothelial cells resulted in intracellular accumulation of tau clusters, which was accompanied by cell injury, interendothelial gap formation, decreased endothelial network stability in Matrigel, and increased lung permeability. Tau oligomer monoclonal antibodies captured monomeric tau from filtered supernatant but did not retrieve higher-molecular-weight endothelial tau and did not rescue the injurious effects of tau. Enrichment and transfer of high-molecular-weight tau to naïve cells was sufficient to cause injury. Thus we provide the first evidence for a pathophysiological stimulus that induces release and transmissibility of high-molecular-weight endothelial tau characteristic of an endothelial proteinopathy.

Incidence rate of fluoroquinolone-resistant gram-negative rod bacteremia among allogeneic hematopoietic cell transplantation patients during an era of levofloxacin prophylaxis

There are concerns that emerging resistance to fluoroquinolones (FQ) may be leading to increasing rates of gram-negative rod (GNR) bacteremia in hematopoietic cell transplant (HCT) recipients. We set out to describe time trends in the incidence rates of GNR bacteremia and FQ-resistant GNR bacteremia in HCT recipients during an era of levofloxacin prophylaxis. We conducted a longitudinal retrospective study of adults undergoing allogeneic HCT between 2003 and 2012 at the Seattle Cancer Care Alliance (SCCA). Annual trends in the incidence rates of GNR bacteremia and FQ-resistant GNR bacteremia through 100 days after transplantation were assessed using Poisson regression. Cox proportional hazards regression was used to compare 30-day mortality between patients with FQ-resistant and those with FQ-sensitive GNR bacteremia. Of the 2306 patients included in this cohort, 280 (12.1%) had GNR bacteremia. The incidence rates of GNR bacteremia and FQ-resistant GNR bacteremia increased from 2003 to 2009 and decreased afterwards; however, the overall annual trends were not significant (incidence rate ratio [IRR], 1.01; 95% confidence interval [CI], .98 to 1.05; IRR, 1.01; 95% CI, .95 to 1.08, respectively). FQ-resistant GNR bacteremia was associated with increased mortality compared with FQ-sensitive GNR bacteremia, even after adjustment for underlying disease severity, conditioning regimen, and age at transplantation (hazard ratio, 2.11; 95% CI, 1.06 to 4.23). On average, rates of FQ-resistant GNR bacteremia have not significantly changed over 10 years of FQ prophylaxis, although FQ-resistant GNR bacteremia is associated with increased mortality compared with FQ-sensitive GNR bacteremia.

Pseudomonas aeruginosa AmpR: an acute-chronic switch regulator

Pseudomonas aeruginosa is one of the most intractable human pathogens that pose serious clinical challenge due to extensive prevalence of multidrug-resistant clinical isolates. Armed with abundant virulence and antibiotic resistance mechanisms, it is a major etiologic agent in a number of acute and chronic infections. A complex and intricate network of regulators dictates the expression of pathogenicity factors in P. aeruginosa. Some proteins within the network play key roles and control multiple pathways. This review discusses the role of one such protein, AmpR, which was initially recognized for its role in antibiotic resistance by regulating AmpC β-lactamase. Recent genomic, proteomic and phenotypic analyses demonstrate that AmpR regulates expression of hundreds of genes that are involved in diverse pathways such as β-lactam and non-β-lactam resistance, quorum sensing and associated virulence phenotypes, protein phosphorylation, and physiological processes. Finally, ampR mutations in clinical isolates are reviewed to shed light on important residues required for its function in antibiotic resistance. The prevalence and evolutionary implications of AmpR in pathogenic and nonpathogenic proteobacteria are also discussed. A comprehensive understanding of proteins at nodal positions in the P. aeruginosa regulatory network is crucial in understanding, and ultimately targeting, the pathogenic stratagems of this organism.

Is admission screening for Pseudomonas aeruginosa useful in haematologic patients? A prospective study with 1310 patients

Screening for Pseudomonas aeruginosa is recommended to guide empirical antimicrobial therapy in patients on high-risk units. However, evidence for this approach is scarce. We therefore screened 1310 patients with severe haematologic diseases for P. aeruginosa colonization at admission: 108 (8.2%) were positive, but only nine (0.7%; six with the same clone as in the screening isolate) subsequently developed a P. aeruginosa bloodstream infection (positive predictive value of screening, 8.6%; negative predictive value of screening, 99.5%). Routine screening for P. aeruginosa at admission did not sufficiently predict subsequent bloodstream infections caused by P. aeruginosa.

Fecal colonization and infection with Pseudomonas aeruginosa in recipients of allogeneic hematopoietic stem cell transplantation

BACKGROUND

Pseudomonas aeruginosa, especially multidrug-resistant (MDR) isolates, is an important pathogen in allogeneic hematopoietic stem cell transplant (HCT) recipients. The ability to identify patients at risk for these infections and administer appropriate empiric therapy, particularly during episodes of neutropenia, may improve outcomes and also direct infection control and antimicrobial stewardship efforts. Many transplant centers obtain routine surveillance stool cultures (SSCs) from HCT recipients to test for colonization with vancomycin-resistant enterococci, and extended-spectrum beta lactamase-producing Enterobacteriaceae. Our center initiated the performance of SSCs for P. aeruginosa, because of a perceived increase in the frequency of infection with MDR strains. The aim of this study was to determine the utility of this practice.

METHODS

We conducted a 2-year (2010-2011) retrospective review of the medical records of all patients who underwent allogeneic HCT at our cancer center to (a) determine the frequency of fecal colonization with P. aeruginosa, including MDR strains; (b) to determine the overall frequency of subsequent P. aeruginosa infection, as well as the frequency of infection with MDR strains; (c) to ascertain the proportion of subsequent infections likely arising from the intestinal tract; and (d) to determine risk factors for progression from colonization to infection.

RESULTS

Of 794 study patients, 58 (7.3%) had at least 1 positive SSC for P. aeruginosa; 19/58 (32.8%) developed a subsequent pseudomonal infection (11 with matching antimicrobial resistance patterns). On the other hand, 37/736 (5%) of the patients who were not colonized, developed a pseudomonal infection. The type of infection observed was pneumonia in 26 (46%) patients, bloodstream infection in 20 (36%), urinary tract infection in 8 (14%), and infections at other sites in 2 (4%). The incidence of MDR P. aeruginosa in the entire cohort was 2.2% (18 of 794): 12 had positive SSCs and 7 of these patients later developed MDR P. aeruginosa infections. Patients with acute myelogenous leukemia were more likely to be colonized and to develop subsequent infection. No infection-related deaths were observed during the first 30 days after infection.

CONCLUSIONS

The incidence of P. aeruginosa colonization and subsequent infection was low. Patients who were not colonized had a low chance of developing P. aeruginosa infection. Most patients who developed infection did not have fecal colonization, suggesting a different source of infection. SSCs for P. aeruginosa provide incomplete information regarding the source of infection.

Transforming growth factor-β induces microRNA-29b to promote murine alveolar macrophage dysfunction after bone marrow transplantation

Hematopoietic stem cell transplantation (HSCT) is complicated by pulmonary infections that manifest posttransplantation. Despite engraftment, susceptibility to infections persists long after reconstitution. Previous work using a murine bone marrow transplant (BMT) model implicated increased cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE2) in promoting impaired alveolar macrophage (AM) responses. However, mechanisms driving COX-2 overexpression remained elusive. Previously, transforming growth factor-β (TGF-β) signaling after BMT was shown to promote hypomethylation of the COX-2 gene. Here, we provide mechanistic insight into how this occurs and show that TGF-β induces microRNA (miR)-29b while decreasing DNA methyltransferases (DNMT)1, DNMT3a, and DNMT3b in AMs after BMT. De novo DNMT3a and DNMT3b were decreased upon transient transfection of miR-29b, resulting in decreased methylation of the COX-2 promoter and induction of COX-2. As a consequence, miR-29b-driven upregulation of COX-2 promoted AM dysfunction, and transfection of BMT AMs with a miR-29b inhibitor rescued the bacterial-killing defect. MiR-29b-mediated defects in BMT AMs were dependent on increased levels of PGE2, as miR-29b-transfected AMs treated with a novel E prostanoid receptor 2 antagonist abrogated the impaired bacterial killing. We also demonstrate that patients that have undergone HSCT exhibit increased miR-29b; thus these studies highlight miR-29b in driving defective AM responses and identify this miRNA as a potential therapeutic target.

Management of febrile neutropenia in the era of bacterial resistance

Managing cancer patients with fever and neutropenia must be considered as a medical emergency since any delay in initiating appropriate empirical antibacterial therapy may result in high rates of mortality and morbidity. Emerging antibacterial resistance in bacterial pathogens infecting febrile neutropenic patients complicates management, and choosing the type of empirical antimicrobial therapy has become a challenge. To further complicate the decision process, not all neutropenic patients are in same category of susceptibility to develop severe infection. While low-risk patients may be treated with oral antibiotics in the outpatient setting, high-risk patients usually need to be admitted to hospital and receive parenteral broad-spectrum antibiotics until the neutrophil levels recover. These strategies have recently been addressed in two international guidelines from the Infectious Diseases Society of America (IDSA) and the European Conference on Infections in Leukaemia (ECIL). This review gives a brief overview of current antimicrobial resistance problems and their effects in febrile neutropenic cancer patients by summarizing the suggestions from the IDSA and ECIL guidelines.

Infection control and prevention considerations

Due to the nature of their underlying illness and treatment regimens, cancer patients are at increased risk of infection. Though the advent and widespread use of anti-infective agents has allowed for the application of ever-greater immune-suppressing therapies with successful treatment of infectious complications, prevention of infection remains the primary goal. The evolutionary changes of microorganisms, whereby resistance to anti-infective therapy is increasingly common, have facilitated a paradigm shift in the field of healthcare epidemiology. No longer is the focus on "control" of infection once established in a healthcare environment. Rather, the emphasis is on prevention of infection before it occurs. The most basic tenet of infection prevention, and the cornerstone of all well-designed infection prevention and control programs, is hand hygiene. The hands of healthcare workers provide a common potential source for transmission of infectious agents, and effective decontamination of the hands reduces the risk of transmission of infectious material to other patients. Once infection is suspected or established; however, implementation of effective control strategies is important to limit the spread of infection within a healthcare environment. This chapter outlines the basic tenets of infection prevention, principles of isolation precautions and control measures, and elements for a successful infection control and prevention program.

Bacterial pathogens

Bacterial infections are frequent complications among patients treated for cancer. The type, severity, and treatment of bacterial infections vary and depend upon the specific malignancy, associated chemotherapies, and transplantation. This chapter discusses commonly encountered bacterial pathogens as well as Nocardia and mycobacteria in patients with cancer and addresses the clinical syndromes and management. Drug-resistant bacteria are becoming an increasingly recognized problem in patients with cancer. Antimicrobial resistance in select gram-positive and gram-negative bacteria are discussed along with the mechanisms of resistance and recommended therapies.

Combining in silico and biophysical methods for the development of Pseudomonas aeruginosa quorum sensing inhibitors: an alternative approach for structure-based drug design

The present work deals with the optimization of an inhibitor of PqsD, an enzyme essential for Pseudomonas aeruginosa quorum sensing apparatus. Molecular docking studies, supported by biophysical methods (surface plasmon resonance, isothermal titration calorimetry, saturation transfer difference NMR), were used to illuminate the binding mode of the 5-aryl-ureidothiophene-2-carboxylic acids. Enabled to make profound predictions, structure-based optimization led to increased inhibitory potency. Finally a covalent inhibitor was obtained. Binding to the active site was confirmed by LC-ESI-MS and MALDI-TOF-MS experiments. Following this rational approach, potent PqsD inhibitors were efficiently developed within a short period of time. This example shows that a combination and careful application of in silico and biophysical methods represents a powerful complement to cocrystallography.

Structure optimization of 2-benzamidobenzoic acids as PqsD inhibitors for Pseudomonas aeruginosa infections and elucidation of binding mode by SPR, STD NMR, and molecular docking

Pseudomonas aeruginosa employs a characteristic pqs quorum sensing (QS) system that functions via the signal molecules PQS and its precursor HHQ. They control the production of a number of virulence factors and biofilm formation. Recently, we have shown that sulfonamide substituted 2-benzamidobenzoic acids, which are known FabH inhibitors, are also able to inhibit PqsD, the enzyme catalyzing the last and key step in the biosynthesis of HHQ. Here, we describe the further optimization and characterization of this class of compounds as PqsD inhibitors. Structural modifications showed that both the carboxylic acid ortho to the amide and 3'-sulfonamide are essential for binding. Introduction of substituents in the anthranilic part of the molecule resulted in compounds with IC50 values in the low micromolar range. Binding mode investigations by SPR with wild-type and mutated PqsD revealed that this compound class does not bind into the active center of PqsD but in the ACoA channel, preventing the substrate from accessing the active site. This binding mode was further confirmed by docking studies and STD NMR.

Delayed opportunistic infections in hematopoietic stem cell transplantation patients: a surmountable challenge

Changes in the transplantation procedure and the implementation of effective supportive care strategies have decreased the incidence of infectious complications early after conditioning therapy for allogeneic hematopoietic stem cell transplantation (HCT) and have extended the duration of risks later. Therefore, the types of infections that cause significant morbidity and the timing of risks have changed. These late infections are caused by all types of organisms, bacterial, viral, and fungal, but risks are predictable and surmountable with the use of tailored prevention strategies. Specifically, recent studies document prolonged risks for bacterial infections in the setting of GVHD, especially those caused by encapsulated organisms and those secondary to impaired Ab responses. Both prophylaxis and vaccination strategies can be used as a means to prevent infections, which typically manifest in the respiratory tract. Multiple viruses cause infection later after HCT, including several herpesviruses (eg, CMV and varicella zoster virus) and other respiratory viruses such as influenza and adenovirus. These infections can cause severe disease with diagnostic challenges, but prevention strategies using enhanced monitoring and/or prophylaxis may be effective. Finally, fungi also cause disease late after HCT, especially filamentous fungi (eg, Aspergillus species and Mucormycoses) and Pneumocystis jiroveci; prophylactic strategies may be used successfully to prevent invasive infection. Late infections and methods to prevent them are reviewed herein.

Risk factors, clinical features, and outcome of Pseudomonas aeruginosa bacteremia in patients with hematologic malignancies: a case-control study

BACKGROUND

We observed an increased rate of Pseudomonas aeruginosa bacteremia in our hematology unit in 2004-2007 without an identified environmental source.

METHODS

We conducted a matched case-control study to investigate factors associated with P aeruginosa bacteremia in patients with hematologic malignancies.

RESULTS

Forty-two episodes of P aeruginosa bacteremia were identified. At presentation, 26 patients (62%) had pneumonia and 9 patients (21%) were in shock. Twenty-five patients (60%) were aplastic. The clinical cure rate was 40%. Comparing the 42 cases with 84 matched controls identified the following independent risk factors for P aeruginosa bacteremia: hospitalization in the previous 3 months (odds ratio [OR], 12.84; 95% confidence interval [CI], 2.98-55.18), antibiotic therapy in the previous 3 months (OR, 5.34; 95% CI, 2.14-13.30), receipt of ceftriaxone in the previous 3 months (OR, 2.38; 95% CI, 1.08-5.27), receipt of aminoglycosides in the previous 3 months (OR, 6.65; 95% CI, 1.15-38.25) and receipt of fluoroquinolones in the previous 3 months (OR, 3.22; 95% CI, 1.48-7.00).

CONCLUSIONS

Local antibiotic therapy algorithms were modified to decrease prescriptions of ceftriaxone and combination therapy with aminoglycosides and fluoroquinolones in an effort to decrease the risk of P aeruginosa bacteremia.

Defective pulmonary innate immune responses post-stem cell transplantation; review and results from one model system

Infectious pulmonary complications limit the success of hematopoietic stem cell transplantation (HSCT) as a therapy for malignant and non-malignant disorders. Susceptibility to pathogens in both autologous and allogeneic HSCT recipients persists despite successful immune reconstitution. As studying the causal effects of these immune defects in the human population can be limiting, a bone marrow transplant (BMT) mouse model can be used to understand the defect in mounting a productive innate immune response post-transplantation. When syngeneic BMT is performed, this system allows the study of BMT-induced alterations in innate immune cell function that are independent of the confounding effects of immunosuppressive therapy and graft-versus-host disease. Studies from several laboratories, including our own show that pulmonary susceptibility to bacterial infections post-BMT are largely due to alterations in the lung alveolar macrophages. Changes in these cells post-BMT include cytokine and eicosanoid dysregulations, scavenger receptor alterations, changes in micro RNA profiles, and alterations in intracellular signaling molecules that limit bacterial phagocytosis and killing. The changes that occur highlight mechanisms that promote susceptibility to infections commonly afflicting HSCT recipients and provide insight into therapeutic targets that may improve patient outcomes post-HSCT.

Prostaglandin E2-induced changes in alveolar macrophage scavenger receptor profiles differentially alter phagocytosis of Pseudomonas aeruginosa and Staphylococcus aureus post-bone marrow transplant

The effectiveness of hematopoietic stem cell transplantation as a therapy for malignant and nonmalignant conditions is complicated by pulmonary infections. Using our syngeneic bone marrow transplant (BMT) mouse model, BMT mice with a reconstituted hematopoietic system displayed increased susceptibility to Pseudomonas aeruginosa and Staphylococcus aureus. BMT alveolar macrophages (AMs) exhibited a defect in P. aeruginosa phagocytosis, whereas S. aureus uptake was surprisingly enhanced. We hypothesized that the difference in phagocytosis was due to an altered scavenger receptor (SR) profile. Interestingly, MARCO expression was decreased, whereas SR-AI/II was increased. To understand how these dysregulated SR profiles might affect macrophage function, CHO cells were transfected with SR-AI/II, and phagocytosis assays revealed that SR-AI/II was important for S. aureus uptake but not for P. aeruginosa. Conversely, AMs treated in vitro with soluble MARCO exhibited similar defects in P. aeruginosa internalization as did BMT AMs. The 3'-untranslated region of SR-AI contains a putative target region for microRNA-155 (miR-155), and miR-155 expression is decreased post-BMT. Anti-miR-155-transfected AMs exhibited an increase in SR-AI/II expression and S. aureus phagocytosis. Elevated PGE2 has been implicated in driving an impaired innate immune response post-BMT. In vitro treatment of AMs with PGE2 increased SR-AI/II and decreased MARCO and miR-155. Despite a difference in phagocytic ability, BMT AMs harbor a killing defect to both P. aeruginosa and S. aureus. Thus, our data suggest that PGE2-driven alterations in SR and miR-155 expression account for the differential phagocytosis of P. aeruginosa and S. aureus, but impaired killing ultimately confers increased susceptibility to pulmonary infection.

Delayed opportunistic infections in hematopoietic stem cell transplantation patients: a surmountable challenge

Changes in the transplantation procedure and the implementation of effective supportive care strategies have decreased the incidence of infectious complications early after conditioning therapy for allogeneic hematopoietic stem cell transplantation (HCT) and have extended the duration of risks later. Therefore, the types of infections that cause significant morbidity and the timing of risks have changed. These late infections are caused by all types of organisms, bacterial, viral, and fungal, but risks are predictable and surmountable with the use of tailored prevention strategies. Specifically, recent studies document prolonged risks for bacterial infections in the setting of GVHD, especially those caused by encapsulated organisms and those secondary to impaired Ab responses. Both prophylaxis and vaccination strategies can be used as a means to prevent infections, which typically manifest in the respiratory tract. Multiple viruses cause infection later after HCT, including several herpesviruses (eg, CMV and varicella zoster virus) and other respiratory viruses such as influenza and adenovirus. These infections can cause severe disease with diagnostic challenges, but prevention strategies using enhanced monitoring and/or prophylaxis may be effective. Finally, fungi also cause disease late after HCT, especially filamentous fungi (eg, Aspergillus species and Mucormycoses) and Pneumocystis jiroveci; prophylactic strategies may be used successfully to prevent invasive infection. Late infections and methods to prevent them are reviewed herein.

Infections in Leukemia and Hematopoietic Stem Cell Transplantation

Infections are one of the most common complications in patients diagnosed with leukemia and serve as a major obstacle to treatment. Through the early 1970s, infections were the most common cause of death in patients diagnosed with acute leukemia, but improvement in treatment and supportive care over the past few decades, coupled with expanded prophylaxis and prevention regimens, have led to reduction in both the frequency and severity of infections. Regardless, due in part to an aging cancer population and the diversity of cancer treatments and procedures, infectious diseases remain a major cause of morbidity and mortality in patients with leukemia.