Central venous catheter-related Stenotrophomonas maltophilia bacteraemia and associated relapsing bacteraemia in haematology and oncology patients

Risk factors for mortality in Stenotrophomonas maltophilia bacteremia - a meta-analysis

BACKGROUND

Stenotrophomonas maltophilia (S. maltophilia) is a nosocomial pathogen causing life-threatening invasive infections with a high mortality rate in some patient populations, especially those who are severely ill or immunocompromised. There is a need for data on mortality in patients with S. maltophilia bacteremia.

OBJECTIVE

In this meta-analysis, we aimed to investigate risk factors for mortality in S. maltophilia bacteremia.

METHODS

Studies comparing patients who died from S. maltophilia bacteremia with patients who survived were considered for inclusion. Studies were included if they reported one or more risk factors for mortality. Mortality risk factors included clinical predisposing factors, predisposing comorbidities and appropriateness of antibiotic therapy.

RESULTS

Nineteen studies with 1248 patients were included in the meta-analysis. Five hundred and six (40.5%) patients died. The following risk factors for mortality were identified: ICU admission, septic shock, need for mechanical ventilation, indwelling central venous catheter, neutropenia, comorbid hematological malignancies, chronic kidney disease, inappropriate antimicrobial therapy and prior antibiotic use.

CONCLUSIONS

Appropriate antimicrobial therapy had a protective effect against mortality in S. maltophilia bacteremia. Indwelling central venous catheter, neutropenia, hematological malignancies and chronic kidney disease were also risk factors for mortality.

Validation of a Stenotrophomonas maltophilia bloodstream infection prediction score in the hematologic malignancy population

Stenotrophomonas maltophilia (SM) bloodstream infections (BSIs) contribute to significant mortality in hematologic malignancy (HM) and hematopoietic stem cell transplantation (HSCT) patients. A risk score to predict SM BSI could reduce time to appropriate antimicrobial therapy (TTAT) and improve patient outcomes. A single center cohort study of hospitalized adults with HM/HSCT was conducted. Patients had ≥ 1 blood culture with a Gram-negative (GN) organism. A StenoSCORE was calculated for each patient. The StenoSCORE2 was developed using risk factors for SM BSI identified via logistic regression. Receiver operating characteristic (ROC) curves were plotted. Sensitivity and specificity for the StenoSCORE and StenoSCORE2 were calculated. Thirty-six SM patients and 534 non-SM patients were assessed. A StenoSCORE ≥ 33 points was 80% sensitive, 68% specific, and accurately classified 69% of GN BSIs. StenoSCORE2 variables included acute leukemia, prolonged neutropenia, mucositis, ICU admission, recent meropenem and/or cefepime exposure. The StenoSCORE2 performed better than the StenoSCORE (ROC AUC 0.84 vs. 0.77). A StenoSCORE2 ≥ 4 points was 86% sensitive, 76% specific, and accurately classified 77% of GN BSIs. TTAT was significantly longer for patients with SM BSI compared with non-SM BSI (45.16 h vs. 0.57 h; p < 0.0001). In-hospital and 28-day mortality were significantly higher for patients with SM BSI compared to non-SM BSI (58.3% vs. 18.5% and 66.7% vs. 26.4%; p-value < 0.0001). The StenoSCORE and StenoSCORE2 performed well in predicting SM BSIs in patients with HM/HSCT and GN BSI. Clinical studies evaluating whether StenoSCORE and/or StenoSCORE2 implementation improves TTAT and clinical outcomes are warranted.

Microbiological Characterization and Clinical Facets of Elizabethkingia Bloodstream Infections in a Tertiary Care Hospital of Eastern India

Purpose

Elizabethkingia is an emerging non-fermenting Gram-negative bacillus (NFGNB) causing bloodstream infections (BSI) associated with high mortality. It demonstrates a unique antimicrobial profile in showing susceptibility to antimicrobials effective against Gram-positive bacteria. This study was undertaken to determine the overall frequency of Elizabethkingia BSI, associated risk factors, microbiological susceptibility, and clonal relationship of Elizabethkingia isolates using Enterobacterial Repetitive Intergenic Consensus Polymerase Chain Reaction (ERIC-PCR).

Patients and Methods

Elizabethkingia isolates obtained from the blood culture of admitted patients (August 2020-December 2021) were identified by the VITEK 2 system and subjected to an antimicrobial susceptibility test by standard procedures. Demographics, co-morbidities, risk factors for survival, and outcome were summarized and analyzed by Chi-square test, Kaplan-Meier curve, and Cox regression. Clonal relatedness between Elizabethkingia isolates was analyzed using ERIC‑PCR fingerprinting with the "PAST: Paleontological statistics software package".

Results

Of 13,747 blood samples received during the study period, 13.59% were culture positive, and 14.60% were NFGNBs. The frequency of Elizabethkingia spp. among all NFGNBs in BSI was 29.30%, and the overall prevalence in BSI was 4.21%. In patients with Elizabethkingia BSI, Foley's catheter was present in 81.25% of the cases. 100% susceptibility was observed to linezolid, followed by vancomycin (98.75%) and chloramphenicol (89.5%). The 30-day mortality rate in the patients of Elizabethkingia BSI was 26.25%. The Presence of COVID-19, pneumonia, diabetes mellitus (DM), mechanical ventilation (MV), and prior antibiotics were significantly different (p<0.05) between the survival and death groups. ERIC-PCR profile dendrogram of Elizabethkingia isolates showed ten major clusters indicating high genetic diversity.

Conclusion

Elizabethkingia was responsible for one-third of NFGNB BSI in a single-center study, with approximately 26% of 30-day all-cause mortality. Most isolates were susceptible to linezolid, vancomycin, and chloramphenicol. COVID-19 was the most significant risk factor associated with mortality. ERIC-PCR of Elizabethkingia isolates exhibited high genetic diversity.

Fulminant Metastatic Cellulitis Caused by Stenotrophomonas Maltophilia Infection and Subsequent Candida Parapsilosis Fungemia After Cord Blood Transplantation

Stenotrophomonas maltophilia is known to be an opportunistic pathogen with intrinsic and acquired resistance mechanisms to multiple antibiotics. Bloodstream infection caused by S. maltophilia is a potentially fatal complication, especially in recipients of umbilical cord blood transplantation (CBT). Infrequent reports of S. maltophilia skin and soft tissue infections (SSTIs), including metastatic cellulitis and ecthyma gangrenosum, have been reported as wound infections. Metastatic cellulitis lesions due to S. maltophilia are typically reported to be tender, erythematous, and to show warm subcutaneous infiltration. There are only a few available reports about the clinical course of metastatic cellulitis due to S. maltophilia. We experienced a case involving the development of metastatic cellulitis with fulminant and extensive exfoliation in a patient who underwent CBT. Despite controlling the bloodstream infection caused by S. maltophilia, the patient succumbed to secondary fungal infection due to the devastation of the skin barrier. Our case highlights that SSTIs due to S. maltophilia can cause the unexpected development of fulminant metastatic cellulitis with systemic epidermal peeling in severely immunocompromised hosts, including CBT recipients undergoing steroid therapy.

Infections With Stenotrophomonas maltophilia in Children Undergoing Anticancer Therapy or Hematopoietic Cell Transplantation: A Multicenter Nationwide Study

BACKGROUND

Infections caused by Stenotrophomonas maltophilia (SM) have documented high mortality rate in immunocompromised patients.

AIM

This nationwide multicenter study was performed to analyze the epidemiology of SM infections in children undergoing anticancer therapy (pediatric hematology and oncology [PHO]) or hematopoietic cell transplantation (HCT) over 2012-2019, including incidence and outcome of SM infections, as well as treatment regimens and multidrug resistance.

METHODS

Cumulative incidence of SM infections was calculated using the competing risk analysis from the day of diagnosis (PHO setting) or from the day of transplantation (HCT setting). The Kaplan-Meier method was used to determine survival from infection.

RESULTS

During the study period of 8 years, a total number of 1356 HCTs and 7337 children newly diagnosed for malignancy were analyzed. Diagnosis of acute leukemia was a predisposing factor for SM infection. The cumulative incidence of SM infections was comparable in HCT patients in comparison to PHO (0.81% vs. 0.76%). High rate of trimethoprim/sulfamethoxazole susceptibility among SM isolates was observed in both groups of patients (80.8%). Although this was the drug of choice, survival rates from SM infections were significantly lower in HCT than in PHO (45% vs. 85%, P = 0.001, log-rank test). We found the transplant procedure and lack of clinical resolution after 18 days of antibiotic therapy to be independent mortality risk factors.

CONCLUSIONS

The risk of SM infections and the occurrence of resistant bacterial strains in allo-HCT patients were comparable to PHO patients. Irrespective of target antibiotic therapy, the outcome of SM infections was better in the PHO setting.

Clinical challenges treating Stenotrophomonas maltophilia infections: an update

Stenotrophomonas maltophilia is a non-fermenting, Gram-negative bacillus that has emerged as an opportunistic nosocomial pathogen. Its intrinsic multidrug resistance makes treating infections caused by S. maltophilia a great clinical challenge. Clinical management is further complicated by its molecular heterogeneity that is reflected in the uneven distribution of antibiotic resistance and virulence determinants among different strains, the shortcomings of available antimicrobial susceptibility tests and the lack of standardized breakpoints for the handful of antibiotics with in vitro activity against this microorganism. Herein, we provide an update on the most recent literature concerning these issues, emphasizing the impact they have on clinical management of S. maltophilia infections.

Healthcare-Associated Stenotrophomonas maltophilia Bacteraemia: Retrospective Evaluation of Treatment and Outcome

Introduction

Stenotrophomonas maltophilia (SM) is one of the common gram-negative pathogens that cause nosocomial infections. The aim of the present study is to evaluate the treatment and outcome of SM bacteraemia.

Materials and Methods

We retrospectively evaluated antimicrobial treatment in adult patients with nosocomial SM bacteraemia, with the 14th and 30th-day mortality as the outcome.

Results

In total, 140 adult patients with SM bacteraemia who were diagnosed between January 1, 2002, and December 31, 2016 were enrolled in the present study. Seventy-one (50.7%) patients were in the intensive care unit (ICU). The 14th and the 30th-day mortality rates were 32.9% (n=46) and 45.7% (n=64), respectively. Female sex (OR, 7.47; 95% CI 1.61-34.47, p<0.01), steroid use within the last month (OR, 10.2; 95% CI 1.27-82.27, p=0.029), Pittsburgh bacteraemia score (PBS) ≥4 (OR, 39.9; 95% CI 4.96-321.32, p<0.001) and solid organ malignancy (OR, 9.6; 95% CI 1.73-53.72, p<0.01) were independent risk factors for 14th day mortality. Removal of the catheter was an independent protective factor for both 14th (OR, 0.05; 95% CI 0.22-0.010, p<0.001) and 30th day (OR, 0.039;95% CI 0.164-0.009, p<0.001) mortality. We did not detect any difference between treatment regimens including trimethoprim-sulfamethoxazole (TMP/SMX) or levofloxacin in terms of mortality. We found that TMP/SMX and levofloxacin combination did not significantly improve patient prognosis.

Conclusion 

Due to the high mortality rates associated with nosocomial SM bacteraemia, adequate antibiotic therapy should be initiated immediately in the suspicion of infection, and prompt removal of any indwelling central venous catheter is important.

Stenotrophomonas maltophilia Infections in Pediatric Patients - Experience at a European Center for Pediatric Hematology and Oncology

Stenotrophomonas maltophilia is an important nosocomial pathogen in immunocom-promised individuals and characterized by intrinsic resistance to broad-spectrum antibacterial agents. Limited data exists on its clinical relevance in immunocompromised pediatric patients, particularly those with hematological or oncological disorders. In a retrospective single center cohort study in pediatric patients receiving care at a large european pediatric hematology and oncology department, ten cases of invasive S.maltophilia infections (blood stream infections (BSI), 4; BSI and pneumonia, 3, or soft tissue infection, 2; and pneumonia, 1) were identified between 2010 and 2020. Seven patients had lymphoblastic leukemia and/or were post allogeneic hematopoietic cell transplantation. Invasive S.maltophilia infections occurred in a setting of indwelling central venous catheters, granulocytopenia, defective mucocutaneous barriers, treatment with broad-spectrum antibacterial agents, and admission to the intensive care unit. Whole genome sequencing based typing revealed no genetic relationship among four individual S.maltophilia isolates. The case fatality rate and mortality at 100 days post diagnosis were 40 and 50%, respectively, and three patients died from pulmonary hemorrhage. Invasive S.maltophilia infections are an emerging cause of infectious morbidity in patients receiving care at departments of pediatric hematology and oncology and carry a high case fatality rate.

Effects of Simulated Microgravity on the Physiology of Stenotrophomonas maltophilia and Multiomic Analysis

Many studies have shown that the space environment plays a pivotal role in changing the characteristics of conditional pathogens, especially their pathogenicity and virulence. However, Stenotrophomonas maltophilia, a type of conditional pathogen that has shown to a gradual increase in clinical morbidity in recent years, has rarely been reported for its impact in space. In this study, S. maltophilia was exposed to a simulated microgravity (SMG) environment in high-aspect ratio rotating-wall vessel bioreactors for 14days, while the control group was exposed to the same bioreactors in a normal gravity (NG) environment. Then, combined phenotypic, genomic, transcriptomic, and proteomic analyses were conducted to compare the influence of the SMG and NG on S. maltophilia. The results showed that S. maltophilia in simulated microgravity displayed an increased growth rate, enhanced biofilm formation ability, increased swimming motility, and metabolic alterations compared with those of S. maltophilia in normal gravity and the original strain of S. maltophilia. Clusters of Orthologous Groups (COG) annotation analysis indicated that the increased growth rate might be related to the upregulation of differentially expressed genes (DEGs) involved in energy metabolism and conversion, secondary metabolite biosynthesis, transport and catabolism, intracellular trafficking, secretion, and vesicular transport. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses showed that the increased motility might be associated the upregulation of differentially expressed proteins (DEPs) involved in locomotion, localization, biological adhesion, and binding, in accordance with the upregulated DEGs in cell motility according to COG classification, including pilP, pilM, flgE, flgG, and ronN. Additionally, the increased biofilm formation ability might be associated with the upregulation of DEPs involved in biofilm formation, the bacterial secretion system, biological adhesion, and cell adhesion, which were shown to be regulated by the differentially expressed genes (chpB, chpC, rpoN, pilA, pilG, pilH, and pilJ) through the integration of transcriptomic and proteomic analyses. These results suggested that simulated microgravity might increase the level of corresponding functional proteins by upregulating related genes to alter physiological characteristics and modulate growth rate, motility, biofilm formation, and metabolism. In conclusion, this study is the first general analysis of the phenotypic, genomic, transcriptomic, and proteomic changes in S. maltophilia under simulated microgravity and provides some suggestions for future studies of space microbiology.

Comparative proteomic analysis to annotate the structural and functional association of the hypothetical proteins of S. maltophilia k279a and predict potential T and B cell targets for vaccination

Stenotrophomonas maltophilia is a multidrug-resistant bacterium with no precise clinical treatment. This bacterium can be a vital cause for death and different organ failures in immune-compromised, immune-competent, and long-time hospitalized patients. Extensive quorum sensing capability has become a challenge to develop new drugs against this pathogen. Moreover, the organism possesses about 789 proteins which function, structure, and pathogenesis remain obscured. In this piece of work, we tried to enlighten the aforementioned sectors using highly reliable bioinformatics tools validated by the scientific community. At first, the whole proteome sequence of the organism was retrieved and stored. Then we separated the hypothetical proteins and searched for the conserved domain with a high confidence level and multi-server validation, which resulted in 24 such proteins. Furthermore, all of their physical and chemical characterizations were performed, such as theoretical isoelectric point, molecular weight, GRAVY value, and many more. Besides, the subcellular localization, protein-protein interactions, functional motifs, 3D structures, antigenicity, and virulence factors were also evaluated. As an extension of this work, 'RTFAMSSER' and 'PAAPQPSAS' were predicted as potential T and B cell epitopes, respectively. We hope our findings will help in better understating the pathogenesis and smoothen the way to the cure.

Characterization of Novel Broad-Host-Range Bacteriophage DLP3 Specific to Stenotrophomonas maltophilia as a Potential Therapeutic Agent

A novel Siphoviridae phage specific to the bacterial species Stenotrophomonas maltophilia was isolated from a pristine soil sample and characterized as a second member of the newly established Delepquintavirus genus. Phage DLP3 possesses one of the broadest host ranges of any S. maltophilia phage yet characterized, infecting 22 of 29 S. maltophilia strains. DLP3 has a genome size of 96,852 bp and a G+C content of 58.4%, which is significantly lower than S. maltophilia host strain D1571 (G+C content of 66.9%). The DLP3 genome encodes 153 coding domain sequences covering 95% of the genome, including five tRNA genes with different specificities. The DLP3 lysogen exhibits a growth rate increase during the exponential phase of growth as compared to the wild type strain. DLP3 also encodes a functional erythromycin resistance protein, causing lysogenic conversion of the host D1571 strain. Although a temperate phage, DLP3 demonstrates excellent therapeutic potential because it exhibits a broad host range, infects host cells through the S. maltophilia type IV pilus, and exhibits lytic activity in vivo. Undesirable traits, such as its temperate lifecycle, can be eliminated using genetic techniques to produce a modified phage useful in the treatment of S. maltophilia bacterial infections.

Clinical Features, Outcomes, and Risk Factors of Bloodstream Infections due to Stenotrophomonas maltophilia in a Tertiary-Care Hospital of China: A Retrospective Analysis

Background. Stenotrophomonas maltophilia bacteremia (SMB) is the most perilous situation as compared to other types of S. maltophilia infection. The present study aimed to investigate the clinical features, distribution, drug resistance, and predictors of survival of SMB in a tertiary-care hospital of China. Methods. SMB that occurred in a tertiary-care hospital in Beijing, China, within 9 years (2010-2018) was investigated in a retrospective study. Demographics, incidence, commodities, drug resistance, mortality, as well as antibiotics administration were summarized according to the electronic medical records. The risk factors for survival were analyzed by Chi-square test, Kaplan-Meier curve and Cox regression. Results. A total of 76 episodes of SMB were analyzed. The overall incidence of SMB fluctuated from 3.4 to 15.4 episodes per 1000 admissions over 9 years. Malignancy was the most common comorbidity. High in vitro sensitivity was observed to minocycline (96.1%), levofloxacin (81.6%), and trimethoprim-sulfamethoxazole (89.5%). Central venous catheter (CVC) (p = 0.004), mechanical ventilation (MV) (p = 0.006), hemodialysis (p = 0.024), and septic shock (p = 0.016) were significantly different between survival and death group. The 30-day mortality was 34.2% within 30 days after confirmation of blood culture. Factors such as hemodialysis (OR 0.287, 95% CI: 0.084-0.977, p = 0.046), T-tube (OR 0.160, 95% CI: 0.029-0.881, p = 0.035), and septic shock (OR 0.234, 95% CI: 0.076-0.719, p = 0.011) were associated with survival. Conclusions. S. maltophilia is the major nosocomial blood stream infectious pathogenic bacteria. Trimethoprim-sulfamethoxazole and minocycline are optimal antibiotics for the treatment of SMB. T-tube, hemodialysis, and septic shock were the risk factors associated with survival of SMB patients.

The clinical impact of Stenotrophomonas maltophilia bacteremia on the 30-day mortality rate in patients with hematologic disorders: a single-institution experience

OBJECTIVE

Stenotrophomonas maltophilia (SM) is an important nosocomial pathogen, particularly in immunocompromised patients due to their adverse antimicrobial susceptibility pattern. The objective of this article was to investigate the clinical impact of SM bacteremia on the 30-day mortality rate and identify the risk factors of the cause of mortality in patients with hematologic disorders.

METHODS

We retrospectively reviewed the clinical data in patients diagnosed with hematological disorders and SM bacteremia over an 8-year period from July 2010 to July 2018 at a 248-bed hematology department. We compared patients' clinical characteristics and outcomes between the non-survivor and survivor groups.

RESULTS

The overall incidence of SM bacteremia was 25.1 per 10,000 admissions. There were 59 patients (median age: 35 years; 57.6% males) included in the study with an overall SM bacteremia-related 30-day mortality of 44.1%. Multi-drug resistance was common. In vitro susceptibility is higher to ceftazidime (72.9%), ciprofloxacin (66.1%) and cefoperazone/sulbactam (59.3%). The risk factors identified in the univariate analysis were catheter re-implantation, accompanying polymicrobial infection, inadequate initial antimicrobial treatment, APACHE II score, temperature > 39 °C, septic shock, respiratory failure, and non-remission post treatment for primary diseases. Multivariate analysis further confirmed that inadequate initial antimicrobial treatment, respiratory failure, and non-remission after treatment for hematological diseases are independent risk factors associated with mortality (P = 0.001, 0.002 and 0.007, respectively).

CONCLUSIONS

Our study suggests that SM bacteremia is highly associated with increased mortality in patients with hematologic diseases. Early detection, prompt comprehensive management including initiation of combined sensitive antibiotics, respiratory monitoring and support, platelet infusion, and strategies to improve patients' remission status are recommended to improve the overall survival in patients with SM bacteremia.

Tetrasodium EDTA Is Effective at Eradicating Biofilms Formed by Clinically Relevant Microorganisms from Patients' Central Venous Catheters

The colonization of catheters by microorganisms often precludes their long-term use, which can be a problem for human patients that have few body sites available for new catheters. The colonizing organisms often form biofilms, and increasingly these organisms are resistant to multiple antibiotics, making them difficult to treat. In this article, we have taken microorganisms that are associated with biofilm formation in catheters from two Canadian hospitals and tested them with tetrasodium EDTA, a new antimicrobial catheter lock solution. Tetrasodium EDTA was effective at eliminating Gram-positive, Gram-negative, and fungal species and represents a promising alternative to antibiotic treatment with less chance of the organisms developing resistance. We expect that our results will be of interest to researchers and clinicians and will lead to improved patient care.

Central venous access devices (CVADs) are an essential component of modern health care. However, their prolonged use commonly results in microbial colonization, which carries the potential risk of hospital-acquired bloodstream infections. These infections complicate the treatment of already sick individuals and cost the existing health care systems around the world millions of dollars. The microbes that colonize CVADs typically form multicellular biofilms that are difficult to dislodge and are resistant to antimicrobial treatments. Clinicians are searching for better ways to extend the working life span of implanted CVADs, by preventing colonization and reducing the risk of bloodstream infections. In this study, we analyzed 210 bacterial and fungal isolates from colonized CVADs or human bloodstream infections from two hospitals geographically separated in the east and west of Canada and screened the isolates for biofilm formation in vitro. Twenty isolates, representing 12 common, biofilm-forming species, were exposed to 4% tetrasodium EDTA, an antimicrobial lock solution that was recently approved in Canada for use as a medical device. The EDTA solution was effective at eradicating surface-attached biofilms from each microbial species, indicating that it could likely be used to prevent biofilm growth within CVADs and to eliminate established biofilms. This new lock solution fits with antibiotic stewardship programs worldwide by sparing the use of important antibiotic agents, targeting prevention rather than the expensive treatment of hospital-acquired infections.

IMPORTANCE The colonization of catheters by microorganisms often precludes their long-term use, which can be a problem for human patients that have few body sites available for new catheters. The colonizing organisms often form biofilms, and increasingly these organisms are resistant to multiple antibiotics, making them difficult to treat. In this article, we have taken microorganisms that are associated with biofilm formation in catheters from two Canadian hospitals and tested them with tetrasodium EDTA, a new antimicrobial catheter lock solution. Tetrasodium EDTA was effective at eliminating Gram-positive, Gram-negative, and fungal species and represents a promising alternative to antibiotic treatment with less chance of the organisms developing resistance. We expect that our results will be of interest to researchers and clinicians and will lead to improved patient care.

Fluoroquinolones versus trimethoprim-sulfamethoxazole for the treatment of Stenotrophomonas maltophilia infections: a systematic review and meta-analysis

BACKGROUND

Fluoroquinolones are a popular alternative to trimethoprim-sulfamethoxazole for Stenotrophomonas maltophilia infections.

OBJECTIVES

To compare the effects of fluoroquinolones and trimethoprim-sulfamethoxazole on mortality of S. maltophilia infections.

DATA SOURCES

PubMed and EMBASE.

STUDY ELIGIBILITY CRITERIA

Clinical studies reporting mortality outcomes of S. maltophilia infections.

PARTICIPANTS

Patients with clinical infections caused by S. maltophilia.

INTERVENTIONS

Fluoroquinolone monotherapy in comparison with trimethoprim-sulfamethoxazole monotherapy.

METHODS

Systematic review with meta-analysis technique.

RESULTS

Seven retrospective cohort and seven case-control studies were included. Three cohort studies were designed to compare the two drugs, whereas others had other purposes. A total of 663 patients were identified, 332 of which were treated with trimethoprim-sulfamethoxazole (50.1%) and 331 with fluoroquinolones (49.9%). Three cohort studies were designed to compare the effect of the two drugs, whereas the others had other purposes. Levofloxacin was most frequently used among fluoroquinolones (187/331, 56.5%), followed by ciprofloxacin (114/331, 34.4%). The overall mortality rate was 29.6%. Using pooled ORs for the mortality of each study, fluoroquinolone treatment (OR 0.62, 95% CI 0.39-0.99) was associated with survival benefit over trimethoprim-sulfamethoxazole treatment, with low heterogeneity (I² = 18%). Specific fluoroquinolones such as ciprofloxacin (OR 0.44, 95% CI 0.17-1.12) and levofloxacin (OR 0.78, 95% CI 0.48-1.26) did not show a significant difference in comparison with trimethoprim-sulfamethoxazole. In the sub-group analyses of adult and bacteraemic patients, significant differences in mortality were not observed between fluoroquinolones and trimethoprim-sulfamethoxazole.

CONCLUSIONS

Based on a meta-analysis of non-randomized studies, fluoroquinolones demonstrated comparable effects on mortality of S. maltophilia infection to trimethoprim-sulfamethoxazole, supporting the use of fluoroquinolones in clinical S. maltophilia infections. Although the pooled analysis of overall studies favoured fluoroquinolones over trimethoprim-sulfamethoxazole, the studies included were observational, and sub-group analyses of certain fluoroquinolone agents did not show statistical differences with trimethoprim-sulfamethoxazole. Randomized clinical studies are needed to address these issues.

Stenotrophomonas maltophilia: From trivial to grievous

Stenotrophomonas maltophilia, once regarded as an organism of low virulence, has evolved as a significant opportunistic pathogen causing severe human infections in both hospital and community settings, especially amongst highly debilitated patients. Globally, S. maltophilia ranks third amongst the four most common pathogenic non-fermenting Gram-negative bacilli (NFGNBs), others being Pseudomonas aeruginosa, Acinetobacter baumannii and Burkholderia cepacia complex (Bcc). The worth of accurate identification of S. maltophilia comes to the forefront as it needs to be differentiated from other NFGNBs such as Acinetobacter, P. aeruginosa and Bcc due to its inherently contrasting antibiotic susceptibility pattern. Consequently, its correct identification is essential as no single drug is amply effective against all NFGNBs, which hinders initiation of appropriate empirical treatment resulting in increased morbidity and mortality.

Identification of immunogenic outer membrane proteins and evaluation of their protective efficacy against Stenotrophomonas maltophilia

Background

Stenotrophomonas maltophilia (S. maltophilia) is an emerging global multiple-drug-resistant organism. It becomes increasingly challenging to treat S. maltophilia infection effectively. Novel therapeutic and preventive approaches targeting S. maltophilia infection are still lacking. This study aims to isolate outer membrane proteins (Omps) from S. maltophilia and use immunoproteomic technology to identify potential vaccine candidates of Omps against S. maltophilia infections.

Methods

Omps from S. maltophilia culture were separated by two-dimensional electrophoresis and identified by matrix-assisted laser desorption/ionization time of flight mass spectrometry and nano liquid chromatography coupled fourier transform ion cyclotron resonance tandem mass spectrometry. Recombinant Omps were prepared and used to immunize mice, and the potency of mouse anti-Omp serum was tested in opsonophagocytic killing assay (OPKA). The effects of immunization with recombinant Omp on blood and tissue bacterial loads in a mouse model of S. maltophilia-induced infection were analyzed.

Results

Outer membrane protein A (OmpA) and Smlt4123 were identified by mass spectrometry. Mouse anti-Smlt4123 serum significantly reduced the bacterial counts in healthy individuals’ blood in OPKA (P < 0.05) but mouse anti-OmpA serum did not. Enzyme-linked immunosorbent assay revealed that the antibody subtype of mouse anti-Smlt4123 antibody was IgG1. Eight hours after an intraperitoneal challenge with S. maltophilia, the bacterial loads in mouse blood were significantly lower in the mice receiving immunization with recombinant Smlt4123 than in the control mice receiving no immunization (P < 0.05), whereas the bacterial loads in other organs, such as the liver, spleen, lung, and kidney were similar in the two groups.

Conclusions

The results revealed that the immunoproteomic approach was an efficient way to screen the immunogenic protein of Stenotrophomonas maltophilia. Moreover, the recombinant Smlt4123 had potential to protect mice from bacteremia caused by S. maltophilia in the early stages.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3258-7) contains supplementary material, which is available to authorized users.

Stenotrophomonas maltophilia colonization during allogeneic hematopoietic stem cell transplantation is associated with impaired survival

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) offers potential cure to acute myeloid leukemia (AML) patients. However, infections with commensal bacteria are an important cause for non-relapse mortality (NRM). We have previously described the impact of multidrug-resistant organism (MDRO) colonization on the survival of allo-HSCT patients. In the aforementioned publication, according to consensus, we there did not consider the opportunistic gram-negative bacterium Stenotrophomonas maltophilia (S. maltophilia) to be an MDRO. Since rate of S. maltophilia colonization is increasing, and it is not known whether this poses a risk for allo-HSCT patients, we here analyzed here its effect on the previously described and now extended patient cohort. We report on 291 AML patients undergoing allo-HSCT. Twenty of 291 patients (6.9%) were colonized with S. maltophilia. Colonized patients did not differ from non-colonized patients with respect to their age, remission status before allo-HSCT, donor type and HSCT-comorbidity index. S. maltophilia colonized patients had a worse overall survival (OS) from 6 months up to 60 months (85% vs. 88.1% and 24.7% vs. 59.7%; p = 0.007) due to a higher NRM after allo-HSCT (6 months: 15% vs. 4.8% and 60 months: 40.1% vs. 16.2% p = 0.003). The main cause of mortality in colonized patients was infection (46.2% of all deaths) and in non-colonized patients relapse (58.8% of all deaths). 5/20 colonized patients developed an invasive infection with S. maltophilia. The worse OS after allo-HSCT due to higher infection related mortality might implicate the screening of allo-HSCT patients for S. maltophilia and a closer observation of colonized patients as outpatients.

Risk factors for mortality in patients with Stenotrophomonas maltophilia bacteremia

Stenotrophomonas maltophilia is a nosocomial pathogen associated with high morbidity and mortality, particularly in immunocompromised or critically ill patients. In this study, we investigated the risk factors for mortality in patients with S. maltophilia bacteremia.Retrospectively, medical records from all patients with S. maltophilia bacteremia between December 2005 and 2014 at Severance Hospital, a 2000-bed tertiary care hospital in Seoul, Korea, were reviewed. Analysis was performed to identify factors associated with 28-day mortality.In total, 142 bacteremia patients were enrolled in this study. The overall 28-day mortality rate was 36.6%. Based on the univariate analysis, hematologic malignancy (P = 0.015), Sepsis-related Organ Failure Assessment (SOFA) score (P < 0.001) and the removal of a central venous catheter (CVC) (P = 0.040) were significantly related to mortality. In the intensive care unit patients, the Acute Physiology and Chronic Health Evaluation II score (P = 0.001) also had significance. Based on the multivariate analysis, the SOFA score (odds ratio [OR] = 1.323; 95% confidence interval [CI]: 1.159, 1.509; P < 0.001) and removal of the CVC (OR = 0.330; 95% CI: 0.109, 0.996; P = 0.049) were independent factors associated with mortality.Our results suggest that removing a CVC may considerably reduce mortality in patients with S. maltophilia bacteremia.

Update on infections caused by Stenotrophomonas maltophilia with particular attention to resistance mechanisms and therapeutic options

Stenotrophomonas maltophilia is a Gram-negative, biofilm-forming bacterium. Although generally regarded as an organism of low virulence, S. maltophilia is an emerging multi-drug resistant opportunistic pathogen in hospital and community settings, especially among immunocompromised hosts. Risk factors associated with S. maltophilia infection include underlying malignancy, cystic fibrosis, corticosteroid or immunosuppressant therapy, the presence of an indwelling central venous catheter and exposure to broad spectrum antibiotics. In this review, we provide a synthesis of information on current global trends in S. maltophilia pathogenicity as well as updated information on the molecular mechanisms contributing to its resistance to an array of antimicrobial agents. The prevalence of S. maltophilia infection in the general population increased from 0.8-1.4% during 1997-2003 to 1.3-1.68% during 2007-2012. The most important molecular mechanisms contributing to its resistance to antibiotics include β-lactamase production, the expression of Qnr genes, and the presence of class 1 integrons and efflux pumps. Trimethoprim/sulfamethoxazole (TMP/SMX) is the antimicrobial drug of choice. Although a few studies have reported increased resistance to TMP/SMX, the majority of studies worldwide show that S. maltophilia continues to be highly susceptible. Drugs with historically good susceptibility results include ceftazidime, ticarcillin-clavulanate, and fluoroquinolones; however, a number of studies show an alarming trend in resistance to those agents. Tetracyclines such as tigecycline, minocycline, and doxycycline are also effective agents and consistently display good activity against S. maltophilia in various geographic regions and across different time periods. Combination therapies, novel agents, and aerosolized forms of antimicrobial drugs are currently being tested for their ability to treat infections caused by this multi-drug resistant organism.

Stenotrophomonas maltophilia bloodstream infection in patients with hematologic malignancies: a retrospective study and in vitro activities of antimicrobial combinations

Background

Stenotrophomonas maltophilia causes serious infections in immunocompromised hosts. Here, we analyzed the clinical characteristics of S. maltophilia bloodstream infection (BSI) in patients with hematologic malignancies and evaluated in vitro synergistic effects of antimicrobial combinations.

Methods

We retrospectively reviewed all consecutive episodes of S. maltophilia BSIs in adult hematologic patients from June 2009 to May 2014, with in vitro susceptibility and synergy tests using high-throughput bioluminescence assay performed for available clinical isolates.

Results

Among 11,004 admissions during 5-year period, 31 cases were identified as S. maltophilia BSIs. The incidence rate of S. maltophilia BSI was 0.134 cases/1,000 patient-days. Overall and attributable mortality of S. maltophilia BSI was 64.5% and 38.7%, respectively. Severe neutropenia (adjusted hazard ratio [HR] 5.24, p =0.013), shock at the onset of BSI (adjusted HR 6.05, p <0.001), and pneumonia (adjusted HR 3.15, p =0.017) were independent risk factors for mortality. In vitro susceptibilities to ceftazidime, levofloxacin, ticarcillin-clavulanic acid (TIM) and trimethoprim-sulfamethoxazole (SXT) were 11.1%, 44.0%, 40.7%, and 88.9%, respectively. MIC₅₀/MIC₉₀ for moxifloxacin and tigecycline were 1/4 mg/L and 4/8 mg/L. The 50% and 90% fractional inhibitory concentrations (FIC⁵⁰/FIC⁹⁰) of clinical isolates against a combination of SXT and TIM were 0.500/0.750. For SXT plus levofloxacin or moxifloxacin, FIC⁵⁰/FIC⁹⁰ were 0.625/1.000 and 0.625/0.625, respectively.

Conclusion

S. maltophilia BSIs show high mortality, which is related to severe neutropenia, shock, and S. maltophilia pneumonia. Based upon drug susceptibility testing, the primary treatment of choice for S. maltophilia BSIs should be SXT in hematologic patients, rather than quinolones, with combination therapies including SXT serving as a feasible treatment option.

Stenotrophomonas maltophilia infection during allogeneic hematopoietic stem cell transplantation: a single-center experience

To examine risk factors for Stenotrophomonas maltophilia (S. maltophilia) infection during allogeneic hematopoietic stem cell transplantation (allo-HSCT), we retrospectively analyzed 259 patients who underwent allo-HSCT. Not only S. maltophilia infection but also S. maltophilia colonization was associated with mortality during allo-HSCT. Among 52 episodes in 39 patients in whom S. maltophilia was detected, documented infection developed in 33 episodes (25 patients). The onset of S. maltophilia infection in the period from the conditioning regimen to engraftment was associated with a high mortality rate. Breakthrough S. maltophilia infection developed in 24% of the patients during prophylactic administration of fluoroquinolones, to which S. maltophilia is sensitive. Reinsertion of a central venous catheter (CVC) immediately after removal was suggested to be a risk for persistent S. maltophilia infection in the period of neutropenia. Our results indicated that (i) onset of S. maltophilia infection in the period from the conditioning therapy to engraftment and (ii) removal and immediate reinsertion of a CVC as treatment after the onset of S. maltophilia infection are possible risk factors for S. maltophilia-related mortality during allo-HSCT.

A review of 11 years of Stenotrophomonas maltophilia blood isolates at a tertiary care institute in Canada

BACKGROUND

Stenotrophomonas maltophilia has emerged as a significant nosocomial pathogen with increasing resistance to trimethoprim/sulphamethoxazole (TMP/SMX), the current drug of choice for treatment.

OBJECTIVES

To describe the microbiological and clinical characteristics of S maltophilia bloodstream infections (BSIs) over an 11-year period at a tertiary care centre in Canada.

METHODS

All adult S maltophilia BSIs from 1999 to 2009 in a 750-bed tertiary care teaching hospital (University of Alberta Hospital, Edmonton, Alberta) were identified through the infection control nosocomial infection surveillance program. Demographic and clinical data were extracted from the infection control database and from patient charts. Microbiological data were confirmed through the laboratory information system.

RESULTS

Twenty-five episodes of S maltophilia BSI (0.9% of all BSIs) involving 24 patients were identified between 1999 and 2009. The patient age range was 18 to 83 years (average 45.7 years). The majority were men (14 of 24 [58.3%]). The mean length of hospital stay was 83.3 days (range eight to 310 days). The rate of S maltophilia BSIs per 1000 admissions ranged from 0.04 to 0.22 (average 0.09). Greater than one-half of the episodes (13 of 25 [52%]) were admitted to the intensive care unit before BSI onset. Laboratory data were available for 24 of the 25 isolates. Polymicrobial infections were present in 11 of 24 (45.8%) patients. Resistance to TMP/SMX occurred in 8.3% of all infections. Fifteen per cent of isolates were resistant to ticarcillin/clavulanate. Mortality attributed to bacteremia was 16.7%.

CONCLUSIONS

In the University of Alberta Hospital, the rate of S maltophilia BSI remains low and constant, and TMP/SMX remains the drug of choice for treatment.

Risk factors influencing mortality related to Stenotrophomonas maltophilia infection in hematology-oncology patients

Stenotrophomonas maltophilia infection is of concern in patients with cancer. Antibiotics active against S. maltophilia are rarely used in the treatment of febrile neutropenia, making it important to identify the factors influencing mortality in cancer patients with S. maltophilia infection. The objective of this study was to analyze the clinical characteristics and outcomes of cancer and hemopathic patients with S. maltophilia infection and assess the factors influencing the mortality. The microbiology laboratory records of Erciyes University, Faculty of Medicine Hospital were reviewed to retrospectively identify patients with S. maltophilia infection between January 2007 and June 2011. A total of 38 patients (25 male, 13 female) were eligible for the study. The median age of the patients was 53 years. The underlying disease was hematological malignancy and disorders in 76.3 % (29 cases), solid tumors in 15.8 % (six cases), aplastic anemia in 7.9 % (three cases), while 18.4 % (seven cases) were hematopoietic stem cell transplantation (HSCT) recipients. An indwelling central venous catheter was used in 32 cases (84.2 %). Twenty-seven patients (71.1 %) were neutropenic at the onset of infection. Nine patients (23.7 %) were receiving corticosteroid therapy. The overall 14-day mortality rate was 50 %. Three of the patients received empirical antibacterial treatment, and three HSCT recipients received trimethoprim-sulfamethoxazole prophylaxis, which is active against S. maltophilia. Severe sepsis (OR 13.24, 95 % confidence interval (CI) 1.62-108.57) and the duration of the treatment (OR 0.73, 95 % CI 0.60-0.90) were related to death based on logistic regression analysis findings. In immunocompromised hematology-oncology patients with severe sepsis, S. maltophilia should be considered as a possible cause of infection, and should be given effective empirical antibiotic treatment immediately; the antimicrobial spectrum may be narrowed according to results of antibiotic susceptibility test.

Stenotrophomonas maltophilia: an emerging global opportunistic pathogen

Stenotrophomonas maltophilia is an emerging multidrug-resistant global opportunistic pathogen. The increasing incidence of nosocomial and community-acquired S. maltophilia infections is of particular concern for immunocompromised individuals, as this bacterial pathogen is associated with a significant fatality/case ratio. S. maltophilia is an environmental bacterium found in aqueous habitats, including plant rhizospheres, animals, foods, and water sources. Infections of S. maltophilia can occur in a range of organs and tissues; the organism is commonly found in respiratory tract infections. This review summarizes the current literature and presents S. maltophilia as an organism with various molecular mechanisms used for colonization and infection. S. maltophilia can be recovered from polymicrobial infections, most notably from the respiratory tract of cystic fibrosis patients, as a cocolonizer with Pseudomonas aeruginosa. Recent evidence of cell-cell communication between these pathogens has implications for the development of novel pharmacological therapies. Animal models of S. maltophilia infection have provided useful information about the type of host immune response induced by this opportunistic pathogen. Current and emerging treatments for patients infected with S. maltophilia are discussed.

Genotyping of environmental and clinical Stenotrophomonas maltophilia isolates and their pathogenic potential

Stenotrophomonas maltophilia is a highly versatile species with useful biotechnological potential but also with pathogenic properties. In light of possible differences in virulence characteristics, knowledge about genomic subgroups is therefore desirable. Two different genotyping methods, rep-PCR fingerprinting and partial gyrB gene sequencing were used to elucidate S. maltophilia intraspecies diversity. Rep-PCR fingerprinting revealed the presence of 12 large subgroups, while gyrB gene sequencing distinguished 10 subgroups. For 8 of them, the same strain composition was shown with both typing methods. A subset of 59 isolates representative for the gyrB groups was further investigated with regards to their pathogenic properties in a virulence model using Dictyostelium discoideum and Acanthamoeba castellanii as host organisms. A clear tendency towards accumulation of virulent strains could be observed for one group with A. castellanii and for two groups with D. discoideum. Several virulent strains did not cluster in any of the genetic groups, while other groups displayed no virulence properties at all. The amoeba pathogenicity model proved suitable in showing differences in S. maltophilia virulence. However, the model is still not sufficient to completely elucidate virulence as critical for a human host, since several strains involved in human infections did not show any virulence against amoeba.

Stenotrophomonas maltophilia in the respiratory tract of medical intensive care unit patients

The purpose of this study was to investigate characteristics of critically ill patients with Stenotrophomonas maltophilia (S. maltophilia) isolated from the respiratory tract, to identify risk factors for S. maltophilia-pneumonia and intensive care unit (ICU) mortality and to analyze antibiotic susceptibility of S. maltophilia. This was a retrospective analysis of 64 medical ICU patients with S. maltophilia in the respiratory tract. Thirty-six patients fulfilled the criteria for diagnosis of pneumonia. A significantly higher lung injury score (LIS) was observed in patients with pneumonia compared to patients with colonization (p=0.010). Independent risk factors for S. maltophilia-pneumonia were higher Sequential Organ Failure Assessment (SOFA) score (p=0.009) and immunosuppression (p=0.014). Patients with S. maltophilia-pneumonia had higher ICU mortality within a 28-day follow-up (p=0.040) and higher hospital mortality (p=0.018) than patients with colonization. The highest antibiotic susceptibility rates were observed to trimethoprim-sulfamethoxazole, tigecycline, and moxifloxacin. Higher SOFA score when S. maltophilia was isolated (p=0.001) and development of renal failure (p=0.021) were independent risk factors for ICU mortality. Higher SOFA score and immunosuppression are independent risk factors for S. maltophilia-pneumonia. Patients with S. maltophilia-pneumonia have a significantly higher ICU mortality within a 28-day follow-up, hospital mortality and LIS compared to patients with S. maltophilia-colonization.

Stenotrophomonas maltophilia: emerging disease patterns and challenges for treatment

Stenotrophomonas maltophilia is a ubiquitous organism associated with opportunistic infections. In the immunocompromised host, increasing prevalence and severity of illness is observed, particularly opportunistic bloodstream infections and pneumonia syndromes. In this article, the classification and microbiology are outlined, together with clinical presentation, outcomes and management of infections due to S. maltophilia. Although virulence mechanisms and the genetic basis of antibiotic resistance have been identified, a role for standardized and uniform reporting of antibiotic sensitivity is not defined. Infections due to S. maltophilia have traditionally been treated with trimethoprim-sulfamethoxazole, ticarcillin-clavulanic acid, or fluoroquinolone agents. The use of combination therapies, newer fluoroquinolone agents and tetracycline derivatives is discussed. Finally, measures to prevent transmission of S. maltophilia within healthcare facilities are reported, especially in at-risk patient populations.

The versatility and adaptation of bacteria from the genus Stenotrophomonas

The genus Stenotrophomonas comprises at least eight species. These bacteria are found throughout the environment, particularly in close association with plants. Strains of the most predominant species, Stenotrophomonas maltophilia, have an extraordinary range of activities that include beneficial effects for plant growth and health, the breakdown of natural and man-made pollutants that are central to bioremediation and phytoremediation strategies and the production of biomolecules of economic value, as well as detrimental effects, such as multidrug resistance, in human pathogenic strains. Here, we discuss the versatility of the bacteria in the genus Stenotrophomonas and the insight that comparative genomic analysis of clinical and endophytic isolates of S. maltophilia has brought to our understanding of the adaptation of this genus to various niches.

Stenotrophomonas maltophilia: an emerging opportunist human pathogen

Stenotrophomonas maltophilia has emerged as an important opportunistic pathogen in the debilitated host. S maltophilia is not an inherently virulent pathogen, but its ability to colonise respiratory-tract epithelial cells and surfaces of medical devices makes it a ready coloniser of hospitalised patients. S maltophilia can cause blood-stream infections and pneumonia with considerable morbidity in immunosuppressed patients. Management of infection is hampered by high-level intrinsic resistance to many antibiotic classes and the increasing occurrence of acquired resistance to the first-line drug co-trimoxazole. Prevention of acquisition and infection depends upon the application of modern infection-control practices, with emphasis on the control of antibiotic use and environmental reservoirs.

Bloodstream infections in haematology: risks and new challenges for prevention

Bloodstream infections are an important cause of morbidity and mortality in the haematology population, and may contribute to delayed administration of chemotherapy, increased length of hospitalisation, and increased healthcare expenditure. For gram-positive, gram-negative, anaerobic and fungal infections, specific risk factors are recognised. Unique host and environmental factors contributing to pathogenesis are acknowledged in this population. Trends in spectrum and antimicrobial susceptibility of pathogens are examined, and potential contributing factors are discussed. These include the widespread use of empiric antimicrobial therapy, increasingly intensive chemotherapeutic regimens, frequent use of central venous catheters, and local infection control practices. In addition, the risks and benefits of prophylaxis, and spectrum of endemic flora are identified as relevant factors within individual centres. Finally, challenges are presented regarding prevention, early detection, surveillance and prophylaxis. To reduce the rate and impact of bloodstream infections multifaceted and customised strategies are required within individual haematology units.

Stenotrophomonas maltophilia: changing spectrum of a serious bacterial pathogen in patients with cancer

Stenotrophomonas maltophilia colonization/infection in patients with cancer has significantly increased over the past 2 decades. Patients with prolonged neutropenia, exposure to broad-spectrum antibiotics, and those requiring mechanical ventilation have higher risk of infection. These micro-organisms are intrinsically resistant to carbapenems, and exposure to these agents has been linked to selection of S. maltophilia. Recently, these infections are being documented in patients without traditional risk factors. The spectrum of infection includes bacteremia, catheter-related infection, pneumonia, complicated biliary and urinary tract infection, and skin and skin-structure infection. Trimethoprim-sulfamethoxazole is the therapeutic agent of choice, but resistance is increasingly being reported. Susceptibility to alternative agents is unpredictable. Combination therapy and alternative routes of drug administration, such as aerosolized aminoglycoside, might be necessary. New insights into the mechanisms of drug resistance might lead to identification of new target sites. Agents that improve outer-membrane permeability and broad-spectrum beta-lactamase inhibitors may favorably impact difficult-to-treat (i.e., multidrug resistant) S. maltophilia infections.