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.

[Haploidentical hematopoietic stem cell transplantation for graft failure in myelodysplastic syndrome/myeloproliferative neoplasm-unclassifiable complicated with Stenotrophomonas maltophilia bacteremia]

A 60-year-old woman with myelodysplastic syndrome/myeloproliferative neoplasm-unclassifiable underwent unrelated bone marrow transplantation from a human leukocyte antigen (HLA) 8/8 allele-matched male donor. Neutrophil engraftment was achieved on day 29. Fluorescence in situ hybridization of sex chromosomes demonstrated complete donor chimerism. The red blood cell and platelet transfusion dependence continued, and the neutrophil count decreased gradually. Despite prolonged administration of broad-spectrum antibiotics for febrile neutropenia, blood cultures on days 46 and 58 returned positive for Stenotrophomonas maltophilia (SM). Contrast-enhanced computed tomography revealed multiple nodules of septic emboli in the lungs and kidneys, suggesting a disseminated SM infection. Antibiotic therapy was conducted based on antimicrobial susceptibility testing. However, the blood cell count failed to normalize and a secondary graft failure was diagnosed. A HLA-haploidentical peripheral-blood stem-cell transplantation from the patient's son was performed on day 134 after the initial transplantation. Neutrophil engraftment was achieved on day 11. Red blood cells and platelets were also engrafted. After the resolution of the SM bacteremia, the patient was discharged on day 63. The prognosis of the SM bacteremia with neutropenia is poor. Antibiotic treatment based on antimicrobial susceptibility testing and a second transplant from an HLA-haploidentical donor likely contributed to the successful outcome in this patient.

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.

The Toxin-Antitoxin Systems of the Opportunistic Pathogen Stenotrophomonas maltophilia of Environmental and Clinical Origin

Stenotrophomonas maltophilia is a ubiquitous environmental bacterium that has recently emerged as a multidrug-resistant opportunistic pathogen causing bloodstream, respiratory, and urinary tract infections. The connection between the commensal environmental S. maltophilia and the opportunistic pathogen strains is still under investigation. Bacterial toxin-antitoxin (TA) systems have been previously associated with pathogenic traits, such as biofilm formation and resistance to antibiotics, which are important in clinical settings. The same species of the bacterium can possess various sets of TAs, possibly influencing their overall stress response. While the TA systems of other important opportunistic pathogens have been researched, nothing is known about the TA systems of S. maltophilia. Here, we report the identification and characterization of S. maltophilia type II TA systems and their prevalence in the isolates of clinical and environmental origins. We found 49 putative TA systems by bioinformatic analysis in S. maltophilia genomes. Despite their even spread in sequenced S. maltophilia genomes, we observed that relBE, hicAB, and previously undescribed COG3832-ArsR operons were present solely in clinical S. maltophilia isolates collected in Lithuania, while hipBA was more frequent in the environmental ones. The kill-rescue experiments in Escherichia coli proved higBA, hicAB, and relBE systems to be functional TA modules. Together with different TA profiles, the clinical S. maltophilia isolates exhibited stronger biofilm formation, increased antibiotic, and serum resistance compared to environmental isolates. Such tendencies suggest that certain TA systems could be used as indicators of virulence traits.

Persistent colonization of non-lymphoid tissue-resident macrophages by Stenotrophomonas maltophilia

Accumulating evidence has revealed that lymphoid tissue-resident commensal bacteria (e.g. Alcaligenes spp.) survive within dendritic cells. We extended our previous study by investigating microbes that persistently colonize colonic macrophages. 16S rRNA-based metagenome analysis using DNA purified from murine colonic macrophages revealed the presence of Stenotrophomonas maltophilia. The in situ intracellular colonization by S. maltophilia was recapitulated in vitro by using bone marrow-derived macrophages (BMDMs). Co-culture of BMDMs with clinically isolated S. maltophilia led to increased mitochondrial respiration and robust IL-10 production. We further identified a 25-kDa protein encoded by the gene assigned as smlt2713 (recently renamed as SMLT_RS12935) and secreted by S. maltophilia as the factor responsible for enhanced IL-10 production by BMDMs. IL-10 production is critical for maintenance of the symbiotic condition, because intracellular colonization by S. maltophilia was impaired in IL-10-deficient BMDMs, and smlt2713-deficient S. maltophilia failed to persistently colonize IL-10-competent BMDMs. These findings indicate a novel commensal network between colonic macrophages and S. maltophilia that is mediated by IL-10 and smlt2713.

Clinical Characteristics of Rapidly Progressive Fatal Hemorrhagic Pneumonia Caused by Stenotrophomonas maltophilia

Objective Hemorrhagic pneumonia due to Stenotrophomonas maltophilia (SM) in severely immunocompromised patients has a very poor prognosis. However, the risk factors for hemorrhagic pneumonia are not clear. Methods This study assessed the predictive factors of hemorrhagic pneumonia caused by SM. The medical records of patients admitted to Osaka City University Hospital with SM bacteremia between January 2008 and December 2017 were retrospectively reviewed. Patients All patients who had positive blood cultures for SM were included in this study. They were categorized into two groups: the SM bacteremia with hemorrhagic pneumonia group and the SM bacteremia without hemorrhagic pneumonia group. The clinical background characteristics and treatments were compared between these groups. Results The 35 patients with SM bacteremia included 4 with hemorrhagic pneumonia and 31 without hemorrhagic pneumonia. Hematologic malignancy (p=0.03) and thrombocytopenia (p=0.04) as well as the prior use of quinolone within 30 days (p=0.04) were more frequent in the SM bacteremia patients with hemorrhagic pneumonia than in those without hemorrhagic pneumonia. The mortality of the SM bacteremia patients with hemorrhagic pneumonia was higher than that of those without hemorrhagic pneumonia group (p=0.02). Conclusion Patients with SM bacteremia who have hematologic malignancy, thrombocytopenia, and a history of using quinolone within the past 30 days should be treated with deliberation.

Moxifloxacin reduces Stenotrophomonas maltophilia adhesion to mouse intestinal tract in vitro

Stenotrophomonas maltophilia is an important opportunistic pathogen that affects immunocompromised individuals. Viable bacterial count method was used to count the number of adhered bacteria. The current study showed the efficiency of S. maltophilia (Sm2) adhesion on different parts of mouse intestinal tract (IT), small intestinal tract (SIT), large intestinal tract (LIT) and rectum (P<0.05) and this ability was equal for each part of IT [ANOVA test (P > 0.05)]. Moxifloxacin (0.03 x MIC) resulted a significant decrease in adhesion of S. maltophilia to SIT (P<0.05) versus control and other sub-inhibitory moxifloxacin concentrations (0.06 x and 1.2 x MIC). It can be concluded from the current study that the S. maltophilia (Sm2) has a good ability to adhere to mouse IT and the lowest concentrations of moxifloxacin (0.03 x MIC) reduced the ability of this bacterium to infect IT by reducing the ability of this bacterium to adhere to IT.

Molecular epidemiology and characteristics of 16 cases with Stenotrophomonas maltophilia bacteraemia in pediatric Intensive Care Units

BACKGROUND

Recently, Stenotrophomonas maltophilia has increasingly been reported as an important nosocomial opportunistic pathogen. Limited therapeutic options of S. maltophilia infections demand early identification and knowledge about the probable risk factors for controlling its spread.

STUDY DESIGN

The present study aimed to investigate the risk factors and trend of antibiotic susceptibility, along with genetic analysis in bacteraemia cases at pediatric intensive care units (PICUs).

METHODS

A total of 16 S. maltophilia isolates were obtained, during 4 months from August to November 2015, from blood cultures of patients admitted to PICUs at Nemazee teaching hospital, Shiraz, Iran. S. maltophilia isolates were identified by conventional tests and confirmed by specific PCR primers. Minimum inhibitory concentrations (MICs) were determined by the MIC strip test as described by the Clinical and Laboratory Standards Institute's (CLSI) recommendation. The genetic relatedness among the isolates was assessed by ERIC-PCR.

RESULTS

All isolates of S. maltophilia were susceptible to ciprofloxacin, co-trimoxazole and colistin, and only 1 (6.2%) isolate was resistant against ceftazidime. The MIC50/MIC90 of ciprofloxacin, trimethoprim/sulfamethoxazole, colistin and ceftazidime was 0.25/0.38 mg/mL, 0.125/0.19 mg/mL, 0.25/0.38 mg/mL, and 2/4 mg/mL, respectively. Genotypic analysis of ERIC-PCR results revealed two distinct types of pattern. Interestingly, the only ceftazidime resistant isolate showed different patterns with other isolates.

CONCLUSIONS

Our findings indicated the importance of routine surveillance in infection control, since early detection of pathogens prevented the spread of nosocomial infections and granted effectiveness to care practices. Moreover, the results suggest that the routine drug of choice for S. maltophilia was mostly active against clinical isolates in our region.

Clinical Characteristics of Stenotrophomonas maltophilia Bacteremia: A Regional Report and a Review of a Japanese Case Series

Objective Stenotrophomonas maltophilia is an emerging nosocomial pathogen that causes fatal infections in critically ill or immunocompromised patients. S. maltophilia bacteremia (SMB) is a rare condition, and its clinical characteristics in Japanese settings are not well known. Methods The medical charts of patients with SMB were retrospectively reviewed at two medical facilities (Okayama University Hospital and Tsuyama Chuo Hospital) for seven years. The data were analyzed along with those previously reported from other Japanese facilities. Result A total of 181 patients (110 men and 71 women) were evaluated. The major underlying diseases included hematologic malignancy (36.5%), solid organ malignancy (25.4%), and neutropenia (31.5%). The recent use of carbapenem was seen in 56.9% of the cases in total, and more than one-third of the patients in our hospitals were treated with carbapenem at the onset of SMB. Of 28 (63.6%) of 44 cases treated for S. maltophilia, those who did not survive were more likely to have been treated with broad-spectrum antibiotics. A multivariate analysis revealed that a higher updated Charlson Comorbidity Index [odds ratio (95% confidence interval), 1.75 (1.11-2.75); p=0.015] and intubation [odds ratio (95% confidence interval), 12.6 (1.62-97.9); p=0.016] were associated with mortality in our cases. Pathogens were often resistant to ceftazidime but susceptible to minocycline, trimethoprim/sulfamethoxazole, and fluoroquinolones. The overall mortality rates within 30 and 90 days were 37.5% and 62.5%, respectively. Conclusion The clinical characteristics of SMB in Japanese cases were similar to those reported from other countries. Clinicians should be aware that breakthrough infection by S. maltophilia may occur during administration of carbapenem.

The outer membrane proteins of Stenotrophomonas maltophilia are potential vaccine candidates for channel catfish (Ictalurus punctatus)

Channel catfish (Ictalurus punctatus) is an important agricultural fish that has been plagued by Stenotrophomonas maltophilia (S. maltophilia) infections in recent years, some of them severe. The outer membrane proteins (OMPs) of S. maltophilia are one of the most immunogenic and highly conserved candidates for vaccine development in aquaculture. The present study investigated OMPs of S. maltophilia as vaccine on immune response and disease resistance against S. maltophilia of channel catfish and investigated the enhancement effect of natural adjuvants Propolis (Pro), FIG polysaccharide (Fcps), Glycyrrhizine (Gly) to OMPs of S. maltophilia for further study. The results indicated that channel catfish injected intraperitoneally with OMPs showed better immune response including leukocytes phagocytosis activity, serum bactericidal activity, complement C3, IgM level and an increasement of resistance against S. maltophilia compared to the control group. Moreover, Pro, Fcps and Gly could enhance the immune response of OMPs. The relative percent of survival (RPS) was 73.33%, 66.67%, 63.33%, 60%, 0% in fish injected OMPs + Pro, OMPs + Fcps, OMPs + Gly, OMPs and 0.65% normal saline, respectively. These results suggested that OMPs used as vaccine could induce and stimulate immune response and enhance disease resistance in channel catfish, especially for Pro as immunoenhancer. Results revealed that OMPs were an effective vaccine against S. maltophilia in channel catfish.

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.

Innate immune responses to Stenotrophomonas maltophilia in immunocompromised pediatric patients and the effect of taurolidine

BACKGROUND

Stenotrophomonas maltophilia is an emerging pathogen causing invasive infections in immunocompromised pediatric patients, including neonates and pediatric oncology patients. Information on innate immune responses to S. maltophilia and its potential modulation are scarce.

METHODS

We established an in vitro S. maltophilia whole blood sepsis model and studied the proinflammatory cytokine production of CD14-positive cells by flow cytometry. We compared the cytokine expression of term newborns (n = 13) and healthy adults (n = 10) and investigated in vitro responses of pediatric oncology patients after recovery from neutropenia (n = 10) with healthy adults (n = 10). We further evaluated the immunomodulatory role of the amino-acid derivative taurolidine in our in vitro sepsis model.

RESULTS

Proinflammatory cytokine responses to S. maltophilia were largely diminished in the neonatal population. No remarkable differences were noted for cytokine responses between pediatric oncology patients and healthy controls. Taurolidine inhibited immunoglobulin (IL)-6, IL-8 and tumor necrosis factor-alpha expression in a dose dependent-fashion in both, pediatric oncology patients and healthy controls.

CONCLUSION

Deficient immune responses to S. maltophilia require optimized prevention strategies against infection in immunocompromised patients, including neonates. Taurolidine may be an effective immunomodulatory agent in a clinical setting.

Immunological and biological relationship among flagellin of Pseudomonas aeruginosa, Burkholderia cepacia and Stenotrophomonas maltophilia

The flagellar protein (flagellin) was isolated and purified from strains of Pseudomonas aeruginosa, Burkholderia cepacia and Stenotrophomonas maltophilia. A significant difference was observed in the molecular weight of different flagellin preparations obtained from these bacterial isolates. Antiserum prepared against S. maltophilia flagellin did not react with flagellin of P. aeruginosa or/and B. cepacia on Immunoblot or in indirect ELISA. In addition the anti-flagellin did not agglutinate P. aeruginosa and B. cepacia. No inhibition of motility of P. aeruginosa and B. cepacia was observed in presence of antiserum; though the latter inhibited the motility of S. maltophilia. The results of the present study prove that no specific relationship existed among all the studied flagellar proteins obtained from closely related bacteria.

Immunoassay method to check the flagellin mediated binding of stenotrophomonas maltophilia to polystyrene

Plate count and spectrophotometric methods have been used to asses the ability of an organism to attach to different surfaces and form biofilms. In the present study we report a highly sensitive, specific and quick method to check the role of flagellin in bacterial adhesion to polystyrene. Flagellin from Stenotrophomonas maltophilia showed high affinity for polystyrene (P < 0.05), which decreased on pretreatment offlagellin with anti-flagellin in a dilution dependent manner. In an enzyme immunoassay format a positive correlation was detected between the anti-flagellin dilutions and flagellin attachment to polystyrene (correlation coefficient +0.860155). These evidences conclusively prove the involvement of flagella in the adhesion ofS. maltophilia to polystyrene surface and enzyme immunoassay, a quick and reliable method to check this phenomenon.

Immunostimulatory properties of the emerging pathogen Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is a multiple-antibiotic-resistant opportunistic pathogen that is being isolated with increasing frequency from patients with health-care-associated infections and especially from patients with cystic fibrosis (CF). While clinicians feel compelled to treat infections involving this organism, its potential for virulence is not well established. We evaluated the immunostimulatory properties and overall virulence of clinical isolates of S. maltophilia using the well-characterized opportunistic pathogen Pseudomonas aeruginosa PAO1 as a control. The properties of CF isolates were examined specifically to see if they have a common phenotype. The immunostimulatory properties of S. maltophilia were studied in vitro by stimulating airway epithelial and macrophage cell lines. A neonatal mouse model of pneumonia was used to determine the rates of pneumonia, bacteremia, and mortality, as well as the inflammatory response elicited by S. maltophilia infection. Respiratory and nonrespiratory S. maltophilia isolates were highly immunostimulatory and elicited significant interleukin-8 expression by airway epithelial cells, as well as tumor necrosis factor alpha (TNF-alpha) expression by macrophages. TNF-alpha signaling appears to be important in the pathogenesis of S. maltophilia infection as less than 20% of TNFR1 null mice (compared with 100% of wild-type mice) developed pneumonia and bacteremia following intranasal inoculation. The S. maltophilia isolates were weakly invasive, and low-level bacteremia with no mortality was observed. Despite the lack of invasiveness of S. maltophilia, the immunostimulatory properties of this organism and its induction of TNF-alpha expression specifically indicate that it is likely to contribute significantly to airway inflammation.

The immunomodulatory effect of antibiotics on the secretion of tumour necrosis factor alpha by peripheral blood mononuclear cells in response to Stenotrophomonas maltophilia stimulation

Some antibiotics have been shown to modify the host immune response. Infection with Stenotrophomonas maltophilia, is often difficult to treat due to multiresistance to antibiotics. The authors examined the effect of four commonly used antimicrobial agents (ciprofloxacin, ceftazidime, cotrimoxazole and piperacillin-tazobactam) on tumour necrosis factor alpha (TNF alpha) production by human peripheral blood mononuclear cells (PBMC) stimulated with heat-killed S maltophilia. Cotrimoxazole was the only antibiotic that suppressed TNFa secretion at clinically achievable concentrations. This may explain its use with good effect in the treatment of S maltophilia infections. However at supratherapeutic concentrations, ceftazidime and ciprofloxacin, but not piperacillin-tazobactam, also inhibited significantly the production of TNF alpha. Cotrimoxazole, in addition to its antimicrobial effect against S maltophilia, has an immunomodulatory effect on peripheral blood mononuclear cells stimulated by S maltophilia.

Characterization of flagella produced by clinical strains of Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is an emerging nosocomial pathogen associated with opportunistic infections in patients with cystic fibrosis, cancer, and HIV. Adherence of this organism to abiotic surfaces such as medical implants and catheters represents a major risk for hospitalized patients. The adhesive surface factors involved in adherence of these bacteria are largely unknown, and their flagella have not yet been characterized biochemically and antigenically. We purified and characterized the flagella produced by S. maltophilia clinical strains. The flagella filaments are composed of a 38-kDa subunit, SM(FliC), and analysis of its N-terminal amino acid sequence showed considerable sequence identity to the flagellins of Serratia marcescens (78.6%), Escherichia coli, Proteus mirabilis, Shigella sonnei (71.4%), and Pseudomonas aeruginosa (57.2%). Ultrastructural analysis by scanning electron microscopy of bacteria adhering to plastic showed flagellalike structures within the bacterial clusters, suggesting that flagella are produced as the bacteria spread on the abiotic surface.

Structures of the O4 and O18 antigens of Stenotrophomonas maltophilia: a case of enantiomeric repeating units

The O-specific side-chain polymers of lipopolysaccharides from the reference strains for Stenotrophomonas maltophilia serogroups 04 and O18 are both xylosylated rhamnans. In the 04 polymer, both sugar components are the D isomers, whereas the O18 polymer contains only the L isomers. By means of NMR spectroscopy, methylation analysis and Smith degradation, the repeating unit of the 04 polymer was identified as a doubly-branched pentasaccharide of the structure shown below. The O18 polymer is based on the enantiomeric pentasaccharide, but the xylosyl substituent at the 4-position is apparently absent from some units. The polymers closely resemble the O antigens found in Xanthomonas campestris pathovars. [structure: see text]

Structure of the O16 antigen of Stenotrophomonas maltophilia

A polysaccharide containing D-ribose, N-acetyl-D-glucosamine, and N-acetyl-D-mannosamine was isolated from the phenol-soluble lipopolysaccharide extracted from defatted cell walls of the reference strain (560) for serogroup O16 of Stenotrophomonas maltophilia. The results of methylation analysis, chemical degradations, and NMR spectroscopy showed that the polysaccharide is based on a branched trisaccharide repeating-unit of the structure shown below. Although ribose was absent from about half of the units in the isolated polymer, the regularity and spacing of the ladder observed on SDS-PAGE of the parent lipopolysaccharide indicate that this was an artefact of the mild acid hydrolysis used to release the polymer. On the other hand, the effects of mild alkaline hydrolysis on the polymer indicated partial O-acetylation. [structure: see text]

Structures of the O21 and O25 antigens of Stenotrophomonas maltophilia

The O-specific side-chain polymers from Stenotrophomonas maltophilia serogroups O21 and O25 were isolated from the lipopolysaccharides of the reference strains. The O21 polymer contained D-arabinose, 2-amino-2-deoxy-D-glucose and 2-amino-2-deoxy-D-galactose in equal proportions. Methylation analysis and NMR spectroscopy showed that the polysaccharide is based on a branched trisaccharide repeating unit of the structure shown below. The O25 polymer is linear with a disaccharide repeating unit identical to that forming the backbone of the O21 polymer.