Infections Caused by Stenotrophomonas maltophilia in Recipients of Hematopoietic Stem Cell Transplantation

Stenotrophomonas maltophilia outbreak in a university hospital: epidemiological investigation and literature review of an emerging healthcare-associated infection

Stenotrophomonas maltophilia was considered to be a low-virulence organism. But it has emerged as a prominent opportunistic pathogen in patients with certain risk factors. This study aimed to describe an outbreak experienced in our hospital with all dynamics while evaluating previous S. maltophilia outbreak reports. S. maltophilia isolates were obtained from a university hospital in Türkiye in a seven-months period. Antimicrobial resistance, type of infections, predisposing factors of infected patients, antibiotic therapy, outcome of infections, and outbreak source were investigated. Also, S. maltophilia outbreaks in the literature were reviewed. In the 12 months prior to the outbreak, prevalence rate of clinical samples including S. maltophilia was 7/1,000 patient per day, opposed to 113/1,000 patient per day during the outbreak. Although a large number of cases were observed in a short seven-month period, a source of contamination could not be detected. Stable mortality rates (or remaining close to the average) during outbreaks can be attributed to the careful attention paid by laboratory and clinic physicians during procedures. S. maltophilia has potential to spread outbreaks and infect patients in operating rooms and intensive care units during invasive procedures.

Correlation between Stenotrophomonas maltophilia incidence and systemic antibiotic use: A 10-year retrospective, observational study in Hungary

Extensive use of carbapenems may lead to selection pressure for Stenotrophomonas maltophilia (SM) in hospital environments. The aim of our study was to assess the possible association between systemic antibiotic use and the incidence of SM. A retrospective, observational study was carried out in a tertiary-care hospital in Hungary, between January 1st 2010 and December 31st 2019. Incidence-density for SM and SM resistant to trimethoprim-sulfamethoxazole (SXT) was standardized for 1000 patient-days, while systemic antibiotic use was expressed as defined daily doses (DDDs) per 100 patient-days. Mean incidence density for SM infections was 0.42/1000 patient-days; 11.08% were were resistant to SXT, the mean incidence density for SXT-resistant SM was 0.047/1000 patient-days. Consumption rate for colistin, glycopeptides and carbapenems increased by 258.82, 278.94 and 372.72% from 2010 to 2019, respectively. Strong and significant positive correlations were observed with the consumption of carbapenems (r: 0.8759; P < 0.001 and r: 0.8968; P < 0.001), SXT (r: 0.7552; P = 0.011 and r: 0.7004; P = 0.024), and glycopeptides (r: 0.7542; P = 0.012 and r: 0.8138; P < 0.001) with SM and SXT-resistant SM incidence-density/1000 patient-days, respectively. Implementation of institutional carbapenem-sparing strategies are critical in preserving these life-saving drugs, and may affect the microbial spectrum of infections in clinical settings.

Three new species, Xanthomonas hawaiiensis sp. nov., Stenotrophomonas aracearum sp. nov., and Stenotrophomonas oahuensis sp. nov., isolated from the Araceae family

Xanthomonas and Stenotrophomonas are closely related genera in the family Lysobacteraceae. In our previous study of aroid-associated bacterial strains, most strains isolated from anthurium and other aroids were reclassified as X. phaseoli and other Xanthomonas species. However, two strains isolated from Spathiphyllum and Colocasia were phylogenetically distant from other strains in the Xanthomonas clade and two strains isolated from Anthurium clustered within the Stenotrophomonas clade. Phylogenetic trees based on 16S rRNA and nine housekeeping genes placed the former strains with the type strain of X. sacchari from sugarcane and the latter strains with the type strain of S. bentonitica from bentonite. In pairwise comparisons with type strains, the overall genomic relatedness indices required delineation of new species; digital DNA-DNA hybridization and average nucleotide identity values were lower than 70 and 95%, respectively. Hence, three new species are proposed: S. aracearum sp. nov. and S. oahuensis sp. nov. for two strains from anthurium and X. hawaiiensis sp. nov. for the strains from spathiphyllum and colocasia, respectively. The genome size of X. hawaiiensis sp. nov. is ~4.88 Mbp and higher than S. aracearum sp. nov. (4.33 Mbp) and S. oahuensis sp. nov. (4.68 Mbp). Gene content analysis revealed 425 and 576 core genes present in 40 xanthomonads and 25 stenotrophomonads, respectively. The average number of unique genes in Stenotrophomonas spp. was higher than in Xanthomonas spp., implying higher genetic diversity in Stenotrophomonas.

Comparison of Doxycycline or Minocycline to Sulfamethoxazole-Trimethoprim for Treatment of Stenotrophomonas maltophilia Pneumonia

BACKGROUND

Stenotrophomonas maltophilia is a multidrug-resistant organism with limited antibiotic treatment options. Minocycline and doxycycline may be appropriate, but clinical data are limited.

OBJECTIVE

To compare tetracyclines (minocycline and doxycycline [TCN]) with standard of care, sulfamethoxazole-trimethoprim (TMP-SMZ), in S. maltophilia pneumonia treatment.

METHODS

This retrospective, 2-center study evaluated patients treated for S. maltophilia pneumonia with TCN or TMP-SMZ for clinical success, defined as resolution of leukocytosis, fever, and tachypnea. Patients were classified as treatment with TCN or TMP-SMZ based on definitive agent used for ≥50% of the treatment course and ≥4 days. Inclusion criteria were age ≥18 years, S. maltophilia confirmed on respiratory culture from January 2013 to November 2020, and appropriate definitive antibiotic dosing. Pregnancy, incarceration, S. maltophilia-resistant or intermediate to definitive therapy, and combination therapy for treatment of S. maltophilia pneumonia were exclusion criteria. Secondary outcomes were microbiologic success and recurrence or reinfection within 30 days requiring treatment.

RESULTS

A total of 80 patients were included (21 TCN [15 minocycline, 6 doxycycline], 59 TMP-SMZ). There was no difference in clinical success (28.6% vs 25.4%; P = 0.994), microbiologic success (n = 28, 55.6% vs 66.4%; P = 0.677), or recurrence or reinfection (n = 24, 66.7% vs 26.7%; P = 0.092) between TCN and TMP-SMZ, respectively.

CONCLUSION AND RELEVANCE

Clinical and microbiologic success rates were similar in patients treated with TCN compared with TMP-SMZ for S. maltophilia pneumonia. These data suggest minocycline and doxycycline may be options to treat S. maltophilia pneumonia, but conclusive clinical data continue to be lacking.

Risk factors and outcome of Stenotrophomonas maltophilia infection after allogeneic hematopoietic stem cell transplantation: JSTCT, Transplant Complications Working Group

Stenotrophomonas maltophilia (S. maltophilia) is an aerobic nonfermenting Gram-negative bacillus widely distributed in the environment that has inherent multidrug resistance to beta-lactam and carbapenem antibiotics. S. maltophilia infection (SMI) is known as an important fatal complication following allogeneic hematopoietic stem cell transplantation (HSCT), but its clinical characteristics have not been well clarified. A retrospective study to identify the incidence, risk factors, and outcomes of SMI after allogeneic HSCT was performed using the database of the Japanese nationwide registry, including 29,052 patients who received allogeneic HSCT in Japan between January 2007 and December 2016. A total of 665 patients developed SMI (sepsis/septic shock, 432; pneumonia, 171; other, 62). The cumulative incidence of SMI at 100 days after HSCT was 2.2%. Among risk factors identified for SMI (age ≥ 50 years, male, performance status 2-4, cord blood transplantation [CBT], myeloablative conditioning, Hematopoietic Cell Transplant-Comorbidity Index [HCT-CI] score 1-2, HCT-CI score ≥ 3, and active infectious disease at HSCT), CBT was the strongest risk factor (hazard ratio, 2.89; 95%CI, 1.94-4.32; p < 0.001). The survival rate at day 30 after SMI was 45.7%, and SMI before neutrophil engraftment was significantly associated with poor survival (survival rate 30 days after SMI, 40.1% and 53.8% in patients with SMI before and after engraftment, respectively; p = 0.002). SMI is rare after allogeneic HSCT, but its prognosis is extremely poor. CBT was a strong risk factor for SMI, and its development prior to neutrophil engraftment was associated with poor survival.

Global prevalence and antibiotic resistance in clinical isolates of Stenotrophomonas maltophilia: a systematic review and meta-analysis

Introduction

Stenotrophomonas maltophilia is a little-known environmental opportunistic bacterium that can cause broad-spectrum infections. Despite the importance of this bacterium as an emerging drug-resistant opportunistic pathogen, a comprehensive analysis of its prevalence and resistance to antibiotics has not yet been conducted.

Methods

A systematic search was performed using four electronic databases (MEDLINE via PubMed, Embase, Scopus, and Web of Science) up to October 2019. Out of 6,770 records, 179 were documented in the current meta-analysis according to our inclusion and exclusion criteria, and 95 studies were enrolled in the meta-analysis.

Results

Present analysis revealed that the global pooled prevalence of S. maltophilia was 5.3 % [95% CI, 4.1-6.7%], with a higher prevalence in the Western Pacific Region [10.5%; 95% CI, 5.7-18.6%] and a lower prevalence in the American regions [4.3%; 95% CI, 3.2-5.7%]. Based on our meta-analysis, the highest antibiotic resistance rate was against cefuroxime [99.1%; 95% CI, 97.3-99.7%], while the lowest resistance was correlated with minocycline [4·8%; 95% CI, 2.6-8.8%].

Discussion

The results of this study indicated that the prevalence of S. maltophilia infections has been increasing over time. A comparison of the antibiotic resistance of S. maltophilia before and after 2010 suggested there was an increasing trend in the resistance to some antibiotics, such as tigecycline and ticarcillin-clavulanic acid. However, trimethoprim-sulfamethoxazole is still considered an effective antibiotic for treating S. maltophilia infections.

Draft Genome Sequence of Stenotrophomonas maltophilia KJ, a Clinical Isolate from Taiwan

We report the draft genome sequence of Stenotrophomonas maltophilia strain KJ, which was isolated from a sputum sample from a patient with a respiratory tract infection. Multilocus sequence typing analysis suggested that strain KJ belongs to a novel S. maltophilia sequence type.

The Contribution of Efflux Systems to Levofloxacin Resistance in Stenotrophomonas maltophilia Clinical Strains Isolated in Warsaw, Poland

Simple Summary

Fluoroquinolones, mainly levofloxacin, are considered an alternative treatment option of Stenotrophomonas maltophilia infections to trimethoprim/sulfamethoxazole. However, an increase in the number of levofloxacin-resistant strains is observed worldwide. The fluoroquinolone resistance in S. maltophilia is usually caused by an overproduction of various multidrug efflux pumps, which are able to extrude antibiotics and chemotherapeutics from the bacterial cells. The purpose of the study was to analyze the contribution of efflux systems to levofloxacin resistance in S. maltophilia clinical strains, isolated in Warsaw, by phenotypic and molecular methods. Previously, the occurrence of genes encoding various ten efflux pumps was shown in 94 studied isolates. Additionally, 44 of 94 isolates demonstrated reduction in susceptibility to levofloxacin. In this study, in the presence of efflux pump inhibitors, an increase in levofloxacin susceptibility was observed in 13 isolates. The overexpression of genes encoding two efflux pump system, such as SmeDEF and Sme VWX (in five and one isolate, respectively), was demonstrated. Sequencing analysis revealed an amino acid change in the local regulators of these efflux pump operons. Our data indicate that the overproduction of the SmeVWX efflux system, unlike SmeDEF, plays a significant role in the levofloxacin resistance of the clinical isolates.

Abstract

Levofloxacin is considered an alternative treatment option of Stenotrophomonas maltophilia infections to trimethoprim/sulfamethoxazole. The fluoroquinolone resistance in S. maltophilia is usually caused by an overproduction of efflux pumps. In this study, the contribution of efflux systems to levofloxacin resistance in S. maltophilia clinical isolates was demonstrated using phenotypic (minimal inhibitory concentrations, MICs, of antibiotics determination ± efflux pump inhibitors, EPIs) and molecular (real-time polymerase-chain-reaction and sequencing) methods. Previously, the occurrence of genes encoding ten efflux pumps was shown in 94 studied isolates. Additionally, 44/94 isolates demonstrated reduction in susceptibility to levofloxacin. Only 5 of 13 isolates (with ≥4-fold reduction in levofloxacin MIC) in the presence of EPIs showed an increased susceptibility to levofloxacin and other antibiotics. The overexpression of smeD and smeV genes (in five and one isolate, respectively) of 5 tested efflux pump operons was demonstrated. Sequencing analysis revealed 20–35 nucleotide mutations in local regulatory genes such as smeT and smeRv. However, mutations leading to an amino acid change were shown only in smeT (Arg123Lys, Asp182Glu, Asp204Glu) for one isolate and in smeRv (Gly266Ser) for the other isolate. Our data indicate that the overproduction of the SmeVWX efflux system, unlike SmeDEF, plays a significant role in the levofloxacin resistance.

Bactericidal Activity of Ceragenin in Combination with Ceftazidime, Levofloxacin, Co-Trimoxazole, and Colistin against the Opportunistic Pathogen Stenotrophomonas maltophilia

Background: Stenotrophomonas maltophilia (S. maltophilia) is an emerging opportunistic Gram-negative rod causing nosocomial infections predominantly in immunocompromised patients. Due to its broad intrinsic resistance to antibiotics, including carbapenems and the ability to form a biofilm, it is difficult to eradicate. Methods: In this study, the benefit of combined administration (potential synergism) and anti-biofilm activity of ceragenins: CSA-13, CSA-44, and CSA-131 (synthetic mimics of natural antimicrobial peptides) with ceftazidime, levofloxacin, co-trimoxazole and colistin against clinical strains of S. maltophilia were determined using MIC/MBC (minimum inhibitory concentration/minimum bactericidal concentration), killing assays and CV staining. Results: Obtained data indicate that the ceragenins exhibit strong activity against the tested strains of S. maltophilia grown in planktonic culture and as stationary biofilms. Moreover, with some strains, the synergy of ceragenins with conventional antibiotics was observed Conclusion: Our data suggest that ceragenins are promising agents for future development of new methods for treatment of infections caused by S. maltophilia, along with its potential use in combination with conventional antibiotics.

In vitro Antibiosis of Chlorella vulgaris Extract against the Phytopathogen, Stenotrophomonas maltophilia

The aim of the current study was to evaluate the antibacterial activity of Chlorella vulgaris extracts against Stenotrophomonas maltophilia CSK1 isolated from a diseased cucumber fruit. To this end, water, methanol and ethanol were used separately as solvents to extract the active compounds from the dried Chlorella vulgaris. S. maltophilia CSK1 was identified using the 16S rRNA gene sequencing at 99.93% of identity level. The identity of the bacterial strain CSK1 was confirmed by phylogenetic analyses. CSK1 was clearly clustered with the reference strain, S. maltophilia MTCC 434 (JALV01000036). The antibiosis of the extract against S. maltophilia CSK1 was estimated using agar well diffusion method. Unlike water and ethanolic extracts, the methanolic one exhibited an inhibition of CSK1 (zone of inhibition 13.4 mm), indicating the antimicrobial activity of this extract. No zone of inhibition was formed around ethanolic and water extracts, indicating that both exhibited no-observed effect against the growth of CSK1. This can be attributed to the active constituents in the extract which may varies based on various factors including the polarity of solvent used in the extraction process. The inhibitory effect of the methanolic extract against the S. maltophilia CSK1 obtained from the diseased cucumber fruit could open the door for potential application of such active ingredient within this extract against this bacteria in future.

Fatal hemorrhagic pneumonia in patients with hematologic diseases and Stenotrophomonas maltophilia bacteremia: a retrospective study

Background

Fatal hemorrhagic pneumonia is one of the most severe manifestations of Stenotrophomonas maltophilia (SM) infections. Here, we aimed to investigate the clinical characteristics of SM bacteremia and to identify the risk factors of hemorrhagic pneumonia caused by SM in patients with hematologic diseases.

Methods

The clinical records of 55 patients diagnosed with hematologic diseases and SM bacteremia were retrospectively reviewed. We compared patients’ clinical characteristics and outcomes between the hemorrhagic pneumonia group and non-hemorrhagic pneumonia group.

Results

Twenty-seven (49.1%) patients developed hemorrhagic pneumonia. The overall mortality rate of SM bacteremia was 67.3%. Hemorrhagic pneumonia (adjusted HR 2.316, 95% CI 1.140–4.705; P = 0.020) was an independent risk factor of 30-day mortality in hematological patients with SM bacteremia. Compared with the non-hemorrhagic pneumonia group, patients in the hemorrhagic pneumonia group were older and showed clinical manifestations as higher proportions of isolated SM in sputum culture, neutropenia and elevated procalcitonin (PCT). Multivariate analysis showed that neutropenia, high levels of PCT, prior tigecycline therapy within 1 month were independent risk factors associated with hemorrhagic pneumonia.

Conclusions

Neutropenia, high level of PCT and prior tigecycline therapy within 1 month were significant independent predictors of hemorrhagic pneumonia in hematologic patients with SM bacteremia. Due to no effective antibiotics to prevent hemorrhagic pneumonia, prophylaxis of SM infection and its progression to hemorrhagic pneumonia is particularly important.

Immunoinformatic Approach for the Identification of Potential Epitopes Against Stenotrophomonas maltophilia: A Global Opportunistic Pathogen

Background:

Stenotrophomonas maltophilia is an aerobic, non-fermentative, gram negative, multidrug resistant and opportunistic nosocomial pathogen. It is associated with high morbidity and mortality in severely immunocompromised paediatric patients, including neonates. Immunoinformatic analysis paved a new way to design epitope-based vaccines which resulted in a potential immunogen with advantages such as lower cost, specific immunity, ease of production, devoid of side effects, and less time consumption than conventional vaccines. Till date, there is no development in the vaccines or antibody-based treatments for S. maltophilia-associated infections.

Introduction:

Currently, epitope-based peptide vaccines against pathogenic bacteria have grasped more attention. In our present study, we have utilized various immunoinformatic tools to find a prominent epitope that interacts with the maximum number of HLA alleles and also with the maximum population coverage for developing a vaccine against Stenotrophomonas maltophilia.

Methods:

This study has incorporated an immunoinformatic based screening approach to explore potential epitope-based vaccine candidates in Stenotrophomonas maltophilia proteome. In this study, 4365 proteins of the Stenotrophomonas maltophilia K279a proteome were screened to identify potential antigens that could be used as a good candidate for the vaccine. Various immunoinformatic tools were used to predict the binding of the promiscuous epitopes with Major Histocompatibility Complex (MHC) class I molecules. Other properties such as allergenicity, physiochemical properties, adhesion properties, antigenicity, population coverage, epitope conservancy and toxicity were analysed for the predicted epitope.

Results:

This study helps in finding the prominent epitope in Stenotrophomonas infections. Hence, the main objective in this research was to screen complete Stenotrophomonas maltophilia proteome to recognize putative epitope candidates for vaccine design. Using computational vaccinology and immunoinformatic tools approach, several aspects are obligatory to be fulfilled by an epitope to be considered as a vaccine candidate. Our findings were promising and showed that the predicted epitopes were non-allergenic and fulfilled other parameters required for being a suitable candidate based on certain physio-chemical, antigenic and adhesion properties.

Conclusion:

The epitopes LLFVLCWPL and KSGEGKCGA have shown the highest binding score of −103 and −78.1 kcal/mol with HLA-A*0201 and HLA-B*0702 MHC class I allele, respectively. They were also predicted to be immunogenic and non-allergenic. Further various immunological tests, both in vivo and in vitro methods, should be performed for finding the efficiency of the predicted epitope in the development of a targeted vaccine against Stenotrophomonas maltophilia infection.

The Potential of Phage Therapy against the Emerging Opportunistic Pathogen Stenotrophomonas maltophilia

The isolation and characterization of bacteriophages for the treatment of infections caused by the multidrug resistant pathogen Stenotrophomonas maltophilia is imperative as nosocomial and community-acquired infections are rapidly increasing in prevalence. This increase is largely due to the numerous virulence factors and antimicrobial resistance genes encoded by this bacterium. Research on S. maltophilia phages to date has focused on the isolation and in vitro characterization of novel phages, often including genomic characterization, from the environment or by induction from bacterial strains. This review summarizes the clinical significance, virulence factors, and antimicrobial resistance mechanisms of S. maltophilia, as well as all phages isolated and characterized to date and strategies for their use. We further address the limited in vivo phage therapy studies conducted against this bacterium and discuss the future research needed to spearhead phages as an alternative treatment option against multidrug resistant S. maltophilia.

Structural basis for an exceptionally strong preference for asparagine residue at the S2 subsite of Stenotrophomonas maltophilia dipeptidyl peptidase 7

The emergence of drug-resistant bacteria has become a major problem worldwide. Bacterial dipeptidyl peptidases 7 and 11 (DPP7s and DPP11s), belonging to the family-S46 peptidases, are important enzymes for bacterial growth and are not present in mammals. Therefore, specific inhibitors for these peptidases are promising as potential antibiotics. While the molecular mechanisms underlining strict specificity at the S1 subsite of S46 peptidases have been well studied, those of relatively broad preference at the S2 subsite of these peptidases are unknown. In this study, we performed structural and biochemical analyses on DPP7 from Stenotrophomonas maltophilia (SmDPP7). SmDPP7 showed preference for the accommodation of hydrophobic amino acids at the S2 subsite in general, but as an exception, also for asparagine, a hydrophilic amino acid. Structural analyses of SmDPP7 revealed that this exceptional preference to asparagine is caused by a hydrogen bonding network at the bottom of the S2 subsite. The residues in the S2 subsite are well conserved among S46 peptidases as compared with those in the S1 subsite. We expect that our findings will contribute toward the development of a universal inhibitor of S46 peptidases.

Oral microorganisms and bloodstream infection in allogeneic hematopoietic stem cell transplantation

OBJECTIVES

We aimed to compare oral and pathogenic microorganisms in bloodstream infections (BSIs) in allogeneic hematopoietic stem cell transplantation (allo-HSCT). We also investigated the relationship between BSIs and oral mucositis to identify the ratio of BSIs caused by oral microorganisms and the pathogenic microorganisms involved.

MATERIALS AND METHODS

We collected data on BSIs in 96 patients who underwent allo-HSCT in our institute between April 2009 and December 2019, including BSI pathogens isolated from blood cultures (BBSIs) and microorganisms isolated from washing the oral cavity with sterile distilled water. Oral microorganisms obtained at the onset of BSI (OBSIs) and during allo-HSCT (OSCTs) were defined as isolates collected during the week of blood culturing. Study entry was limited to samples collected up to 1 month after allo-HSCT without BSI. When the BBSI and OBSI were the same, we considered the oral microorganism to have caused the BSI.

RESULTS

The incidence rate of BSIs was 27%, and the predominant microorganism was coagulase-negative Staphylococci. Normal bacterial flora were decreased to 15.8% in OBSIs and 25.5% in OSCTs. The distribution of microorganisms without normal bacterial flora showed significant difference between BBSIs and OSCTs (p < 0.05). Oral mucositis was found in 72.9%, and BSI caused by oral microorganisms occurred in 46.2% of BSIs in allo-HSCT patients.

CONCLUSION

The distribution of microorganisms obtained from blood in patients with BSI during allo-HSCT was found to be similar to that of microorganisms from oral cultures.

CLINICAL RELEVANCE

Oral microorganism monitoring may be able to predict BSI during allo-HSCT.

Detection of multidrug resistant environmental isolates of acinetobacter and Stenotrophomonas maltophilia: a possible threat for community acquired infections?

Acinetobacter spp. and Stenotrophomonas maltophilia are bacteria commonly associated with infections at the clinical settings. Reports of infections caused by environmental isolates are rare. Therefore, this study focused on determination of the antibiotic resistance patterns, antibiotic resistance genes, efflux pumps and virulence signatures of Acinetobacter spp. and S. maltophilia recovered from river water, plant rhizosphere and river sediment samples. The isolates were identified and confirmed using biochemical tests and PCR. The antimicrobial resistance profiles of the isolates were determined using Kirby Bauer disk diffusion assay and presence of antibiotic resistance and virulence genes were detected using PCR. S. maltophilia was more frequent in plant rhizosphere and sediment samples than the water samples. Acinetobacter spp. were mostly resistant to trimethoprim-sulfamethoxazole (96% of isolates), followed by polymyxin b (86%), cefixime (54%), colistin (42%), ampicillin (35%) and meropenem (19%). The S. maltophilia isolates displayed total resistance (100%) to trimethoprim- sulfamethoxazole, meropenem, imipenem, ampicillin and cefixime, while 80% of the isolates were resistant to ceftazidime. Acinetobacter spp. contained different antibiotic resistance genes such as sul1 (24% of isolates), sul2 (29%), blaOXA 23/51 (21%) and blaTEM (29%), while S. maltophilia harbored sul1 (8%) and blaTEM (20%). Additionally, efflux pump genes were present in all S. maltophilia isolates. The presence of multidrug resistant Acinetobacter spp. and Stenotrophomonas maltophilia in surface water raises concerns for community-acquired infections as this water is directly been used by the community for various purposes. Therefore, there is the need to institute measures aimed at reducing the risks of these infections and the resulting burden this may have on the health care system within the study area.

Successful treatment of pulmonary haemorrhage and acute respiratory distress syndrome caused by fulminant Stenotrophomonas maltophilia respiratory infection in a patient with acute lymphoblastic leukaemia - case report

Background

Stenotrophomonas maltophilia-induced pulmonary haemorrhage is considered a fatal infection among haematological patients. The outcome can be explained by the patients’ immunity status and late diagnosis and treatment.

Case presentation

We present the rare case of successful outcome in a 61-year-old female who developed alveolar haemorrhage and acute respiratory distress syndrome 8 days after a chemotherapy session for her acute lymphoblastic leukaemia, in the context of secondary bone marrow aplasia. Stenotrophomonas maltophilia was isolated in sputum culture. The patient benefitted from early empirical treatment with colistin followed by trimethoprim/sulfamethoxazole, according to the antibiogram. Despite a severe initial clinical presentation in need of mechanical ventilation, neuromuscular blocking agents infusion, and ventilation in prone position, the patient had a favourable outcome and was discharged from intensive care after 26 days.

Conclusions

Stenotrophomonas maltophilia severe pneumonia complicated with pulmonary haemorrhage is not always fatal in haematological patients. Empirical treatment of multidrug-resistant Stenotrophomonas maltophilia in an immunocompromised haematological patient presenting with hemoptysis should be taken into consideration.

Performance and Application of 16S rRNA Gene Cycle Sequencing for Routine Identification of Bacteria in the Clinical Microbiology Laboratory

This review provides a state-of-the-art description of the performance of Sanger cycle sequencing of the 16S rRNA gene for routine identification of bacteria in the clinical microbiology laboratory. A detailed description of the technology and current methodology is outlined with a major focus on proper data analyses and interpretation of sequences. The remainder of the article is focused on a comprehensive evaluation of the application of this method for identification of bacterial pathogens based on analyses of 16S multialignment sequences. In particular, the existing limitations of similarity within 16S for genus- and species-level differentiation of clinically relevant pathogens and the lack of sequence data currently available in public databases is highlighted. A multiyear experience is described of a large regional clinical microbiology service with direct 16S broad-range PCR followed by cycle sequencing for direct detection of pathogens in appropriate clinical samples. The ability of proteomics (matrix-assisted desorption ionization-time of flight) versus 16S sequencing for bacterial identification and genotyping is compared. Finally, the potential for whole-genome analysis by next-generation sequencing (NGS) to replace 16S sequencing for routine diagnostic use is presented for several applications, including the barriers that must be overcome to fully implement newer genomic methods in clinical microbiology. A future challenge for large clinical, reference, and research laboratories, as well as for industry, will be the translation of vast amounts of accrued NGS microbial data into convenient algorithm testing schemes for various applications (i.e., microbial identification, genotyping, and metagenomics and microbiome analyses) so that clinically relevant information can be reported to physicians in a format that is understood and actionable. These challenges will not be faced by clinical microbiologists alone but by every scientist involved in a domain where natural diversity of genes and gene sequences plays a critical role in disease, health, pathogenicity, epidemiology, and other aspects of life-forms. Overcoming these challenges will require global multidisciplinary efforts across fields that do not normally interact with the clinical arena to make vast amounts of sequencing data clinically interpretable and actionable at the bedside.

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.

Stenotrophomonas maltophilia: An Emerging Pathogen of the Respiratory Tract

Patient: Female, 70-year-old

Final Diagnosis:Stenotrophomonas maltophilia

Symptoms: Difficult to breath, patient could not wean from oxygen/premature

Medication: —

Clinical Procedure: —

Specialty: General and Internal Medicine

Comparative In Vivo Antibacterial Activity of Human-Simulated Exposures of Cefiderocol and Ceftazidime against Stenotrophomonas maltophilia in the Murine Thigh Model

Cefiderocol is a novel siderophore cephalosporin that utilizes bacterial ferric iron transports to cross the outer membrane. Cefiderocol shows high stability against all classes of β-lactamases, rendering it extremely potent against carbapenem- and multidrug-resistant Gram-negative organisms. Using a neutropenic murine thigh model, we compared the efficacies of human-simulated exposures of cefiderocol (2 g Q8H 3 h infusion) and ceftazidime (2 g Q8H 2 h infusion) against Stenotrophomonas maltophilia, an emerging opportunistic Gram-negative organism associated with serious and often fatal nosocomial infections. Twenty-four S. maltophilia isolates were studied, including isolates resistant to ceftazidime, trimethoprim-sulfate, and/or levofloxacin. The thighs were inoculated with bacterial suspensions of 10⁸ CFU/mL and the human-simulated regimens were administered over 24 h. Efficacy was measured as the change in log₁₀CFU/thigh at 24 h compared with 0 h controls. Cefiderocol human-simulated exposure demonstrated potent bacterial killing; mean bacterial reduction at 24 h was -2.67 ± 0.68 log₁₀CFU/thigh with ≥ 2 log-reduction achieved in 21 isolates (87.5%) and ≥ 1 log-reduction achieved in the remaining three isolates (12.5%). In comparison, ceftazidime human-simulated exposure produced mean bacterial reduction of -1.38 ± 1.49 log₁₀CFU/thigh among 10 ceftazidime-susceptible isolates and mean bacterial growth of 0.64 ± 0.79 log₁₀CFU/thigh among 14 ceftazidime-non-susceptible isolates. While ceftazidime showed modest efficacy against most susceptible isolates, humanized cefiderocol exposures resulted in remarkable in vivo activity against all S. maltophilia isolates examined, inclusive of ceftazidime-non-susceptible isolates. The potent in vitro and in vivo activity of cefiderocol supports the development of this novel compound for managing S. maltophilia infections.

Prevalence and Antibiotic Resistance of Stenotrophomonas maltophilia in Respiratory Tract Samples: A 10-Year Epidemiological Snapshot

Background:

Since the 1980s, Stenotrophomonas maltophilia has emerged as an important pathogen associated with significant mortality in pneumonia and bacteremia of severely immunocompromised, hospitalized patients. The drug of choice in S maltophilia infections is sulfamethoxazole-trimethoprim (SMX/TMP); SMX/TMP resistance is a serious concern in clinical practice. The aim of this study was to assess the prevalence of S maltophilia in lower respiratory tract (LRTI) samples at a tertiary-care university hospital.

Methods:

This retrospective cohort study was carried out using microbiological data collected between January 2008 and December 2017. Routine antimicrobial susceptibility testing was performed for SMX/TMP and levofloxacin; in case of resistance, susceptibility testing for additional antibiotics (tigecycline, amikacin, and colistin) was also performed.

Results:

A total of 579 individual S maltophilia isolates were identified (2008-2012: n = 160, 2013-2017: n = 419; P = .0008). In all, 78.46% of patients were younger than 5 or older than 50 years of age and had recent trauma, surgery, or underlying conditions (malignancies, respiratory distress syndrome, congenital disorders, and cystic fibrosis). In 28.16% of samples, more than 1 pathogen was identified, and 5.35% of coisolated pathogens were multidrug resistant (MDR). In all, 12.1% of isolates were SMX/TMP-resistant (2008-2012: 6.12%, 2013-2017: 18.06%; P = .034), while 8.99% were resistant to levofloxacin (2008-2012: 7.86%, 2013-2017: 10.12%; P > .05). SMX/TMP resistance was detected more frequently in samples originating from inpatients (n = 2.50 ± 2.39 vs n = 11.50 ± 3.76; P = .0002).

Conclusions:

In all, 5.87% of isolates were extensively drug resistant (XDR), that is, in addition to SMX/TMP, they were resistant to levofloxacin, amikacin, colistin, and tigecycline. The results of our study correspond to the findings in the literature.

Stenotrophomonas maltophilia right-sided endocarditis in an adult patient with uncorrected congenital heart disease

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Stenotrophomonas maltophilia is a Gram negative, low virulence, one of the leading multiple-drug-resistant pathogen and quite often causes nosocomial infection.

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Bacteremia with Stenotrophomonas maltophilia has higher mortality than Pseudomonas aeruginosa.

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Stenotrophomonas maltophilia endocarditis is too scarce, however, it accompanied with high rates of mortality and morbidity.

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Acute bacterial endocarditis due to Stenotrophomonas maltophilia can occur even in patients with uncorrected congenital heart disease and lack of immune deficiency, therefore. clinicians should be aware.

Characterization of Phenotypic and Genotypic Diversity of Stenotrophomonas maltophilia Strains Isolated From Selected Hospitals in Iran

Stenotrophomonas maltophilia is an environmental Gram-negative bacterium that has rapidly emerged as an important nosocomial pathogen in hospitalized patients. Treatment of S. maltophilia infections is difficult due to increasing resistance to multiple antibacterial agents. The purpose of this study was to determine the phenotypic and genotypic characterization of S. maltophilia isolates recovered from patients referred to several hospitals. A total of 164 clinical isolates of S. maltophilia were collected from hospitals in various regions in Iran between 2016 and 2017. Antibiotic susceptibility testing was performed by disc diffusion method and E-test assay according to the Clinical and Laboratory Standards Institute (CLSI) guideline. The ability of biofilm formation was assessed with crystal violet staining and then, biofilm-associated genes were investigated by PCR-sequencing method. The presence of L1 (a metallo-β-lactamase), L2 (a clavulanic acid-sensitive cephalosporinase), sul1 and sul2 (resistance to Trimethoprim/Sulfamethoxazole), Smqnr (intrinsic resistance to quinolones), and dfrA genes (dihydrofolate reductase enzyme that contributes to trimethoprim resistance) was also examined by PCR-sequencing. Relative gene expression of smeDEF efflux pump was assessed by real-time PCR. Genotyping was performed using the multi-locus sequencing typing (MLST) and repetitive extragenic palindromic-PCR (Rep-PCR). Isolates were resistant to imipenem (100%), meropenem (96%), doripenem (96%), and ceftazidime (36.58%). Notably, 5 (3.04%) isolates showed resistant to trimethoprim-sulfamethoxazole (TMP-SMX), an alarming trend of decreased susceptibility to TMP-SMX in Iran. Minocycline and levofloxacin exhibited the highest susceptibility of 91.46 and 99.39%, respectively. Using the crystal violet staining, 157 (95.73%) isolates had biofilm phenotype: 49 (29.87%), 63 (38.41%), and 45 (27.43%) isolates were categorized as strong-, moderate- and weak-biofilm producer while 7 isolates (4.26%) were identified a non-biofilm producer. Biofilm genes had an overall prevalence of 145 (88.41%), 137 (83.53%), and 164 (100%) of rmlA, rpfF, and spgM, respectively. L1, L2, Smqnr, sul1, and sul2 resistance genes were detected in 145 (88.41%), 156 (96.12%), 103 (62.80%), 89 (54.26%), and 92 (56.09%) isolates, respectively. None of the S. maltophilia isolates were positive for dfrA12, dfrA17, and dfrA27 genes. Gene expression analysis showed that smeD efflux system was overexpressed in two out of the five clinical isolates (40%) that showed resistance to TMP-SMX. Most of the isolates were genetically unrelated. Two new sequence types (ST139 and ST259) were determined. Our results showed that TMP-SMX was still an effective antibiotic against S. maltophilia. The findings of the current study revealed an increasing prevalence of antibiotic resistance and biofilm genes in clinical S. maltophilia isolates in Iran.

Fatal Neutropenic Enterocolitis Caused by Stenotrophomonas maltophilia: A Rare and Underrecognized Entity

Although Stenotrophomonas maltophilia causes substantial morbidity and mortality in immunocompromised patients, it has not been described as a causal pathogen of neutropenic enterocolitis (NEC). We describe the first case of histologically-confirmed NEC caused by S. maltophilia accompanied by bacteremia and pneumonia after salvage chemotherapy for acute myeloid leukemia relapse following a second hematopoietic stem cell transplantation. S. maltophilia should be included as a pathogenic organism of NEC in severely immunocompromised patients to prevent a delayed diagnosis, which carries a high risk of inappropriate antimicrobial selection and fatal outcome.

Putative Iron Acquisition Systems in Stenotrophomonas maltophilia

Iron has been shown to regulate biofilm formation, oxidative stress response and several pathogenic mechanisms in Stenotrophomonas maltophilia. Thus, the present study is aimed at identifying various iron acquisition systems and iron sources utilized during iron starvation in S. maltophilia. The annotations of the complete genome of strains K279a, R551-3, D457 and JV3 through Rapid Annotations using Subsystems Technology (RAST) revealed two putative subsystems to be involved in iron acquisition: the iron siderophore sensor and receptor system and the heme, hemin uptake and utilization systems/hemin transport system. Screening for these acquisition systems in S. maltophilia showed the presence of all tested functional genes in clinical isolates, but only a few in environmental isolates. NanoString nCounter Elements technology, applied to determine the expression pattern of the genes under iron-depleted condition, showed significant expression for FeSR (6.15-fold), HmuT (12.21-fold), Hup (5.46-fold), ETFb (2.28-fold), TonB (2.03-fold) and Fur (3.30-fold). The isolates, when further screened for the production and chemical nature of siderophores using CAS agar diffusion (CASAD) and Arnows's colorimetric assay, revealed S. maltophilia to produce catechol-type siderophore. Siderophore production was also tested through liquid CAS assay and was found to be greater in the clinical isolate (30.8%) compared to environmental isolates (4%). Both clinical and environmental isolates utilized hemoglobin, hemin, transferrin and lactoferrin as iron sources. All data put together indicates that S. maltophilia utilizes siderophore-mediated and heme-mediated systems for iron acquisition during iron starvation. These data need to be further confirmed through several knockout studies.

S. maltophilia pneumonia: A case report

Case report of Community-acquired pneumonia in a male patient without co-morbidities. Empiric antibiotic treatment did not resolve the clinical picture of productive cough, and a chest computerized tomography and sputum culture with antibiogram were performed, identifying S. maltophilia infection with sensitivity to levofloxacin and sulfamethoxazole/trimethoprim. Treatment with levofloxacin (500 mg/day for 15 days) resulted in resolution of the clinical picture.

Stenotrophomonas maltophilia as an Emerging Ubiquitous Pathogen: Looking Beyond Contemporary Antibiotic Therapy

Stenotrophomonas maltophilia is a commensal and an emerging pathogen earlier noted in broad-spectrum life threatening infections among the vulnerable, but more recently as a pathogen in immunocompetent individuals. The bacteria are consistently being implicated in necrotizing otitis, cutaneous infections including soft tissue infection and keratitis, endocarditis, meningitis, acute respiratory tract infection (RTI), bacteraemia (with/without hematological malignancies), tropical pyomyositis, cystic fibrosis, septic arthritis, among others. S. maltophilia is also an environmental bacteria occurring in water, rhizospheres, as part of the animals' microflora, in foods, and several other microbiota. This review highlights clinical reports on S. maltophilia both as an opportunistic and as true pathogen. Also, biofilm formation as well as quorum sensing, extracellular enzymes, flagella, pili/fimbriae, small colony variant, other virulence or virulence-associated factors, the antibiotic resistance factors, and their implications are considered. Low outer membrane permeability, natural MDR efflux systems, and/or resistance genes, resistance mechanisms like the production of two inducible chromosomally encoded β-lactamases, and lack of carefully compiled patient history are factors that pose great challenges to the S. maltophilia control arsenals. The fluoroquinolone, some tetracycline derivatives and trimethoprim-sulphamethaxole (TMP-SMX) were reported as effective antibiotics with good therapeutic outcome. However, TMP-SMX resistance and allergies to sulfa together with high toxicity of fluoroquinolone are notable setbacks. S. maltophilia's production and sustenance of biofilm by quorum sensing enhance their virulence, resistance to antibiotics and gene transfer, making quorum quenching an imperative step in Stenotrophomonas control. Incorporating several other proven approaches like bioengineered bacteriophage therapy, Epigallocatechin-3-gallate (EGCG), essential oil, nanoemulsions, and use of cationic compounds are promising alternatives which can be incorporated in Stenotrophomonas control arsenal.

[A multicenter, retrospective study of pathogenic bacteria distribution and drug resistance in febrile neutropenic patients with hematological diseases in Shanghai]

Objective: To investigate the pathogen spectrum distribution and drug resistance of febrile neutropenic patients with hematological diseases in Shanghai. Methods: A retrospective study was conducted on the clinical isolates from the febrile neutropenic patients hospitalized in the departments of hematology in 12 general hospitals in Shanghai from January 2012 to December 2014. The drug susceptibility test was carried out by Kirby-Bauer method. WHONET 5.6 software was used to analyze pathogenic bacteria and drug susceptibility data. Results: A total of 1 260 clinical isolates were collected from the febrile neutropenic patients. Gram-positive bacteria accounted for 33.3% and Gram-negative bacteria accounted for 66.7%. Klebsiella pneumoniae (12.5%) , Stenotrophomonas maltophilia (9.5%) , Escherichia coli (9.1%) , Pseudomonas aeruginosa (8.7%) , Acinetobacter baumannii (6.6%) , Staphylococcus aureus (5.6%) and Enterococcus faecium (5.0%) were ranked in the first 7 of all pathogens. In the respiratory tract secretions specimens, non-fermented strains accounted for 56.2%. Stenotrophomonas maltophilia accounted for 15.2%. Enterobacteriaceae and coagulase-negative Staphylococci accounted for 42.3% (104/246) and 32.6% (85/246) respectively in blood samples. Enterobacteriaceae and Enterococcus bacteria accounted for 39.4% (76/193) and 28.5% (55/193) respectively in pus specimens. The detection rates of methicillin resistant Staphylococcus aureus (MRSA) and methicillin resistant coagulase negative Staphylococci (MRCNS) were 54.3% and 82.5%, respectively. Staphylococcus bacterial strain was not found to be resistant to linezolid, vancomycin and teicoplanin. The detection rate of Enterococcus vancomycin-resistant strains was 8.9%. Enterococcus was not detected resistance to oxazolidinone strains. Enterobacteriaceae bacteria were highly sensitive to carbapenems. The resistance rate of Pseudomonas aeruginosa to imipenem and meropenem was 34.1% and 15.8%, respectively. Stenotrophomonas maltophilia was more sensitive to minocycline hydrochloride, levofloxacin and sulfamethoxazole. The resistance rate of Acinetobacter baumannii only to cefoperazone-sulbactam was less than 10.0%. The antibiotic resistance rate of Klebsiella pneumoniae, Stenotrophomonas maltophilia, Pseudomonas aeruginosa and Acinetobacter baumanii to most of common antibiotics was lower than that of the CHINET surveillance. Conclusions: The pathogenic strain distribution in common infection sites of febrile neutropenic patients was characterized. Bacterial resistance surveillance was better than the CHINET nationwide large sample surveillance in China.

Evaluation of a Stenotrophomonas maltophilia bacteremia cluster in hematopoietic stem cell transplantation recipients using whole genome sequencing

Background

Stenotrophomonas maltophilia ubiquitously occurs in the hospital environment. This opportunistic pathogen can cause severe infections in immunocompromised hosts such as hematopoietic stem cell transplantation (HSCT) recipients. Between February and July 2016, a cluster of four patients on the HSCT unit suffered from S. maltophilia bloodstream infections (BSI).

Methods

For epidemiological investigation we retrospectively identified the colonization status of patients admitted to the ward during this time period and performed environmental monitoring of shower heads, shower outlets, washbasins and toilets in patient rooms. We tested antibiotic susceptibility of detected S. maltophilia isolates. Environmental and blood culture samples were subjected to whole genome sequence (WGS)-based typing.

Results

Of four patients with S. maltophlilia BSI, three were found to be colonized previously. In addition, retrospective investigations revealed two patients being colonized in anal swab samples but not infected. Environmental monitoring revealed one shower outlet contaminated with S. maltophilia. Antibiotic susceptibility testing of seven S. maltophlia strains resulted in two trimethoprim/sulfamethoxazole resistant and five susceptible isolates, however, not excluding an outbreak scenario. WGS-based typing did not result in any close genotypic relationship among the patients' isolates. In contrast, one environmental isolate from a shower outlet was closely related to a single patient's isolate.

Conclusion

WGS-based typing successfully refuted an outbreak of S. maltophilia on a HSCT ward but uncoverd that sanitary installations can be an actual source of S. maltophilia transmissions.

Predictive implications of albumin and C-reactive protein for progression to pneumonia and poor prognosis in Stenotrophomonas maltophilia bacteremia following allogeneic hematopoietic stem cell transplantation

Background

Stenotrophomonas maltophilia (S. maltophilia) bacteremia causes significant morbidity and mortality in immunocompromised hosts. However, incidence and risk factors for mortality in S. maltophilia bacteremia following allogeneic hematopoietic stem cell transplantation (allo-HSCT) remain controversial. The primary aim of this study is to clarify factors associated with poor prognosis of allo-HSCT recipients with S. maltophilia bacteremia.

Methods

From January 2005 to December 2014, patients with hematological diseases and S. maltophilia bacteremia at a single transplantation center in Japan were examined for incidence and 90-day mortality. Prognostic factors associated with 90-day mortality among allo-HSCT recipients were analyzed by log-rank test, and significant variables in the univariate analysis were included in the multivariate Cox proportional-hazards regression model.

Results

A total of 65 patients, including 47 patients undergoing allo-HSCT, developed S. maltophilia bacteremia. The incidence of S. maltophilia bacteremia was significantly higher in allo-HSCT recipients compared to patients not receiving allo-HSCT (6.53 vs. 0.36 per 100 admissions, respectively; p < 0.01). The overall 90-day mortality in allo-HSCT recipients was 43%. Independent risk factors for 90-day mortality were low serum albumin (<3.0 g/dl) (HR = 10.86; 95% CI, 3.27–36.12) and high serum C-reactive protein (CRP) (≥10.0 mg/dl) (HR = 3.28; 95% CI, 1.00–10.72). Among 9 patients with both high CRP and low albumin, 5 had pneumonia at the onset of bacteremia and the remaining 4 patients developed pneumonia in a median of 3 days (range, 1 to 8 days) even under effective treatment. All 9 patients eventually died in a median of 2 days (range, 2 to 32 days). The probabilities of developing pneumonia in patients with or without high CRP and low albumin levels were 100% (9/9) and 10.5% (4/38), respectively (p < 0.01).

Conclusions

Allo-HSCT recipients had higher rates of S. maltophilia bacteremia than did patients not receiving allo-HSCT. High serum CRP and low serum albumin at the onset of bacteremia are predictive of disease progression to pneumonia and poor prognosis.

Electronic supplementary material

The online version of this article (10.1186/s12879-017-2745-6) contains supplementary material, which is available to authorized users.

Fatal hemorrhagic pneumonia: Don't forget Stenotrophomonas maltophilia

We present a case of fatal hemorrhagic pneumonia secondary to Stenotrophomonas maltophilia in a patient with acute myeloid leukemia. S. maltophilia is commonly a non-virulent pathogen. However, in the immunocompromised, it is generally associated with bacteremia after central venous catheter placement or pneumonia. Hemorrhagic pneumonia is a rare presentation of this bacteria, with only 31 cases reported in the literature, and has 100% mortality within 72 hours. Rapid recognition and early suspicion should be key in the treatment of these patients.

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.