Community-acquired Stenotrophomonas maltophilia infections: a systematic review

Clinical characteristics and genome epidemiology of Stenotrophomonas maltophilia in Japan

BACKGROUND

Stenotrophomonas maltophilia is a carbapenem-resistant Gram-negative pathogen increasingly responsible for difficult-to-treat nosocomial infections.

OBJECTIVES

To describe the contemporary clinical characteristics and genome epidemiology of patients colonized or infected by S. maltophilia in a multicentre, prospective cohort.

METHODS

All patients with a clinical culture growing S. maltophilia were enrolled at six tertiary hospitals across Japan between April 2019 and March 2022. The clinical characteristics, outcomes, antimicrobial susceptibility and genomic epidemiology of cases with S. maltophilia were investigated.

RESULTS

In total, 78 patients were included representing 34 infection and 44 colonization cases. The median age was 72.5 years (IQR, 61-78), and males accounted for 53 cases (68%). The most common comorbidity was localized solid malignancy (39%). Nearly half of the patients (44%) were immunosuppressed, with antineoplastic chemotherapy accounting for 31%. The respiratory tract was the most common site of colonization (86%), whereas bacteraemia accounted for most infection cases (56%). The 30 day all-cause mortality rate was 21%, which was significantly higher in infection cases than colonization cases (35% versus 9%; adjusted HR, 3.81; 95% CI, 1.22-11.96). Susceptibility rates to ceftazidime, levofloxacin, minocycline and sulfamethoxazole/trimethoprim were 14%, 65%, 87% and 100%, respectively. The percentage of infection ranged from 13% in the unclassified group to 86% in genomic group 6A. The percentage of non-susceptibility to ceftazidime ranged from 33% in genomic group C to 100% in genomic groups 6 and 7 and genomic group geniculate.

CONCLUSIONS

In this contemporary multicentre cohort, S. maltophilia primarily colonized the respiratory tract, whereas patients with bacteraemia had the highest the mortality from this pathogen. Sulfamethoxazole/trimethoprim remained consistently active, but susceptibility to levofloxacin was relatively low. The proportions of cases representing infection and susceptibility to ceftazidime differed significantly based on genomic groups.

Stenotrophomonas maltophilia Belonging to Novel Sequence Types ST473 and ST474 in Wild Birds Inhabiting the Brazilian Amazonia

Stenotrophomonas maltophilia is an opportunistic human pathogen associated with nosocomial and community-acquired infections. We have conducted a microbiological and genomic surveillance study of broad-spectrum cephalosporin- and carbapenem-resistant Gram-negative bacteria colonizing wild birds inhabiting the Brazilian Amazonia. Strikingly, two S. maltophilia strains (SM79 and SM115) were identified in Plain-throated antwren (Isleria hauxwelli) passerines affected by Amazonian fragmentation and degradation. Noteworthy, SM79 and SM115 strains belonged to new sequence types (STs) ST474 and ST473, respectively, displaying resistance to broad-spectrum β-lactams, aminoglycosides and/or fluoroquinolones. In this regard, resistome analysis confirmed efflux pumps (smeABC, smeDEF, emrAB-tolC and macB), blaL1 and blaL2, aph(3')-IIc and aac(6')-Iak, and Smqnr resistance genes. Comparative phylogenomic analysis with publicly available S. maltophilia genomes clustered ST473 and ST474 with human strains, whereas the ST474 was also grouped with S. maltophilia strains isolated from water and poultry samples. In summary, we report two novel sequence types of S. maltophilia colonizing wild Amazonian birds. The presence of opportunistic multidrug-resistant pathogens in wild birds, from remotes areas, could represent an ecological problem since these animals could easily promote long-distance dispersal of medically important antimicrobial-resistant bacteria. Therefore, while our results could provide a baseline for future epidemiological genomic studies, considering the limited information regarding S. maltophilia circulating among wild animals, additional studies are necessary to evaluate the clinical impact and degree of pathogenicity of this human opportunistic pathogen in wild birds.

Community-acquired Stenotrophomonas maltophilia bacteremia in liver cirrhosis: A case report

Stenotrophomonas maltophilia is a Gram-negative bacterium, usually considered a nosocomial pathogen. Its role in community-acquired infections has been reported, but it is still not typically included in differential diagnoses of patients not exposed to the healthcare system. Recently, some reports suggested that liver diseases might also act as a possible risk factor for community-acquired S. maltophilia bloodstream infection. We report a case of a 77-year-old woman with a history of cirrhosis who was diagnosed with community-acquired S. maltophilia bloodstream infection. S. maltophilia not only causes hospital-acquired infections but is also emerging as a pathogen in community settings. Although community-onset infection is still rare and might have lower mortality, this antibiotic-resistant bacterial species should be considered a possible pathogen in patients with liver cirrhosis. Although trimethoprim-sulfamethoxazole is considered the first-line treatment, a study in vitro and a 4-year review of S. maltophilia susceptibility in our institution found that the bacteria were more susceptible to minocycline than to trimethoprim-sulfamethoxazole. Therefore, minocycline might become the first-line treatment in the future.

Steno-sphere: Navigating the enigmatic world of emerging multidrug-resistant Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is an opportunistic pathogen and frequent cause of serious nosocomial infections. Patient populations at greatest risk for these infections include the immunocompromised and those with chronic respiratory illnesses and prior antibiotic exposure, notably to carbapenems. Its complex virulence and resistance profile drastically limit available antibiotics, and incomplete breakpoint and pharmacokinetic/pharmacodynamic (PK/PD) data to inform dose optimization further complicates therapeutic approaches. Clinical comparison data of first-line agents, including trimethoprim-sulfamethoxazole (TMP-SMX), quinolones, and minocycline, are limited to conflicting observational data with no clear benefit of a single agent or combination therapy. Newer antibiotic approaches, including cefiderocol and aztreonam- avibactam, are promising alternatives for extensively drug-resistant isolates; however, clinical outcomes data are needed. The potential clinical utility of bacteriophage for compassionate use in treating S. maltophilia infections remains to be determined since data is limited to in-vitro and sparse in-vivo work. This article provides a review of available literature for S. maltophilia infection management focused on related epidemiology, resistance mechanisms, identification, susceptibility testing, antimicrobial PK/PD, and emerging therapeutic strategies.

Necrotizing Pancreatitis Infected with Stenotrophomonas maltophilia: An Emerging Rare Multidrug-Resistant Organism

Stenotrophomonas maltophilia (SM) is a multidrug-resistant, Gram-negative (GN) bacillus that is an increasingly recognized nosocomial and environment pathogen. It is intrinsically resistant to carbapenems, a drug commonly utilized in the management of necrotizing pancreatitis (NP). We report a 21-year-old immunocompetent female with NP complicated by pancreatic fluid collection (PFC) infected with SM. One-third of patients with NP will develop infections by GN bacteria, while broad-spectrum antibiotics, including carbapenems, cover most infections, trimethoprim-sulfamethoxazole (TMP-SMX) is the first-line treatment antibiotic for SM. This case is critical because it highlights a rare pathogen that should be considered a causal pathogen in patients who do not respond to their care plan.

Efficacy in Galleria mellonella Larvae and Application Potential Assessment of a New Bacteriophage BUCT700 Extensively Lyse Stenotrophomonas maltophilia

In recent years, Stenotrophomonas maltophilia (S. maltophilia) has become an important pathogen of clinically acquired infections accompanied by high pathogenicity and high mortality. Moreover, infections caused by multidrug-resistant S. maltophilia have emerged as a serious challenge in clinical practice. Bacteriophages are considered a promising alternative for the treatment of S. maltophilia infections due to their unique antibacterial mechanism and superior bactericidal ability compared with traditional antibiotic agents. Here, we reported a new phage BUCT700 that has a double-stranded DNA genome of 43,214 bp with 70% GC content. A total of 55 ORFs and no virulence or antimicrobial resistance genes were annotated in the genome of phage BUCT700. Phage BUCT700 has a broad host range (28/43) and can lyse multiple ST types of clinical S. maltophilia (21/33). Furthermore, bacteriophage BUCT700 used the Type IV fimbrial biogenesis protein PilX as an adsorption receptor. In the stability test, phage BUCT700 showed excellent thermal stability (4 to 60°C) and pH tolerance (pH = 4 to 12). Moreover, phage BUCT700 was able to maintain a high titer during long-term storage. The adsorption curve and one-step growth curve showed that phage BUCT700 could rapidly adsorb to the surface of S. maltophilia and produce a significant number of phage virions. In vivo, BUCT700 significantly increased the survival rate of S. maltophilia-infected Galleria mellonella (G. mellonella) larvae from 0% to 100% within 72 h, especially in the prophylactic model. In conclusion, these findings indicate that phage BUCT700 has promising potential for clinical application either as a prophylactic or therapeutic agent. IMPORTANCE The risk of Stenotrophomonas maltophilia infections mediated by the medical devices is exacerbated with an increase in the number of ICU patients during the Corona Virus Disease 2019 (COVID-19) epidemic. Complications caused by S. maltophilia infections could complicate the state of an illness, greatly extending the length of hospitalization and increasing the financial burden. Phage therapy might be a potential and promising alternative for clinical treatment of multidrug-resistant bacterial infections. Here, we investigated the protective effects of phage BUCT700 as prophylactic and therapeutic agents in Galleria mellonella models of infection, respectively. This study demonstrates that phage therapy can provide protection in targeting S. maltophilia-related infection, especially as prophylaxis.

A 20-year trend of prevalence and susceptibility to trimethoprim/sulfamethoxazole of Stenotrophomonas maltophilia in a single secondary care hospital in Korea

Stenotrophomonas maltophilia is a Gram-negative opportunistic pathogen that can cause serious infection. We aimed to analyze the prevalence and susceptibility rates to trimethoprim/sulfamethoxazole of S. maltophilia. We conducted a retrospective study of S. maltophilia isolates from a university hospital from 2001 to 2020. Clinical information, the numbers of isolates and susceptibility rates were analyzed by year. Susceptibility rates and changes in respiratory and non-respiratory samples were compared. 1805 S. maltophilia isolates were identified, of which 81.4% (1469/1805) were from respiratory samples. There was a male predominance and 52% of the isolates were from general wards. The average susceptibility rate was 87.7% and there was no significant annual trend (P = .519). The susceptibility rate was 88.7% in respiratory samples and 84.1% in non-respiratory samples (P = .018). Susceptibility analyses using clinical data over long periods can guide the choice of antimicrobials especially for pathogen whose treatment options are limited.

Multidrug-Resistant Uropathogens Causing Community Acquired Urinary Tract Infections among Patients Attending Health Facilities in Mwanza and Dar es Salaam, Tanzania

In low-income countries, the empirical treatment of urinary tract infections (UTIs) without laboratory confirmation is very common, especially in primary health facilities. This scenario often leads to unnecessary and ineffective antibiotic prescriptions, prompting the emergence and spread of antimicrobial resistance. We conducted this study to examine the antibiogram of uropathogens causing community-acquired urinary tract infections among outpatients attending selected health facilities in Tanzania.

METHOD

This was a cross-sectional health centre-based survey conducted for a period of five months, from July to November 2021, in the Mwanza and Dar es Salaam regions in Tanzania. We enrolled consecutively a total of 1327 patients aged between 2 and 96 years with a median [IQR] age of 28 [22-39] from Dar es Salaam (n = 649) and Mwanza (n = 678).

RESULTS

Significant bacteriuria was observed in 364 (27.4% [95%CI: 25.0-29.9]) patients, from whom 412 urinary pathogens were isolated. Gram-negative bacteria contributed to 57.8% (238) of the 412 uropathogens isolated, of which 221 were Enterobacterales, and Escherichia coli was the most frequent. Staphylococcus aureus and Staphylococcus haemolyticus were the most frequently isolated among Gram-positive uropathogens (n = 156). Generally, resistance among Escherichia coli ranged from 0.7% (meropenem) to 86.0% (ampicillin) and from 0.0% (meropenem) to 75.6% (ampicillin) in other Enterobacterales. Moreover, about 45.4% (108) of Enterobacterales and 22.4% (35) of Gram-positive bacteria were multidrug resistant (MDR), p = 0.008. We observed 33 MDR patterns among Gram-negative bacteria, predominantly AMP-CIP-TCY (23/108; 21.3%), and 10 MDR patterns among Gram-positive bacteria, most commonly CIP-GEN-TCY (22/35; 62.9%).

CONCLUSION

the presence of a high number of wide-ranging uropathogens that are multidrug resistant to a variety of antibiotics points to the need to strengthen the laboratory diagnostic systems for the regular surveillance of the antimicrobial resistance of uropathogens to guide and update empirical treatment guidelines.

Trends in Stenotrophomonas maltophilia antibiotic resistance rates in the United States Veterans Affairs Health System

Introduction. Stenotrophomonas maltophilia is an important multidrug-resistant Gram-negative pathogen. While largely a hospital-acquired pathogen, there have been increasing reports of the pathogen in the community.

Gap Statement. Trends in S. maltophilia prevalence and resistance rates that include outpatient isolates are unknown.

Aim. We described recent trends in prevalence and resistance of S. maltophilia in the national Veterans Affairs (VA) Healthcare system.

Methodology. The study identified positive S. maltophilia clinical cultures among VA adult patients from 2010 to 2018 across all VA hospitals, long-term care facilities/units, and outpatient settings. Annual S. maltophilia resistance rates were evaluated. Multidrug resistant (MDR) was defined as resistance to sulfamethoxazole/trimethoprim (SMX/TMP) and minocycline or levofloxacin. Time trends were assessed with regression analyses to estimate annual average percent changes (AAPC) with 95 % confidence intervals using Joinpoint software.

Results. Over the 9 year study period, 18 285  S . maltophilia cultures were identified (57 % hospital, 3 % long-term care, 40 % outpatient). The most common source of S. maltophilia cultures were respiratory cultures (34.6 %) followed by urine cultures (30.4 %). In VA hospitals and long-term care facilities, the number of S. maltophilia cultures decreased significantly (by 5.4% and 8.4 % per year respectively). Overall, 3.1 % of isolates were MDR which remained stable over the study period. Resistance to other antibiotics assessed mostly remained stable, except SMX/TMP resistance decreased significantly by 8.5 % (2010, 15 %; 2018, 6 %) per year in VA hospitals.

Conclusion. While previous work has recognized S. maltophilia as primarily a nosocomial pathogen, the present study found that 40 % of cultures collected were among outpatients. Between 2010 and 2018, the number of positive S. maltophilia cultures decreased significantly in the national VA Healthcare System. Resistance to SMX/TMP decreased over the study period in VA hospitals and now more closely reflects previously reported resistance rates worldwide (0–10 %). MDR S. maltophilia remained stable and low in the national VA Healthcare System.

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.

Characterisation of Bacteriophage vB_SmaM_Ps15 Infective to Stenotrophomonas maltophilia Clinical Ocular Isolates

Recent acknowledgment that multidrug resistant Stenotrophomonas maltophilia strains can cause severe infections has led to increasing global interest in addressing its pathogenicity. While being primarily associated with hospital-acquired respiratory tract infections, this bacterial species is also relevant to ophthalmology, particularly to contact lens-related diseases. In the current study, the capacity of Stenotrophomonas phage vB_SmaM_Ps15 to infect ocular S. maltophilia strains was investigated to explore its future potential as a phage therapeutic. The phage proved to be lytic to a range of clinical isolates collected in Australia from eye swabs, contact lenses and contact lens cases that had previously shown to be resistant to several antibiotics and multipurpose contact lenses disinfectant solutions. Morphological analysis by transmission electron microscopy placed the phage into the Myoviridae family. Its genome size was 161,350 bp with a G + C content of 54.2%, containing 276 putative protein-encoding genes and 24 tRNAs. A detailed comparative genomic analysis positioned vB_SmaM_Ps15 as a new species of the Menderavirus genus, which currently contains six very similar globally distributed members. It was confirmed as a virulent phage, free of known lysogenic and pathogenicity determinants, which supports its potential use for the treatment of S. maltophilia eye infections.

Cellulitis: A Review of Current Practice Guidelines and Differentiation from Pseudocellulitis

Cellulitis, an infection involving the deep dermis and subcutaneous tissue, is the most common reason for skin-related hospitalization and is seen by clinicians across various disciplines in the inpatient, outpatient, and emergency room settings, but it can present as a diagnostic and therapeutic challenge. Cellulitis is a clinical diagnosis based on the history of present illness and physical examination and lacks a gold standard for diagnosis. Clinical presentation with acute onset of redness, warmth, swelling, and tenderness and pain is typical. However, cellulitis can be difficult to diagnose due to a number of infectious and non-infectious clinical mimickers such as venous stasis dermatitis, contact dermatitis, eczema, lymphedema, and erythema migrans. Microbiological diagnosis is often unobtainable due to poor sensitivity of culture specimens. The majority of non-purulent, uncomplicated cases of cellulitis are caused by β-hemolytic streptococci or methicillin-sensitive Staphylococcus aureus, and appropriate targeted coverage of this pathogen with oral antibiotics such as penicillin, amoxicillin, and cephalexin is sufficient. Even with rising rates of community-acquired methicillin-resistant Staphylococcus aureus, coverage for non-purulent cellulitis is generally not recommended.

Degradation of CP4-EPSPS with a Psychrophilic Bacterium Stenotrophomonas maltophilia 780

CP4-EPSPS (Agrobacterium sp. strain CP4 5-enolpyruvylshikimate-3-phosphate synthase) protein showed remarkable thermostability and was highly resistant to proteases, such as trypsin. In order to eliminate the pollution of CP4-EPSPS from the accumulated straws to the surrounding environment during the winter, the present study investigated the extracellular proteases of 21 psychrophilic strains isolated from the south polar region. The results indicated that Stenotrophomonas maltophilia 780 was able to degrade CP4-EPSPS at 18 °C efficiently. Further study indicated that it was able to grow in the extract of Roundup Ready soybean at 18 °C, with CP4-EPSPS degraded to an undetectable level within 72 h. The extracellular proteases of Stenotrophomonas maltophilia 780 are thermo-sensitive, with an optimal temperature of 65 °C. The genomic sequencing result indicated that this strain had more than a hundred putative protease and peptidase coding genes, which may explain its high capability in decomposing CP4-EPSPS.

Multiplexed detection of respiratory pathogens with a portable analyzer in a "raw-sample-in and answer-out" manner

Coronavirus disease 2019 (COVID-19) has emerged, rapidly spread and caused significant morbidity and mortality worldwide. There is an urgent public health need for rapid, sensitive, specific, and on-site diagnostic tests for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. In this study, a fully integrated and portable analyzer was developed to detect SARS-CoV-2 from swab samples based on solid-phase nucleic acid extraction and reverse transcription loop-mediated isothermal amplification (RT-LAMP). The swab can be directly inserted into a cassette for multiplexed detection of respiratory pathogens without pre-preparation. The overall detection process, including swab rinsing, magnetic bead-based nucleic acid extraction, and 8-plex real-time RT-LAMP, can be automatically performed in the cassette within 80 min. The functionality of the cassette was validated by detecting the presence of a SARS-CoV-2 pseudovirus and three other respiratory pathogens, i.e., Klebsiella pneumoniae, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia. The limit of detection (LoD) for the SARS-CoV-2 pseudovirus was 2.5 copies/μL with both primer sets (N gene and ORF1ab gene), and the three bacterial species were successfully detected with an LoD of 2.5 colony-forming units (CFU)/μL in 800 μL of swab rinse. Thus, the analyzer developed in this study has the potential to rapidly detect SARS-CoV-2 and other respiratory pathogens on site in a “raw-sample-in and answer-out” manner.

Carbapenem Resistance among Marine Bacteria-An Emerging Threat to the Global Health Sector

The emergence of antibiotic resistance among pathogenic microorganisms is a major issue for global public health, as it results in acute or chronic infections, debilitating diseases, and mortality. Of particular concern is the rapid and common spread of carbapenem resistance in healthcare settings. Carbapenems are a class of critical antibiotics reserved for treatment against multidrug-resistant microorganisms, and resistance to this antibiotic may result in limited treatment against infections. In addition to in clinical facilities, carbapenem resistance has also been identified in aquatic niches, including marine environments. Various carbapenem-resistant genes (CRGs) have been detected in different marine settings, with the majority of the genes incorporated in mobile genetic elements, i.e., transposons or plasmids, which may contribute to efficient genetic transfer. This review highlights the potential of the marine environment as a reservoir for carbapenem resistance and provides a general overview of CRG transmission among marine microbes.

Antimicrobial Treatment Strategies for Stenotrophomonas maltophilia: A Focus on Novel Therapies

Stenotrophomonas maltophilia is an urgent global threat due to its increasing incidence and intrinsic antibiotic resistance. Antibiotic development has focused on carbapenem-resistant Enterobacteriaceae, Pseudomonas, and Acinetobacter, with approved antibiotics in recent years having limited activity for Stenotrophomonas. Accordingly, novel treatment strategies for Stenotrophomonas are desperately needed. We conducted a systemic literature review and offer recommendations based on current evidence for a treatment strategy of Stenotrophomonas infection.

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.

Recombinant Ax21 protein is a promising subunit vaccine candidate against Stenotrophomonas maltophilia in a murine infection model

Stenotrophomonas maltophilia is an emerging pathogen that can cause several disease manifestations such as bacteremia, meningitis, respiratory tract infections and others. More seriously, this pathogen has a highly evolving antibiotic resistance profile. Antibiotic misuse is further aggravating the situation by inducing the development of multi- and even pan-resistance. Thus, employing diverse strategies to overcome this increasing antibiotic resistance is of paramount importance. In general, vaccination is one of these strategies that prevents the onset of infection, provides long term protection against infection, and most importantly diminishes the antibiotic consumption, thus, resulting in controlling resistance. Unfortunately, vaccine research concerning S. maltophilia is very scarce in the literature. Ax21 protein is an outer membrane protein implicated in several virulence mechanisms of S. maltophilia such as quorum sensing, biofilm formation, and antibiotic resistance. Our computational analysis of Ax21 revealed its potential immunogenicity. In the current study, Ax21 protein of S. maltophilia was cloned and heterologously expressed in Escherichia coli. Mice were immunized with the purified recombinant antigen using Bacillus Calmette-Guérin(BCG) and incomplete Freund's adjuvant (IFA) as immune-adjuvants. Enzyme-linked immunosorbent assay (ELISA) revealed significant antigen-specific IgG1, IgG2a and total IgG levels in immunized mice which reflected successful immune stimulation. Immunized mice that were challenged with S. maltophilia showed a substantialreduction in bacterial bioburden in lungs, liver, kidneys, and heart. In addition, liver histological examination demonstrated a remarkable decrease in pathological signs such as necrosis, vacuolation, bile duct fibrosis and necrosis, infiltration of inflammatory cells, and hemorrhage. Whole cell ELISA and opsonophagocytic assay confirmed the ability of serum antibodies from immunized mice to bind and facilitate phagocytosis of S. maltophilia, respectively. To our knowledge, this is the first report to demonstrate the vaccine protective efficacy of Ax21 outer membrane protein against S. maltophilia infection.

Stenotrophomonas maltophilia: An uncommon cause of liver abscess

We report an uncommon case of pyogenic liver abscess due to Stenotrophomonas maltophilia in an apparently immune-competent individual, the timely recognition of which could avoid a potentially fatal course of infection in the patient. A 45-year-old man, with history of moderate alcohol intake since the last 10 years, was admitted with intense right-sided upper abdominal pain and right-sided chest pain of 10-days duration. Culture of the ultrasound-guided liver aspirate sample yielded a pure growth of S. maltophilia identified by the VITEK-2™ automated microbial identification system. Treatment with parenteral levofloxacin and oral trimethoprim-sulfamethoxazole along with pigtail catheter drainage and other appropriate supportive management led to resolution of the abscess with no recurrence of infection at two months follow-up. Physicians need to be aware that S. maltophilia infections may not be restricted to hospitalized patients as a low-virulence opportunistic pathogen, but may occur as an important emerging pathogen in community-acquired infections as well.

Alterations in skin microbiome mediated by radiotherapy and their potential roles in the prognosis of radiotherapy-induced dermatitis: a pilot study

Radiotherapy-induced dermatitis (RID) is an inflammatory cutaneous disorder that is acquired as an adverse effect of undergoing radiotherapy. Skin microbiome dysbiosis has been linked to the outcomes of several dermatological diseases. To explore the skin microbiota of RID and deduce their underlying impact on the outcome of RID, cutaneous microbiomes of 78 RID patients and 20 healthy subjects were characterized by sequencing V1-V3 regions of 16S rRNA gene. In total, a significantly apparent reduction in bacterial diversity was detected in microbiomes of RID in comparison to controls. Overall, the raised Proteobacteria/ Firmicutes ratio was significantly linked to delayed recovery or tendency toward the permanence of RID (Kruskal Wallis: P = 2.66 × 10^–4). Moreover, applying enterotyping on our samples stratified microbiomes into A, B, and C dermotypes. Dermotype C included overrepresentation of Pseudomonas, Staphylococcus and Stenotrophomonas and was markedly associated with delayed healing of RID. Strikingly, coexistence of diabetes mellitus and RID was remarkably correlated with a significant overrepresentation of Klebsiella or Pseudomonas and Staphylococcus. Metabolic abilities of skin microbiome could support their potential roles in the pathogenesis of RID. Cutaneous microbiome profiling at the early stages of RID could be indicative of prospective clinical outcomes and maybe a helpful guide for personalized therapy.

Avibactam potentiated the activity of both ceftazidime and aztreonam against S. maltophilia clinical isolates in vitro

Background

Treatment options for Stenotrophomonas maltophilia (S. maltophilia) infections were limited. We assessed the efficacy of ceftazidime (CAZ), ceftazidime-avibactam (CAZ-AVI), aztreonam (ATM), and aztreonam-avibactam (ATM-AVI) against a selection of 76 S. maltophilia out of the 1179 strains isolated from the First Affiliated Hospital of Chongqing Medical University during 2011–2018.

Methods

We investigated the antimicrobial resistance profiles of the 1179 S. maltophilia clinical isolates from the first affiliated hospital of Chongqing Medical University during 2011–2018, a collection of 76 isolates were selected for further study of microbiological characterization. Minimum inhibitory concentrations (MICs) of CAZ, CAZ-AVI, ATM and ATM-AVI were determined via the broth microdilution method. We deemed that CAZ-AVI or ATM-AVI was more active in vitro than CAZ or ATM alone when CAZ-AVI or ATM-AVI led to a category change from “Resistant” or “Intermediate” with CAZ or ATM alone to “Susceptible” with CAZ-AVI or ATM-AVI, or if the MIC of CAZ-AVI or ATM-AVI was at least 4-fold lower than the MIC of CAZ or ATM alone.

Results

For the 76 clinical isolates included in the study, MICs of CAZ, ATM, CAZ-AVI and ATM-AVI ranged from 0.03–64, 1–1024, 0.016–64, and 0.06–64 μg/mL, respectively. In combined therapy, AVI was active at restoring the activity of 48.48% (16/33) and 89.71% (61/68) of S. maltophilia to CAZ and ATM, respectively. Furthermore, CAZ-AVI showed better results in terms of the proportion of susceptible isolates (77.63% vs. 56.58%, P < 0.001), and MIC50 (2 μg/mL vs. 8 μg/mL, P < 0.05) when compared to CAZ. According to our definition, CAZ-AVI was more active in vitro than CAZ alone for 81.58% (62/76) of the isolates. Similarly, ATM-AVI also showed better results in terms of the proportion of susceptible isolates (90.79% vs.10.53%, P < 0.001) and MIC50 (2 μg/mL vs. 64 μg/mL, P < 0.001) when compared to ATM. According to our definition, ATM-AVI was also more active in vitro than ATM alone for 94.74% (72/76) of the isolates.

Conclusions

AVI potentiated the activity of both CAZ and ATM against S. maltophilia clinical isolates in vitro. We demonstrated that CAZ-AVI and ATM-AVI are both useful therapeutic options to treat infections caused by S. maltophilia.

Risk Factors of Stenotrophomonas maltophilia Blood Stream Infections: Comparison With Other Gram-Negative Blood Stream Infections in Children

BACKGROUND

Stenotrophomonas maltophilia, is a nonfermentative, aerobic, Gram-negative bacilli which is intrinsically resistance to several antibiotics. Treatment options for this bacteria are quite different from the other Gram-negative bacilli, which can represent a therapeutic challenge. To initiate appropriate empiric treatment and to reduce mortality, differentiation of S. maltophilia from other Gram-negative bacteria is critically important. The aim of this study is to distinguish the risk factors of S. maltophilia blood stream infections (BSI) from other Gram-negative BSI.

METHODS

This was a retrospective, case-control study. Patients with S. maltophilia BSI were selected as cases and patients with non-S. maltophilia Gram-negative BSI were selected as controls. Demographic and clinical characteristics of patients were recorded.

RESULTS

Forty-eight cases with S. maltophilia BSI and 144 controls were enrolled in the study. Risk factors for S. maltophilia BSI compared with the control group includes prior use of antibiotics, especially carbapenem, pediatric intensive care unit stay, mechanical ventilator use, indwelling catheters and duration of hospitalization.

CONCLUSIONS

Breakthrough infection by S. maltophilia can occur in severely ill patients being treated with carbapenem. In the presence of risk factors, to reduce morbidity and mortality, S. maltophilia should be kept in mind when starting empiric treatment.

Mechanisms and phenotypic consequences of acquisition of tigecycline resistance by Stenotrophomonas maltophilia

OBJECTIVES

To elucidate the potential mutation-driven mechanisms involved in the acquisition of tigecycline resistance by the opportunistic pathogen Stenotrophomonas maltophilia. The mutational trajectories and their effects on bacterial fitness, as well as cross-resistance and/or collateral susceptibility to other antibiotics, were also addressed.

METHODS

S. maltophilia populations were submitted to experimental evolution in the presence of increasing concentrations of tigecycline for 30 days. The genetic mechanisms involved in the acquisition of tigecycline resistance were determined by WGS. Resistance was evaluated by performing MIC assays. Fitness of the evolved populations and individual clones was assessed by measurement of the maximum growth rates.

RESULTS

All the tigecycline-evolved populations attained high-level resistance to tigecycline following different mutational trajectories, yet with some common elements. Among the mechanisms involved in low susceptibility to tigecycline, mutations in the SmeDEF efflux pump negative regulator smeT, changes in proteins involved in the biogenesis of the ribosome and modifications in the LPS biosynthesis pathway seem to play a major role. Besides tigecycline resistance, the evolved populations presented cross-resistance to other antibiotics, such as aztreonam and quinolones, and they were hypersusceptible to fosfomycin, suggesting a possible combination treatment. Further, we found that the selected resistance mechanisms impose a relevant fitness cost when bacteria grow in the absence of antibiotic.

CONCLUSIONS

Mutational resistance to tigecycline was easily selected during exposure to this antibiotic. However, the fitness cost may compromise the maintenance of S. maltophilia tigecycline-resistant populations in the absence of antibiotic.

Imaging findings of Stenotrophomonas maltophilia pneumonia: emphasis on CT findings between immunocompromised and immunocompetent patients

BACKGROUND

Stenotrophomonas maltophilia (S. maltophilia) is a globally emerging, rare, waterborne, aerobic, gram-negative, multiple-drug-resistant organism, most commonly associated with respiratory tract infection in humans. Computed tomography (CT) findings in patients with S. maltophilia pneumonia are rarely reported.

PURPOSE

To compare CT findings between immunocompromised and immunocompetent patients, and to determine characteristic imaging findings of S. maltophilia pneumonia.

MATERIAL AND METHODS

CT findings of eight immunocompromised and 29 immunocompetent patients with proven S. maltophilia pneumonia were reviewed retrospectively. Different patterns of CT abnormalities between immunocompromised and immunocompetent patients were compared by Fisher's exact test.

RESULTS

Patchy ground-glass opacities (GGOs) were the most common CT findings, present in 36 (97.3%) of the 37 patients. Among the patients with patchy GGOs, consolidation was seen in 29 (78.4%) patients, and centrilobular nodules were noted in 15 (40.5%) patients. The transaxial distribution of the parenchymal abnormalities was predominantly randomly distributed in 30 (81.1%) cases. Regarding longitudinal plane involvement, the predominant zonal distributions were the diffuse distribution (n=23, 62.2%) and the lower lung zone (n=14, 37.8%). None of the patients showed upper lung zone predominance. The proportion of patients with parenchymal CT findings or associated findings in the immunocompromised patients was not significantly different from that of the immunocompetent patients. However, lower lung zone predominance on the longitudinal plane was significantly more common in immunocompetent patients than in immunocompromised patients (14/29 vs. 0/8, P=0.015). And diffuse distribution of parenchymal abnormalities on a longitudinal plane was significantly more frequent in immunocompromised patients than in immunocompetent patients (8/8 vs. 15/29, P=0.015).

CONCLUSION

The most common CT patterns of S. maltophilia pneumonia in immunocompromised and immunocompetent patients were patchy GGOs and consolidation. However, in immunocompetent patients, parenchymal abnormalities were more predominately distributed in lower lung zone than in immunocompromised patients; and in immunocompromised patients, parenchymal abnormalities were more diffusely distributed than in immunocompetent patients.

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 Infection in a Patient with Acute Exacerbation of Chronic Obstructive Pulmonary Disease (COPD): A Colonizer or True Infection?

BACKGROUND This article describes a finding of sputum culture positive for Stenotrophomonas maltophilia in an elderly woman with past medical history of chronic obstructive pulmonary disease (COPD) and hypertension, presenting with acute hypoxemic hypercapnic respiratory failure secondary to COPD exacerbation from bronchitis/bronchopneumonia. CASE REPORT Computed tomography (CT) of the chest showed secretions in the lower lobe bronchi and small scattered clustered nodules consistent with bronchitis/mild bronchopneumonia without evidence of pulmonary embolism. A sputum culture was positive for Stenotrophomonas maltophilia. She was treated with trimethoprim/sulfamethoxazole for 10 days. She recovered and was subsequently discharged from the hospital. CONCLUSIONS Stenotrophomonas maltophilia, previously known as a colonizer, is now being recognized as a true respiratory infection, especially in immunocompromised patients and those with chronic diseases like COPD presenting with signs and symptoms of infection. Therefore, early identification and prompt treatment of Stenotrophomonas maltophilia infection is important for a favorable outcome.

The phylogenetic landscape and nosocomial spread of the multidrug-resistant opportunist Stenotrophomonas maltophilia

Recent studies portend a rising global spread and adaptation of human- or healthcare-associated pathogens. Here, we analyse an international collection of the emerging, multidrug-resistant, opportunistic pathogen Stenotrophomonas maltophilia from 22 countries to infer population structure and clonality at a global level. We show that the S. maltophilia complex is divided into 23 monophyletic lineages, most of which harbour strains of all degrees of human virulence. Lineage Sm6 comprises the highest rate of human-associated strains, linked to key virulence and resistance genes. Transmission analysis identifies potential outbreak events of genetically closely related strains isolated within days or weeks in the same hospitals.

Multidrug resistance of the opportunistic pathogen Stenotrophomonas maltophilia is an increasing problem. Here, analyzing strains from 22 countries, the authors show that the S. maltophilia complex is divided into 23 monophyletic lineages and find evidence for intra-hospital transmission.

A 10-year single-center experience on Stenotrophomonas maltophilia resistotyping in Szeged, Hungary

Stenotrophomonas maltophilia is an aerobic, oxidase-negative and catalase-positive bacillus. S. maltophilia is a recognized opportunistic pathogen. Due to the advancements in invasive medical procedures, organ transplantation and chemotherapy of malignant illnesses, the relevance of this pathogen increased significantly. The therapy of S. maltophilia infections is challenging, as these bacteria show intrinsic resistance to multiple classes of antibiotics, the first-choice drug is sulfamethoxazole/trimethoprim. Our aim was to assess the epidemiology of S. maltophilia from various clinical samples and the characterization of resistance-levels and resistotyping of these samples over a long surveillance period. The study included S. maltophilia bacterial isolates from blood culture samples, respiratory samples and urine samples and the data for the samples, received between January 2008 until December 2017, a total of 817 S. maltophilia isolates were identified (respiratory samples n = 579, 70.9%, blood culture samples n = 175, 21.4% and urine samples n = 63, 7.7%). Levofloxacin and colistin-susceptibility rates were the highest (92.2%; n = 753), followed by tigecycline (90.5%, n = 739), the first-line agent sulfamethoxazole/trimethoprim (87.4%, n = 714), while phenotypic resistance rate was highest for amikacin (72.5% of isolates were resistant, n = 592). The clinical problem of sulfamethoxazole/trimethoprim-resistance is a complex issue, because there is no guideline available for the therapy of these infections.

Occurrence of Multidrug-resistant Uropathogens Implicated in Asymptomatic Bacteriuria in Adults with Sickle Cell Disease in Ile-Ife, Southwest Nigeria

OBJECTIVES

We sought to determine the prevalence of asymptomatic bacteriuria (ASB) in patients with sickle cell disease (SCD), the susceptibility profile of its agents and their extended-spectrum β-lactamase (ESBL) production.

METHODS

Fifty-nine patients with SCD and 116 healthy controls were investigated. Urine samples were collected and cultured by standard techniques. We used the disc diffusion technique to determine antibiotic susceptibility. ESBL was detected by the combination disc method and detection of bla SHV, bla TEM, and bla CTX-M genes by multiplex-polymerase chain reaction.

RESULTS

The prevalence of ASB was higher among patients with SCD (8.6%) than controls (0.9%) (p = 0.016), predominantly among females. Coagulase-negative staphylococci (n = 2; 33.3%) predominated among the isolates. Other uropathogens included Stenotrophomonas maltophilia, Acinetobacter baumannii, and Enterobacter cloacae. All isolates were sensitive to meropenem but were resistant to ceftazidime, ampicillin, and tetracycline. bla SHV, bla TEM, and bla CTX-M-15 were detected in Enterobacter cloacae.

CONCLUSIONS

The prevalence of ASB is high in patients with SCD predominantly among females. Rare multidrug-resistant uropathogens were implicated. We posit a need for resistance surveillance programs and antibiotic stewardship to prevent treatment failure and reduce drug resistance.

Activity of Potential Alternative Treatment Agents for Stenotrophomonas maltophilia Isolates Nonsusceptible to Levofloxacin and/or Trimethoprim-Sulfamethoxazole

Stenotrophomonas maltophilia is difficult to treat due to the production of multiple intrinsic and acquired mechanisms of resistance. Trimethoprim-sulfamethoxazole (TMP-SMZ) and the fluoroquinolones have traditionally been considered the drugs of choice but are plagued by increasing resistance and adverse drug effects. The objective of this study was to evaluate the in vitro activities of 12 clinically relevant antimicrobials against clinical S. maltophilia isolates nonsusceptible to levofloxacin and/or TMP-SMZ. A diverse panel of 41 clinical S. maltophilia isolates collected through the SENTRY Antimicrobial Surveillance Program from 2008 to 2018 was evaluated against ceftazidime, ceftazidime-avibactam, chloramphenicol, delafloxacin, levofloxacin, moxifloxacin, eravacycline, minocycline, omadacycline, polymyxin B, and tigecycline. MICs were determined in triplicate via reference broth microdilution and interpreted according to CLSI guidelines where available. MIC distributions and susceptibilities were also compared across infection type, acquisition setting, and geographic origin. Susceptibilities to levofloxacin and TMP-SMZ were 29.3% and 36.6%, respectively. Minocycline displayed the highest susceptibility rate overall (92.7%) and the lowest MIC₉₀ value (4 mg/liter) of any of the 12 agents tested. Only 3 isolates were resistant to levofloxacin, TMP-SMZ, and minocycline. Polymyxin B and tigecycline were the second most active agents. No significant differences were observed in MIC distributions across the 3 strata evaluated. These data demonstrate that few antimicrobials, old or new, maintain reliable activity against resistant S. maltophilia The role of minocycline in the treatment of infections due to S. maltophilia warrants further clinical investigation given its potent in vitro activity and favorable adverse effect profile.

Quantitative real-time PCR assay for the rapid identification of the intrinsically multidrug-resistant bacterial pathogen Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is emerging as an important cause of disease in nosocomial and community-acquired settings, including bloodstream, wound and catheter-associated infections. Cystic fibrosis (CF) airways also provide optimal growth conditions for various opportunistic pathogens with high antibiotic tolerance, including S. maltophilia. Currently, there is no rapid, cost-effective and accurate molecular method for detecting this potentially life-threatening pathogen, particularly in polymicrobial specimens, suggesting that its true prevalence is underestimated. Here, we used large-scale comparative genomics to identify a specific genetic target for S. maltophilia, with subsequent development and validation of a real-time PCR assay for its detection. Analysis of 167 Stenotrophomonas spp. genomes identified a conserved 4 kb region in S. maltophilia, which was targeted for Black Hole Quencher assay design. Our assay yielded the positive detection of 89 of 89 (100%) clinical S. maltophilia strains, and no amplification of 23 non-S. maltophilia clinical isolates. S. maltophilia was detected in 10 of 16 CF sputa, demonstrating the assay's utility for direct detection in respiratory specimens. The assay demonstrated good sensitivity, with limits of detection and quantitation on pure culture of ~10 and ~100 genome equivalents, respectively. Our assay provides a highly specific, sensitive and cost-effective method for the accurate identification of S. maltophilia, and will improve the diagnosis and treatment of this under-recognized pathogen by enabling its accurate and rapid detection from polymicrobial clinical and environmental samples.

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.

Population Structure, Molecular Epidemiology, and β-Lactamase Diversity among Stenotrophomonas maltophilia Isolates in the United States

Stenotrophomonas maltophilia is a Gram-negative, nonfermenting, environmental bacillus that is an important cause of nosocomial infections, primarily associated with the respiratory tract in the immunocompromised population. Aiming to understand the population structure, microbiological characteristics and impact of allelic variation on β-lactamase structure and function, we collected 130 clinical isolates from across the United States. Identification of 90 different sequence types (STs), of which 63 are new allelic combinations, demonstrates the high diversity of this species. The majority of the isolates (45%) belong to genomic group 6. We also report excellent activity of the ceftazidime-avibactam and aztreonam combination, especially against strains recovered from blood and respiratory infections for which the susceptibility is higher than the susceptibility to trimethoprim-sulfamethoxazole, considered the "first-line" antibiotic to treat S. maltophilia Analysis of 73 blaL1 and 116 blaL2 genes identified 35 and 43 novel variants of L1 and L2 β-lactamases, respectively. Investigation of the derived amino acid sequences showed that substitutions are mostly conservative and scattered throughout the protein, preferentially affecting positions that do not compromise enzyme function but that may have an impact on substrate and inhibitor binding. Interestingly, we detected a probable association between a specific type of L1 and L2 and genomic group 6. Taken together, our results provide an overview of the molecular epidemiology of S. maltophilia clinical strains from the United States. In particular, the discovery of new L1 and L2 variants warrants further study to fully understand the relationship between them and the β-lactam resistance phenotype in this pathogen.IMPORTANCE Multiple antibiotic resistance mechanisms, including two β-lactamases, L1, a metallo-β-lactamase, and L2, a class A cephalosporinase, make S. maltophilia naturally multidrug resistant. Thus, infections caused by S. maltophilia pose a big therapeutic challenge. Our study aims to understand the microbiological and molecular characteristics of S. maltophilia isolates recovered from human sources. A highlight of the resistance profile of this collection is the excellent activity of the ceftazidime-avibactam and aztreonam combination. We hope this result prompts controlled and observational studies to add clinical data on the utility and safety of this therapy. We also identify 35 and 43 novel variants of L1 and L2, respectively, some of which harbor novel substitutions that could potentially affect substrate and/or inhibitor binding. We believe our results provide valuable knowledge to understand the epidemiology of this species and to advance mechanism-based inhibitor design to add to the limited arsenal of antibiotics active against this pathogen.

Epidemiological Trends and Resistance Associated with Stenotrophomonas maltophilia Bacteremia: A 10-Year Retrospective Cohort Study in a Tertiary-Care Hospital in Hungary

Stenotrophomonas maltophilia has been recognized as an emerging nosocomial pathogen in invasive infections of immunocompromised, severely debilitated patients with significant underlying illnesses. The first-choice drug in these infections is sulfamethoxazole-trimethoprim (SMX/TMP), and resistance to this antimicrobial is a daunting challenge for clinicians. The aim of this study was to assess the prevalence of S. maltophilia bacteremia and SMX/TMP-resistance levels at a tertiary-care university hospital. A total of 175 episodes of S. maltophilia bacteremia were identified (2008-2012: n = 82, 2013-2017: n = 93; p = 0.061), 52% of affected patients were 60 years of age, and had recent surgery, severe injuries or underlying conditions (malignant hematologic diseases and solid tumors) in their history. Sixteen percent of isolates were resistant to SMX/TMP (2008-2012: n = 13.8%, 2013-2017: n = 17.2%; p = 0.076), and out of the resistant strains, 32.7% were also resistant to levofloxacin and colistin. Our findings on the SMX/TMP-resistance were similar to global literature data.

Multidrug Resistant Gram-Negative Bacteria in Community-Acquired Pneumonia

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2019. Other selected articles can be found online at https://www.biomedcentral.com/collections/annualupdate2019. Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901.

Community acquired Stenotrophomonas maltophilia discitis: Diagnosis aided by shotgun metagenomic sequencing

We report a rare case of culture negative L4-L5 discitis and epidural abscess in an immunocompetent child who had dry cupping therapy performed to treat low back strain. The causative pathogen was identified as Stenotrophomonas maltophilia by shotgun metagenomic sequencing of spinal cord aspirate after more than one month of unsuccessful empirical treatment with 6 different antibiotics. The patient was successfully treated with Sulfamethoxazole-trimethoprim and minocycline. Cupping therapy is a very popular medical procedure widely used in China, but the potential risk for severe infections such as discitis and epidural abscess described in this case should be recognized.

Multidrug Resistant Gram-Negative Bacteria in Community-Acquired Pneumonia

Community-acquired pneumonia (CAP) is associated with high morbidity and mortality worldwide [1]. Although several different bacteria and respiratory viruses can be responsible for CAP, Streptococcus pneumoniae (pneumococcus) remains the most common causative pathogen. A small proportion of CAP cases are caused by Gram-negative bacteria, especially Pseudomonas aeruginosa, Klebsiella pneumoniae, Acinetobacter baumannii and Stenotrophomona maltophilia [2, 3]. The main problem concerning the treatment of Gram-negative bacterial infections is their related antibiotic resistance, reported as multidrug resistant (MDR = resistant to at least one agent in three or more groups of antibiotics), extensively drug resistant (XDR = resistant to at least one agent in all but two or fewer groups of antibiotics) and pan-drug resistant (PDR = resistant to all groups of antibiotics) [4]. This makes the clinical management of pneumonia caused by such pathogens a challenge for physicians. Taking into account the clinical severity that may be associated with CAP caused by Gram-negative bacteria (respiratory failure, bacteremia, shock, acute respiratory distress syndrome [ARDS]) the magnitude of the global health problem is tremendous.

Severe hepatic abscess: Conservative treatment of multi-organ infection by Stenotrophomonas maltophilia. A case report

Introduction

Stenotrophomonas Malthophilia (SM) is generally considered a nosocomial pathogen but it has also been reported as a cause of community-acquired systemic infection. We reported a rare case of SM multi-organ infection involving the liver and the left ocular region.

Presentation of the case

A 64 years old man presented with fever for 4 days and acute blindness of the left eye. We performed an abdomen and head CT scan that identified respectively a liver lesion in central region, likely a hepatic abscess, and inflammation process involving the left eye. After 5 days of antibiotic therapy, no improvement of the clinical condition was noted. A CT guided drainage of the hepatic abscess was performed. SM was identified in the content of the drain and selected antibiotic therapy with combination of tygecycline and TMP-SMX was immediately initiated.After 15 days of the selected therapy, the hepatic abscess and the left eye infection were completely resolved but unfortunately the patient reported permanent blindness.

Discussion

Several studies identified most of the SM infections as nosocomial, however that can be excluded in this case because the patient presented signs of severe systemic infection 72 h before the hospitalization. The conservative treatment, with a combination of CT guided drainage and selected antibiotic therapy, gave good results.

Conclusion

Although SM is thought to be a nosocomial pathogen, it can be involved in severe systemic sepsis affecting different organs outside the hospital setting. Fortunately, the combination of tigecycline with TMP-SMX seems to be the best therapeutic option.

Transcriptomic, Functional, and Network Analyses Reveal Novel Genes Involved in the Interaction Between Caenorhabditis elegans and Stenotrophomonas maltophilia

The bacterivorous nematode Caenorhabditis elegans is an excellent model for the study of innate immune responses to a variety of bacterial pathogens, including the emerging nosocomial bacterial pathogen Stenotrophomonas maltophilia. The study of this interaction has ecological and medical relevance as S. maltophilia is found in association with C. elegans and other nematodes in the wild and is an emerging opportunistic bacterial pathogen. We identified 393 genes that were differentially expressed when exposed to virulent and avirulent strains of S. maltophilia and an avirulent strain of E. coli. We then used a probabilistic functional gene network model (WormNet) to determine that 118 of the 393 differentially expressed genes formed an interacting network and identified a set of highly connected genes with eight or more predicted interactions. We hypothesized that these highly connected genes might play an important role in the defense against S. maltophila and found that mutations of six of seven highly connected genes have a significant effect on nematode survival in response to these bacteria. Of these genes, C48B4.1, mpk-2, cpr-4, clec-67, and lys-6 are needed for combating the virulent S. maltophilia JCMS strain, while dod-22 was solely involved in response to the avirulent S. maltophilia K279a strain. We further found that dod-22 and clec-67 were up regulated in response to JCMS vs. K279a, while C48B4.1, mpk-2, cpr-4, and lys-6 were down regulated. Only dod-22 had a documented role in innate immunity, which demonstrates the merit of our approach in the identification of novel genes that are involved in combating S. maltophilia infection.

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.

Risk factors for death from Stenotrophomonas maltophilia bacteremia

PURPOSE

Stenotrophomonas maltophilia has low pathogenicity potential, but if it causes bacteremia it can be fatal, because it has shown high resistance to many antibiotics and can be difficult to treat. Patient death from S. maltophilia bacteremia has increased since 2014 in our hospital. In this study, we investigated risk factors for death due to S. maltophilia bacteremia.

METHODS

Seventy patients from the hospital database with S. maltophilia bacteremia between January 2010 and July 2017 were investigated. We retrospectively analyzed risk factors including gender, age, wards, hospitalized duration, clinical history, devices, source of S. maltophilia identification, polymicrobial bacteremia, prior antimicrobial therapy, antimicrobial therapy after bacteremia, and resistance to antibiotics. The statistical analysis was performed to compare the period from 2010 to 2013 to from 2014 to 2017.

RESULTS

Comparing the 2010-2013 period to the 2014-2017 period, it revealed that history of hospitalization, identification of S. maltophilia from sputum, polymicrobial bacteremia, prior carbapenem use, and mortality was significantly different in S. maltophilia bacteremia (p = 0.028, p = 0.004, p < 0.001, p = 0.034, and p = 0.007, respectively). Comparison between non-survivors and survivors for 2010-2013 and 2014-2017 found ICU admission and ventilator use were seen more often in non-survivors (p = 0.030 vs p = 0.013 and p = 0.027 vs p = 0.010, respectively).

CONCLUSIONS

Our analyses showed increase in mortality from S. maltophilia bacteremia from 2014 to 2017, and that non-survivors had a higher frequency of ICU admission and ventilator use in both the 2010-2013 and 2014-2017 periods. There were more combination antimicrobial therapy cases after bacteremia in 2014-2017. Further prospective studies with larger numbers of patients should be undertaken for definitive conclusions.

Clinical Features, Antibiotic Susceptibility Profile, and Outcomes of Infectious Keratitis Caused by Stenotrophomonas maltophilia

PURPOSE

Stenotrophomonas maltophilia, an uncommon cause of infectious keratitis, is difficult to treat because of its resistance to multiple antibiotics. The purpose of this study is to describe the clinical features, antibiotic susceptibility profile, and outcomes of S. maltophilia keratitis.

METHODS

A retrospective review of records from 1987 to 2016 identified 26 eyes of 26 patients who were treated at the Bascom Palmer Eye Institute for an S. maltophilia corneal ulcer. Clinical data were analyzed as to predisposing factors, clinical presentation, antibiotic susceptibility, treatment selection, and clinical outcomes.

RESULTS

Median age at presentation was 65 years (range, 16-98). Twelve patients were using topical corticosteroids, 8 patients had a history of penetrating keratoplasty, and 9 were contact lens wearers. All patients received topical antibiotics, 2 required therapeutic penetrating keratoplasty, and 1 was enucleated. At presentation, 57.7% (15/26) of the patients had visual acuity of 20/400 or worse. At the final visit, only 30.4% (7/23) of the patients had visual acuity worse than 20/400, whereas 65.2% (15/23) of the patients had 20/100 or better. Almost all isolates (25/26, 96.2%) were susceptible to fluoroquinolones and 77.3% (17/22) of them to polymyxin B/trimethoprim. Only 33.3% (5/15) of the tested isolates were susceptible to aminoglycosides and 58.3% (7/12) to cephalosporins.

CONCLUSIONS

Infectious keratitis due to S. maltophilia presents a treatment challenge because of its resistance to aminoglycosides and cephalosporins, which are typically used for empiric broad-spectrum gram-negative coverage as fortified solutions. Fluoroquinolones and polymyxin B/trimethoprim should be considered instead in cases of S. maltophilia infection.

Are animals a source of Stenotrophomonas maltophilia in human infections? Contributions of a nationwide molecular study

Stenotrophomonas maltophilia (Sm) is an archetypal environmental opportunistic bacterium responsible for health care-associated infections. The role of animals in human Sm infections is unknown. This study aims to reveal the genetic and phylogenetic relationships between pathogenic strains of Sm, both animal and human, and identify a putative role for animals as a reservoir in human infection. We phenotypically and genotypically characterized 61 Sm strains responsible for animal infections (mainly respiratory tract infections in horses) from a French nationwide veterinary laboratory network. We tested antimicrobial susceptibility and performed MLST and genogrouping using the concatenation of the seven housekeeping genes from the original MLST scheme. Excluding the eight untypeable strains owing to the lack of gene amplification, only 10 out of the 53 strains yielded a known ST (ST5, ST39, ST162, ST8, ST27, ST126, ST131). The genogroup distribution highlighted not only genogroups (genogroups 5 and 9) comprised exclusively of animal strains but also genogroups shared by human and animal strains. Interestingly, these shared genogroups were primarily groups 2 and 6, which have previously been identified as the two most frequent genogroups among human-pathogenic Sm strains, especially among respiratory pathogens. The antimicrobial susceptibility testing underlined the presence of acquired resistance: 18.8 and 7.5% of the tested isolates were resistant to the sulfonamide-trimethoprim combination and ciprofloxacin, respectively. Animal strains of Sm shared phylogenetic traits with some of the most successful human strains. The exact relationships between the human and animal strains, and the genetic support of these common traits, need to be determined.

Stenotrophomonas maltophilia: an emerging multidrug-resistant opportunistic pathogen in the immunocompromised host

Stenotrophomonas maltophilia is a multidrug-resistant opportunistic pathogen with increasing prevalence and high morbidity and mortality. In addition to its classic association with pulmonary infections, S. maltophilia can cause skin and soft tissue infections with varying clinical presentations. We describe the case of a man in his 30s with B-cell acute lymphoblastic leukaemia who presented with a solitary patch of faint but tender purpura found to have rapidly progressive S. maltophilia infection diagnosed on skin biopsy. S. maltophilia infection should be considered in the cutaneous evaluation of the immunocompromised host.

Stenotrophomonas maltophilia Serine Protease StmPr1 Induces Matrilysis, Anoikis, and Protease-Activated Receptor 2 Activation in Human Lung Epithelial Cells

Stenotrophomonas maltophilia is an emerging, opportunistic nosocomial pathogen that can cause severe disease in immunocompromised individuals. We recently identified the StmPr1 and StmPr2 serine proteases to be the substrates of the Xps type II secretion system in S. maltophilia strain K279a. Here, we report that a third serine protease, StmPr3, is also secreted in an Xps-dependent manner. By constructing a panel of protease mutants in strain K279a, we were able to determine that StmPr3 contributes to the previously described Xps-mediated rounding and detachment of cells of the A549 human lung epithelial cell line as well as the Xps-mediated degradation of fibronectin, fibrinogen, and the cytokine interleukin-8 (IL-8). We also determined that StmPr1, StmPr2, and StmPr3 account for all Xps-mediated effects toward A549 cells and that StmPr1 contributes the most to Xps-mediated activities. Thus, we purified StmPr1 from the S. maltophilia strain K279a culture supernatant and evaluated the protease's activity toward A549 cells. Our analyses revealed that purified StmPr1 behaves more similarly to subtilisin than to trypsin. We also determined that purified StmPr1 likely induces cell rounding and detachment of A549 cells by targeting cell integrin-extracellular matrix connections (matrilysis) as well as adherence and tight junction proteins for degradation. In this study, we also identified anoikis as the mechanism by which StmPr1 induces the death of A549 cells and found that StmPr1 induces A549 IL-8 secretion via activation of protease-activated receptor 2. Altogether, these results suggest that the degradative and cytotoxic activities exhibited by StmPr1 may contribute to S. maltophilia pathogenesis in the lung by inducing tissue damage and inflammation.

Bacterial bloodstream infections in a tertiary infectious diseases hospital in Northern Vietnam: aetiology, drug resistance, and treatment outcome

Background

Bloodstream infections (BSIs) are associated with high morbidity and mortality worldwide. However their aetiology, antimicrobial susceptibilities and associated outcomes differ between developed and developing countries. Systematic data from Vietnam are scarce. Here we present aetiologic data on BSI in adults admitted to a large tertiary referral hospital for infectious diseases in Hanoi, Vietnam.

Methods

A retrospective study was conducted at the National Hospital for Tropical Diseases between January 2011 and December 2013. Cases of BSI were determined from records in the microbiology department. Case records were obtained where possible and clinical findings, treatment and outcome were recorded. BSI were classified as community acquired if the blood sample was drawn ≤48 h after hospitalization or hospital acquired if >48 h.

Results

A total of 738 patients with BSI were included for microbiological analysis. The predominant pathogens were: Klebsiella pneumoniae (17.5%), Escherichia coli (17.3%), Staphylococcus aureus (14.9%), Stenotrophomonas maltophilia (9.6%) and Streptococcus suis (7.6%). The overall proportion of extended spectrum beta-lactamase (ESBL) production among Enterobacteriaceae was 25.1% (67/267 isolates) and of methicillin-resistance in S. aureus (MRSA) 37% (40/108). Clinical data was retrieved for 477 (64.6%) patients; median age was 48 years (IQR 36–60) with 27.7% female. The overall case fatality rate was 28.9% and the highest case fatality was associated with Enterobacteriaceae BSI (34.7%) which accounted for 61.6% of all BSI fatalities.

Conclusions

Enterobacteriaceae (predominantly K. pneumoniae and E. coli) are the most common cause of both community and hospital acquired bloodstream infections in a tertiary referral clinic in northern Vietnam.

Unusual case of rapid growing intraabdominal abscess caused by Stenotrophomonas maltophilia after laparoscopic appendectomy due to perforated appendicitis: A case report

INTRODUCTION

An intraabdominal abscess due to Stenotrophomonas maltophilia (S maltophilia) infection is a very rare clinical manifestation. S maltophilia is a glucose nonfermentative, aerobic, gram-negative, mobile, and biofilm-forming bacterium. It is an opportunistic pathogen and uncommon cause of infection. Respiratory tract infections (pneumonia) and bloodstream infections (bacteremia) are the most common clinical manifestations of S maltophilia infection.

CONCLUSIONS

This case report describes an unusual case of a rapidly growing, extremely large intraabdominal abscess (within 1 week during antibiotic therapy), which was detected 2 weeks after a laparoscopic appendectomy was performed for perforated appendicitis and was caused by multidrug-resistant S maltophilia infection.

Vitamin K3 Induces the Expression of the Stenotrophomonas maltophilia SmeVWX Multidrug Efflux Pump

Stenotrophomonas maltophilia is an opportunistic pathogen with increasing prevalence, which is able to cause infections in immunocompromised patients or in those with a previous pathology. The treatment of the infections caused by this bacterium is often complicated due to the several intrinsic antibiotic resistance mechanisms that it presents. Multidrug efflux pumps are among the best-studied mechanisms of S. maltophilia antibiotic resistance. Some of these efflux pumps have a basal expression level but, in general, their expression is often low and only reaches high levels when the local regulator is mutated or bacteria are in the presence of an effector. In the current work, we have developed a yellow fluorescent protein (YFP)-based sensor with the aim to identify effectors able to trigger the expression of SmeVWX, an efflux pump that confers resistance to quinolones, chloramphenicol, and tetracycline when it is expressed at high levels. With this purpose in mind, we tested a variety of different compounds and analyzed the fluorescence signal given by the expression of YFP under the control of the smeVWX promoter. Among the tested compounds, vitamin K₃, which is a compound belonging to the 2-methyl-1,4-naphthoquinone family, is produced by plants in defense against infection, and has increasing importance in human therapy, was able to induce the expression of the SmeVWX efflux pump. In addition, a decrease in the susceptibility of S. maltophilia to ofloxacin and chloramphenicol was observed in the presence of vitamin K₃, in both wild-type and smeW-deficient strains.

Genotypic and Phenotypic Characterization of Stenotrophomonas maltophilia Strains from a Pediatric Tertiary Care Hospital in Serbia

Background

Stenotrophomonas maltophilia is an environmental bacterium and an opportunistic pathogen usually associated with healthcare-associated infections, which has recently been recognized as a globally multi-drug resistant organism. The aim of this study was genotyping and physiological characterization of Stenotrophomonas maltophilia isolated in a large, tertiary care pediatric hospital in Belgrade, Serbia, hosting the national reference cystic fibrosis (CF) center for pediatric and adult patients.

Methods

We characterized 42 strains of cystic fibrosis (CF) and 46 strains of non-cystic fibrosis (non-CF) origin isolated from 2013 to 2015 in order to investigate their genetic relatedness and phenotypic traits. Genotyping was performed using sequencing of 16S rRNA gene, Pulse Field Gel Electrophoresis (PFGE) and Multi locus sequencing typing (MLST) analysis. Sensitivity to five relevant antimicrobial agents was determined, namely trimethoprim/sulfamethoxazole (TMP/SMX), chloramphenicol, ciprofloxacin, levofloxacin and tetracycline. Surface characteristics, motility, biofilm formation and adhesion to mucin were tested in all strains. Statistical approach was used to determine correlations between obtained results.

Results

Most of the isolates were not genetically related. Six new sequence types were determined. Strains were uniformly sensitive to all tested antimicrobial agents. The majority of isolates (89.8%) were able to form biofilm with almost equal representation in both CF and non-CF strains. Swimming motility was observed in all strains, while none of them exhibited swarming motility. Among strains able to adhere to mucin, no differences between CF and non-CF isolates were observed.

Conclusions

High genetic diversity among isolates implies the absence of clonal spread within the hospital. Positive correlation between motility, biofilm formation and adhesion to mucin was demonstrated. Biofilm formation and motility were more pronounced among non-CF than CF isolates.