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

The type VI secretion system of the emerging pathogen Stenotrophomonas maltophilia complex has antibacterial properties

IMPORTANCE

Infections with the opportunistic pathogen Stenotrophomonas maltophilia complex can be fatal for immunocompromised patients. The mechanisms used by the bacterium to compete against other prokaryotes are not well understood. We found that the type VI secretion system (T6SS) allows S. maltophilia complex to eliminate other bacteria and contributes to the competitive fitness against a co-infecting isolate. The presence of T6SS genes in isolates across the globe highlights the importance of this apparatus as a weapon in the antibacterial arsenal of S. maltophilia complex. The T6SS may confer survival advantages to S. maltophilia complex isolates in polymicrobial communities in both environmental settings and during infections.

The Type VI Secretion System of the Emerging Pathogen Stenotrophomonas maltophilia has Antibacterial Properties

Antagonistic behaviors between bacterial cells can have profound effects on microbial populations and disease outcomes. Polymicrobial interactions may be mediated by contact-dependent proteins with antibacterial properties. The Type VI Secretion System (T6SS) is a macromolecular weapon used by Gram-negative bacteria to translocate proteins into adjacent cells. The T6SS is used by pathogens to escape immune cells, eliminate commensal bacteria, and facilitate infection. Stenotrophomonas maltophilia is a Gram-negative opportunistic pathogen that causes a wide range of infections in immunocompromised patients and infects the lungs of patients with cystic fibrosis. Infections with the bacterium can be deadly and are challenging to treat because many isolates are multidrug-resistant. We found that globally dispersed S. maltophilia clinical and environmental strains possess T6SS genes. We demonstrate that the T6SS of an S. maltophilia patient isolate is active and can eliminate other bacteria. Furthermore, we provide evidence that the T6SS contributes to the competitive fitness of S. maltophilia against a co-infecting Pseudomonas aeruginosa isolate, and that the T6SS alters the cellular organization of S. maltophilia and P. aeruginosa co-cultures. This study expands our knowledge of the mechanisms employed by S. maltophilia to secrete antibacterial proteins and compete against other bacteria.

IMPORTANCE

Infections with the opportunistic pathogen Stenotrophomonas maltophilia can be fatal for immunocompromised patients. The mechanisms used by the bacterium to compete against other prokaryotes are not well understood. We found that the T6SS allows S. maltophilia to eliminate other bacteria and contributes to the competitive fitness against a co-infecting isolate. The presence of T6SS genes in isolates across the globe highlights the importance of this apparatus as a weapon in the antibacterial arsenal of S. maltophilia . The T6SS may confer survival advantages to S. maltophilia isolates in polymicrobial communities in both environmental settings and during infections.

Characterization of Antibiotic-Resistant Stenotrophomonas Isolates from Painted Turtles Living in the Wild

Stenotrophomonas maltophilia is a ubiquitous multidrug-resistant opportunistic pathogen commonly associated with nosocomial infections. The purpose of this study was to isolate and characterize extended-spectrum beta-lactamase (ESBL) producing bacteria from painted turtles (Chrysemys picta) living in the wild and captured in southeastern Wisconsin. Fecal samples from ten turtles were examined for ESBL producing bacteria after incubation on HardyCHROM™ ESBL agar. Two isolates were cultivated and identified by 16S rRNA gene sequencing and whole genome sequencing (WGS) as Stenotrophomonas sp. 9A and S. maltophilia 15A. They were multidrug-resistant, as determined by antibiotic susceptibility testing. Stenotrophomonas sp. 9A was found to produce an extended spectrum beta-lactamase (ESBL) and both isolates were found to be carbapenem-resistant. EDTA-modified carbapenem inactivation method (eCIM) and the modified carbapenem inactivation method (mCIM) tests were used to examine the carbapenemase production and the test results were negative. Through WGS several antimicrobial resistance genes were identified in S. maltophilia 15A. For example a chromosomal L1 β-lactamase gene, which is known to hydrolyze carbapenems, a L2 β-lactamase gene, genes for the efflux systems smeABC and smeDEF and the aminoglycosides resistance genes aac(6')-lz and aph(3')-llc were found. An L2 β-lactamase gene in Stenotrophomonas sp. 9A was identified through WGS.

Combination Therapy versus Monotherapy in the Treatment of Stenotrophomonas maltophilia Infections: A Systematic Review and Meta-Analysis

Stenotrophomonas maltophilia is a multidrug-resistant bacterium that is difficult to treat in hospitals worldwide, leading to high mortality. Published data describing the use of monotherapy or combination therapy and which one is better is still unclear. We aimed to investigate the efficacy of monotherapy and combination therapy in the treatment of S. maltophilia infections. We performed a systematic review of combination therapy and additionally a systematic review and meta-analysis to determine the effects of monotherapy versus combination therapy on mortality in S. maltophilia infections. Electronic databases: Cochrane Library, PubMed, Embase, ClinicalTrials.gov, Scopus, and OpenGrey were accessed. Of the 5030 articles identified, 17 studies were included for a systematic review of combination therapy, of which 4 cohort studies were finally included for meta-analysis. We found there is a trend of favorable outcomes with respect to mortality in the use of combination therapy to treat complex or severe S. maltopholia infections. A meta-analysis of monotherapy showed a statistical significance in the decreasing rate of mortality in hospital-acquired pneumonia (hazard ratio 1.42; 95% confidence interval, 1.04-1.94) compared to combination therapy, but not significant in bacteremia (hazard ratio 0.76; 95% confidence interval, 0.18-3.18). Further studies should continue to explore this association.

Interaction between gut microbiota and immune checkpoint inhibitor-related colitis

Immune checkpoint inhibitors (ICIs) have become a promising therapeutic strategy for malignant tumors, improving patient prognosis, along with a spectrum of immune-related adverse events (irAEs), including gastrointestinal toxicity, ICI-related colitis (IRC), and diarrhea. The gut microbiota has been suggested as an important regulator in the pathogenesis of IRC, and microbiota modulations like probiotics and fecal microbiota transplantation have been explored to treat the disease. This review discusses the interaction between the gut microbiota and IRC, focusing on the potential pathogenic mechanisms and promising interventions.

Outcome and Determinants of Neutropenic Enterocolitis in Pediatric Cancer Patients

BACKGROUND

Neutropenic enterocolitis (NEC) is a dreaded complication of chemotherapy. There is scant literature regarding incidence, clinical features, and determinants. The understanding of gut dysbiosis in NEC and pediatric cancer is evolving.

METHODS

Pediatric cancer patients with neutropenia and gastrointestinal symptoms were evaluated for NEC with contrast-enhanced computed tomography abdomen. Clinical, imaging, and laboratory features were analyzed. Fecal samples were analyzed for fecal calprotectin by sandwich enzyme-linked immunoassay and gut microbiota by conventional culture and compared with healthy controls and children without NEC.

RESULTS

NEC was diagnosed in 44 children based on clinical and imaging features with incidence of 7.4% (4 had recurrent episodes). Common manifestations included fever (98%), pain abdomen (88%), and diarrhea (83%). Hypoalbuminemia was observed in 78% of patients. Large bowel involvement (94%) with diffuse bowel involvement (63%) and pancolitis (64%) were common. Fecal calprotectin was significantly elevated in NEC group than non-NEC group and healthy controls (median: 87, 53, and 42 µg/g, respectively). A higher degree of gut dysbiosis was observed in children with NEC with higher isolation of Bacteroides and infrequent isolation of Lactobacilli. Mortality rate of 23% was observed. Only the presence of free fluid predicted higher mortality. Though levels of fecal calprotectin and gut dysbiosis were higher in NEC, they did not increase mortality. Isolation of Bacteroides and absence of Lactobacilli predicted a longer duration of intravenous alimentation.

CONCLUSIONS

NEC caused significant morbidity and mortality in pediatric cancer patients. Gut dysbiosis was significantly higher in NEC group suggesting a role in pathogenesis and influencing outcome. This highlights the role of targeted interventions towards gut dysbiosis like prebiotics and probiotics.

Neutropenic Enterocolitis as a Complication of Autologous Stem Cell Transplant in Patients With Multiple Myeloma: A Case Series

Neutropenic enterocolitis (NE) is a rare but severe complication occurring in neutropenic patients undergoing intensive chemotherapy. Mortality is high, so early diagnosis is required to start urgent medical or surgical treatment. Data analysis of the development of NE after hematopoietic stem cell transplantation remains scarce. The aim of this case series is to discuss five out of 100 patients receiving autologous stem cell transplants (ASCTs) for multiple myeloma complicated with NE between 2016 and 2020 in the hematology department of the Cheikh Khalifa International University Hospital, Casablanca, Morocco. The patients were diagnosed with IgA and IgG multiple myeloma and aged between 58 to 64 years. They received induction therapy with four cycles of a triplet regimen including a proteasome inhibitor, an immunomodulatory drug, and corticosteroids, allowing a complete remission. Intensification was based on ASCT with melphalan at 200 mg/m2. The period of aplasia was marked by the sudden appearance of NE, diagnosed based on clinical, biological, and imaging criteria. Treatment included antibiotherapy and supportive care. We report no complications in our cases, nor the need for surgical care. Therefore, we consider that early diagnosis and treatment allowed a good evolution in our case series. The management of NE must be multidisciplinary associating hematologists, gastroenterologists, radiologists, and biologists. More studies and trials are needed to establish specific diagnostic criteria and better treatment options.

Neutropenic Enterocolitis and Sepsis: Towards the Definition of a Pathologic Profile

Background: Neutropenic enterocolitis (NE), which in the past was also known as typhlitis or ileocecal syndrome for the segment of the gastrointestinal tract most affected, is a nosological entity that is difficult to diagnose and whose pathogenesis is not fully known to date. Initially described in pediatric patients with leukemic diseases, it has been gradually reported in adults with hematological malignancies and non-hematological conditions, such as leukemia, lymphoma, multiple myeloma, aplastic anemia, and also myelodysplastic syndromes, as well as being associated with other immunosuppressive causes such as AIDS treatment, therapy for solid tumors, and organ transplantation. Therefore, it is associated with high mortality due to the rapid evolution in worse clinical pictures: rapid progression to ischemia, necrosis, hemorrhage, perforation, multisystem organ failure, and sepsis. Case report: A case report is included to exemplify the clinical profile of patients with NE who develop sepsis. Literature Review: To identify a specific profile of subjects affected by neutropenic enterocolitis and the entity of the clinical condition most frequently associated with septic evolution, a systematic review of the literature was conducted. The inclusion criteria were as follows: English language, full-text availability, human subjects, and adult subjects. Finally, the papers were selected after the evaluation of the title and abstract to evaluate their congruity with the subject of this manuscript. Following these procedures, 19 eligible empirical studies were included in the present review. Conclusions: Despite the recent interest and the growing number of publications targeting sepsis and intending to identify biomarkers useful for its diagnosis, prognosis, and for the understanding of its pathogenesis, and especially for multi-organ dysfunction, and despite the extensive research period of the literature review, the number of publications on the topic "neutropenic enterocolitis and sepsis" appears to be very small. In any case, the extrapolated data allowed us to conclude that the integration of medical history, clinical and laboratory data, radiological imaging, and macroscopic and histological investigations can allow us to identify a specific pathological profile.

Advances in the Microbiology of Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is an opportunistic pathogen of significant concern to susceptible patient populations. This pathogen can cause nosocomial and community-acquired respiratory and bloodstream infections and various other infections in humans. Sources include water, plant rhizospheres, animals, and foods. Studies of the genetic heterogeneity of S. maltophilia strains have identified several new genogroups and suggested adaptation of this pathogen to its habitats. The mechanisms used by S. maltophilia during pathogenesis continue to be uncovered and explored. S. maltophilia virulence factors include use of motility, biofilm formation, iron acquisition mechanisms, outer membrane components, protein secretion systems, extracellular enzymes, and antimicrobial resistance mechanisms. S. maltophilia is intrinsically drug resistant to an array of different antibiotics and uses a broad arsenal to protect itself against antimicrobials. Surveillance studies have recorded increases in drug resistance for S. maltophilia, prompting new strategies to be developed against this opportunist. The interactions of this environmental bacterium with other microorganisms are being elucidated. S. maltophilia and its products have applications in biotechnology, including agriculture, biocontrol, and bioremediation.

Neutropenic enterocolitis: A clinico-pathological review

Neutropenic enterocolitis (NE) is a predominantly cecum-based disease with high mortality seen in patients post chemotherapy. The pathogenesis of NE is poorly understood and probably multifactorial involving mucosal injury, neutropenia, and impaired host defense to intestinal organisms. The clinical presentation is characterized as ileocolonic inflammation and bowel wall thickening in patients with neutropenia, fever, and abdominal pain. The pathological features of NE include patchy necrosis, hemorrhage, ulcer, edema, perforation, infiltrating organisms, and characteristically, depletion of inflammatory cells (neutrophils). NE should always be considered as a possible diagnosis in immunosuppressed patients, especially those receiving chemotherapy. High clinical and histological diagnostic discordance rate exists. High index of clinical suspicion and prompt appropriate personalized management are essential to achieve a lower mortality rate.