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

Innovative strategies against superbugs: Developing an AI-CDSS for precise Stenotrophomonas maltophilia treatment

OBJECTIVES

The World Health Organization named Stenotrophomonas maltophilia (SM) a critical multi-drug resistant threat, necessitating rapid diagnostic strategies. Traditional culturing methods require up to 96 h, including 72 h for bacterial growth, identification with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) through protein profile analysis, and 24 h for antibiotic susceptibility testing. In this study, we aimed at developing an artificial intelligence-clinical decision support system (AI-CDSS) by integrating MALDI-TOF MS and machine learning to quickly identify levofloxacin and trimethoprim/sulfamethoxazole resistance in SM, optimizing treatment decisions.

METHODS

We selected 8,662 SM from 165,299 MALDI-TOF MS-analysed bacterial specimens, collected from a major medical centre and four secondary hospitals. We exported mass-to-charge values and intensity spectral profiles from MALDI-TOF MS .mzML files to predict antibiotic susceptibility testing results, obtained with the VITEK-2 system using machine learning algorithms. We optimized the models with GridSearchCV and 5-fold cross-validation.

RESULTS

We identified distinct spectral differences between resistant and susceptible SM strains, demonstrating crucial resistance features. The machine learning models, including random forest, light-gradient boosting machine, and XGBoost, exhibited high accuracy. We established an AI-CDSS to offer healthcare professionals swift, data-driven advice on antibiotic use.

CONCLUSIONS

MALDI-TOF MS and machine learning integration into an AI-CDSS significantly improved rapid SM resistance detection. This system reduced the identification time of resistant strains from 24 h to minutes after MALDI-TOF MS identification, providing timely and data-driven guidance. Combining MALDI-TOF MS with machine learning could enhance clinical decision-making and improve SM infection treatment outcomes.

Optimizing Antibiotic Therapy for Stenotrophomonas maltophilia Infections in Critically Ill Patients: A Pharmacokinetic/Pharmacodynamic Approach

Stenotrophomonas maltophilia is an opportunistic, multidrug-resistant non-fermentative Gram-negative bacillus, posing a significant challenge in clinical treatment due to its numerous intrinsic and acquired resistance mechanisms. This study aimed to evaluate the adequacy of antibiotics used for the treatment of S. maltophilia infections in critically ill patients using a pharmacokinetic/pharmacodynamic (PK/PD) approach. The antibiotics studied included cotrimoxazole, levofloxacin, minocycline, tigecycline, cefiderocol, and the new combination aztreonam/avibactam, which is not yet approved. By Monte Carlo simulations, the probability of target attainment (PTA), the PK/PD breakpoints, and the cumulative fraction of response (CFR) were estimated. PK parameters and MIC distributions were sourced from the literature, the European Committee on Antimicrobial Susceptibility Testing (EUCAST), and the SENTRY Antimicrobial Surveillance Program collection. Cefiderocol 2 g q8h, minocycline 200 mg q12h, tigecycline 100 mg q12h, and aztreonam/avibactam 1500/500 mg q6h were the best options to treat empirically infections due to S. maltophilia. Cotrimoxazole provided a higher probability of treatment success for the U.S. isolates than for European isolates. For all antibiotics, discrepancies between the PK/PD breakpoints and the clinical breakpoints defined by EUCAST (or the ECOFF) and CLSI were detected.

Trimethoprim-sulfamethoxazole versus levofloxacin for the treatment of Stenotrophomonas maltophilia infections: A multicentre cohort study

BACKGROUND

Trimethoprim-sulfamethoxazole (TMP-SMX) has long been considered the treatment of choice for infections caused by Stenotrophomonas maltophilia. Levofloxacin has emerged as a potential option for treating these infections. This study aimed to evaluate the clinical outcomes in patients who received TMP-SMX versus levofloxacin for treating S. maltophilia infections.

METHODS

A retrospective, cohort study was conducted in 4 tertiary centres and included patients who were treated with either TMP-SMX or levofloxacin for infections caused by S. maltophilia. The main study outcomes were overall in-hospital mortality, 30-d mortality, and clinical cure. Safety outcomes were also evaluated. Multivariate analysis using logistic regression was used to control for the effect of the covariables.

RESULTS

We included 371 patients in this study, 316 received TMP-SMX and 55 patients received levofloxacin. A total of 70% were in the intensive care unit and 21% presented with bacteraemia. No statistically significant differences were observed in overall in-hospital mortality (52% vs. 40%; P = 0.113; odd ratio [OR], 1.59; 95% confidence interval [CI], 0.89-2.86), 30-d mortality (28% vs. 25%; P = 0.712; OR, 1.13; 95% CI, 0.59-2.18), or clinical cure (55% vs. 64%; P = 0.237; OR, 0.70; 95% CI, 0.37-1.31). Rates of acute kidney injury were comparable between the two groups (11% vs. 7%; P = 0.413).

CONCLUSION

Patients receiving levofloxacin for the treatment of infections caused by S. maltophilia demonstrated clinical outcomes similar to those receiving TMP-SMX. Our study suggests that levofloxacin can be a reasonable alternative to TMP-SMX to treat these infections.

Clinical Outcomes of Trimethoprim/Sulfamethoxazole in Critically Ill Patients with Stenotrophomonas maltophilia Bacteremia and Pneumonia Utilizing Renal Replacement Therapies

Background: The clinical outcomes of usual doses of Trimethoprim-sulfamethoxazole (TMP/SMZ) for treating S. maltophilia in critically ill patients on renal replacement therapies (RRT) have not been established. We sought to assess the clinical outcomes of TMP/SMZ in patients with sepsis utilizing RRT. Methods: A retrospective study was performed on all critically ill adult patients with S. maltophilia infections who received RRT between May 2015 and January 2022. The primary endpoint was clinical cure while the secondary endpoints were microbiologic cure, 30-day infection recurrence, and mortality. Results: Forty-five subjects met the inclusion criteria. The median age was 70.0 [interquartile range (IQR): 63.5-77] years, 57.8% were males, and the median body mass index was 25.7 [IQR: 22-30.2] kg/m2. Clinical success and failure were reported in 18 (40%) and 27 (60%) cases, respectively. There was no significant difference between the 30-day reinfection rates of both groups; however, mortality was significantly higher in the clinical failure group, involving 12 patients (44.4%), versus none in the clinical success group (p = 0.001). The median daily dose of TMP/SMZ upon continuous veno-venous hemofiltration was 1064 [IQR: 776-1380] mg in the clinical cure group vs. 768 [IQR:540-1200] mg in the clinical failure group (p = 0.035). Meanwhile, the median dose for those who received intermittent hemodialysis was 500 [IQR: 320-928] mg in the clinical success group compared to 640 [IQR: 360-1005] mg in the clinical failure group (p = 0.372). A total of 55% experienced thrombocytopenia, 42% hyperkalemia, and 2.2% neutropenia. The multivariable logistic regression analysis showed that the total daily dose at therapy initiation was the only independent factor associated with clinical success after adjusting for different variables including the body mass index [Odds ratio 1.004; 95% confidence interval: (1-1.007), p = 0.044]. Conclusions: Although the S. maltophilia isolates were reported as susceptible, TMP/SMZ with conventional doses to treat bacteremia and pneumonia in critically ill patients utilizing RRT was associated with high rates of clinical and microbiologic failure as well as with mortality. Larger outcomes and pharmacokinetics studies are needed to confirm our findings.

Unusual and complicated peritonitis: Your questions answered

Effective treatment of infections is a growing challenge owing to antimicrobial resistance. Peritoneal dialysis (PD) patients experience more frequent hospitalisations than the general population and have greater exposure to antibiotics, making them particularly vulnerable to this threat. Over the last decade, we have noted a surge in cases of complicated peritoneal dialysis-associated peritonitis (PD peritonitis) caused by antimicrobial-resistant organisms, including extended-spectrum beta-lactamase (ESBL), AmpC beta-lactamase-producing Enterobacterales, Pseudomonas aeruginosa and fungi. Practitioners must be alert to these organisms, seek early recognition of these resistance patterns and make timely adjustments in order to avoid delay in treatment that may increase risk of PD catheter removal and technique failure. We present a case of successful treatment of ESBL peritonitis, highlight its challenges, while providing guidance on management of other unusual and complicated PD peritonitis.

Emerging importance of multidrug-resistant Stenotrophomonas maltophilia infections in neonatal intensive care unit in a tertiary center in Turkey

OBJECTIVE

Stenotrophomonas maltophilia is an emerging multi-drug resistant, opportunistic pathogen in the neonatal intensive care unit (NICU). In this study, we aimed to assess the incidence, clinical features, antibiotic susceptibility, and treatment options of S. maltophilia infection among the healthcare-associated infections (HAIs) in the neonatal unit.

METHODS

In this study, the patients who were hospitalized in the NICU between January 2020 and December 2021 with S. maltophilia isolated from clinical samples were included. Demographic, clinic features, and microbiological findings of the patients were retrospectively evaluated by using the medical records. The samples (lower respiratory tract, urine, peritoneal fluid) were first examined microscopically by gram preparation and cultured. Antibiotic susceptibility tests were performed according to the recommendations of The European Committee on Antimicrobial Susceptibility Testing (EUCAST) for TMP-SMX.

RESULTS

S. maltophilia was isolated in 38 clinical samples of the 20 patients who were hospitalized at the NICU between January 2020 and December 2021. A total of 40 % (n = 8) of samples from different patients were accepted as colonization. Ventilator-associated pneumonia was determined in 55 % (n = 11), and urinary tract infection in 5 % (n = 1). S. maltophilia-associated bacteremia was not detected in any of the cases. The TMP-SMX susceptibilities of the strains were as it follows: 3 (15 %) were resistant (R), 7 (28 %) were susceptible (S), and 10 (47 %) were susceptible-increased exposure (I). Three of these patients were given dual antibiotics therapy (levofloxacin plus TMP-SMX) and nine of them were given only TMP-SMX. The most common hospital-acquired infectious agents are Gram negative microorganisms (51 %), followed by coagulase negative staphylococci (CNS), Staphylococcus aureus (24 %) and S. maltophilia (24 %).

CONCLUSION

Increasing TMP-SMX resistance and specific drug and dosage-related problems in the neonatal unit are important problems in treatment management.

Emerging infections in vulnerable hosts: Stenotrophomonas maltophilia and Elizabethkingia anophelis

PURPOSE OF REVIEW

This systematic review aimed to explore the recent trends in the epidemiology, risk factors, and antimicrobial susceptibility of two emerging opportunistic pathogens, Stenotrophomonas maltophilia and Elizabethkingia anophelis .

RECENT FINDINGS

Since 2020, numerous outbreaks of S. maltophilia and E. anophelis have been reported worldwide. Most of these outbreaks have been associated with healthcare facilities, although one outbreak caused by E. anophelis in France was considered a community-associated infection. In terms of antimicrobial susceptibility, trimethoprim/sulfamethoxazole (TMP-SMZ), levofloxacin, and minocycline have exhibited good efficacy against S. maltophilia . Additionally, cefiderocol and a combination of aztreonam and avibactam have shown promising results in in vitro susceptibility testing. For E. anophelis , there is currently no consensus on the optimal treatment. Although some studies have reported good efficacy with rifampin, TMP-SMZ, piperacillin/tazobactam, and cefoperazone/sulbactam, minocycline had the most favourable in vitro susceptibility rates. Cefiderocol may serve as an alternative due to its low minimum inhibitory concentration (MIC) against E. anophelis . The role of vancomycin in treatment is still uncertain, although several successful cases with vancomycin treatment, even with high MIC values, have been reported.

SUMMARY

Immunocompromised patients are particularly vulnerable to infections caused by S. maltophilia and E. anophelis , but the optimal treatment strategy remains inconclusive. Further research is necessary to determine the most effective use of conventional and novel antimicrobial agents in combatting these multidrug-resistant pathogens.

Comparative genomics analysis of Stenotrophomonas maltophilia strains from a community

Background

Stenotrophomonas maltophilia is a multidrug-resistant (MDR) opportunistic pathogen with high resistance to most clinically used antimicrobials. The dissemination of MDR S. maltophilia and difficult treatment of its infection in clinical settings are global issues.

Methods

To provide more genetic information on S. maltophilia and find a better treatment strategy, we isolated five S. maltophilia, SMYN41-SMYN45, from a Chinese community that were subjected to antibiotic susceptibility testing, biofilm formation assay, and whole-genome sequencing. Whole-genome sequences were compared with other thirty-seven S. maltophilia sequences.

Results

The five S. maltophilia strains had similar antibiotic resistance profiles and were resistant to β-lactams, aminoglycosides, and macrolides. They showed similar antimicrobial resistance (AMR) genes, including various efflux pumps, β-lactamase resistance genes (blaL1/2), aminoglycoside resistance genes [aac(6'), aph(3'/6)], and macrolide-resistant gene (MacB). Genome sequencing analysis revealed that SMYN41-SMYN45 belonged to sequence type 925 (ST925), ST926, ST926, ST31, and ST928, respectively, and three new STs were identified (ST925, ST926, and ST928).

Conclusion

This study provides genetic information by comparing genome sequences of several S. maltophilia isolates from a community of various origins, with the aim of optimizing empirical antibiotic medication and contributing to worldwide efforts to tackle antibiotic resistance.

Looking for Stenotrophomonas maltophilia treatment: in vitro activity of ceftazidime/avibactam alone and in combination with aztreonam

During the Sars-Cov-2 pandemic, Stenotrophomonas maltophilia (S.maltophilia) secondary pulmonary infections have increased, especially in critically ill patients, highlighting the need for new therapeutic options. Trimethoprim-sulfamethoxazole (SXT) is the treatment of choice but the increase of resistant strains or adverse drug reactions limited its clinical use. Recently ceftazidime/avibactam (CZA) has been approved for the treatment of multi drug resistant (MDR) Gram-negative bacteria infections, including hospital acquired pneumonia. The aim of this study was to evaluate the in vitro activity of ceftazidime/avibactam (CZA) alone and in combination with aztreonam (ATM) against S. maltophilia clinical isolates by E-test method. Susceptibility of SXT and levofloxacin (LEV) was also investigated. Our results showed 22% of resistance to CZA, 2% to SXT and 26% to LEV. CZA in combination with ATM demonstrated synergistic activity against 86% of the strains, including all those resistant to CZA. The combination of CZA with ATM provides a new therapeutic option for the treatment of severe respiratory infections in critically ill patients.

In vitro Antimicrobial Activity and Dose Optimization of Eravacycline and Other Tetracycline Derivatives Against Levofloxacin-Non-Susceptible and/or Trimethoprim-Sulfamethoxazole-Resistant Stenotrophomonas maltophilia

Purpose

To better guide clinical use, we determined the in vitro antimicrobial activity of the new drug eravacycline and other tetracycline derivatives against levofloxacin (LVFX)-non-susceptible and/or trimethoprim-sulfamethoxazole (TMP-SMZ)-resistant Stenotrophomonas maltophilia and evaluated their dosing regimens.

Methods

Seventy-seven unique strains of S. maltophilia were isolated from sputa samples and airway aspirate samples that were either LVFX-non-susceptible and/or TMP-SMZ-resistant. Monte Carlo simulations were performed for different dosing regimens according to the population pharmacokinetic parameters of antibiotics in patients with respiratory tract infections at the minimum inhibitory concentration (MIC).

Results

Eravacycline had excellent in vitro antibacterial activity against LVFX-non-susceptible and/or TMP-SMZ-resistant S. maltophilia. Monte Carlo simulations showed that for LVFX-non-susceptible strains, the cumulative fraction of response (CFR) of minocycline at the conventional recommended dose of 100 mg q12 h was 90.90%; for TMP-SMZ-resistant strains, the CFR of minocycline at a high dose of 200 mg q12 h was only 91.64%. For strains resistant to both LVFX and TMP-SMZ, the CFR of minocycline at a high dose of 200 mg q12 h was 89.81%. In contrast, the CFR of tigecycline was less than 40%, even at a dose of 100 mg q12 h.

Conclusion

For pneumonia, minocycline is better for S. maltophilia that is non-susceptible to LVFX; for TMP-SMZ-resistant strains and strains that are not susceptible to either LVFX or TMP-SMZ, the efficiency of eravacycline requires further evaluation. Eravacycline may be a better choice for extremely resistant S. maltophilia strains that are non-susceptible to LVFX, TMP-SMZ, and minocycline.

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

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

The Relationship between the Biofilm Genes and Antibiotic Resistance in Stenotrophomonas maltophilia

Objectives

Today, Stenotrophomonas maltophilia (S. maltophilia) is a major opportunistic pathogen among hospitalized or immunocompromised patients. Antibiotic-resistant clinical isolates are increasing in several parts of the world. Various antibiotic-resistance and biofilm-forming genes are identified in this bacterium. Its capacity to form biofilms is an important virulence factor that may impact antibiotic-resistance patterns. In the current study, we evaluated the biofilm-formation capacity, antibiotic-resistance profile, and prevalence of biofilm-forming genes as well as antibiotic resistance genes among S. maltophilia isolates.

Materials and Methods

In this cross-sectional study, 94 clinical S. maltophilia isolates were recovered from four tertiary-care hospitals in Iran between 2021 and 2022. The presence of the selected antibiotic-resistance genes and biofilm-forming genes was examined by polymerase chain reaction (PCR). The ability of biofilm formation was examined by microtiter plate assay. The Kirby-Bauer disc diffusion method was used to evaluate the trimethoprim-sulfamethoxazole (TMP-SMX), levofloxacin, and minocycline resistance.

Results

S. maltophilia is mainly isolated from bloodstream infections. Notably, 98.93% of isolates were biofilm producers, of which 19.35%, 60.22%, and 20.43% produced strong, moderate, and weak biofilm, respectively. The frequency of biofilm genes was 100%, 97.88%, 96.80%, and 75.53% for spgM, rmlA, smf-1, and rpfF, respectively. Isolates with the genotype of smf-1+/rmlA+/spgM+/rpfF+ were mostly strong biofilm producers. Among the antibiotic-resistance genes, the Smqnr, L1, and sul1 had the highest prevalence (76.59%, 72.34%, and 64.89), respectively. Antimicrobial susceptibility evaluation showed 1.06%, 3.19%, and 6.3% resistance to minocycline, TMP-SMX, and levofloxacin.

Conclusion

The results of the current study demonstrated that S. maltophilia isolates differ in biofilm-forming ability. Moreover, smf-1, rmlA, and spgM genes were presented in all strong biofilm producers. Although the overall resistance rate to the evaluated antibiotics was high, there was no statistically significant relation between antibiotic resistance and the type of biofilm.

The Activities of Antimicrobials Against Stenotrophomonas maltophilia Isolates and Evaluation of Clinical Outcomes Among Treatment Regimens in Patients with Stenotrophomonas maltophilia Infections: A Retrospective Multicenter Cohort Study

Purpose

Stenotrophomonas maltophilia, a multidrug-resistant pathogen can cause hospital-acquired infections such as pneumonia, or bloodstream infection. S. maltophilia infection is associated with high mortality rates. This retrospective study examined the antimicrobial susceptibility profile of clinical S. maltophilia isolates and evaluated clinical outcomes, treatment regimens, and risk factors associated with 30-day mortality or treatment failure of S. maltophilia infections at three tertiary care hospitals in Central Thailand.

Patients and Methods

The characteristics, microbiological data, and clinical treatment outcomes were derived from medical records obtained from three tertiary care hospitals in Central Thailand from January 2017 to October 2022. The primary outcomes were treatment failure and 30-day mortality. The antimicrobial susceptibility rates of trimethoprim-sulfamethoxazole (TMP-SMX), levofloxacin, and ceftazidime were determined by minimum inhibitory concentration (MIC), which were based on broth microdilution and clear zone diameters using the disk diffusion method. However, we also report the susceptibility of minocycline and tigecycline in some clinical S. maltophilia strains (n = 149) and determined by MIC with E-test method.

Results

The antimicrobial susceptibility rates to TMP-SMX, levofloxacin, and ceftazidime were 97.1%, 93%, and 55.3%, respectively. The treatment failure rate and 30-day mortality were 66.3% and 49%, respectively. Significant factors associated with treatment failure included APACHE II score ≥15 (OR 3.37, 95% confidence interval (CI) 1.46-7.76), polymicrobial infections (OR 3.20, 95% CI 1.35-7.55). The significant factors associated with reduced treatment failure was treatment with TMP-SMX-based regimen (OR 0.29, 95% CI 0.11-0.76). The 30-day mortality rate was associated with APACHE II score ≥15 (OR 3.27, 95% CI 1.45-7.39) and septic shock (OR 2.53, 95% CI 1.36-4.69).

Conclusion

The results indicate a high mortality rate for S. maltophilia infection. The predictive factors for an unfavourable outcome were severity of illness, septic shock, and non-use of TMP-SMX. Therefore, a TMP-SMX-based regimen is recommended for the treatment of S. maltophilia infections.

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.

Stenotrophomonas maltophilia Infections: A Systematic Review and Meta-Analysis of Comparative Efficacy of Available Treatments, with Critical Assessment of Novel Therapeutic Options

Stenotrophomonas maltophilia (SM) represents a challenging pathogen due to its resistance profile. A systematic review of the available evidence was conducted to evaluate the best treatment of SM infections to date, focusing on trimethoprim/sulfamethoxazole (TMP/SMX), fluoroquinolones (FQs), and tetracycline derivatives (TDs).

MATERIALS

PubMed/MEDLINE and Embase were searched from inception to 30 November 2022. The primary outcome was all-cause mortality. Secondary outcomes included clinical failure, adverse events, and length of stay. A random effects meta-analysis was performed. This study was registered with PROSPERO (CRD42022321893).

RESULTS

Twenty-four studies, all retrospective, were included. A significant difference in terms of overall mortality was observed when comparing as a monotherapy TMP/SMX versus FQs (odds ratio (OR) 1.46, 95% confidence interval (CI) 1.15-1.86, I² = 33%; 11 studies, 2407 patients). The prediction interval (PI) did not touch the no effect line (1.06-1.93), but the results were not robust for the unmeasured confounding (E-value for point estimate of 1.71). When comparing TMP/SMX with TDs, the former showed an association with higher mortality but not significant and with a wide PI (OR 1.95, 95% CI 0.79-4.82, PI 0.01-685.99, I² = 0%; 3 studies, 346 patients). Monotherapies in general exerted a protective effect against death opposed to the combination regimens but were not significant (OR 0.71, 95% CI 0.41-1.22, PI 0.16-3.08, I² = 0%; 4 studies, 438 patients).

CONCLUSIONS

Against SM infections, FQs and, possibly, TDs seem to be reasonable alternative choices to TMP/SMX. Data from clinical trials are urgently needed to better inform therapeutic choices in this setting by also taking into account newer agents.

Association between minimum inhibitory concentration values and mortality risk in patients with Stenotrophomonas maltophilia infections: a retrospective cohort study of electronic health records from 148 US hospitals

Background

Clinical data informing antimicrobial susceptibility breakpoints for Stenotrophomonas maltophilia infections are lacking. We sought to leverage real-world data to identify MIC values within the currently defined susceptible range that could discriminate mortality risk for patients with S. maltophilia infections and guide future breakpoint revisions.

Methods

Inpatients with S. maltophilia infection who received single-agent targeted therapy with levofloxacin or trimethoprim/sulfamethoxazole were identified in the Cerner HealthFacts electronic health record database. Encounters were restricted to those with MIC values reported to be in the susceptible range for both agents. Curation for exact (non-range) MIC values yielded sequentially granular model populations. Logistic regression was used to calculate adjusted OR (aOR) of mortality or hospice discharge associated with different susceptible-range MICs, controlling for patient- and centre-related factors, and infection site, polymicrobial infection and receipt of empirical therapy.

Results

Seventy-three of 851 levofloxacin-treated patients had levofloxacin MIC of exactly 2 mg/L (current Clinical and Laboratory Standards Institute (CLSI) susceptibility breakpoint) and served as the reference category for levofloxacin breakpoint models. In breakpoint model I (n = 501), aOR of mortality associated with infection due to isolates with levofloxacin MIC of ≤1 versus 2 mg/L were similar [aOR = 1.79 (95% CI 0.88-3.62), P = 0.11]. In breakpoint model IIa (n = 358), aOR of mortality associated with MIC ≤0.5 versus 2 mg/L were also similar [aOR 0.1.36 (95% CI 0.65-2.83), P = 0.41]. However, breakpoint model IIb (n = 297) displayed higher aOR of mortality associated with an MIC of 1 versus 2 mg/L [aOR 2.36 (95% CI 1.14-4.88), P = 0.02]. Only 9/645 trimethoprim/sulfamethoxazole-treated patients had trimethoprim/sulfamethoxazole MIC of exactly 2/38 mg/L precluding informative models for this agent.

Conclusions

In this retrospective study of real-world patients with S. maltophilia infection, risk-adjusted survival data do not appear to stratify patients clinically within current susceptible-range MIC breakpoint for levofloxacin (≤2 mg/L) by mortality.

Upraising Stenotrophomonas maltophilia in Critically Ill Patients: A New Enemy?

Stenotrophomonas maltophilia (S. maltophilia), an important pathogen in immuno-compromised patients, has recently gained attention in patients admitted in intensive care units (ICU). We sought to investigate clinical features of infections caused by S. maltophilia in ICU patients and identify risk factors for mortality. We conducted a retrospective study in two multivalent non-COVID-19 ICUs of tertiary-teaching hospitals in Greece and Spain, including patients with isolated S. maltophilia from at least one clinical specimen along with clinical signs of infection. A total of 103 patients (66% male) were analyzed. Median age was 65.5 (54–73.3) years and mean APACHE II and SOFA scores upon ICU admission were 18.36 (±7.22) and 18.17 (±6.95), respectively. Pneumonia was the predominant clinical syndrome (72.8%), while 22% of cases were among hemato/oncology patients. Crude 28-day mortality rate was 54.8%, even though, 14-day clinical and microbiological response was 96%. Age, APACHE II on ICU admission, hemato-oncologic disease, and multi-organ failure were initially identified as potential predictors of mortality. In the multivariable analysis, only increasing age and hemato-oncologic disease were shown to be independent risk factors for 28-day mortality. High all-cause mortality was observed in critically ill patients with predominantly respiratory infections by S. maltophilia, despite initial clinical and laboratory response after targeted treatment. The study elucidates a potentially worrisome emerging pathogen in the ICU.

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.

Stenotrophomonas maltophilia Bacteremia: From Diagnosis to Treatment

Objective

There are many difficulties in diagnosing and treating Stenotrophomonas maltophilia bacteremia. In this study, we aimed to evaluate "true" and "false-positive bacteremia" and assess mortality risk factors and the impact of different treatment regimens.

Materials and Methods

Hospitalized adult patients with S. maltophilia-positive blood cultures were assessed by a two-stage analysis. First, the clinical significance of blood cultures was assessed, and patients were divided into "true" and "false-positive bacteremia" groups. Then, excluding false positives, we analyzed the antimicrobial regimens and the factors associated with 28-day mortality in true bacteremia cases performing univariate and multivariate analyses.

Results

The study included 127 out of 138 patients with S. maltophilia bacteremia. True bacteremia was identified in 51.2% and false-positive bacteremia in 48.8% of patients. In the true bacteremia group, hypotension, nosocomial bacteremia, concomitant infections, a source of bacteremia, two positive blood culture sets, and 28-day mortality were more common. The 28-day mortality was 50.7% among true bacteremia cases. In multivariate analysis, age and solid tumor were the independent predictors of 28-day mortality. Early effective antimicrobial therapy and different antimicrobial regimens, including trimethoprim-sulfamethoxazole (SXT), fluoroquinolones (FQs), and tigecycline (TGC), did not have any significant impact on survival.

Conclusion

Patients with S. maltophilia bacteremia should first be assessed regarding clinical significance. Clinical findings, the presence of multiple positive blood culture sets and the primary sources of bacteremia are useful parameters while discriminating true from false-positive bacteremia. Patients with advanced age and solid tumors should be followed carefully in terms of mortality. Antimicrobial regimens, including SXT, FQs, or TGC, can be preferred in patients with S. maltophilia bacteremia considering antimicrobial resistance and adverse effects or toxicity.

Genome-wide analysis reveals the emergence of multidrug resistant Stenotrophomonas acidaminiphila strain SINDOREI isolated from a patient with sepsis

Stenotrophomonas acidaminiphila, the most recent reported species in genus Stenotrophomonas, is a relatively rare bacteria and is an aerobic, glucose non-fermentative, Gram-negative bacterium. However, little information of S. acidaminiphila is known to cause human infections. In this research, we firstly reported a multidrug-resistant strain S. acidaminiphila SINDOREI isolated from the blood of a patient with sepsis, who was dead of infection eventually. The whole genome of strain SINDOREI was sequenced, and genome comparisons were performed among six closely related S. acidaminiphila strains. The core genes (2,506 genes) and strain-specific genes were identified, respectively, to know about the strain-level diversity in six S. acidaminiphila stains. The presence of a unique gene (narG) and essential genes involved in biofilm formation in strain SINDOREI are important for the pathogenesis of infections. Strain SINDOREI was resistant to trimethoprim/sulfamethoxazole, ciprofloxacin, ofloxacin, cefepime, ceftazidime, and aztreonam. Several common and specific antibiotic resistance genes were identified in strain SINDOREI. The presence of two sul genes and exclusive determinants GES-1, aadA3, qacL, and cmlA5 is responsible for the resistance to multidrug. The virulence factors and resistance determinants can show the relationship between the phenotype and genotype and afford potential therapeutic strategies for infections.

Epidemiology, Mechanisms of Resistance and Treatment Algorithm for Infections Due to Carbapenem-Resistant Gram-Negative Bacteria: An Expert Panel Opinion

Antimicrobial resistance represents a serious threat for global health, causing an unacceptable burden in terms of morbidity, mortality and healthcare costs. In particular, in 2017, carbapenem-resistant organisms were listed by the WHO among the group of pathogens for which novel treatment strategies are urgently needed. Fortunately, several drugs and combinations have been introduced in recent years to treat multi-drug-resistant (MDR) bacteria. However, a correct use of these molecules is needed to preserve their efficacy. In the present paper, we will provide an overview on the epidemiology and mechanisms of resistance of the most common MDR Gram-negative bacteria, proposing a treatment algorithm for the management of infections due to carbapenem-resistant bacteria based on the most recent clinical evidence.

Efficacy and safety of plazomicin in the treatment of Enterobacterales infections: A meta-analysis of randomized controlled trials

Background

In the present study, we aimed to compare the efficacy and safety of plazomicin with comparators for the treatment of Enterobacterales infections.

Methods

Randomized controlled trials (RCTs) assessing plazomicin for Enterobacterales infections were searched on the PubMed, Embase, and Cochrane Library databases. Meta-analyses were used to evaluate the efficacy and safety in RCTs.

Results

A total of 3 RCTs consisting of 761 patients were included in the present analysis. The study population included complex urinary tract infections (cUTIs), bloodstream infections (BSIs), and hospital-acquired pneumonia (HAP). Plazomicin had a clinical remission rate in the modified intention-to-treat (MITT) population that was similar to that of comparators (odds ratio [OR], 1.02; 95% CI, 0.60–1.73; I² = 45%) in the pooled analysis of the 3 studies. The overall microbiologic eradication rate in the microbiological MITT (mMITT) population was similar to that of the comparators group (OR, 1.46; 95% CI, 0.72–2.95; I² = 0%). However, the microbiologic recurrence rate of plazomicin for Enterobacterales was lower than that in the comparators group (OR, 0.38; 95% CI, 0.17–0.86; P = .02; I² = 0%). No significant differences were found between plazomicin and comparators for the risk of any adverse events (OR, 0.78; 95% CI, 0.55–1.11; I² = 0%).

Conclusions

Plazomicin is as good as comparators in terms of efficacy and tolerance in the treatment of Enterobacterales infections. Therefore, plazomicin is a suitable choice for antibiotic treatment in adult patients with cUTIs, BSIs, or HAP.

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

Simple Summary

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

Abstract

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

Characterization of the Bacteriophage BUCT603 and Therapeutic Potential Evaluation Against Drug-Resistant Stenotrophomonas maltophilia in a Mouse Model

Stenotrophomonas maltophilia (S. maltophilia) is a common opportunistic pathogen that is resistant to many antibiotics. Bacteriophages are considered to be an effective alternative to antibiotics for the treatment of drug-resistant bacterial infections. In this study, we isolated and characterized a phage, BUCT603, infecting drug-resistant S. maltophilia. Genome sequencing showed BUCT603 genome was composed of 44,912 bp (32.5% G + C content) with 64 predicted open reading frames (ORFs), whereas no virulence-related genes, antibiotic-resistant genes or tRNA were identified. Whole-genome alignments showed BUCT603 shared 1% homology with other phages in the National Center for Biotechnology Information (NCBI) database, and a phylogenetic analysis indicated BUCT603 can be classified as a new member of the Siphoviridae family. Bacteriophage BUCT603 infected 10 of 15 S. maltophilia and used the TonB protein as an adsorption receptor. BUCT603 also inhibited the growth of the host bacterium within 1 h in vitro and effectively increased the survival rate of infected mice in a mouse model. These findings suggest that bacteriophage BUCT603 has potential for development as a candidate treatment of S. maltophilia infection.

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.

FadACB and smeU1VWU2X Contribute to Oxidative Stress-Mediated Fluoroquinolone Resistance in Stenotrophomonas maltophilia

Pathogenic bacteria experience diverse stresses induced by host cells during infection and have developed intricate systems to trigger appropriate responses. Bacterial stress responses have been reported to defend against these stresses and cross-protect bacteria from antibiotic attack. In this study, we aimed to assess whether oxidative stress affects bacterial susceptibility to fluoroquinolone (FQ) and the underlying mechanism. Stenotrophomonas maltophilia, a species with high genetic diversity, is distributed ubiquitously and is an emerging multidrug-resistant opportunistic pathogen. FQs are among the limited antibiotic treatment options for S. maltophilia infection. The minimum inhibitory concentrations (MICs) of 103 S. maltophilia clinical isolates against ciprofloxacin (CIP) and levofloxacin (LVX) were determined using the agar dilution method in Mueller-Hinton plates with or without menadione (MD), a superoxide generator. The resistance rates for ciprofloxacin and levofloxacin were 40% and 18% in the MD-null group and increased to 91% and 23%, respectively, in the MD-treated group. Of the 103 isolates tested, 54% and 27% had elevated MICs against ciprofloxacin and levofloxacin, respectively, in the presence of MD. The involvement of oxidative stress responses in the MD-mediated FQ resistance was further assessed by mutants construction and viability assay. Among the 16 oxidative stress alleviation systems evaluated, fadACB and smeU1VWU2X contributed to MD-mediated FQ resistance. The antibiotic susceptibility test is an accredited clinical method to evaluate bacterial susceptibility to antibiotics in clinical practice. However, oxidative stress-mediated antibiotic resistance was not detected using this test, which may lead to treatment failure.

Overcoming Stenotrophomonas maltophilia Resistance for a More Rational Therapeutic Approach

Stenotrophomonas maltophilia is an underappreciated source of morbidity and mortality among Gram-negative pathogens. Effective treatment options with acceptable toxicity profiles are limited. Phenotypic susceptibility testing via commercial automated test systems is problematic and no FDA breakpoints are approved for any of the first-line treatment options for S. maltophilia. The lack of modern pharmacokinetic/ pharmacodynamic data for many agents impedes dose optimization and the lack of robust efficacy and safety data limits their clinical utility. Levofloxacin has demonstrated similar efficacy to SMX-TMP, although rapid development of resistance is a concern. Minocycline demonstrates the highest rate of in vitro susceptibility, however, evidence to support its clinical use are scant. Novel agents such as cefiderocol have exhibited promising activity in pre-clinical investigations, though additional outcomes data are needed to determine its place in therapy for S. maltophilia. Combination therapy is often employed despite the dearth of adequate supporting data.

ISPD peritonitis guideline recommendations: 2022 update on prevention and treatment

Peritoneal dialysis (PD)-associated peritonitis is a serious complication of PD and prevention and treatment of such is important in reducing patient morbidity and mortality. The ISPD 2022 updated recommendations have revised and clarified definitions for refractory peritonitis, relapsing peritonitis, peritonitis-associated catheter removal, PD-associated haemodialysis transfer, peritonitis-associated death and peritonitis-associated hospitalisation. New peritonitis categories and outcomes including pre-PD peritonitis, enteric peritonitis, catheter-related peritonitis and medical cure are defined. The new targets recommended for overall peritonitis rate should be no more than 0.40 episodes per year at risk and the percentage of patients free of peritonitis per unit time should be targeted at >80% per year. Revised recommendations regarding management of contamination of PD systems, antibiotic prophylaxis for invasive procedures and PD training and reassessment are included. New recommendations regarding management of modifiable peritonitis risk factors like domestic pets, hypokalaemia and histamine-2 receptor antagonists are highlighted. Updated recommendations regarding empirical antibiotic selection and dosage of antibiotics and also treatment of peritonitis due to specific microorganisms are made with new recommendation regarding adjunctive oral N-acetylcysteine therapy for mitigating aminoglycoside ototoxicity. Areas for future research in prevention and treatment of PD-related peritonitis are suggested.

VG, Kadri SS. Trimethoprim-Sulfamethoxazole versus Levofloxacin for Stenotrophomonas maltophilia Infections: A Retrospective Comparative Effectiveness Study of Electronic Health Records from 154 U.S. Hospitals

Background

Trimethoprim-sulfamethoxazole (TMP-SMX) is considered first-line therapy for Stenotrophomonas maltophilia infections based on observational data from small studies. Levofloxacin has emerged as a popular alternative due to tolerability concerns related to TMP-SMX. Data comparing levofloxacin to TMP-SMX as targeted therapy are lacking.

Methods

Adult inpatient encounters January 2005 through December 2017 with growth of S maltophilia in blood and/or lower respiratory cultures were identified in the Cerner Healthfacts database. Patients included received targeted therapy with either levofloxacin or TMP-SMX. Overlap weighting was used followed by downstream weighted regression. The primary outcome was adjusted odds ratio (aOR) for in-hospital mortality or discharge to hospice. The secondary outcome was number of days from index S maltophilia culture to hospital discharge.

Results

Among 1581 patients with S maltophilia infections, levofloxacin (n = 823) displayed statistically similar mortality risk (aOR, 0.76 [95% confidence interval {CI}, .58–1.01]; P = .06) compared to TMP-SMX (n = 758). Levofloxacin (vs TMP-SMX) use was associated with a lower aOR of death in patients with lower respiratory tract infection (n = 1452) (aOR, 0.73 [95% CI, .54–.98]; P = .03) and if initiated empirically (n = 89) (aOR, 0.16 [95% CI, .03–.95]; P = .04). The levofloxacin cohort had fewer hospital days between index culture collection and discharge (weighted median [interquartile range], 7 [4–13] vs 9 [6–16] days; P < .0001).

Conclusions

Based on observational evidence, levofloxacin is a reasonable alternative to TMP-SMX for the treatment of bloodstream and lower respiratory tract infections caused by S maltophilia.

Infectious Diseases Society of America Guidance on the Treatment of AmpC β-lactamase-Producing Enterobacterales, Carbapenem-Resistant Acinetobacter baumannii, and Stenotrophomonas maltophilia Infections

BACKGROUND

The Infectious Diseases Society of America (IDSA) is committed to providing up-to-date guidance on the treatment of antimicrobial-resistant infections. A previous guidance document focused on infections caused by extended-spectrum β-lactamase-producing Enterobacterales (ESBL-E), carbapenem-resistant Enterobacterales (CRE), and Pseudomonas aeruginosa with difficult-to-treat resistance (DTR-P. aeruginosa). Here, guidance is provided for treating AmpC β-lactamase-producing Enterobacterales (AmpC-E), carbapenem-resistant Acinetobacter baumannii (CRAB), and Stenotrophomonas maltophilia infections.

METHODS

A panel of six infectious diseases specialists with expertise in managing antimicrobial-resistant infections formulated questions about the treatment of AmpC-E, CRAB, and S. maltophilia infections. Answers are presented as suggestions and corresponding rationales. In contrast to guidance in the previous document, published data on optimal treatment of AmpC-E, CRAB, and S. maltophilia infections are limited. As such, guidance in this document is provided as "suggested approaches" based on clinical experience, expert opinion, and a review of the available literature. Because of differences in the epidemiology of resistance and availability of specific anti-infectives internationally, this document focuses on the treatment of infections in the United States.

RESULTS

Preferred and alternative treatment suggestions are provided, assuming the causative organism has been identified and antibiotic susceptibility results are known. Approaches to empiric treatment, duration of therapy, and other management considerations are also discussed briefly. Suggestions apply for both adult and pediatric populations.

CONCLUSIONS

The field of antimicrobial resistance is highly dynamic. Consultation with an infectious diseases specialist is recommended for the treatment of antimicrobial-resistant infections. This document is current as of September 17, 2021 and will be updated annually. The most current versions of IDSA documents, including dates of publication, are available at www.idsociety.org/practice-guideline/amr-guidance-2.0/.

Effect of antibiotic therapy on the prognosis of ventilator-associated pneumonia caused by Stenotrophomonas maltophilia

BACKGROUND

Ventilator-associated pneumonia (VAP) caused by Stenotrophomonas maltophilia is poorly described in the literature. However, it has been shown to be associated with increased morbidity and mortality. Probabilistic antibiotic therapy against S. maltophilia is often ineffective as this pathogen is resistant to many antibiotics. There is no consensus at present on the best therapeutic strategy to adopt (class of antibiotics, antibiotic combination, dosage, treatment duration). The aim of this study was to evaluate the effect of antibiotic therapy strategy on the prognosis of patients with VAP caused by S. maltophilia.

RESULTS

This retrospective study evaluated all consecutive patients who developed VAP caused by S. maltophilia between 2010 and 2018 while hospitalized in the intensive care unit (ICU) of a French university hospital in Reunion Island, in the Indian Ocean region. A total of 130 patients with a median Simplified Acute Physiology Score II of 58 [43-73] had VAP caused by S. maltophilia after a median duration of mechanical ventilation of 12 [5-18] days. Ventilator-associated pneumonia was polymicrobial in 44.6% of cases, and ICU mortality was 50.0%. After multivariate Cox regression analysis, the factors associated with increased ICU mortality were older age (hazard ratio (HR): 1.03; 95% CI 1.01-1.04, p = 0.001) and high Sequential Organ Failure Assessment score on the day of VAP onset (HR: 1.08; 95% CI 1.03-1.14, p = 0.002). Appropriate antibiotic therapy, and in particular trimethoprim-sulfamethoxazole, was associated with decreased ICU mortality (HR: 0.42; 95% CI 0.24-0.74, p = 0.003) and decreased hospital mortality (HR: 0.47; 95% CI 0.28-0.79, p = 0.04). Time to start of appropriate antibiotic therapy, combination therapy, and duration of appropriate antibiotic therapy had no effect on ICU mortality (p > 0.5).

CONCLUSION

In our study, appropriate antibiotic therapy, and in particular trimethoprim-sulfamethoxazole, was associated with decreased ICU and hospital mortality in patients with VAP caused by S. maltophilia.

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

Introduction

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

Materials and Methods

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

Results

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

Conclusion 

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

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

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

Ecthyma gangrenosum: a rare manifestation of Stenotrophomonas maltophilia infection in acute myelogenous leukemia patient

Ecthyma gangrenosum is a cutaneous infection typically associated with Pseudomonas aeruginosa. However, it is rarely caused by Stenotrophomonas maltophilia which might be overlooked leading to devastating consequences. We describe this case to avoid delays in the diagnosis and treatment of this aggressive infection, especially in immunocompromised patients.

Prevalence of resistance genes and antibiotic resistance profile among Stenotrophomonas maltophilia isolates from hospitalized patients in Iran

Stenotrophomonas maltophilia has emerged as an important nosocomial pathogen. Treatment of S. maltophilia infections is difficult due to increasing resistance to multiple antibacterial agents. In this 12-month cross-sectional study, from 2017 to 2018, 117 isolates were obtained from different clinical sources and identified by conventional biochemical methods. Antibiotic susceptibility tests were performed according to CLSI 2018. Minocycline disk (30 μg) and E-test strips for ceftazidime, trimethoprim-sulfamethoxazole and chloramphenicol were used. PCR confirmed isolates. The frequency of different classes of integrons (I, II) and resistance gene cassettes (sul1, sul2, dfrA1, dfrA5 and aadB) were determined by PCR. The results showed the highest frequency of resistance to chloramphenicol and ceftazidime with 32 cases (27.11%). Among strains, 12 cases (10.25%) were resistant to trimethoprim-sulfamethoxazole (the lowest frequency of resistance), while 19 (16.1%) isolates were resistant to minocycline. Frequency of sul1, int1, aadB, sul2, dfrA5 genes were 64 (55.08%), 26 (22.3 %), 18 (15.25%) and 17 (14.4%), 14 (11.86%), respectively. int2 and dfrA1 were not detected. Although we have not yet reached a high level of resistance to effective antibiotics such as trimethoprim-sulfamethoxazole, as these resistances can be carried by a plasmid, greater precision should be given to the administration of these antibiotics.

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.

Stenotrophomonas maltophilia Susceptibility Testing Challenges and Strategies

Stenotrophomonas maltophilia is intrinsically resistant to many beta-lactam antibiotics, including carbapenems, and is resistant to aminoglycosides, which limits the therapeutic repertoire for managing S. maltophilia infections. Additionally, employing automated in vitro susceptibility testing of S. maltophilia is challenging because commercial test systems' performance is limited (A. Khan, C. A. Arias, A. Abbott, J. Dien Bard, et al., J Clin Microbiol 59:e00654-21, 2021, https://doi.org/10.1128/JCM.00654-21). This commentary will briefly discuss the opportunity to use automated commercial susceptibility testing systems with S. maltophilia, with a focus on how to implement their use practically while mitigating risk of error.

Stenotrophomonas maltophilia bacteraemia: 61 cases in a tertiary hospital in Denmark

BACKGROUND

Stenotrophomonas maltophilia is an opportunistic pathogen and a dreaded cause of bacteraemia with 30-day mortality rates ranging from 14 to 69%. The purpose of this cohort study was to evaluate outcomes of S. maltophilia bacteraemia, at Rigshospitalet, a tertiary hospital in Copenhagen, Denmark.

METHODS

We included all patients with a blood culture positive for S. maltophilia, from January 1, 2015 to April 1, 2020. We extracted data on antimicrobial susceptibility, treatment, central venous catheter intervention and severe haematological disease.

RESULTS

Sixty-one cases of S. maltophilia bacteraemia were identified. The overall 90-day mortality was 18%. Sixty percent of patients had a central venous catheter intervention performed. Seventy-nine percent of patients were treated with trimethoprim/sulfamethoxazole (TMP/SMX). Patients with central venous catheter intervention had significantly better survival than those without (HR: 0.16 [95% CI: 0.03-0.73]). Severe haematological disease and patients, who received intensive care unit (ICU) care, were at higher risk of death than other patients (HR: 5.93 [95% CI: 1.18 - 29.94] and HR: 8.37 [95% CI: 1.79 - 39.20], respectively). We found no evidence that any antibiotic regime was superior with regard to 90-day mortality.

CONCLUSIONS

We did not find evidence to support a change in the current standard-of-care regimen of TMP/SMX and CVC removal. Larger clinical trials are needed to guide such recommendations.

Tigecycline in the Treatment of Ventilator-Associated Pneumonia Due to Stenotrophomonas maltophilia: A Multicenter Retrospective Cohort Study

Introduction

Tigecycline is a potential alternative to trimethoprim–sulfamethoxazole in treating Stenotrophomonas maltophilia infections due to its potent in vitro antimicrobial activity. Clinical evidence regarding the use of tigecycline in the treatment of S. maltophilia infections is scarce. In this study, we assessed the efficacy of tigecycline treating ventilator-associated pneumonia (VAP) due to S. maltophilia in comparison with fluoroquinolones.

Methods

This is a multicenter retrospective cohort study of patients admitted between January 2017 and December 2020 with the diagnosis of VAP caused by S. maltophilia receiving either tigecycline or fluoroquinolones as the definitive therapy ≥ 48 h. Clinical outcomes including 28-day mortality, clinical cure and microbiological cure were analyzed.

Results

Of 82 patients with S. maltophilia VAP included, 46 received tigecycline, and 36 received fluoroquinolones; 70.7% of patients had polymicrobial pneumonia, and the appropriate empiric therapy was applied to only 14.6% of patients. The overall 28-day mortality was 39%. Compared with patients receiving fluoroquinolones, tigecycline therapy resulted in worse clinical cure (32.6% vs. 63.9%, p = 0.009) and microbiological cure (28.6% vs. 59.1%, p = 0.045), while there was no statistical difference between 28-day mortality (47.8% vs. 27.8%, p = 0.105) in the two groups. Similar results were also shown in the inverse probability of treatment weighted univariable regression model and multivariable regression model.

Conclusions

The standard dose of tigecycline therapy was associated with a lower clinical and microbiological cure rate but not associated with an increased 28-day mortality in patients with S. maltophilia VAP compared with fluoroquinolones. Considering the unfavorable clinical outcomes, we therefore recommend against using the standard dose of tigecycline in treating S. maltophilia VAP unless new clinical evidence emerges.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40121-021-00516-5.

StenoSCORE: Predicting Stenotrophomonas maltophilia Bloodstream Infections in the Hematologic Malignancy Population

Stenotrophomonas maltophilia bloodstream infections (BSI) are associated with considerable mortality in the hematologic malignancy population. Trimethoprim-sulfamethoxazole (TMP-SMX) is the treatment of choice; however, it is not routinely included in empirical treatment regimens, both because of its adverse event profile and the relative rarity of S. maltophilia infections. We developed a risk score to predict hematologic malignancy patients at increased risk for S. maltophilia BSI to guide early (TMP-SMX) therapy. Patients ≥12 years of age admitted to five hospitals between July 2016 and December 2019 were included. Two separate risk scores were developed, (i) a "knowledge-driven" risk score based upon previously identified risk factors in the literature in addition to variables identified by regression analysis using the current cohort, and (ii) a risk score based upon automatic variable selection. For both scores, discrimination (receiver operator characteristic [ROC] curves and C statistics) and calibration (Hosmer-Lemeshow goodness-of-fit test and graphical calibration plots) were assessed. Internal validation was assessed using leave-one-out cross-validation. In total, 337 unique patients were included; 21 (6.2%) had S. maltophilia BSI. The knowledge-driven risk score (acute leukemia, absolute neutrophil count category, mucositis, central line, and ≥3 days of carbapenem therapy) had superior performance (C statistic = 0.75; 0.71 after cross-validation) compared to that of the risk score utilizing automatic variable selection (C statistic = 0.63; 0.38 after cross-validation). A user-friendly risk score incorporating five variables easily accessible to clinicians performed moderately well to predict hematologic malignancy patients at increased risk for S. maltophilia BSI. External validation using a larger cohort is necessary to create a refined risk score before broad clinical application.

Clinical outcomes of Stenotrophomonas maltophilia infection treated with trimethoprim/sulfamethoxazole, minocycline, or fluoroquinolone monotherapy

OBJECTIVES

The historical treatment of choice for Stenotrophomonas maltophilia infection is trimethoprim/sulfamethoxazole and this is primarily based on preclinical studies. The objective of this study was to examine the clinical outcomes of patients receiving monotherapy with different agents.

METHODS

This was a retrospective study of adult patients receiving monotherapy for S. maltophilia infection with trimethoprim/sulfamethoxazole (TMP/SMX), a fluoroquinolone, or minocycline from 2010 to 2016. The primary outcome was clinical failure, a composite of recurrence, alteration of therapy due to adverse reaction or concern for clinical failure, or 30-day in-hospital mortality. The secondary outcome was 30-day in-hospital mortality. To account for treatment selection bias, multivariate regression and propensity score weighting were conducted.

RESULTS

284 patients were included (217 received TMP/SMX, 28 received a fluoroquinolone, and 39 received minocycline). The TMP/SMX and minocycline groups appeared to include similar patients whereas the fluoroquinolone group appeared to represent a slightly less severely ill population. Clinical failure was similar between groups (36%, 29%, and 31% in the TMP/SMX, fluoroquinolone, and minocycline groups, respectively, P=0.69) as was 30-day mortality (15%, 7%, and 5% in the TMP/SMX, fluoroquinolone, and minocycline groups, respectively, P=0.16). After controlling for confounding factors, receipt of minocycline (adjusted odds ratio [OR]=0.2 [0.1-0.7]) but not a fluoroquinolone (adjusted OR=0.3 [0.1 to 2.1]) was associated with lower mortality compared with TMP/SMX. This association persisted after propensity score weighting.

CONCLUSIONS

Outcomes were similar or better with alternatives to TMP/SMX monotherapy, which indicates this may not be the treatment of choice for infections caused by S. maltophilia.

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.

Alterations of the Oral Microbiome and Cumulative Carbapenem Exposure Are Associated With Stenotrophomonas maltophilia Infection in Patients With Acute Myeloid Leukemia Receiving Chemotherapy

BACKGROUND

Stenotrophomonas maltophilia is increasingly common in patients with acute myeloid leukemia (AML). Little is known about factors that drive S. maltophilia infection. We evaluated the microbiome and cumulative antibiotic use as predictors of S. maltophilia infection in AML patients receiving remission induction chemotherapy (RIC).

METHODS

Subanalysis of a prospective, observational cohort of patients with AML receiving RIC between September 2013 and August 2015 was performed. Fecal and oral microbiome samples collected from initiation of RIC until neutrophil recovery were assessed for the relative abundance of Stenotrophomonas via 16S rRNA gene quantitation. The primary outcome, microbiologically proven S. maltophilia infection, was analyzed using a time-varying Cox proportional hazards model.

RESULTS

Of 90 included patients, 8 (9%) developed S. maltophilia infection (pneumonia, n = 6; skin-soft tissue, n = 2); 4/8 (50%) patients were bacteremic; and 7/8 (88%) patients with S. maltophilia infection had detectable levels of Stenotrophomonas vs 22/82 (27%) without infection (P < .01). An oral Stenotrophomonas relative abundance of 36% predicted infection (sensitivity, 96%; specificity, 93%). No association of S. maltophilia infection with fecal relative abundance was found. Cumulative meropenem exposure was associated with increased infection risk (hazard ratio, 1.17; 95% confidence interval, 1.01-1.35; P = .03).

CONCLUSIONS

Here, we identify the oral microbiome as a potential source for S. maltophilia infection and highlight cumulative carbapenem use as a risk factor for S. maltophilia in leukemia patients. These data suggest that real-time monitoring of the oral cavity might identify patients at risk for S. maltophilia infection.

Nosocomial Non-fermentative gram negative bacteria bloodstream infections in children; Risk factors and clinical outcomes of carbapenem resistance

INTRODUCTION

Non-fermentative Gram-negative bacterias (NFGNBs) are a major cause of life threatening infections in hospitalized children. In this study, we aimed to evaluate the demographic and clinical characteristics of NFGNBs infections and identify the risk factors and outcomes of bloodstream infections (BSIs) caused by carbapenem-resistant (CR) NFGNBs infections.

METHODS

A retrospective cohort was designed to evaluate the patients with a BSI caused by NFGNBs between in January 2014 and December 2017.

RESULTS

A total of 131 episodes from 115 patients were evaluated. The mean age of the patients was 4.79±(4.74) year. The most commonly isolated NFGNBs species was Acinetobacter spp. (35.9%), Pseudomonas spp. (34.4%), and Stenotrophomonas maltophilia (13%). The rate of carbapenem-resistance was 38.2% in Acinetobacter spp. and 26.6% in Pseudomonas spp. The comparison of CR group with carbapenem-susceptible (CS) group showed statistical significance for the length of hospital stay prior to onset of infection and total hospital stay (P values were 0.001, 0.008). Based on the univariate analysis, requirement of mechanical ventilation, central venous catheter, nasogastric tube, Foley catheter, severe neutropenia (<100/mm3), prolonged neutropenia (≥14 days), prior intensive care unit admission and prior antimicrobial treatment (carbapenems, colistin, glycopeptide) were more common in carbapenem-resistant NFGNBs infections (P values are 0.001, 0.012, 0.000, 0.005, 0.042, 0.027, 0.007, 0.007). In patients with NFGNBs infections 14-day and 30-day mortality rates were %16.8 and 21.4%.

CONCLUSION

CR infections were more common in children with prolonged and severe neutropenia. Prior antimicrobial use and intensive care unit admission were more common in CR infections.

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

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

Stenotrophomonas maltophilia bloodstream infections in adult recipients of umbilical cord blood transplantation

Limited data are available on Stenotrophomonas maltophilia bloodstream infections (SM-BSIs) and the therapeutic efficacy of trimethoprim-sulfamethoxazole (SXT) against SM-BSI in umbilical cord blood transplant (uCBT) recipients. Medical and microbiological records of adult patients who received uCBTs between December 2008 and December 2015 at Toranomon Hospital (Tokyo, Japan) were reviewed. The efficacy and safety of SXT were evaluated only for recipients who were treated with ≥7 days of intravenous SXT for SM-BSI (evaluation cohort). Of 561 uCBT recipients, 34 developed SM-BSI. Diabetes mellitus (P = .005) and age ≥ 60 years (P = .013) were significant independent risk factors for SM-BSI. Moreover, SM-BSI was identified as an independent risk factor for all-cause mortality up to 100 days following uCBT (P = .025). Of the 34 recipients with SM-BSI, 24 were treated with an intravenous SXT-containing regimen (iSXT-CR). Septic shock (P = .0021), pneumonia (P = .011), neutropenia (P = .0015), and systemic steroid administration (P = .018) were identified as significant independent risk factors for 7-day crude mortality. The evaluation cohort included nine recipients. Doses of SXT were 2.4 to 6.9 mg/kg/day of the trimethoprim component. Of the nine recipients, five developed SM-BSI during the pre-engraftment phase. The 30-day crude-mortality rate and clinical cure rate of the cohort were 22% and 67%, respectively. Only one of the nine recipients experienced significant neutrophil toxicity. In this study, the epidemiology of SM-BSI in uCBT recipients was determined and its negative impact on survival was demonstrated. A low- to moderate-dose iSXT-CR appeared to be a tolerable and important therapeutic option for SM-BSI in the uCBT setting, including during the pre-engraftment phase.

Novel Mechanisms of Efflux-Mediated Levofloxacin Resistance and Reduced Amikacin Susceptibility in Stenotrophomonas maltophilia

Fluoroquinolone resistance in Stenotrophomonas maltophilia is multifactorial, but the most significant factor is overproduction of efflux pumps, particularly SmeDEF, following mutation. Here, we report that mutations in the glycosyl transferase gene smlt0622 in S. maltophilia K279a mutant K M6 cause constitutive activation of SmeDEF production, leading to elevated levofloxacin MIC. Selection of a levofloxacin-resistant K M6 derivative, K M6 LEV^r, allowed identification of a novel two-component regulatory system, Smlt2645/6 (renamed SmaRS). The sensor kinase Smlt2646 (SmaS) is activated by mutation in K M6 LEV^r causing overproduction of two novel ABC transporters and the known aminoglycoside efflux pump SmeYZ. Overproduction of one ABC transporter, Smlt1651-4 (renamed SmaCDEF), causes levofloxacin resistance in K M6 LEV^r Overproduction of the other ABC transporter, Smlt2642/3 (renamed SmaAB), and SmeYZ both contribute to the elevated amikacin MIC against K M6 LEV^r Accordingly, we have identified two novel ABC transporters associated with antimicrobial drug resistance in S. maltophilia and two novel regulatory systems whose mutation causes resistance to levofloxacin, clinically important as a promising drug for monotherapy against this highly resistant pathogen.

Activity of Aztreonam in Combination with Avibactam, Clavulanate, Relebactam, and Vaborbactam against Multidrug-Resistant Stenotrophomonas maltophilia

The intrinsic L1 metallo- and L2 serine-β-lactamases in Stenotrophomonas maltophilia make it naturally multidrug resistant and difficult to treat. There is a need to identify novel treatment strategies for this pathogen, especially against isolates resistant to first-line agents. Aztreonam in combination with avibactam has demonstrated potential, although data on other aztreonam-β-lactamase inhibitor (BLI) combinations are lacking. Additionally, molecular mechanisms for reduced susceptibility to these combinations have not been explored. The objectives of this study were to evaluate and compare the in vitro activities and to understand the mechanisms of resistance to aztreonam in combination with avibactam, clavulanate, relebactam, and vaborbactam against S. maltophilia A panel of 47 clinical S. maltophilia strains nonsusceptible to levofloxacin and/or trimethoprim-sulfamethoxazole were tested against each aztreonam-BLI combination via broth microdilution, and 6 isolates were then evaluated in time-kill analyses. Three isolates with various aztreonam-BLI MICs were subjected to whole-genome sequencing and quantitative reverse transcriptase PCR. Avibactam restored aztreonam susceptibility in 98% of aztreonam-resistant isolates, compared to 61, 71, and 15% with clavulanate, relebactam, and vaborbactam, respectively. The addition of avibactam to aztreonam resulted in a ≥2-log₁₀-CFU/ml decrease at 24 h versus aztreonam alone against 5/6 isolates compared to 1/6 with clavulanate, 4/6 with relebactam, and 2/6 with vaborbactam. Molecular analyses revealed that decreased susceptibility to aztreonam-avibactam was associated with increased expression of genes encoding L1 and L2, as well as the efflux pump (smeABC). Aztreonam-avibactam is the most promising BLI-combination against multidrug-resistant S. maltophilia Decreased susceptibility may be due to the combination of overexpressed β-lactamases and efflux pumps. Further studies evaluating this combination against S. maltophilia are warranted.