Growing resistance in Stenotrophomonas maltophilia?

Real-World, Multicenter Evaluation of the Incidence and Risk Factors for Non-susceptible Stenotrophomonas maltophilia Isolates

BACKGROUND

Stenotrophomonas maltophilia is a cause of infection most commonly in the opportunistic host. Trimethoprim-sulfamethoxazole and levofloxacin are considered first line treatment agents. With reports of increasing resistance to these first line agents it is important to determine risk factors associated with a non-susceptible isolate.

METHODS

This was a real-world, multicenter, retrospective case-control study from five centers in the southeast United States evaluating S. maltophilia. The primary outcome was risk factors associated with non-susceptibility of S. maltophilia isolates to ≥1 antimicrobial agent. Secondary outcomes include incidence of S. maltophilia non-susceptibility, all-cause mortality, and 30-day readmission rates.

RESULTS

There were 325 patients included in the study. For the primary outcome, the only factor associated with non-susceptibility per univariate analysis was isolation from urine culture (13.3% vs. 5.4%; p=0.014); while presence of mechanical ventilation (37.7% vs. 21.5%) and ICU admission (35.3% vs. 18.4%) were associated with susceptibility (p<0.001). For the secondary outcomes, non-susceptibility was present in 49% of isolates with 43/325 (13.2%), 53/324 (16.4%), and 105/172 (61%) to TMP-SMX, levofloxacin, and ceftazidime, respectively. Resistance to chloramphenicol and tigecycline was observed among 5/26 and 11/16 of tested isolates, respectively. Sixty-six patients (20%) experienced all-cause, inpatient mortality (18% susceptible vs. 23% non-susceptible; p=0.280) and forty-four patients (17%) were readmitted within 30 days of discharge (16% susceptible vs. 18% non-susceptible; p=0.673).

CONCLUSION

S. maltophilia non-susceptibility had a prevalence of ∼50% to at least one first-line or commonly used agent. More research is needed to delineate risk factors for non-susceptible isolates.

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.

Effect of antimicrobials on Stenotrophomonas maltophilia biofilm

Aim: To evaluate the activity of five antimicrobials against young and mature Stenotrophomonas maltophilia biofilms. Materials & methods: Nineteen clinical strains from hemoculture of hemodialysis patients were tested for biofilm kinetics, MIC and minimum biofilm inhibitory concentration (MBIC) in young and mature biofilms. Results: All strains were moderate biofilm producers. MIC showed total susceptibility to levofloxacin and trimethoprim-sulfamethoxazole and partial resistance to ceftazidime (63.2%) and gentamicin (21%). Young and mature biofilms showed the lowest MBIC/MIC ratio for gentamicin, chloramphenicol and levofloxacin, respectively. The highest MBIC/MIC was for trimethoprim-sulfamethoxazole (young) and ceftazidime (mature). Conclusion: Gentamicin displayed surprising activity against S. maltophilia biofilms. Chloramphenicol was indicated as a good option against young S. maltophilia biofilms, and trimethoprim-sulfamethoxazole showed limited antibiofilm activity.

Dorsolateral medullary infarction during skin infection by Stenotrophomonas maltophilia in a patient with triple antiphospholipid antibody positivity: a case-based review

Thrombotic events are the most frequent causes of death in patients with antiphospholipid syndrome (APS). Previous studies have reported infection to be the most important trigger of thrombosis in APS, with molecular mimicry considered to be a major mechanism. Although timely management of infections has been recommended in patients with high suspicion of infection, anti-infective therapy would not take effect in a short time due to the dilemma in determining the origins of infection, especially in patients undergoing immunosuppressive therapy. Here, we describe a 26-year-old patient with systemic lupus erythematosus with triple antiphospholipid antibody positivity who had a stroke involving her dorsolateral medulla, despite timely anti-infective treatment within the context of skin infection caused by Stenotrophomonas maltophilia. To the best of our knowledge, it is the first report about the association between Stenotrophomonas maltophilia infection and thrombotic complications in APS. Thus, solely focusing on anti-infective therapy by the current recommendation for the management of APS may be insufficient within the context of infection; early initiation of effective anticoagulation should also be suggested until the anti-infective therapy becomes effective, especially in patients with high-risk antiphospholipid antibody profiles, in whom the potential benefit would outweigh the risk of bleeding.

Antimicrobial Activity of Aztreonam-Avibactam and Comparator Agents When Tested against a Large Collection of Contemporary Stenotrophomonas maltophilia Isolates from Medical Centers Worldwide

Aztreonam-avibactam was tested against 1,839 Stenotrophomonas maltophilia isolates collected worldwide and demonstrated potent activity against isolates from all geographic regions and infection types (overall MIC_50/90, 4/4 mg/liter; 97.8% inhibited at ≤8 mg/liter). Trimethoprim-sulfamethoxazole (TMP-SMX) (MIC_50/90, ≤0.5/1 mg/liter; 95.4% susceptible) and minocycline (MIC_50/90, 0.5/2 mg/liter; 99.5% susceptible) were also very active. Aztreonam-avibactam inhibited 84.7% of non-TMP-SMX-susceptible isolates at ≤8 mg/liter. Aztreonam-avibactam may represent a valuable option for the treatment of S. maltophilia infections, addressing a major unmet medical need.