Comparisons between patients with trimethoprim-sulfamethoxazole-susceptible and trimethoprim-sulfamethoxazole-resistant Stenotrophomonas maltophilia monomicrobial bacteremia: A 10-year retrospective study

Global mapping of antibiotic resistance rates among clinical isolates of Stenotrophomonas maltophilia: a systematic review and meta-analysis

INTRODUCTION

Infections caused by Stenotrophomonas maltophilia are clinically important due to its intrinsic resistance to a broad range of antibiotics. Therefore, selecting the most appropriate antibiotic to treat S. maltophilia infection is a major challenge.

AIM

The current meta-analysis aimed to investigate the global prevalence of antibiotic resistance among S. maltophilia isolates to the develop more effective therapeutic strategies.

METHOD

A systematic literature search was performed using the appropriate search syntax after searching Pubmed, Embase, Web of Science and Scopus databases (May 2023). Statistical analysis was performed using Pooled and the random effects model in R and the metafor package. A total of 11,438 articles were retrieved. After a thorough evaluation, 289 studies were finally eligible for inclusion in this systematic review and meta-analysis.

RESULT

Present analysis indicated that the highest incidences of resistance were associated with doripenem (97%), cefoxitin (96%), imipenem and cefuroxime (95%), ampicillin (94%), ceftriaxone (92%), aztreonam (91%) and meropenem (90%) which resistance to Carbapenems is intrinsic. The lowest resistance rates were documented for minocycline (3%), cefiderocol (4%). The global resistance rate to TMP-SMX remained constant in two periods before and after 2010 (14.4% vs. 14.6%). A significant increase in resistance to tigecycline and ceftolozane/tazobactam was observed before and after 2010.

CONCLUSIONS

Minocycline and cefiderocol can be considered the preferred treatment options due to low resistance rates, although regional differences in resistance rates to other antibiotics should be considered. The low global prevalence of resistance to TMP-SMX as a first-line treatment for S. maltophilia suggests that it remains an effective treatment option.

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.

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.

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

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

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

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

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

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

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

Clinical associations with carriage of pulmonary Stenotrophomonas maltophilia

Background:

Stenotrophomonas maltophilia causes opportunistic respiratory infections and is associated with declining lung function in patients with cystic fibrosis (CF). Risk factors for carrying S. maltophilia remain unclear.

Methods:

We conducted a retrospective study of patients yielding ⩾1 respiratory S. maltophilia isolate at the Oxford University Hospitals Trust between 2014 and 2019 and a cohort study of S. maltophilia carriage in CF patients attending annual review in 2018.

Results:

Seven hundred and forty isolates were identified from 238 patients (median 1.0 isolate/patient). Predisposing conditions included invasive ventilation (29.8%), CF (25.6%) and non-CF bronchiectasis (24.4%). The rates of Stenotrophomonas isolates and co-trimoxazole resistance were stable over time. About 10.8% of isolates were co-trimoxazole-resistant, with resistance more common in CF than in other diagnoses (29.5% vs 5.8%, p < 0.001). No clinical features were significantly associated with S. maltophilia carriage in the CF population.

Discussion:

We present new insight into the epidemiology of Stenotrophomonas colonisation/infection and identify increased co-trimoxazole resistance in CF isolates.

Phenotypic and Molecular Characteristics of the MDR Efflux Pump Gene-Carrying Stenotrophomonas maltophilia Strains Isolated in Warsaw, Poland

Simple Summary

Nosocomial infections caused by Stenotrophomonas maltophilia have been increasing worldwide. These bacteria are intrinsically resistant to most antibiotics. The underestimated resistance mechanism of Gram-negative rods is an overexpression of multidrug-resistant (MDR) efflux pumps. The aim of this study was to analyze the genetic diversity of isolates derived from various clinical materials, including blood, and the prevalence of MDR efflux pump genes and susceptibility profiles to the anti-S. maltophilia drugs. The research was conducted on 94 S. maltophilia isolates derived from hospitalized patients and outpatients in Warsaw, Poland. All isolates were susceptible to trimethoprim-sulfamethoxazole and minocycline, while 44/94 isolates demonstrated reduction in susceptibility to levofloxacin. A large genetic variation was observed among these isolates. However, a clonal relationship was revealed among two groups of bloodstream isolates from one hospital ward: (1) nine isolates, (2) six isolates. Moreover, the presence of genes encoding ten different efflux pumps from the resistance-nodulation-division family and the ATP-binding cassette family was shown in the majority of the 94 isolates. The obtained knowledge about the prevalence of efflux pump genes in clinical S. maltophilia strains makes it possible to predict the scale of the risk of resistance emergence in strains as a result of gene overexpression.

Abstract

An increase of nosocomial infections caused by Stenotrophomonas maltophilia strains has recently been observed all over the world. The isolation of these bacteria from the blood is of particular concern. In this study we performed the phenotypic and genotypic characterization of 94 S. maltophilia isolates, including isolates from patients hospitalized in a tertiary Warsaw hospital (n = 79) and from outpatients (n = 15). All isolates were found to be susceptible to trimethoprim-sulfamethoxazole and minocycline, while 44/94 isolates demonstrated a reduction in susceptibility to levofloxacin. A large genetic variation was observed among the isolates tested by pulsed-field gel electrophoresis. A clonal relationship with 100% similarity was observed between isolates within two sub-pulsotypes: the first included nine bloodstream isolates and the second involved six. Multilocus sequence typing showed two new sequence types (ST498 and ST499) deposited in public databases for molecular typing. Moreover, the presence of genes encoding ten different efflux pumps from the resistance-nodulation-division family and the ATP-binding cassette family was shown in the majority of the 94 isolates. The obtained knowledge about the prevalence of efflux pump genes in clinical S. maltophilia strains makes it possible to predict the scale of the risk of resistance emergence in strains as a result of gene overexpression.

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.

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.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Characterization of Novel Broad-Host-Range Bacteriophage DLP3 Specific to Stenotrophomonas maltophilia as a Potential Therapeutic Agent

A novel Siphoviridae phage specific to the bacterial species Stenotrophomonas maltophilia was isolated from a pristine soil sample and characterized as a second member of the newly established Delepquintavirus genus. Phage DLP3 possesses one of the broadest host ranges of any S. maltophilia phage yet characterized, infecting 22 of 29 S. maltophilia strains. DLP3 has a genome size of 96,852 bp and a G+C content of 58.4%, which is significantly lower than S. maltophilia host strain D1571 (G+C content of 66.9%). The DLP3 genome encodes 153 coding domain sequences covering 95% of the genome, including five tRNA genes with different specificities. The DLP3 lysogen exhibits a growth rate increase during the exponential phase of growth as compared to the wild type strain. DLP3 also encodes a functional erythromycin resistance protein, causing lysogenic conversion of the host D1571 strain. Although a temperate phage, DLP3 demonstrates excellent therapeutic potential because it exhibits a broad host range, infects host cells through the S. maltophilia type IV pilus, and exhibits lytic activity in vivo. Undesirable traits, such as its temperate lifecycle, can be eliminated using genetic techniques to produce a modified phage useful in the treatment of S. maltophilia bacterial infections.

Clinical characteristics and prognostic factors of patients with Stenotrophomonas maltophilia infections

INTRODUCTION:

Stenotrophomonas maltophilia earlier had limited pathogenic potential, but now with growing degree of immunosuppression in general population, it is being recognized as an important nosocomial pathogen.

METHODOLOGY:

A retrospective 7 years study was carried out to determine the clinical characteristics of all patients with Stenotrophomonas infections, antibiotic resistance pattern, and risk factors associated with hospital mortality. All patients with Stenotrophomonas culture positivity were identified and their medical records were reviewed. Risk factor associated with hospital mortality was analyzed.

RESULTS:

A total of 123 samples obtained from 88 patients were culture positive. Most patients presented with bacteremia (45, 51%) followed by pneumonia (37, 42%) and skin and soft tissue infections (6, 7%). About 23 of 88 Stenotrophomonas infected patients had co-infection. Percentage resistance to cotrimoxazole; 8 (5.4%) was lower than that for levofloxacin; 18 (12%). Twenty-eight patients died during hospital stay. Intensive Care Unit admission (P = 0.0002), mechanical ventilation (P = 0.0004), central venous catheterization (P = 0.0227), urethral catheterization (P = 0.0484), and previous antibiotic intake (P = 0.0026) were independent risk factors associated with mortality.

CONCLUSION:

Our findings suggest that Stenotrophomonas can cause various infections irrespective of patient's immune status and irrespective of potential source. Thus, Stenotrophomonas should be thought of as potential pathogen and its isolation should be looked with clinical suspicion.

Characteristics of Stenotrophomonas maltophilia infection in children in Sichuan, China, from 2010 to 2017

Stenotrophomonas maltophilia (S. maltophilia) is an important nosocomial bacterial pathogen. However, the clinical features of children with S. maltophilia infection, the predisposing factors, and the antibiotic susceptibility of the bacteria have not been fully evaluated.In this study, the data of children with S. maltophilia infection from the West China Second University Hospital of Sichuan University (Chengdu, China) between July 2010 and October 2017 were collected and analyzed. The clinical features of enrolled children, the predisposing factors, and the antibiotic susceptibility were reported.In total, infection of S. maltophilia was identified in 128 patients. Most of these patients were under 1 year old (67.2%) and were mainly diagnosed as pneumonia (69%). A large proportion had underlying diseases (45.3%), received immunosuppressive therapy (53.1%), had undergone invasive operations (41.4%), had a history of carbapenem antibiotics use within 7 days before culture acquisition (54.7%), history of intensive care unit (ICU) hospitalization within previous 30 days (34.4%), and other risk factors. In particular, invasive operation (95% confidence interval [CI]: 1.125-14.324, P = .032), especially mechanical ventilation (95% CI: 1.277-20.469, P = .021), and ICU admission (95% CI: 1.743-22.956, P = .005) were independent risk factors for the children to develop severe S. maltophilia infection. As for antibiotic susceptibility, trimethoprim sulfamethoxazole (TMP-SMX), piperacillin tazobactam, ticarcillin clavulanate, and ceftazidime exhibited strong antibacterial activities against S. maltophilia, the susceptibility rates were 97.5%, 86.7%, 92.9%, and 81.5%, respectively.We report the clinical features of children with S. maltophilia infection, the predisposing factors and the antibiotic susceptibility. TMP-SMX can continue to be the first choice for the treatment of S. maltophilia infection. Piperacillin tazobactam, ticarcillin clavulanate, and the third generation cephalosporins can be used as alternative drugs.

Stenotrophomonas Bacteremia Antibiotic Susceptibility and Prognostic Determinants: Mayo Clinic 10-Year Experience

Background

Stenotrophomonas maltophilia is a gram-negative, opportunistic infection that is usually hospital-acquired and associated with high morbidity and mortality. The reported increase in S. maltophilia infections is presumed to be due to an increase in the population at risk.

Methods

We retrospectively reviewed 10-year data for S. maltophilia bacteremia in hospitalized adults at our institution to determine the population at risk, sources of infection, common complications, antimicrobial susceptibility profiles, and clinical outcome trends over the past decade.

Results

Among the 98 patients analyzed, the most common source of infection was catheter-related (62, 63.3%). Most isolates (61, 65%) were resistant to ceftazidime; fewer were resistant to trimethoprim-sulfamethoxazole (TMP-SMX; 2, 2.1%) and levofloxacin (22, 23.4%). All-cause in-hospital mortality was 29.6% (29 patients). The highest mortality, 53.8%, was observed in pulmonary sources of bacteremia.

Conclusions

Although TMP-SMX continues to have reliable activity in our cohort, we noted resistance to TMP-SMX in patients with recent TMP-SMX exposure, including a case with developing resistance to TMP-SMX while on therapy.

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

BACKGROUND

Fluoroquinolones are a popular alternative to trimethoprim-sulfamethoxazole for Stenotrophomonas maltophilia infections.

OBJECTIVES

To compare the effects of fluoroquinolones and trimethoprim-sulfamethoxazole on mortality of S. maltophilia infections.

DATA SOURCES

PubMed and EMBASE.

STUDY ELIGIBILITY CRITERIA

Clinical studies reporting mortality outcomes of S. maltophilia infections.

PARTICIPANTS

Patients with clinical infections caused by S. maltophilia.

INTERVENTIONS

Fluoroquinolone monotherapy in comparison with trimethoprim-sulfamethoxazole monotherapy.

METHODS

Systematic review with meta-analysis technique.

RESULTS

Seven retrospective cohort and seven case-control studies were included. Three cohort studies were designed to compare the two drugs, whereas others had other purposes. A total of 663 patients were identified, 332 of which were treated with trimethoprim-sulfamethoxazole (50.1%) and 331 with fluoroquinolones (49.9%). Three cohort studies were designed to compare the effect of the two drugs, whereas the others had other purposes. Levofloxacin was most frequently used among fluoroquinolones (187/331, 56.5%), followed by ciprofloxacin (114/331, 34.4%). The overall mortality rate was 29.6%. Using pooled ORs for the mortality of each study, fluoroquinolone treatment (OR 0.62, 95% CI 0.39-0.99) was associated with survival benefit over trimethoprim-sulfamethoxazole treatment, with low heterogeneity (I² = 18%). Specific fluoroquinolones such as ciprofloxacin (OR 0.44, 95% CI 0.17-1.12) and levofloxacin (OR 0.78, 95% CI 0.48-1.26) did not show a significant difference in comparison with trimethoprim-sulfamethoxazole. In the sub-group analyses of adult and bacteraemic patients, significant differences in mortality were not observed between fluoroquinolones and trimethoprim-sulfamethoxazole.

CONCLUSIONS

Based on a meta-analysis of non-randomized studies, fluoroquinolones demonstrated comparable effects on mortality of S. maltophilia infection to trimethoprim-sulfamethoxazole, supporting the use of fluoroquinolones in clinical S. maltophilia infections. Although the pooled analysis of overall studies favoured fluoroquinolones over trimethoprim-sulfamethoxazole, the studies included were observational, and sub-group analyses of certain fluoroquinolone agents did not show statistical differences with trimethoprim-sulfamethoxazole. Randomized clinical studies are needed to address these issues.

Comparison of clinical characteristics of bacteremia from Elizabethkingia meningoseptica and other carbapenem-resistant, non-fermenting Gram-negative bacilli at a tertiary medical center

BACKGROUND

Acquired carbapenem resistance among non-fermenting Gram-negative bacilli (NFGNB), such as Pseudomonas aeruginosa and Acinetobacter calcoaceticus-Acinetobacter baumannii complex (ACB complex), is a serious problem in nosocomial infections. We previously reported that patients infected with the intrinsically carbapenem-resistant Elizabethkingia meningoseptica were associated with high mortality. However, little information is available regarding the clinical outcome of E. meningoseptica bacteremia when compared to that of other carbapenem-resistant NFGNB.

METHODS

We conducted an observational study that included consecutive patients with E. meningoseptica, carbapenem-resistant ACB complex, carbapenem-resistant P. aeruginosa, and Stenotrophomonas maltophilia bacteremia at a Taiwanese medical center in 2015. We compared the clinical characteristics and outcomes between patients with E. meningoseptica bacteremia and those with other carbapenem-resistant NFGNB bacteremia.

RESULTS

We identified 30 patients with E. meningoseptica, 71 with carbapenem-resistant ACB complex, 25 with S. maltophilia, and 17 with carbapenem-resistant P. aeruginosa bacteremia. The clinical characteristics, disease severity, and previous antibiotic exposures were similar between patients with bacteremia either due to E. meningoseptica or other carbapenem-resistant NFGNB. Patients with E. meningoseptica bacteremia had a higher rate of appropriate empirical antibiotics than those with other carbapenem-resistant NFGNB and was less associated with central venous catheterization. The 28-day mortality rates were similar between patients with E. meningoseptica and the other carbapenem-resistant NFGNB bacteremia (46.7% vs 46%, p = 0.949).

CONCLUSION

The mortality rate of E. meningoseptica bacteremia was as high as other carbapenem-resistant NFGNB infections. The emerging E. meningoseptica infection calls for active surveillance and continued awareness from clinical physicians for this serious carbapenem-resistant infection.

Overexpression of the Efflux Pumps SmeVWX and SmeDEF Is a Major Cause of Resistance to Co-trimoxazole in Stenotrophomonas maltophilia

Co-trimoxazole is one of the antimicrobials of choice for treating Stenotrophomonas maltophilia infections. Most works on the molecular epidemiology of the resistance to this drug combination are based on the analysis of sul genes. Nevertheless, the existence of clinical co-trimoxazole-resistant S. maltophilia isolates that do not harbor sul genes has been reported. To investigate potential mutations that can reduce the susceptibility of S. maltophilia to co-trimoxazole, spontaneous S. maltophilia co-trimoxazole-resistant mutants isolated under different co-trimoxazole concentrations were studied. All mutants presented phenotypes compatible with the overexpression of either SmeVWX (94.6%) or SmeDEF (5.4%). Indeed, the analysis of a selected set of strains showed that the overexpression of either of these efflux pumps, which was due to mutations in their regulators smeRv and smeT, respectively, was the cause of co-trimoxazole resistance. No other efflux pump was overexpressed in any of the studied mutants, indicating that they do not participate in the observed resistance phenotype. The analysis of mutants overexpressing or lacking SmeDEF or SmeVWX shows that SmeDEF contributes to the intrinsic and acquired resistance to co-trimoxazole in S. maltophilia, whereas SmeVWX only contributes to acquired resistance. It is important to highlight that all mutants were less susceptible to other antibiotics, including chloramphenicol and quinolones. Since both SmeVWX and SmeDEF are major determinants of quinolone resistance, the potential cross-selection of resistance to co-trimoxazole and quinolones, when either of the antimicrobials is used, is of particular concern for the treatment of S. maltophilia infections.

Stenotrophomonas maltophilia bacteremia and pneumonia at a tertiary-care oncology center: a review of 16 years

PURPOSE

The aim of this study was to describe the clinical characteristics and antimicrobial patterns of Stenotrophomonas maltophilia bloodstream infections (BSI) and pneumonia episodes in patients with cancer.

METHODS

Patients with S. maltophilia BSI or pneumonia admitted from 1 Jan. 2000 to 31 Dec. 2016 were identified at the Instituto Nacional de Cancerología (INCan), a tertiary-care oncology hospital in Mexico City.

RESULTS

During the study period, there were 171 isolates identified. The mean age of the whole group was 46.9 ± 17.4 years; 99 (57.9%) were women. There were 95 BSI: 64 ambulatory catheter-related BSI (CRBSI), 20 nosocomial CRBSI, and 11 secondary BSI. Mortality was higher in nosocomial CRBSI (40%) vs. that in ambulatory CRBSI (7.8%) (p = 0.001). There were 76 pneumonia episodes; all were nosocomial acquired; 46 (60.5%) ventilator-associated. From all the group, nine strains (5.2%) were resistant to sulfamethoxazole/trimethoprim/(SMX/TMP). At the first month, 54 patients (31.6%) have died, 38 due to pneumonia (70%) and 16 due to BSI (30%, p < 0.001). Multivariate analysis showed that removal of central venous catheter was associated with a favorable outcome in patients with bacteremia. For patients with pneumonia, age ≥ 65 years and inappropriate antimicrobial treatment were risk factors associated with 30-day mortality.

CONCLUSIONS

S. maltophilia related with ambulatory CRBSI have a better prognosis than other sources of BSI. Older patients with pneumonia who do not receive appropriate antibiotics have higher mortality. SMX/TMP is still the antibiotic of choice.

Risk factors for hospital acquisition of trimethoprim-sulfamethoxazole resistant Stenotrophomonas maltophilia in adults: A matched case-control study

BACKGROUND/PURPOSE

The emergence of trimethoprim-sulfamethoxazole resistant Stenotrophomonas maltophilia (TSRSM) represents a serious threat to patients. The aim of current study was to identify risk factors associated with hospital-acquired TSRSM occurrence in adult inpatients.

METHODS

We conducted a matched case-control study in Tri-Service General Hospital, Taipei, Taiwan. From January 2014 through June 2015, case patients with TSRSM and control patients with trimethoprim-sulfamethoxazole susceptible S. maltophilia (TSSSM) during hospitalization were identified. Control patients were matched with TSRSM cases for age (within five years), sex, and site of isolation at a ratio of 1:1.

RESULTS

A total of 266 patients were included in our study (133 cases and 133 matched controls). Bivariable analysis showed that previous exposure to fluoroquinolone [odds ratio (OR), 2.693; 95% confidence interval (CI, 1.492-5.884; p = 0.002)], length of intensive care unit stay (OR, 1.015 per day; 95% CI, 1.001-1.030; p = 0.041), and length of hospital stay (OR, 1.012 per day; 95% CI, 1.002-1.023; p = 0.018) prior to S. maltophilia isolation were associated with TSRSM occurrence. A multivariable analysis showed that previous exposure to fluoroquinolone (OR, 3.158; 95% CI, 1.551-6.430; p = 0.002) was an independent risk factor for TSRSM occurrence after adjustment.

CONCLUSION

Previous fluoroquinolone use was an independent risk factor for hospital-acquired TSRSM occurrence in adult inpatients, suggesting that judicious administration of fluoroquinolone may be important for limiting TSRSM occurrence.

Standard susceptibility testing overlooks potent azithromycin activity and cationic peptide synergy against MDR Stenotrophomonas maltophilia

OBJECTIVES

The Gram-negative bacillus Stenotrophomonas maltophilia (SM) is an emerging MDR opportunistic pathogen. Recent studies identify a potentially relevant activity of azithromycin against Gram-negative bacteria overlooked in standard bacteriological testing. We investigated azithromycin activity against SM in testing conditions incorporating mammalian tissue culture medium and host defence factors.

METHODS

MIC testing, chequerboard assays, time-kill assays and fluorescence microscopy were performed for azithromycin, the cationic peptide antibiotic colistin and the human defence peptide cathelicidin LL-37 alone or in combination in cation-adjusted Mueller-Hinton broth or mammalian tissue culture media. Azithromycin sensitization of SM to host immune clearance was tested in a human neutrophil killing assay and a murine pneumonia model.

RESULTS

We observed potent bactericidal activity of azithromycin against SM in mammalian tissue culture medium absent in bacteriological medium. Colistin and LL-37 strongly potentiated azithromycin killing of SM by increasing drug entry. Additionally, azithromycin sensitized SM to neutrophil killing and increased SM clearance in the murine pneumonia model.

CONCLUSIONS

Despite lack of activity in standard MIC testing, azithromycin synergizes with cationic peptide antibiotics to kill SM in medium mimicking tissue fluid conditions. Azithromycin, alone or in combination with colistin, merits further exploration in therapy of drug-resistant SM infections.

Update on infections caused by Stenotrophomonas maltophilia with particular attention to resistance mechanisms and therapeutic options

Stenotrophomonas maltophilia is a Gram-negative, biofilm-forming bacterium. Although generally regarded as an organism of low virulence, S. maltophilia is an emerging multi-drug resistant opportunistic pathogen in hospital and community settings, especially among immunocompromised hosts. Risk factors associated with S. maltophilia infection include underlying malignancy, cystic fibrosis, corticosteroid or immunosuppressant therapy, the presence of an indwelling central venous catheter and exposure to broad spectrum antibiotics. In this review, we provide a synthesis of information on current global trends in S. maltophilia pathogenicity as well as updated information on the molecular mechanisms contributing to its resistance to an array of antimicrobial agents. The prevalence of S. maltophilia infection in the general population increased from 0.8-1.4% during 1997-2003 to 1.3-1.68% during 2007-2012. The most important molecular mechanisms contributing to its resistance to antibiotics include β-lactamase production, the expression of Qnr genes, and the presence of class 1 integrons and efflux pumps. Trimethoprim/sulfamethoxazole (TMP/SMX) is the antimicrobial drug of choice. Although a few studies have reported increased resistance to TMP/SMX, the majority of studies worldwide show that S. maltophilia continues to be highly susceptible. Drugs with historically good susceptibility results include ceftazidime, ticarcillin-clavulanate, and fluoroquinolones; however, a number of studies show an alarming trend in resistance to those agents. Tetracyclines such as tigecycline, minocycline, and doxycycline are also effective agents and consistently display good activity against S. maltophilia in various geographic regions and across different time periods. Combination therapies, novel agents, and aerosolized forms of antimicrobial drugs are currently being tested for their ability to treat infections caused by this multi-drug resistant organism.

The efflux pump SmeDEF contributes to trimethoprim-sulfamethoxazole resistance in Stenotrophomonas maltophilia

Trimethoprim-sulfamethoxazole (co-trimoxazole) is one of the antimicrobials of choice for the treatment of Stenotrophomonas maltophilia infections. The analysis of mutants either lacking or overexpressing the efflux pump SmeDEF shows that this efflux pump contributes to intrinsic and acquired co-trimoxazole resistance in S. maltophilia. Since SmeDEF can extrude a variety of antibiotics, selection with such antimicrobials, including quinolones, might also select for S. maltophilia co-trimoxazole resistance.