Maltophilia Isolation Research Articles

A-254 Increase of Stenotrophomonas maltophilia Isolates Non-Susceptible to Trimethoprim-Sulfamethoxazole and/or Levofloxacin at Brazilian Hospitals

Abstract Background Stenotrophomonas maltophilia is an emerging multidrug-resistant pathogen that exhibits intrinsic and acquired resistance to a wide variety of antimicrobial agents such as β-lactams, aminoglycosides, quinolone, tetracyclines and disinfectants. In addition to that, the increased resistance to sulfamethoxazole/trimethoprim (SMX/TMP) and Levofloxacin has been reported in the past few years, leading to few therapeutic options. This study aimed to describe the increase of Stenotrophomonas maltophilia clinical isolates recovered from Brazilian hospitals over a 6-year analysis (January 2018 to December 2023). Methods This study design was a retrospective, observational analysis based on microbiological data of emergent BGN-NF isolates detected in several Brazilian tertiary hospitals. The bacterial identification was performed by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF/MS) and the antimicrobial susceptibility profile to trimethoprim-sulfamethoxazole and levofloxacin was determined using disk-diffusion method and epsilometer method, respectively. Only one sample per patient was considered in this analysis. Results During the 6 year period, a total of 1,706 (2018; 221), (2019; 203), (2020; 294), (2021; 276), (2022; 294) and (2023; 418) Stenotrophomonas maltophilia strains were isolated from blood (n=626), respiratory tract (n=365), fluid and secretion (n=235), skin and soft tissue (n=162), urine (n=132), catheter tip (n=112), swab (n=36), bone fragment (n=29) and cerebrospinal fluid (n=9). The major frequency of S. maltophilia isolation occurred among man (52.6%) and the main age range was over 60 years (42.7%), while 0-10 comprised 16.6% of cases. Compared the 6-years period, the resistance rate to trimethoprim-sulfamethoxazole was 2.7%; 5.4%; 5.8%; 2.2%; 5.8%; 7.9% and levofloxacin was 3.6%; 3.4%; 3.1%; 3.3%; 1.7%; 2.9%, respectively. The resistance rate to trimethoprim-sulfamethoxazole and levofloxacin, simultaneously, was 0.23%. Conclusions The incidence rate of S. maltophilia infections has increased significantly, especially in the last year, followed by an increase in the pattern of resistance to trimethoprim-sulfamethoxazole. Regarding trimethoprim-sulfamethoxazole and levofloxacin co-resistance, very low rates were detected in our analysis. Our data point to a scenario wherein the presence of S. maltophilia may have been intensified by the covid-19 pandemic. Regional surveillance reports are extremely important and should be out to understand some aspects of the dynamics of bacterial resistance in both hospital and community settings.

The airway microbiome of persons with cystic fibrosis correlates with acquisition and microbiological outcomes of incident Stenotrophomonas maltophilia infection.

Chronic infection with Stenotrophomonas maltophilia in persons with cystic fibrosis (pwCF) has been linked to an increased risk of pulmonary exacerbations and lung function decline. We sought to establish whether baseline sputum microbiome associates with risk of S. maltophilia incident infection and persistence in pwCF. pwCF experiencing incident S. maltophilia infections attending the Calgary Adult CF Clinic from 2010-2018 were compared with S. maltophilia-negative sex, age (+/-2 years), and birth-cohort-matched controls. Infection outcomes were classified as persistent (when the pathogen was recovered in ≥50% of cultures in the subsequent year) or transient. We assessed microbial communities from prospectively biobanked sputum using V3-V4 16S ribosomal RNA (rRNA) gene sequencing, in the year preceding (Pre) (n = 57), at (At) (n = 22), and after (Post) (n = 31) incident infection. We verified relative abundance data using S. maltophilia-specific qPCR and 16S rRNA-targeted qPCR to assess bioburden. Strains were typed using pulse-field gel electrophoresis. Twenty-five pwCF with incident S. maltophilia (56% female, median 29 years, median FEV1 61%) with 33 total episodes were compared with 56 uninfected pwCF controls. Demographics and clinical characteristics were similar between cohorts. Among those with incident S. maltophilia infection, sputum communities did not cluster based on infection timeline (Pre, At, Post). Communities differed between the infection cohort and controls (n = 56) based on Shannon Diversity Index (SDI, p = 0.04) and clustered based on Aitchison distance (PERMANOVA, p = 0.01) prior to infection. At the time of incident S. maltophilia isolation, communities did not differ in SDI but clustered based on Aitchison distance (PERMANOVA, p = 0.03) in those that ultimately developed persistent infection versus those that were transient. S. maltophilia abundance within sputum was increased in samples from patients (Pre) relative to controls, measuring both relative (p = 0.004) and absolute (p = 0.001). Furthermore, S. maltophilia abundance was increased in sputum at incident infection in those who ultimately developed persistent infection relative to those with transient infection, measured relatively (p = 0.04) or absolute (p = 0.04), respectively. Microbial community composition of CF sputum associates with S. maltophilia infection acquisition as well as infection outcome. Our study suggests sputum microbiome may serve as a surrogate for identifying infection risk and persistence risk.

1704. Stenotrophomonas maltophilia Infection in a Neonatal Intensive Care Unit (NICU): A Retrospective Study of Risk Factors and Outcomes in an Inner-City Hospital

Abstract Background Stenotrophomonas maltophilia is an aerobic, non-fermenting, Gram-negative bacillus associated with opportunistic and multi-drug resistant infections. The objective of this study was to identify risk factors and outcomes associated with S. maltophilia isolation or infection in a level IIIB neonatal intensive care unit (NICU). Methods This was a retrospective matched case-control study. Cases were matched 2:1 for birth weight, gestational age, and year of NICU admission. The Chi-square test and Fisher’s exact test were used for comparisons of categorical variables. Continuous variables were analyzed with the Mann-Whitney U test. Results A total of 15 S. maltophilia isolates were identified from 15 neonates between January 1, 2008 and April 1, 2020 and matched to 30 controls. Median birth weight and gestational age of the cases was 675 g (IQR, 522.5-997.5 g) and 26 weeks (IQR, 24.86-27.14 weeks), respectively. The trachea was the most frequent site of isolation (9 of 15 isolates); colonization was suspected in 2 cases. Other sites included blood (1 case), conjunctiva (2 cases), and peritoneum (3 cases). The following factors were associated with risk of isolation or infection in cases compared to controls: total days of antibiotic exposure (24 vs 15 days, P = 0.01), total number of antibiotic courses (3 vs 2.5, P = 0.043), total days of broad-spectrum antibiotic exposure (19 vs 9.25 days, P = 0.015), and total days of meropenem exposure (9 vs 3 days, P = 0.008). Total length of NICU stay was significantly longer among cases versus controls (134 vs 68.5 days, P = 0.006). Mortality rate was also significantly higher in cases versus controls (N = 15, 33.33% vs N = 30, 0%; P < 0.001); 3 of 3 infants with peritoneal infection died. All 15 isolates were initially susceptible to levofloxacin, and 14 were susceptible to trimethoprim-sulfamethoxazole. Conclusion Broad-spectrum antibiotic exposure, especially to meropenem, may lead to selection of resistant bacteria and promote S. maltophilia colonization and infection. S. maltophilia isolation or infection was associated with increased length of NICU stay and mortality. Disclosures All Authors: No reported disclosures

<i>Stenotrophomonas maltophilia</i> Infection in Trauma and Orthopedic Patients: Clinical Experience and Review

Background. Stenotrophomonas maltophilia (S. maltophilia) is a gram-negative non-fermenting bacillus and is a rare pathogen of orthopedic infection. Due to the relatively low virulence of S. maltophilia, many clinicians are still faced with the question of whether this bacterial species is simply a colonizing agent or the true cause of infection.
 Aim of the study to raise the awareness of practitioners about S. maltophilia as a rare pathogen of orthopedic infection.
 Methods. A retrospective analysis was performed concerning the frequency of S. maltophilia isolation from patients treated at the Vreden Center for periprosthetic infection and/or osteomyelitis from January 1, 2009 to October 31, 2022. The literature search by keywords was carried out in the PubMed/MEDLINE, Scopus, eLIBRARY, and Cyberleninka databases. The search retrieved 587 articles published in Russian or English over the period from 2012 to November 2022.
 Results. During the study period, 9 cases of orthopedic monoinfection with S. maltophilia were identified in 9 patients aged 36 to 83 years. At the time of admission, no leukocytosis was detected in patients, and only 2 of 9 patients had elevated C-reactive protein level. S. maltophilia is naturally resistant to many broad-spectrum antibiotics. Co-trimoxazole is considered the drug of choice for the treatment of S. maltophilia infection. The limited choice of drugs for targeted therapy, the presence of multiple determinants of antibiotic resistance, the existence of microbial associations and patient risks including implantation, chronic nature of infection, elderly age, as well as the presence of significant concomitant somatic pathology can lead to the ineffectiveness of the ongoing treatment of infections caused by S. maltophilia. Our experience shows that in the case of sensitivity of S. maltophilia strain to co-trimoxazole it is possible to prescribe this drug for a long course as monotherapy, provided that the radical surgical treatment of the focus is performed.

Role of Stenotrophomonas maltophilia isolation in patients with non-CF bronchiectasis

Stenotrophomonas maltophilia is a bacteria whose role in patients with cystic fibrosis (CF) bronchiectasis has been previously studied; little is known about its role in non-CF bronchiectasis. Aim of our study is to investigate the risk factors for S. maltophilia acquisition and its clinical impact on bronchiectasis patients. A retrospective observational cohort study enrolling patients attending the Bronchiectasis Clinic at the Royal Infirmary of Edinburgh, Scotland, UK. A total of 167 bronchiectasis patients undergoing intravenous (IV) antibiotic therapy were selected and divided according to single or chronic S. maltophilia isolation in sputum. The risk factors and prognostic impact were studied. Single isolation was independently associated with lower baseline % predicted forced expiratory volume in 1 s [odds ratio (OR) 0.98; 95% confidence interval (CI) 0.970-1.044; P = 0.025] and with less radiological involvement (OR 0.379; 95% CI 0.175-0.819; P = 0.01). Chronic isolation was associated with the number of IV antibiotic courses in the year before and after the first isolation (OR 1.2; 95% CI 1.053-1.398; P = 0.007) and with the absence of Pseudomonas aeruginosa colonization (OR 0.207; 95% CI 0.056-0.764; P = 0.02). In the chronic isolation group, there were more exacerbations and more need of IV antibiotics in the year after the first isolation. Poor lung function is the main independent risk factor for single isolation of S. maltophilia. For chronic colonization, the main independent risk factor is the number of IV antibiotic courses and the absence of P. aeruginosa chronic colonization. Only when chronically present, S. maltophilia had a clinical impact with more exacerbations.

Treatment Outcomes of Stenotrophomonas maltophilia Bacteremia in Critically Ill Children: A Multicenter Experience.

Stenotrophomonas maltophilia is a gram-negative opportunistic bacterium that may cause a myriad of clinical diseases in immunocompromised individuals. We aimed to describe the clinical characteristics, risk factors, mortality, and treatment of S. maltophilia bacteremia in critically ill children, a topic on which data are sparse. A multicenter observational retrospective study in which medical charts of critically ill children with S. maltophilia bacteremia were reviewed between 2012 and 2017. Data were collected from each of the four largest PICUs nationwide, allocated in tertiary medical centers to which children with complex conditions are referred regularly. A total of 68 suitable cases of S. maltophilia bacteremia were retrieved and reviewed. The total occurrence rate of S. maltophilia isolation had increased significantly during the study period (r = 0.65; p = 0.02). The crude mortality was 42%, and the attributed mortality was 18%. Significant risk factors for mortality were a longer length of hospital stay prior to infection (33 d in nonsurvivors vs 28 in survivors; p = 0.03), a nosocomial source of infection (p = 0.02), presentation with septic shock (p < 0.001), and treatment with chemotherapy (p = 0.007) or carbapenem antibiotics (p = 0.05) prior to culture retrieval. On multivariate analysis, septic shock (odds ratio, 14.6; 95% CI, 1.45-147.05; p = 0.023) and being treated with chemotherapy prior to infection (odds ratio, 5.2; 95% CI, 1.59-17.19; p = 0.006)] were associated with mortality. The combination of ciprofloxacin, trimethoprim-sulfamethoxazole, and minocycline resulted in the longest survival time (p < 0.01). The significant attributed mortality associated with S. maltophilia bacteremia in critically ill children calls for an aggressive therapeutic approach. The findings of this investigation favor a combination of trimethoprim-sulfamethoxazole, ciprofloxacin, and minocycline.

Management of Stenotrophomonas maltophilia Infections in Critically Ill Children.

Stenotrophomonas maltophilia is a life-threatening nosocomial pathogen with profound multidrug-resistant attributes. It is associated with high mortality, particularly in immunocompromised patients. Data on therapy for S. maltophilia infections are scarce, especially in children hospitalized in intensive care settings (pediatric intensive care unit). A retrospective chart review of pediatric patients with isolates of S. maltophilia hospitalized over a 5-year period in 2 pediatric intensive care units. Thirty-one patients and 91 isolates from blood, respiratory secretions and soft tissues were identified and reviewed. The overall incidence of S. maltophilia infections increased during the study period (P = 0.003). The all-cause crude mortality was 61%, and the attributed mortality was approximately 16%. Risk factors associated with mortality included longer hospitalization before infection (P = 0.002), septic shock (P = 0.003), mechanical ventilation (P = 0.004), an indwelling central vein catheter (P = 0.03) and prior use of steroids (P = 0.04) and carbapenems (P = 0.004). On multivariate analysis, mortality was associated with mechanical ventilation (P = 0.02) and preinfection hospitalization days (P = 0.01). Combination treatment of trimethoprim and sulfamethoxazole, ciprofloxacin and/or minocycline significantly extended survival time (P < 0.001). The method of treatment did not significantly affect the interval between S. maltophilia isolation to resolution of infection (P = 0.200). Combinations of trimethoprim and sulfamethoxazole, ciprofloxacin and minocycline are proposed for pediatric intensive care unit patients harboring S. maltophilia. Meticulous evaluation of central vascular access and prior treatment with carbapenems are indicated, especially for mechanically ventilated and septic children.

Resurgence of Global Opportunistic Multidrug-resistant Stenotrophomonas maltophilia.

Context:Stenotrophomonas maltophilia is a known nosocomial pathogen which is intrinsically resistant to multiple antibiotics. In India, S. maltophilia infection has only few case reports.Aim:To determine the incidence of S. maltophilia infection from clinical isolates based on the specimen type, antibiotic susceptibility pattern, and impact on outcome.Settings and Design:One-year retrospective study was done at a tertiary liver care center.Methods:Patients with S. maltophilia isolation in clinical samples were selected. Serial levels of serum procalcitonin and total leukocyte count were recorded. Environmental surveillance was done from the wards of S. maltophilia isolation as part of routine practice.Statistical Analysis:Continuous data were compared using Kruskal–Wallis test/Mann–Whitney test. The categorical data were compared by Chi-square/Fisher's exact test, wherever necessary. Besides this, an appropriate analysis like survival was carried out at the time of data analysis.Results:One hundred isolates were obtained from eighty patients of six wards. The greatest number (44/100, 44%) were from the Liver Coma Intensive Care Unit and the lowest (3/100) from the day care. Isolation from the respiratory samples was 1.32% and bloodstream infection 0.6%. Of 100 isolates, 12 (12%) were resistant to both trimethoprim–sulfamethoxazole and levofloxacin.Conclusion:S. maltophilia was effectively isolated from the hospital environment, with two of hand impression and three of water samples’ positive. Patients with respiratory infection had most S. maltophilia isolates. Antibiotic susceptibility revealed more resistance than reported in this region.

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

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. 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. 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. 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.

Stenotrophomonas maltophilia Pseudo-outbreak at a University Hospital Bronchoscopy Unit in Turkey.

Stenotrophomonas maltophilia is an opportunistic pathogen found predominantly in the environment and hospital setting. Invasive procedures and treatment methods, instruments used for diagnosis and irrational antibiotic use play major roles in the spread of this pathogen. The study aimed to evaluate consecutive S maltophilia isolation from bronchoalveolar lavage samples during bronchoscopy procedure during a week. Four patients consecutively had S maltophilia isolated during bronchoscopy between September 8 and 15, 2012. The identification of the isolates and their antibiotic susceptibility were studied by automated Vitek version 2.0 (Biomerieux, France) system. The clonal relationship between the isolates was studied by enterobacterial repetitive intergenic consensus (ERIC) polymerase chain reaction (PCR). Four consecutive S maltophilia isolates had identical band patterns and showed clonal relatedness. Bronchoscopy is a common invasive procedure that is utilized in chest diseases departments and intensive care units (ICUs). Contamination may take place due to inappropriate use and cause spread of infectious pathogens. In the current study, we detected consecutive S maltophilia strains with identical band patterns isolated within a week. After appropriate disinfection and cleaning procedures, no further isolation was detected.

돼지 정액에서 분리된 Stenotrophomonas maltophilia 확인을 위한 PCR 기법 개발 및 분리 균주의 항생제 감수성 양상

Bacteria are frequently contaminated during the collection and processing procedures of boar semen. Of the contaminants, Stenotrophomonas (S.) maltophilia is a Gram-negative bacterium that is widely distributed in a variety of habitats. Although PCR assays have been developed for the detection of S. maltophilia, they cross-react with some species of Xanthomonas. In this study, we designed a primer set for the detection of S. maltophilia in order to target the chiA (GenBank accession no. NC_010943) gene. The specific PCR products were amplified from S. maltophilia only, not from other tested strains that are frequently found in semen. The detection limit of the PCR was 1.5×10³ CFU/ml with pure-cultured S. maltophilia and 1.5×10⁴ CFU/ml with S. maltophilia spiked in semen. Twenty-six (5.9%) S. maltophilia were isolated from 440 semen samples. The PCR results exhibited 98.9% agreement with a comparison of S. maltophilia isolation. Also, the sensitivity and specificity of the PCR were 100% and 98.7%, respectively. In the antimicrobial susceptibility test, S. maltophilia isolates were highly susceptible to enrofloxacin and florfenicol, while the majority of them were resistant to amoxicillin/clavulanic acid, apramycin, ceftiofur, penicillin, and spectinomycin. These results indicated that the PCR using the chiA gene was proven to be reliable and effective for the detection of S. maltophilia with high levels of sensitivity and specificity.

Stenotrophomonas maltophilia in Cystic Fibrosis

Stenotrophomonas maltophilia is one of the more common multidrug-resistant organisms isolated from the respiratory tract of patients with cystic fibrosis (CF), but the effect of chronic S. maltophilia infection on CF lung disease is unknown. To determine the impact of chronic S. maltophilia infection on lung disease in CF. We developed a serologic assay specific for S. maltophilia and in a cross-sectional study, measured serum antibodies to S. maltophilia in patients with CF to determine if a definition of chronic S. maltophilia isolation based on culture results corresponded to an immunologic response (serologic study). We then used this validated definition to examine the effect of chronic S. maltophilia on the severity of lung disease in a retrospective cohort study using the Toronto CF Database from 1997-2008 (cohort study). Serum antibody levels to S. maltophilia were measured in 179 patients with CF. Patients with chronic S. maltophilia had significantly higher mean antibody levels to S. maltophilia flagellin (P < 0.0001) and whole cell (P = 0.0004) compared with patients with intermittent or no S. maltophilia. The cohort study included 692 patients with an average follow-up of 8.3 years. In an adjusted log linear model, patients with chronic S. maltophilia infection had a significantly increased risk of pulmonary exacerbation requiring hospitalization and antibiotics compared with patients who had never had S. maltophilia (relative risk = 1.63; P = 0.0002). Chronic S. maltophilia infection in patients with CF is associated with a specific immune response to this organism and is an independent risk factor for pulmonary exacerbations.

P1535 Risk factors for Stenotrophomonas maltophilia isolation from patients with cysticfibrosis

P1535 Risk factors for Stenotrophomonas maltophilia isolation from patients with cysticfibrosis

Is the prevalence of Stenotrophomonas maltophilia isolation and nosocomial infection increasing in intensive care units?

The study presented here was conducted over a period of 4 years (2001-2004) to investigate changes in the number of S. maltophilia isolates detected per 1,000 patient days and to look at the incidence density of nosocomial infections caused by S. maltophilia. The analysis was based on data provided by 34 German intensive care units participating continuously in the national project "Surveillance of Antimicrobial Use and Resistance in ICUs"; 31 of these ICUs reported nosocomial infections to the German infection surveillance system, KISS, during the study period.

Stenotrophomonas maltophilia: antimicrobial resistance and molecular typing of an emerging pathogen in a Turkish university hospital

Despite its limited pathogenicity, Stenotrophomonas maltophilia is an emerging nosocomial pathogen. This study investigated the isolation frequency, antimicrobial resistance and genotypic relationships of 205 S. maltophilia isolates from 188 patients in a university hospital between 1998 and 2003. Susceptibility profiles for 11 antimicrobial agents were determined by the NCCLS agar dilution method for non-fermentative bacteria, while enterobacterial repetitive intergenic consensus sequence (ERIC)-PCR and pulsed-field gel electrophoresis (PFGE) were used for genotyping of the isolates. Of the 205 isolates, 56.1% were isolated in the last 2 years of the study. The risk of S. maltophilia isolation was higher in intensive care units, S. maltophilia was isolated mostly (86.8%) after hospitalisation for >or= 48 h, and 90.4% of the patients had underlying diseases. Resistance levels were>60% for all antimicrobial agents tested except co-trimoxazole. High genetic diversity was found among the S. maltophilia isolates, and cross-infection with S. maltophilia was not common. Although ERIC-PCR revealed fewer genotypes than PFGE, it proved to be a rapid and easy method for S. maltophilia genotyping, and was more economical than PFGE.

Factors Affecting the Incidence of Stenotrophomonas maltophilia Isolation in Cystic Fibrosis

To identify factors predisposing cystic fibrosis (CF) patients to Stenotrophomonas maltophilia infection and to determine whether coinfection with S maltophilia affects the clinical response to therapy with tobramycin solution for inhalation (TSI), 300 mg bid. Retrospective review of data collected from two identical, 6-month, randomized, placebo-controlled trials. Sixty-nine CF centers in the United States. Active drug administration of 300 mg TSI. Five hundred twenty CF patients with chronic Pseudomonas aeruginosa endobronchial infections. A logistic regression analysis identified factors contributing to increased S maltophilia isolation frequency. In this multivariate analysis, the only significant predictors of S maltophilia isolation during the last month of the trial were the concomitant use of oral quinolones (primarily ciprofloxacin; p = 0.0015) and S maltophilia isolation prior to treatment (p < 0.0001). Treatment group, gender, age, use of systemic or inhaled steroids, use of oral sulfonamide, IV cephalosporins, or penicillin antibiotics, baseline FEV(1) percent predicted, and pretreatment Aspergillus isolation were not significant predictors of subsequent S maltophilia infection. In addition, S maltophilia-positive culture frequency was compared to the change in pulmonary function. Patients who either never had culture results positive for S maltophilia or who were positive at <25% of observations had greater clinical response to TSI at the final study visit compared to patients who were positive at > or = 25% of observations. TSI therapy did not result in a greater risk for isolation of S maltophilia than standard care alone. In contrast, oral quinolone antibiotic use during the trial was associated with a 2.7-fold increased risk of having a culture positive for S maltophilia (p = 0.0015). The use of TSI to suppress P aeruginosa resulted in improved lung function, regardless of S maltophilia culture frequency. However, improvement was not as great among patients who were persistently coinfected with S maltophilia.