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 Table of Contents  
Year : 2020  |  Volume : 8  |  Issue : 3  |  Page : 64-67

Stenotrophomonas maltophilia: An emerging pathogen in sepsis

Department of Microbiology, Bangalore Medical College and Research Institute, Bengaluru, Karnataka, India

Date of Submission13-Oct-2020
Date of Acceptance04-Nov-2020
Date of Web Publication25-Nov-2020

Correspondence Address:
Dr. J S Soumya
#809, Alpine Regency Apartment, 10th D main, Jayanagar 1st Block, Bengaluru, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/mjhs.mjhs_15_20

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Background: Stenotrophomonas maltophilia, once regarded as an organism of low virulence, has evolved as a significant opportunistic pathogen causing severe human infections in both hospital and community settings, especially among highly debilitated patients.
Objectives: (1) Identification of S. maltophilia in sepsis and (2) assessment of sensitivity pattern/minimum inhibitory concentration (MIC) of S. maltophilia and its multidrug resistance by VITEK 2 Compact system and by Kirby–Bauer (KB) disk diffusion method.
Materials and Methods: This is a retrospective laboratory-based study analysis conducted in a tertiary care center, i.e., Bangalore Medical College and Research Institute, from July 2018 to June 2019. Samples from clinically suspected sepsis patients were processed by standard microbiological methods. VITEK 2 compact (Biomerieux) was used for final identification and MIC. Antibiotic susceptibility was tested by KB disk diffusion method for cotrimoxazole (1.25/23.75 μg) and levofloxacin (5 μg) following the Clinical and Laboratory Standards Institute guidelines M100.
Results: Among 18,949 samples collected from suspected sepsis patients, during a 1-year period, 50 isolates were identified as S. maltophilia. Nineteen were isolated from blood; 6 from pus and ascitic fluid; 4 from cerebrospinal fluid, endotracheal aspirate, and pleural fluid; 1 from urine and cornea; and 4 from other sites. The organisms showed multidrug resistances and were sensitive to trimethoprim-sulfamethoxazole and levofloxacin.
Conclusion: S. maltophilia was found to be the third most common nonfermenters after Acinetobacter spp. and Pseudomonas aeruginosa with multidrug resistance. As its isolation is increasing, it is important to study the epidemiology, antimicrobial susceptibility profile, and clinical outcomes of these isolates.

Keywords: Clinical and Laboratory Standards Institute, Kirby–Bauer disk diffusion method, minimum inhibitory concentration, Stenotrophomonas maltophilia

How to cite this article:
Soumya J S, Kabbin JS, Ambica R. Stenotrophomonas maltophilia: An emerging pathogen in sepsis. MRIMS J Health Sci 2020;8:64-7

How to cite this URL:
Soumya J S, Kabbin JS, Ambica R. Stenotrophomonas maltophilia: An emerging pathogen in sepsis. MRIMS J Health Sci [serial online] 2020 [cited 2023 Oct 4];8:64-7. Available from: http://www.mrimsjournal.com/text.asp?2020/8/3/64/301479

  Introduction Top

Stenotrophomonas maltophilia, previously called Pseudomonas maltophilia or Xanthomonas maltophilia, has emerged as an important nosocomial pathogen in clinical environments.[1]

S. maltophilia is a motile nonfermentative, Gram-negative bacillus. The species is ubiquitous and has been isolated from a range of water sources including rivers, wells, bottled water, and sewage. A strain of S. maltophilia has also been shown to grow in a medium containing benzene, toluene, or ethylbenzene as the carbon source.[2] Members of the species are common food contaminants and have been isolated from frozen fish, milk, and meat carcasses.

It has been reported as etiological agents in bacteremia, ocular infection, endocarditis and respiratory tract infections (associated with cystic fibrosis), wound infection, and urinary tract infections. It is also an etiologic agent of meningitis, sepsis, skin, and soft-tissue infections, and it has been diagnosed with rare cases of pyomyositis.[3] Intensive care unit (ICU) stay, mechanical ventilation, previous antibiotic intake, and central venous and urinary catheterization were found to be independent risk factors for mortality by univariate analysis.

Clinical microbiologists have long recognized the importance of identifying the infectious microbial pathogens as the cause of disease in humans. The emergence of multidrug-resistant organisms (MDROs) found in nonclinical environments, the increasing reports of community-acquired infections, and the spread of these pathogens in the clinical setting have all underscored the need to monitor these organisms.[3] The increase in incidence of MDRO-associated infections has resulted in efforts to examine the possible sources of these pathogens.

Infections caused by S. maltophilia are difficult to treat because of their intrinsic resistance to a variety of antibiotics, ability to form biofilm, and production of various extracellular enzymes.[4] Cotrimoxazole and levofloxacin still remain the most effective treatment modality for Stenotrophomonas infections. However, drug resistance has been increasingly noted against this drug also.

The study aims to isolate S. maltophilia in clinical isolates of suspected sepsis cases received during July 2018–June 2019 and to determine the MIC by VITEK 2 Compact system (Biomerieux, France) and antibiotic susceptibility through Kirby–Bauer (KB) disk diffusion method as per the Clinical and Laboratory Standards Institute (CLSI) guidelines M100.[5]

  Materials and Methods Top

  • Study design: Retrospective study
  • Place of study: Infosys Central Laboratory, Bangalore Medical College and Research Institute
  • Study period: July 2018 to June 2019
  • Department where the work was conducted and name of the institution: Department of Microbiology, Bangalore Medical College and Research Institute
  • Sample size: 18,949
  • Inclusion criteria: Various samples from the infected sites in suspected sepsis cases
  • Exclusion criteria: Cases identified with S. maltophilia
  • Ethics permission: Yes
  • Informed consent from the participants: Yes
  • Statistical analysis: The results are expressed as the number of patients (%) for categorical variables.

  Results Top

A total of 18,949 samples were collected from suspected sepsis patients during a 1-year period, i.e., July 2018 to June 2019. 6316 (33.33%) were found to be pathogenic isolates, 5084 (80.4%) were Gram-negative organisms, 1439 (28.3%) were Gram-negative nonfermenters (GNNFs), and 50 (3.47%) were S. maltophilia. [Figure 1] shows the distribution of various pathogens.
Figure 1: The distribution of various pathogens from the samples

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Out of 50 isolates, 33 (66%) were from males and 17 (34%) were from females. [Figure 2] shows distribution as per gender.
Figure 2: Distribution as per gender

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Most of the patients were in the age group of 0–10 years (22) followed by 31–40 years (9). [Figure 3] and [Table 1] show the age-wise distribution of all patients.
Figure 3: Age-wise distribution of all patients

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Table 1: Age wise distribution of all patients

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In our study, out of 50 isolates, 19 were isolated from blood samples; 6 from pus and ascitic fluid; 4 from cerebrospinal fluid, endotracheal aspirate, and pleural fluid each; 1 from urine and cornea each; and 4 from samples from other sites.

[Figure 4] shows the isolation of S. maltophilia in various samples.
Figure 4: Isolates of Stenotrophomonas maltophilia from various samples

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Antibiotic susceptibility pattern (AST): Drug susceptibility among S. maltophilia isolates was determined by KB disk diffusion test against the following recommended antimicrobial agents (trimethoprim-sulfamethoxazole [TMP-SMX], 1.25/23.75 μg; minocycline, 30 μg; and levofloxacin, 5 μg) according to the CLSI guidelines M100.[5] As per the CLSI guidelines only, minimum inhibitory concentration (MIC) is determined against ticarcillin-clavulanate (sensitive, S ≤ 16/2: resistant, R ≥128/2), ceftazidime (S ≤8: R ≥ 32), minocycline (S ≤4: R ≥16), levofloxacin (S ≤2: R ≥ 8), TMP-SMX (S ≤2/38: R ≥ 4/76), and chloramphenicol (S ≤ 8: R ≥32) (CLSI M100, 2019).

TMP-SMX and levofloxacin are considered as the treatment of choice for S. maltophilia infections.

In our study, out of 50 isolates, 8 (16%) were resistant to all the antibiotics, 13 (26%) were sensitive to both TMP-SMX and levofloxacin, 20 (40%) were sensitive to only TMP-SMX, and 9 (18%) were sensitive to only levofloxacin.

[Figure 5] shows the AST of S. maltophilia in isolates.
Figure 5: Antibiotic susceptibility pattern of Stenotrophomonas maltophilia in isolates

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  Discussion Top

Herein, we report the retrospective study of samples received from suspected sepsis cases and S. maltophilia being isolated as the causative pathogen.

Our study population shares common features with previously published reports.

Isolates of S. maltophilia were 50 (3.47%) out of 1439 GNNFs in our 1-year study period.

In a study conducted by Lokart et al., 4.3% of S. maltophilia were isolated from 74,394 Gram-negative bacilli during the 12-year study period from 1993 to 2004.[6]

Study conducted by Malini et al., from Kolar, Karnataka; had a total of 193 Non fermenting Gram negative bacilli from 189 clinical specimens.  Stenotrophomonas maltophilia Scientific Name Search ed for 2.6% of total non fermenters during the study period, fromNovember 2005 and July 2006.[7]

In a study conducted by Arora et al., 3% of isolates were S. maltophilia from 18% (1781/9662) GNNFs from blood cultures during January–September 2011.[8]

A retrospective study conducted by Charu nayar, over a period of 8 months i.e., October 2015 to May 2016, 23 isolates of Stenotrophomonas maltophilia were isolated from 414 of non- fermenting Gram negative bacilli. Out of the 23 patient isolates, 18 (78.2%) were males and 5 (21.7%) were females. In our study, among the 50 isolates of Stenotrophomaonas maltophilia, 66% were males and 34% were females.[9]

In this study, isolates were higher between the age group of 0 and 10 years, followed by 31–40 years, whereas in a study conducted by Nonikarajkumari, the median age (interquartile range) of the participants was 38 years (1–75) among the patients whose samples yielded S. maltophilia.[9]

Isolates were higher in blood samples, i.e., 19 out of 50 isolates, which were similar to the studies conducted by Nonikarajkumari and Aitekin Cikman.[10]

The results of our study were similar to a study conducted by Charu Nayar; 70.5% of strains were susceptible to levofloxacin, 91.3% were sensitive to TMP-SMX, and 8.6% were resistant.[9]

Chawla et al. reported 78.8% susceptibility for levofloxacin and 72.7% for TMP-SMX.[11]

S. maltophilia is well known to be resistant to several antibiotics that are commonly used empirically for nosocomial infections. Mechanisms of resistance include production of beta-lactamase, efflux, biofilm formation, and aminoglycoside-modifying enzyme activity.[12]

  Conclusion Top

S. maltophilia has gained importance since the past decade, especially in the ICU setting with the growing level of immunosuppression, and has become the third most common GNNF responsible for nosocomial infections after P. aeruginosa and Acinetobacter spp.

To combat the increasing incidence of S. maltophilia infections in hospitals and clinics, education to increase the awareness of health-care personnel is a key step in preventing the transmission and spread of this opportunistic pathogen.

Its isolation in samples should be looked at with clinical suspicion and should not be disregarded as a mere commensal.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Stenol E, Des Jardin J, Stark, PC. Attributable mortality of Stenotrophomonas maltophilia bacteremia. Clin Infect Dis 2002;34:1653-6.  Back to cited text no. 1
Cheong HS, Lee JA, Kang CI, Chung DR, Peck KR, Kim ES, et al. Risk factors for mortality and clinical implications of catheter-related infections in patients with bacteraemia caused by Stenotrophomonas maltophilia. Int J Antimicrob Agents 2008;32:538-40.  Back to cited text no. 2
Adegoke AA, Stenström TA, Okoh AI. Stenotrophomonas maltophilia as an emerging ubiquitous pathogen: Looking beyond contemporary antibiotic therapy. Front Microbiol 2017;8:2276.  Back to cited text no. 3
Brooke JS. Stenotrophomonas maltophilia: An emerging global opportunistic pathogen. Clin Microbiol Rev 2011;25:2-41.  Back to cited text no. 4
Clinical and Laboratory Standards Institute (CLSI). Performance Standards for Antimicrobial Susceptibility Testing; 22nd Informational Supplement M100-S22. Wayne, USA: Clinical and Laboratory Standards Institute; 2019.  Back to cited text no. 5
Lockhart SR, Abramson MA, Beekmann SE, Gallagher G, Riedel S, Diekema DJ, et al. Antimicrobial resistance among Gram-negative bacilli causing infections in intensive care unit patients in the United States between 1993 and 2004. J Clin Microbiol 2007;45:3352-9.  Back to cited text no. 6
Malini A, Deepa E, Gokul B, Prasad S. Nonfermenting gram-negative bacilli infections in a tertiary care hospital in Kolar, Karnataka. J Lab Physicians 2009;1:62-6.  Back to cited text no. 7
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8. Arora S, Gautam V, Ray P. Changing susceptibility patterns of nonfermenting Gram-negative bacilli. Indian J Med Microbiol 2012;30:485-6.  Back to cited text no. 8
Nayyar C, Thakur P, Tak V, Saigal K. Stenotrophomonas maltophilia: An emerging pathogen in paediatric population. J Cli Diag Res 2017;11:08-11.  Back to cited text no. 9
Nonika R, Mathur P, Gupta AK, Sharma K, Misra MC. Epidemiology and outcomes of Stenotrophomonas maltophilia and Burkholderia cepacia infections among trauma patients of India: A five year experience. J Infect Prev 2014;16:103-10.  Back to cited text no. 10
Chawla K, Vishwanath S, Munim FC. Nonfermenting gram-negative bacilli other than Pseudomonas aeruginosa and Acinetobacter spp. causing respiratory tract infections in a tertiary care center. J Glob Infect Dis 2013;5:144-8.  Back to cited text no. 11
Sood S, Vaid VK, Bhartiya H. Meningitis due to Stenotrophomonas maltophilia after a neurosurgical procedure. J Clin Diagn Res 2013;8:1696-7.  Back to cited text no. 12


  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]

  [Table 1]


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