Abstract
ObjectiveThe purpose of the present study was to investigate the antimicrobial susceptibility pattern, biofilm production, and the presence of biofilm genes among the S. maltophilia clinical isolates. A total of 85 clinical isolates of S. maltophilia were collected from patients referred to several hospitals. Susceptibility to antibiotics was investigated by disc diffusion method according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI). By the crystal violet staining method, the capability of biofilm formation was examined. The genes associated with biofilm production were investigated by the PCR-sequencing techniques.ResultsAll isolates were resistant to doripenem, imipenem, and meropenem. Minocycline, trimethoprim/sulfamethoxazole and levofloxacin exhibited the highest susceptibility of 100%, 97.65%, and 95.29%, respectively. The results of crystal violet staining assay showed that all isolates (100%) form biofilm. Moreover, 24 (28.23%), 32 (37.65%), and 29 (34.12%) of isolates were categorized as weak, moderate, and strong biofilm producers, respectively. Biofilm genes including rpfF, spgM and rmlA had an overall prevalence of 89.41% (76/85), 100% (85/85) and 84.71% (72/85), respectively. Rational prescribing of antibiotics and implementation of infection control protocols are necessary to prevent further infection and development of antimicrobial resistance. Combination strategies based on the appropriate antibiotics along with anti-biofilm agents can also be selected to eliminate biofilm-associated infections.
Highlights
Stenotrophomonas maltophilia, previously known as Pseudomonas maltophilia or Xanthomonas maltophilia, has become nowadays a major opportunistic pathogen in hospitalized or immunocompromised patients worldwide [1]
The rmlA gene encodes glucose-1-phosphate thymidyltransferas that is involved in LPS/Extracellular matrix polysaccharides (EPS)-coupled biosynthetic pathway It is reported that mutations in rmlA and rpfF genes resulted in reduced biofilm formation in S. maltophilia [4, 19]
Antimicrobial susceptibility The results of susceptibility testing on planktonic cells showed that approximately 100%, 96%, 96%, 36.58%, 2.35% of the S. maltophilia isolates were resistant to imipenem, doripenem, meropenem, ceftazidime and SMX/TMP, respectively
Summary
Patients and bacterial isolates During one-year period, 85 S. maltophilia isolates were gathered from several health centers in Tehran, Iran. Most of the S. maltophilia (90.03%) were isolated from the blood, while the rest (9.97%) were from the cough swabs. Antimicrobial susceptibility The results of susceptibility testing on planktonic cells showed that approximately 100%, 96%, 96%, 36.58%, 2.35% of the S. maltophilia isolates were resistant to imipenem, doripenem, meropenem, ceftazidime and SMX/TMP-, respectively. Levofloxacin and minocycline (95.29% and 100% susceptibile, respectively) exhibited the highest activity against S. maltophilia, with a rate of (Table 2). Biofilm‐encoding genes The frequency of biofilm-related genes among the S. maltophilia isolates was generally as high as 89.41%, 100%, and 84.71% for rmlA, spgM and rpfF genes, respectively (Fig. 1). S. maltophilia isolates with spgM + /rpfF + /rmlA + genotype showed strong or moderate biofilm-producer phenotype
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