Antibiotic resistance, biofilm formation, and biofilm-associated genes among Stenotrophomonas maltophilia clinical isolates

Abstract

Objective: The 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.

Results: All 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.

Keywords: Antibiotic resistance; Biofilm; Biofilm formation genes; Stenotrophomonas maltophilia.

Fig. 1

The amplification of biofilm-encoding genes in S. maltophilia isolates. L: 100 bp DNA ladder, P: positive control, N: negative control, Lanes 1 to 7: PCR products of the corresponding genes: a; rmlA gene, b; rpfF gene, c; spgM gene