Discrimination of biofilm-producing Stenotrophomonas maltophilia clinical strains by matrix-assisted laser desorption ionization-time of flight

Abstract

Stenotrophomonas maltophilia is a Gram-negative drug-resistant pathogen responsible for healthcare-associated infections. The aim was to search for biomarker peaks that could rapidly detect biofilm production in S. maltophilia clinical isolates obtained from two tertiary care hospitals in Mexico. Isolates were screened for the presence of biofilm-associated genes, in which the fsnR gene was associated with biofilm production (p = 0.047), whereas the rmlA+ genotype was associated with the rpfF- genotype (p = 0.017). Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectra comparison yielded three potential biomarker peaks (4661, 6074, and 6102 m/z) of biofilm-producing rmlA+ and rpfF- genotypes with >90% sensitivity (p<0.001). MALDI-TOF MS analyses showed a correlation between the relative abundance of 50S ribosomal proteins (L30 and L33) and the presence of the fnsR, rmlA and rpfF-2 genes, suggested to play a role in biofilm formation. Isolates obtained in the intensive care unit showed low clonality, suggesting no transmission within the hospital ward. The detection of biomarkers peaks by MALDI-TOF MS could potentially be used to early recognize and discriminate biofilm-producing S. maltophilia strains and aid in establishing appropriate antibiotic therapy.

Fig 1. Representative mass spectra comparison of potential biomarker peaks of rmlA⁺ and rpF-2⁻ genotype in biofilm-producing S. maltophilia isolates.

In the rmlA⁺ genotype the 4661 m/z and 6102 m/z peaks are present and the 6074 m/z peak is absent (A) whereas in the rmlA^- genotype the 4661 m/z and 6074 m/z peaks are present and the 6102 m/z peak is absent (B). In the rpF-2⁻ genotype the 4661 m/z and 6074 m/z peaks are absent and the 6102 m/z peak is present.

Fig 2. Representative mass spectra comparison of two potential biomarker peaks of rmlA genotype in biofilm-producing S. maltophilia isolates.

The rmlA⁺ genotype group exhibits a 6074^-/6102⁺ phenotype (A), whereas the rmlA^- genotype group exhibits a 6074⁺/6102^- phenotype (B).

Fig 3. Representative mass spectra comparison of two potential biomarker peaks of rpfF genotype in biofilm-producing S. maltophilia isolates.

The rpfF⁺ genotype group exhibits a 4661^- (A) and a 6074^-/6102⁺ (C) phenotype, whereas the rpfF^- genotype group exhibits a 4661⁺ (B) and a 6074⁺/6102^- (D) phenotype.