Expression of multidrug efflux pump SmeDEF by clinical isolates of Stenotrophomonas maltophilia

Abstract

The presence of the multidrug efflux pump SmeDEF was assessed in a collection of clinical isolates of Stenotrophomonas maltophilia. All isolates encoded this pump, as demonstrated by PCR. Forty-seven percent of the strains overproduced a protein of the same size that was immunoreactive against an anti-SmeF antibody, and 33% overexpressed the gene semD when they were tested by reverse transcription-PCR. A correlation between smeDEF overexpression and antibiotic resistance was observed.

FIG. 1

Presence of the smeDEF efflux pump in the genomes of clinical isolates of S. maltophilia. Lane M, molecular size markers; lane C−, negative control, for which the same PCR reaction was performed but without the addition of DNA. A band of the predicted size was observed in all isolates.

FIG. 2

Expression of SmeF by clinical isolates of S. maltophilia. Whole-cell protein extracts of S. maltophilia were obtained and electrophoresed in SDS–10% polyacrylamide gels. Western blot analysis was performed with an anti-SmeF antibody.

FIG. 3

Expression of smeDEF RNA by clinical isolates of S. maltophilia. The expression of smeDEF was analyzed by RT-PCR. RNAs obtained at the exponential (lanes a) and stationary (lanes b) growth phases were analyzed. A clear band of the predicted size was observed for strains D457R, C357, E729, E923, and F375; and a very faint band was observed for strain D457. Note that strain D457R is not a clinical isolate but a multidrug-resistant mutant derived from strain D457 (3), and it has been included in the present analysis as a control for smeDEF expression. Lane M, molecular size markers (from top to bottom, 404, 331, 242, 190, 157, 147, and 112 bp); C+, positive control, for which PCR was performed with chromosomal DNA from S. maltophilia D457 as the template; C−, negative control, for which PCR was performed without DNA.