Universidad Complutense de Madrid
E-Prints Complutense

VanB-type Enterococcus faecium clinical isolate successively inducibly resistant to, dependent on, and constitutively resistant to vancomycin

Impacto

Downloads

Downloads per month over past year



San Millán, Álvaro and Depardieu, Florence and Godreuil, Sylvain and Courvalin, Patrice (2009) VanB-type Enterococcus faecium clinical isolate successively inducibly resistant to, dependent on, and constitutively resistant to vancomycin. Antimicrobial agents and chemotherapy, 53 (5). pp. 1974-82. ISSN 1098-6596

[img] PDF
Restringido a Repository staff only

601kB

Official URL: http://aac.asm.org/content/53/5/1974.full



Abstract

Three Enterococcus faecium strains isolated successively from the same patient, vancomycin-resistant strain BM4659, vancomycin-dependent strain BM4660, and vancomycin-revertant strain BM4661, were indistinguishable by pulsed-field gel electrophoresis and harbored plasmid pIP846, which confers VanB-type resistance. The vancomycin dependence of strain BM4660 was due to mutation P(175)L, which suppressed the activity of the host Ddl D-Ala:D-Ala ligase. Reversion to resistance in strain BM4661 was due to a G-to-C transversion in the transcription terminator of the vanRS(B) operon that lowered the free energy of pairing from -13.08 to -6.65 kcal/mol, leading to low-level constitutive expression of the resistance genes from the P(RB) promoter, as indicated by analysis of peptidoglycan precursors and of VanX(B) D,D-dipeptidase activity. Transcription of the resistance genes, studied by Northern hybridization and reverse transcription, initiated from the P(YB) resistance promoter, was inducible in strains BM4659 and BM4660, whereas it started from the P(RB) regulatory promoter in strain BM4661, where it was superinducible. Strain BM4661 provides the first example of reversion to vancomycin resistance of a VanB-type dependent strain not due to a compensatory mutation in the ddl or vanS(B) gene. Instead, a mutation in the transcription terminator of the regulatory genes resulted in transcriptional readthrough of the resistance genes from the P(RB) promoter in the absence of vancomycin.


Item Type:Article
Subjects:Medical sciences > Veterinary
ID Code:39697
Deposited On:09 Jan 2017 16:19
Last Modified:09 Jan 2017 16:19

Origin of downloads

Repository Staff Only: item control page