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Antimicrobial Agents and Chemotherapy, November 2001, p. 3070-3075, Vol. 45, No. 11
Departments of
Medicine1 and
Microbiology/Immunology,2 Medical
College of Virginia at Virginia Commonwealth University, and
Hunter Holmes McGuire Veterans Affairs Medical
Center,4 Richmond, Virginia, and The
Bristol-Meyers Squibb Pharmaceutical Institute, Wallingford,
Connecticut3
Received 30 January 2001/Returned for modification 30 April
2001/Accepted 23 July 2001
It has been reported that penicillin-binding protein 4 (PBP4) activity decreases when a vancomycin-susceptible
Staphylococcus aureus isolate is passaged in vitro to
vancomycin resistance. We analyzed the PBP profiles of four vancomycin
intermediately susceptible S. aureus (VISA)
clinical isolates and found that PBP4 was undetectable in three
isolates (HIP 5827, HIP 5836, and HIP 6297) and markedly reduced in a
fourth (Mu50). PBP4 was readily visible in five vancomycin-susceptible,
oxacillin-resistant S. aureus (ORSA) isolates. The
nucleotide sequences of the pbp4 structural gene and
flanking sequences did not different between the VISA and
vancomycin-susceptible isolates. Overproduction of PBP4 on a
high-copy-number plasmid in the VISA isolates produced a two- to
threefold decrease in vancomycin MICs. Inactivation of
pbp4 by allelic replacement mutagenesis in three
vancomycin-susceptible ORSA strains (COL, RN450M, and N315) led to a
decrease in vancomycin susceptibility, an increase in highly
vancomycin-resistant subpopulations, and decreased cell wall
cross-linking by high-performance liquid chromatography analysis.
Complementation of the COL mutant with plasmid-encoded
pbp4 restored the vancomycin MIC and increased cell wall
cross-linking. These data suggest that alterations in PBP4 expression
are at least partially responsible for the VISA phenotype.
0066-4804/01/$04.00+0 DOI: 10.1128/AAC.45.11.3070-3075.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Role of Penicillin-Binding Protein 4 in Expression of Vancomycin
Resistance among Clinical Isolates of Oxacillin-Resistant
Staphylococcus aureus
*
Corresponding author. Mailing address: Hunter Holmes
McGuire Veterans Affairs Medical Center, 1201 Broad Rock Blvd., Section 111-C, Richmond, VA 23249. Phone: (804) 675-5018. Fax: (804) 675-5437. E-mail: michael.climo{at}med.va.gov.
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