Overproduction of a low-affinity penicillin-binding protein and high-level ampicillin resistance in Enterococcus faecium

Antimicrob Agents Chemother. 1994 Sep;38(9):1980-3. doi: 10.1128/AAC.38.9.1980.

Abstract

Five ampicillin-resistant clinical isolates of Enterococcus faecium were analyzed for a correlation between overproduction of the low-affinity penicillin-binding protein (PBP 5) and the level of ampicillin resistance. Comparison was made with one susceptible clinical isolate and its ampicillin-resistant derivative obtained in the laboratory by selection with increasing concentrations of penicillin. Overproduction of the low-affinity PBP relative to the susceptible isolate was noted in moderately resistant strains (MIC, 32 micrograms/ml) but not in highly resistant strains (MIC, 128 micrograms/ml). Polyclonal antibodies specifically reacting with the low-affinity PBP of Enterococcus hirae, Enterococcus faecalis, and Enterococcus faecium (M. Ligozzi, M. Aldegheri, S. C. Predari, and R. Fontana, FEMS Microbiol. Lett. 83:335-340, 1991) were used to determine the amount of this PBP in the E. faecium isolates. In all strains, the antibody preparation reacted with a membrane protein of the same molecular mass as PBP 5. The amount of this protein was very small in the susceptible strain but large in all of the resistant strains. These results suggest that the highly resistant strains also overproduced the low-affinity PBP, which, compared with PBP 5 of moderately resistant strains, appeared to be modified in its penicillin-binding capability.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Ampicillin Resistance*
  • Bacterial Proteins / biosynthesis*
  • Bacterial Proteins / metabolism
  • Bacterial Proteins / physiology
  • Carrier Proteins / biosynthesis*
  • Carrier Proteins / metabolism
  • Carrier Proteins / physiology
  • Enterococcus faecium / drug effects
  • Enterococcus faecium / metabolism*
  • Hexosyltransferases*
  • Immunoblotting
  • Microbial Sensitivity Tests
  • Muramoylpentapeptide Carboxypeptidase / biosynthesis*
  • Muramoylpentapeptide Carboxypeptidase / metabolism
  • Muramoylpentapeptide Carboxypeptidase / physiology
  • Penicillin-Binding Proteins
  • Penicillins / metabolism
  • Peptidyl Transferases*

Substances

  • Bacterial Proteins
  • Carrier Proteins
  • Penicillin-Binding Proteins
  • Penicillins
  • Peptidyl Transferases
  • Hexosyltransferases
  • Muramoylpentapeptide Carboxypeptidase