title: Analysis of PBP5 of early U.S. isolates of Enterococcus faecium: sequence variation alone does not explain increasing ampicillin resistance over time.
abstract: Recent studies have shown that ampicillin resistance has increased steadily over the past 3 decades within U.S. Enterococcus faecium isolates. Analysis of the predicted PBP5 protein of 41 isolates showed a consensus PBP5 pattern for the 9 isolates with MICs of <4 μg/ml that is distinctly different from the PBP5 consensus of the 32 isolates with MICs of >4 μg/ml with ∼5% difference between these; however, there were no consistent amino acid changes that correlated with specific increases in the MICs of ampicillin within the latter group. Analysis of three other genes encoding cell wall/surface proteins also showed that there are two distinct evolutionary groups for each gene, but with occasional mixing of genes, consistent with a species that evolves by recombination.
authors.affiliation: Division of Infectious Disease, Department of Medicine, Center for the Study of Emerging and Re-emerging Pathogens, University of Texas Medical School, Houston, Texas 77030, USA.
authors.forename: Jessica R
authors.initials: JR
authors.lastname: Galloway-Peña
authors.forename: Louis B
authors.initials: LB
authors.lastname: Rice
authors.forename: Barbara E
authors.initials: BE
authors.lastname: Murray
mesh_terms: D000667:Ampicillin / Q000494:pharmacology; D000668:Ampicillin Resistance / Q000235:genetics*; D001426:Bacterial Proteins / Q000145:classification / Q000235:genetics*; D016984:Enterococcus faecium / Q000187:drug effects / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D046915:Penicillin-Binding Proteins / Q000235:genetics*; D010802:Phylogeny; D016133:Polymerase Chain Reaction
chemical_list: D001426:Bacterial Proteins; D046915:Penicillin-Binding Proteins; D000667:Ampicillin