@article{mbs:/content/journal/micro/10.1099/00221287-131-8-1933, author = "Williamson, Russell and Le Bouguénec, Chantal and Gutmann, Laurent and Horaud, Thea", title = "One or Two Low Affinity Penicillin-binding Proteins May Be Responsible for the Range of Susceptibility of Enterococcus faecium to Benzylpenicillin", journal= "Microbiology", year = "1985", volume = "131", number = "8", pages = "1933-1940", doi = "https://doi.org/10.1099/00221287-131-8-1933", url = "https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-131-8-1933", publisher = "Microbiology Society", issn = "1465-2080", type = "Journal Article", abstract = "Summary: Three benzylpenicillin-resistant, clinical isolates of Enterococcus faecium (MIC values 16-64 μ;g ml−1) contained six penicillin-binding proteins (PBPs), of which PBP5 was the most abundant and had the lowest affinity for the antibiotic. Four benzylpenicillin-susceptible strains (MIC values 0·031-0·5 μ;g ml−1) were obtained as spontaneous derivatives from these above organisms. There were significant decreases in the amounts of PBP5 in each of the derivatives, with the concomitant appearance of a new, higher affinity PBP (5*) in three strains. Increased amounts of PBP5, with no changes in PBP5*, were found in several mutants with intermediate-level benzylpenicillin-resistance (MIC values 1-8 μ;g ml−1) selected from two of the susceptible strains. Examination of 18 other clinical isolates, with a wide range of susceptibilities to benzylpenicillin (MIC values 0·062-128 μ;g ml−1), showed that PBP5* was present in 13 strains, and PBP5 in all of them, but in differing amounts. The results concerning the relative amounts and relative affinities of PBPs 5* and 5 allowed the categorization of the various strains into six groups, within which organisms had somewhat similar susceptibilities to benzylpenicillin.", }