title: Synergy and mechanism of interaction between pefloxacin and penicillin G against enterococci.
abstract: In vitro synergy between penicillin and pefloxacin against Enterococcus hirae and Enterococcus faecium strains with different penicillin susceptibility was studied. The combination was synergistic against penicillin-resistant strains. E. hirae R40 and E. faecium 28R, but not against the penicillin-susceptible ones (E. hirae ATCC 9790 and E. faecium 28S). Analysis of PBPs of cells, grown in the presence of pefloxacin, showed that PBP5 of penicillin-resistant strains, the PBP responsible for the resistance of enterococci to beta-lactam antibiotics, is consistently reduced while it is almost unaffected in the penicillin-susceptible strains even at the highest concentrations of pefloxacin. These results indicate that pefloxacin interferes with the mechanism of synthesis of PBPs and particularly of PBP5, a protein whose production has already been modified in resistant strains, in some way rectifying the previous alteration.
authors.affiliation: Instituto di Microbiologia, Università di Padova, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Grossato
authors.forename: R
authors.initials: R
authors.lastname: Fontana
mesh_terms: D042462:4-Quinolones; D000890:Anti-Infective Agents / Q000494:pharmacology*; D001426:Bacterial Proteins; D002352:Carrier Proteins / Q000032:analysis; D004357:Drug Synergism; D016983:Enterococcus / Q000187:drug effects*; D016984:Enterococcus faecium / Q000737:chemistry / Q000187:drug effects; D024841:Fluoroquinolones; D006602:Hexosyltransferases; D008826:Microbial Sensitivity Tests; D002267:Muramoylpentapeptide Carboxypeptidase / Q000032:analysis; D010400:Penicillin G / Q000494:pharmacology*; D010403:Penicillin Resistance; D046915:Penicillin-Binding Proteins; D010406:Penicillins / Q000494:pharmacology*; D010458:Peptidyl Transferases; D015363:Quinolones / Q000494:pharmacology*; D015366:Pefloxacin
chemical_list: D042462:4-Quinolones; D000890:Anti-Infective Agents; D001426:Bacterial Proteins; D002352:Carrier Proteins; D024841:Fluoroquinolones; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase; D010400:Penicillin G; D046915:Penicillin-Binding Proteins; D010406:Penicillins; D010458:Peptidyl Transferases; D015363:Quinolones; D015366:Pefloxacin