Genetic analysis of faropenem-resistant Enterococcus faecalis in urinary isolates.
We isolated faropenem-resistant Enterococcus faecalis in urine specimens and studied the mechanisms of resistance to faropenem in these isolates. Three mechanisms of penicillin resistance have been reported in E. faecalis; (1) beta-lactamase production, (2) overproduction of penicillin-binding protein (PBP) 4 or PBP5, and (3) decreasing affinities of penicillins for PBP4 by the occurrence of point mutations of the penicillin-binding domain. None of the E. faecalis isolates examined produced beta-lactamase or overproduced any PBPs, but the affinities of faropenem for PBP4 were decreased in faropenem-insensitive and -resistant strains. We found single amino acid substitutions at positions 475, 520 or 605 in PBP4 in the insensitive strains and two amino acid substitutions at positions 520 and 605 in PBP4 in the resistant strains by sequencing the entire pbp4 gene from each isolate. We conclude that development of resistance to faropenem in E. faecalis is due to decreasing affinities for PBP4 that are the result of the occurrence of one or two point mutations.
Hiraga
Noriyuki
N
Department of Urology, Graduate School of Medical Sciences, Kyushu University, Japan.
Muratani
Tetsuro
T
Naito
Seiji
S
Matsumoto
Tetsuro
T
D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016521:Electrophoresis, Gel, Pulsed-Field; D013293:Enterococcus faecalis / Q000187:drug effects* / Q000235:genetics*; D005838:Genotype; D006801:Humans; D008826:Microbial Sensitivity Tests; D046915:Penicillin-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D014552:Urinary Tract Infections / Q000382:microbiology*; D018440:beta-Lactam Resistance; D047090:beta-Lactams / Q000378:metabolism / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D046915:Penicillin-Binding Proteins; D047090:beta-Lactams; C107057:fropenem