The penicillin resistance of Enterococcus faecalis JH2-2r results from an overproduction of the low-affinity penicillin-binding protein PBP4 and does not involve a psr-like gene.
A penicillin-resistant mutant, JH2-2r (MIC 75 microg ml(-1)), was isolated from Enterococcus faecalis JH2-2 (MIC 5 microg ml(-1)) by successive passages on plates containing increasing concentrations of benzylpenicillin. A comparison of the penicillin-binding protein (PBP) profiles in the two strains revealed a more intensely labelled PBP4 in JH2-2r. Because the sequences of the JH2-2 and JH2-2r pbp4 genes were strictly identical, even in their promoter regions, this intensive labelling could only be associated with an overproduction of the low-affinity PBP4. No psr gene analogous to that proposed to act as a regulator of PBP5 synthesis in Enterococcus hirae and Enterococcus faecium could be identified in the vicinity of pbp4 in E. faecalis JH2-2 and JH2-2r. However, a psr-like gene distant from pbp4 was identified. The cloning and sequencing of that psr-like gene from both E. faecalis strains indicated that they were identical. It is therefore postulated that the PBP4 overproduction in E. faecalis JH2-2r results from the modification of an as yet unidentified factor.
Duez
Colette
C
Centre d'Ingénierie des Protéines, Institut de Chimie, B6, Université de Liège, (Sart Tilman), B-4000 Liège, Belgium1.
Zorzi
Willy
W
Centre d'Ingénierie des Protéines, Institut de Chimie, B6, Université de Liège, (Sart Tilman), B-4000 Liège, Belgium1.
Sapunaric
Frédéric
F
Centre d'Ingénierie des Protéines, Institut de Chimie, B6, Université de Liège, (Sart Tilman), B-4000 Liège, Belgium1.
Amoroso
Ana
A
Centre d'Ingénierie des Protéines, Institut de Chimie, B6, Université de Liège, (Sart Tilman), B-4000 Liège, Belgium1.
Thamm
Iris
I
Centre d'Ingénierie des Protéines, Institut de Chimie, B6, Université de Liège, (Sart Tilman), B-4000 Liège, Belgium1.
Coyette
Jacques
J
Centre d'Ingénierie des Protéines, Institut de Chimie, B6, Université de Liège, (Sart Tilman), B-4000 Liège, Belgium1.
D001426:Bacterial Proteins; D001483:Base Sequence; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000235:genetics; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics; D013293:Enterococcus faecalis / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D005798:Genes, Bacterial; D006602:Hexosyltransferases; D006801:Humans; D008969:Molecular Sequence Data; D002267:Muramoylpentapeptide Carboxypeptidase / Q000096:biosynthesis* / Q000235:genetics; D010403:Penicillin Resistance / Q000235:genetics / Q000502:physiology*; D046915:Penicillin-Binding Proteins; D010458:Peptidyl Transferases; D010957:Plasmids / Q000235:genetics
D001426:Bacterial Proteins; D002352:Carrier Proteins; D004269:DNA, Bacterial; D046915:Penicillin-Binding Proteins; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase