Chemistry: molecular biology and microbiology – Measuring or testing process involving enzymes or... – Involving nucleic acid
Reexamination Certificate
1999-04-14
2003-05-27
Campbell, Eggerton A. (Department: 1656)
Chemistry: molecular biology and microbiology
Measuring or testing process involving enzymes or...
Involving nucleic acid
C536S022100, C536S023100
Reexamination Certificate
active
06569622
ABSTRACT:
The invention relates to the polypeptides associated with the expression of a resistance to antibiotics of the glycopeptide family, this resistance being of a type inducible by vancomycin and not inducible by teicoplanin, particular in the Gram-positive bacteria, in particular in the family of the Gram-positive cocci. The invention also relates to a nucleotide sequence coding for these polypeptides. It also relates to the use of these polypeptides and their nucleotide sequence as agents for the in vitro detection of resistance to glycopeptides. Among the Gram-positive cocci, the invention relates more particularly to the enterococci, the streptococci and the staphylococci.
The glycopeptides, which include vancomycin and teicoplanin, are antibiotic inhibitors of the synthesis of the bacterial cell wall. These antibiotics are very much used for the treatment of severe infections due to Gram-positive coca (enterococci, streptococci and staphylococci) in particular in cases of allergy and resistance to the penicillins.
Up to 1986 vancomycin proved to be efficacious against almost all strains of enterococci.
The activity of the glycopeptides depends on the formation of a complex between the antibiotic and the peptidoglycan precursors more than on their direct interaction with enzymes of cell wall metabolism. In particular, it has been observed that the glycopeptides bind to the terminal D-alanyl-D-alanine (D-ala-D-ala) residues of the peptidoglycan precursors.
Several phenotypes of resistance to the glycopeptides have been demonstrated; in particular, strains resistant to a high level of glycopeptides and strains resistant to low concentration levels.
By strain resistant to a high level is meant a strain of bacteria, in particular a strain of Gram-positive cocci, for which the minimal inhibitory concentrations (MC) of vancomycin and teicoplanin are higher than 32 and 8 &mgr;g/ml, respectively. The MIC of vancomycin towards strains with low-level resistance are included between 8 and 32 &mgr;g/ml. The VanB phenotype is characterized by a resistance inducible by vancomycin but not inducible by teicoplanin. Once induced, this resistance may exist against different glycopeptides, in particular against vancomycin and/or teicoplanin, and at variable levels.
The strains of enterococci corresponding to the VanB phenotype (class B) are in particular strains of
E. faecalis
and
E. faecium.
Al-Obeici S et al. (FEMS Microbiology Letters 70 (1990) 101-106) have thus compared the resistance proteins to glycopeptides, inducible by vancanycin, in four strains at Enterococci, and have deduced from their comparison the existence of three types of proteins, one of these types being present in the
E. faecium
strain resistant to low levels of vancomycin. According to the authors of this publication, a protein of molecular weight of about 39.5 kDa is induced in the strains with low-level resistance and this resistance is linked to induction by vancomycin. These strains were also reported to exhibit a resistance to teicoplanin, also induced by vancomycin.
According to Al-Obeid et al., this protein of 39.5 kDa is present in multiple forms but the nature of this multiplicity has not been studied. According to these authors there might exist a structural specificity depending on the species of bacteria concerned and the level of resistance, which needs to be confirmed.
In this publication Al-Obeid et al. described 11 amino acids of the N-terminal sequence of the protein of 39.5 kDa and observed that this sequence exhibited about 70% homology with many membrane proteins of prokaryotic or eukaryotic origin having diverse functions. According to the authors this comparison did not allow the possible function of the protein to be established. Finally, Al-Obeid et al. noticed that other proteins are induced, although to a lesser degree.
The invention relates to peptides, polypeptides or proteins implicated in the expression of a resistance to antibiotics of the glycopeptide family and in particular to vancomycin and/or teicoplanin as well as nucleotide sequences coding for such polypeptides. The resistance in question above is of a type inducible by vancomycin but not by teicoplanin.
The expressions “implicated in the expression of a resistance” or “implicated in a resistance” signify that the protein of the invention is necessary in order for the resistance to be manifest.
The invention also relates to nucleotide probes utilizable for the detection of a resistance to the glycopeptides, in particular by means of the polymerase chain reaction (PCR), or by assays involving antibodies.
Thus, the object of the invention is a VanB protein characterized in that it comprises the following amino acid sequence I, and in that it participates in the resistance to glycopeptides, in particular to vancomycin, this resistance being of a type inducible by vancomycin and not by teicoplanin in Gram-positive bacteria (SEQ ID NO:2).
M N K I X V A I I F G G C S E E H D V S V K S A I E I A A N I N T E K F D P H Y I G I T K N G V W K L C K K P C T E W E A D S L P A I F S P D R K T H G L L V M K E R E Y E T R R I D V A F P V L H G K C G E D G A I Q G L F E L S G I P Y V G C D I Q S S A A C M D K S L A Y I L T K N A G I A V P E F Q M I E K G D K P E A R T L T Y P V F V K P A R S G S S F G V T K V N S T E E L N A A I E A A G Q Y D G K I L I E Q A I S G C E V G C A V M G N E D D L I V G E V D Q I R L S H G I F R I H Q E N E P E K G S E N A M I I V P A D I P V E E R N R V Q E T A K K V Y R V L G C R G L A R V D L F L Q E D G G I V L N E V N T L P G F T S Y S R Y P R M A A A A G I T L P A L I D S L I T L A I E R
By the expression “inducible resistance” is meant the capacity of a specific Gram-positive bacterium, in particular of a specific Enterococcus strain, to produce a VanB protein in the presence of a concentration of 0.05 to 1 &mgr;l/ml of vancomycin.
The resistance to one or more defined glycopeptides may result in the persistence of an infection due to microbes usually sensitive to the glycopeptides, or may be detected by means of an antibiogram (particularly for high levels of resistance), the MIC, hybridization with probes (after amplification by the PCR, for example).
According to a first embodiment of the invention, the VanB protein is characterized in that it is implicated in an inducible resistance to glycopeptides, and in particular to vancomycin, in enterococci and for example in strains of the genus
E. faecium
or
E. faecalis.
The invention also relates to a VanB protein characterized in that it comprises an amino acid sequence modified with respect to sequence I by deletion, insertion, or replacement of one or more amino acids, provided that the VanB protein thus modified is implicated in Gram-positive bacteria in a resistance to glycopeptides, in particular to vancomycin, this resistance being of a type inducible by vancomycin, but not inducible by teicoplanin.
Also included in the framework of the invention is any peptide fragment of the VanB protein characterized in that it corresponds to the amino acid sequence I or any part of this sequence functionally associated with the inducible resistance to glycopeptides, in particular to vancomycin, in Gram-positive bacteria, for example bacteria of the family of the enterococci.
Advantageously peptide fragments of the invention exhibit additionally or alternatively antigenic properties and are hence recognized by antibodies formed against the VanB protein
A particular fragment of sequence I corresponds for example to the following sequence or includes this sequence (residues 110-305 of SEQ ID NO:2):
L F E L S G I P Y V G C D I Q S S A A C M D K S L A Y I L T K N A G I A V P E F Q M I E K G D K P E A R T L T Y P V F V K P A R S G S S F G V T K V N S T E E L N A A I E A A G Q Y D G K I L I E Q A I S G C E V G C A V M G N E D D L I V G E V D Q I R L S H G I F R I H Q E N E P E K G S E N A M I I V P A D I P V E E R N R V Q E T A K K V Y R V L G C R G L A R V D L F L Q E D G G I V L N E V
According to another embodiment of the invention, these antigens are specific for the
Arthur Michel
Courvalin Patrice
Dutka-Malen Sylvie
Evers Stefan
Campbell Eggerton A.
Institut Pasteur
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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