Inducible carboxypeptidase activity in vancomycin-resistant enterococci.

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Enterococci exhibit resistance to glycopeptide antibiotics like vancomycin.
• The mechanisms underlying vancomycin resistance in enterococci are not fully elucidated.
• DD-carboxypeptidase activity has been implicated in bacterial cell wall metabolism.

Purpose of the Study:

• To investigate the role of DD-carboxypeptidase activity in vancomycin resistance in enterococci.
• To determine if vancomycin can induce DD-carboxypeptidase activity.
• To characterize the enzymatic properties of the induced DD-carboxypeptidase.

Main Methods:

• Testing eight strains of enterococci for vancomycin-induced resistance and DD-carboxypeptidase activity.
• Analyzing a constitutively resistant mutant (MT10) of Enterococcus faecium (D366).
• In vitro enzymatic assays using various substrates and inhibitors.

Main Results:

• Vancomycin coinduced DD-carboxypeptidase activity and resistance in susceptible enterococcal strains.
• A resistant mutant (MT10) exhibited spontaneous carboxypeptidase activity.
• The enzyme utilized pentapeptide, UDP-MurNac-pentapeptide, and D-alanyl-D-alanine as substrates and was penicillin-insensitive.
• A correlation was observed between vancomycin resistance levels and carboxypeptidase activity.

Conclusions:

• DD-carboxypeptidase is a key component of the vancomycin resistance mechanism in enterococci.
• The enzyme's activity is linked to the modification of peptidoglycan precursors.
• Understanding this mechanism could inform strategies to combat antibiotic resistance.