CMY-31 and CMY-36 cephalosporinases encoded by ColE1-like plasmids

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• The emergence of antibiotic resistance is a significant global health concern.
• Cephalosporinases are enzymes that confer resistance to beta-lactam antibiotics, including cephalosporins.
• CMY-2 is a well-characterized AmpC-type cephalosporinase.

Purpose of the Study:

• To characterize two novel CMY-2 derivatives, CMY-31 and CMY-36.
• To investigate the genetic context and plasmid-borne nature of these new bla(CMY) alleles.

Main Methods:

• Enzyme characterization of CMY-31 and CMY-36.
• Genetic analysis of the bla(CMY) alleles and their surrounding sequences.
• Plasmid analysis to determine the genetic elements and their origins.

Main Results:

• CMY-31 (Gln(215)-->Arg) from Salmonella enterica serotype Newport and CMY-36 (Ala(77)-->Cys and Gln(193)-->Glu) from Klebsiella pneumoniae were functionally similar to CMY-2.
• The bla(CMY) alleles were identified as part of a putative transposon.
• This transposon contained ISEcp1B and a sequence derived from Citrobacter freundii.
• The bla(CMY) alleles were carried by ColE1-like plasmids, similar to those encoding CMY-5.

Conclusions:

• The characterization of CMY-31 and CMY-36 expands our understanding of AmpC cephalosporinase diversity.
• The genetic context suggests a potential mechanism for the dissemination of these resistance genes via transposons and plasmids.
• These findings highlight the ongoing evolution and spread of antibiotic resistance mechanisms in Gram-negative bacteria.