Emergence of Proteus mirabilis carrying the bla metallo-beta-lactamase gene

Area of Science:

• Microbiology
• Genetics
• Antimicrobial Resistance

Background:

• Proteus mirabilis is a common cause of hospital-acquired infections.
• Metallo-beta-lactamases (MBLs) confer resistance to a broad range of beta-lactam antibiotics, including carbapenems.
• The emergence of MBL-producing bacteria poses a significant threat to public health.

Purpose of the Study:

• To investigate the genetic basis of imipenem resistance in clinical isolates of Proteus mirabilis.
• To characterize the metallo-beta-lactamase gene identified in these isolates.
• To report the first instance of the bla(VIM-1) gene in Proteus mirabilis.

Main Methods:

• Isolation and genetic relatedness assessment of Proteus mirabilis strains.
• Phenotypic testing for antimicrobial susceptibility, including to imipenem.
• Polymerase Chain Reaction (PCR) mapping to identify and locate the bla(VIM-1) gene and associated genetic elements within integrons.

Main Results:

• Seven genetically related Proteus mirabilis clinical isolates displayed decreased susceptibility to imipenem.
• The bla(VIM-1) metallo-beta-lactamase gene was detected in all seven isolates.
• PCR mapping confirmed bla(VIM-1) was part of a class 1 integron on the chromosome, also containing aacA7, dhfr, and aadA genes.

Conclusions:

• This study reports the first detection of the bla(VIM-1) metallo-beta-lactamase gene in Proteus mirabilis.
• The presence of this gene in a class 1 integron suggests potential for horizontal gene transfer and spread of resistance.
• These findings highlight the need for ongoing surveillance of carbapenem resistance mechanisms in Gram-negative bacteria.