Epidemiology and genetics of CTX-M extended-spectrum β-lactamases in Gram-negative bacteria

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Extended-spectrum beta-lactamases (ESBLs) are enzymes that confer bacterial resistance to antibiotics.
• CTX-M enzymes, a type of plasmid-mediated cefotaximase, represent a rapidly expanding family of ESBLs with considerable clinical significance.
• These enzymes are prevalent across numerous bacterial species, notably in Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis.

Purpose of the Study:

• To provide an overview of the CTX-M enzyme family, including their diversity, prevalence, and mechanisms of spread.
• To highlight the clinical impact and evolutionary origins of CTX-M enzymes.

Main Methods:

• Phylogenetic analysis to classify CTX-M variants.
• Literature review to assess prevalence and dissemination mechanisms.

Main Results:

• Over 109 CTX-M members have been identified, categorized into seven distinct phylogenetic clusters.
• CTX-M-15 and CTX-M-14 are the most frequently identified variants.
• Evidence suggests chromosome-encoded cefotaximases in Kluyvera spp. are the likely progenitors of CTX-Ms.
• Mobile genetic elements like ISEcp1 and ISCR1, along with plasmids, are strongly implicated in the mobilization and dissemination of CTX-M genes.

Conclusions:

• The CTX-M family is diverse and expanding, posing a significant challenge in combating bacterial infections.
• Understanding the evolutionary origins and dissemination pathways of CTX-M enzymes is crucial for developing effective control strategies.