Global Escherichia coli Sequence Type 131 Clade with bla_CTX-M-27 Gene

Area of Science:

• Microbiology
• Genomics
• Infectious Diseases

Background:

• The C2/H30Rx clade of Escherichia coli sequence type (ST) 131, carrying blaCTX-M-15, has been a major driver of global extended-spectrum β-lactamase (ESBL)-producing E. coli dissemination.
• In Japan, ST131 C1/H30R strains with blaCTX-M-27 emerged in the late 2000s, suggesting potential clade expansion.

Purpose of the Study:

• To investigate the potential expansion of a single clade within ESBL-producing E. coli.
• To characterize the genetic makeup and evolutionary relationships of ST131 isolates carrying different bla genes, particularly blaCTX-M-27.

Main Methods:

• Whole-genome sequencing was performed on 43 Japanese and 10 global ST131 isolates.
• Genomes included isolates with blaCTX-M-27, blaCTX-M-14, and blaCTX-M-15, along with 8 publicly available ST131 genomes.
• Core genome and accessory genome analyses were conducted on a total of 61 isolates.

Main Results:

• Core genome analysis revealed that ST131 isolates with blaCTX-M-27 from five countries formed a distinct cluster within the C1/H30R clade, designated the C1-M27 clade.
• Accessory genome analysis identified a unique prophage-like region specific to the C1-M27 clade.
• The emergence and expansion of the C1-M27 clade were identified as the primary cause for the increase in ESBL-producing E. coli in Japan.

Conclusions:

• The C1-M27 clade represents a distinct evolutionary lineage within ST131 E. coli.
• This newly identified clade is significantly contributing to the prevalence of ESBL-producing E. coli in Japan.
• Further surveillance is warranted to monitor the spread and impact of the C1-M27 clade globally.