To the Editor: We read with great interest the Matsumura et al. paper describing extended-spectrum β-lactamase (ESBL) CTX-M-27–producing Escherichia coli of sequence type (ST) 131 clonal group, an emerging clade called C1-M27 (1). ST131 E. coli having bla_CTX-M-27 has been described in several countries. We observed an alarming increase of this clonal group in the fecal carriage of children in France (0% in 2010 to 65% in 2015 among ESBL-producing ST131 E. coli) (2).

We wondered whether this clonal group’s expansion in France was attributable to the same clade (C1-M27). For that, we designed primers (M27PP1-B-F, 5′-TTACTCCGACTATGCGTTCAC-3′; M27PP1-B-R, 5′-CAAACTTGCCCCTGATAGCG-3′; amplicon length, 1.5 kb) to amplify the insertion site of the structure comprising the direct repeat and prophage-like genomic island of E. coli PCN033, as previously described (1). PCR was performed on our recently described collection of 39 ESBL-producing ST131 E. coli, including 16 CTX-M-27–producing E. coli: 13 of subgroup O25b with fimH30 allele and 3 of O16 subgroup with fimH41 allele (2). Results showed that 81% (13/16) of the CTX-M-27–producing E. coli ST131 had the M27PP1 structure, similar to strain PCN033, and thus belong to the C1-M27 clade. Therefore, the C1-M27 clade found in Asia and America is also present in Europe in the fecal flora of young children. The 3 isolates belonging to the O16 subgroup with fimH41 lacked M27PP1, suggesting that bla_CTX-M-27 might diffuse among non-H30 ST131 E. coli without this prophage-like genomic island. Finally, the non–CTX-M-27–producing ST131 E. coli of our collection were negative for M27PP1 elements.

Our results show that CTX-M-27–producing E. coli ST131 subgroup O25b with fimH30 allele (one third of the ESBL-producing ST131 carriage isolates) isolated from children in France belong to C1-M27 and that CTX-M-27–producing O16 strains display distinct genetic characteristics. Altogether, our data confirm the worldwide distribution of C1-M27 and its high prevalence in children in France.