<p>Multilocus sequence typing and <em>bla</em><sub>ESBL</sub> characterization of extended-spectrum beta-lactamase-producing <em>Escherichia coli</em> isolated from healthy humans and swine in Northern Thailand</p>

Abstract

Purpose: Here, we investigated the genetic relationships and characteristics of extended- spectrum beta-lactamase-producing Escherichia coli (ESBL- E. coli ) isolates from healthy hosts, humans in the community and swine among the livestock of Amphor Mueang, Lamphun Province, Thailand. Patients and methods: Four hundred and nine rectal swabs were collected from healthy people and swine. A total of 212 ESBL- E. coli was isolated and phenotypically confirmed by a combination disk method. Putative ESBL-encoding genes, including bla CTX-M , bla TEM , and bla SHV , were examined by multiplex-PCR. Randomly selected 42 ESBL- E. coli isolates were whole genome sequenced to characterize the ESBL-encoding genes and identify additional antimicrobial resistance genes. The genetic relatedness of 212 ESBL- E. coli was investigated by multilocus sequence typing. Results: Overall, bla CTX-M was the dominant ESBL-encoding gene found in 95.75% of the isolates, followed by bla TEM (60.85%) and bla SHV (2.40%). While bla CTX-M-55 was the most common bla ESBL subgroup found in this study. Whole genome sequencing showed a total of 15 different antimicrobial resistance genes other than bla ESBL , including sul, qnr, aph(3ʹ)-Ia , among the selected 42 ESBL- E. coli isolates. Over half of the ESBL- E. coli (56.60%) carried bla CTX-M co-existing with bla TEM . The most common sequence types (STs) identified from human isolates were ST131, ST101, and ST70 while those isolated from swine were ST10, ST48, and ST131. ST131 strains carrying bla CTX-M were the major isolated ESBL- E. coli strains, supporting a previous study that considered this strain truly pathogenic. Noticeably, 66.51% of ESBL- E. coli strains shared 19 identical STs, including a host-restricted ST131 between humans and swine, suggesting that transmission between these two hosts might be possible. Conclusion: Proof of a direct transfer of ESBL- E. coli from animals to humans, or vice versa, is required for further elucidation. The ESBL- E. coli isolated from both types of healthy hosts may serve as a reservoir for community-acquired antimicrobial resistance. Keywords: ESBL- E. coli , bla CTX-M , bla TEM , and bla SHV , MLST, genetic relatedness