Enterotoxigenic Escherichia coli (ETEC) is an enteric pathogen that causes traveler’s diarrhea and is a leading cause of infectious diarrhea in children under the age of five in developing nations. ETEC is one of the four enteric pathogens that causes more than one-half of all diarrheal deaths in the world and by itself causes ~200 million cases of watery diarrhea and about 300,000 to 400,000 diarrheal deaths annually in children under the age of five (1). The heat-labile enterotoxin (LT), heat-stable enterotoxins 1a (ST1a), and ST1b are classical ETEC virulence genes that induce water and electrolyte loss from the infected intestines, leading to diarrhea (2–4). The complete genomes of four human ETEC strains, E. coli H10407 (5), E24377A (6), B2C (7), and W25K (8), have been published. In this announcement, we report the first draft whole-genome sequences of 10 serogroup O6 ETEC strains from historical and recent outbreaks (Table 1).

ETEC genomic DNA was extracted using the DNeasy blood and tissue kit (Qiagen, MD), according to the manufacturer’s protocol. A library preparation for whole-genome sequencing was generated using the Nextera DNA sample preparation kit (Illumina, Inc., CA) from 10 isolates, with a starting concentration of 10 ng/µl. Whole-genome sequencing was performed using MiSeq (Illumina, CA), according to the manufacturer’s protocols, to generate 2 × 150-bp reads. The raw reads were trimmed and assembled in CLC Genomics Workbench 7.0 by de novo assembly. The sequences were annotated with the NCBI Prokaryotic Genome Automation Pipeline (http://www.ncbi.nlm.nih.gov/genome/annotation_prok/).

The average size of the ETEC genomes in this study is 4.88 Mb, with 4.7 Mb being the smallest genome size (isolate 2013EL-1319, Table 1) and 5.18 Mb the largest genome size (isolate F6097, Table 1). On average, 4,094 coding sequences were identified in the 10 ETEC genomes (Table 1). BLAST and virulence finder software tools identified the classical enterotoxin genes: LT and ST1b, which were experimentally confirmed by real-time PCR assays (Table 1). The ingA gene, which encodes longus type IV pilus, a classical ETEC colonization surface antigen, was found in five ETEC genomes, and the prfB gene, which encodes a P-related fimbriae regulatory gene, was found in all 10 ETEC genomes (Table 1).