Genomic epidemiology of enteropathogenic Escherichia coli (EPEC) in southwestern Nigeria

Abstract

Enteropathogenic Escherichia coli (EPEC) are etiological agents of diarrhea. We studied the genetic diversity and virulence factors of EPEC in southwestern Nigeria, where this pathotype is rarely characterized. EPEC isolates (n=96) recovered from recent southwestern Nigeria diarrhea case-control studies were whole genome-sequenced using Illumina technology. Genomes were assembled using SPAdes and quality was evaluated using QUAST. Virulencefinder, SeroTypefinder, and Resfinder were used to identify virulence genes, serotypes, and resistance genes, while multilocus sequence typing was done by STtyping. Single nucleotide polymorphisms (SNPs) were called out of whole genome alignment using SNP-sites and a phylogenetic tree was constructed using IQtree. Thirty-nine of the 96 (40.6%) EPEC isolates were from cases of diarrhea. Nine isolates from diarrhea patients and four from healthy controls were typical EPEC, harboring bundle-forming pilus (bfp) genes whilst the rest were atypical EPEC. Fifteen isolates were EPEC-EAEC hybrids. Atypical serotypes O71:H19 (16, 16.6%), O108:H21 (6, 6.3%), O157:H39 (5, 5.2%), and O165:H9 (4, 4.2%) were most prevalent; only 8(8.3%) isolates belonged to classical EPEC serovars. The largest clade comprised ST517 isolates, of O71:H19 and O165:H9 serovars harboring multiple siderophore and serine protease autotransporter genes. An O71:H19 subclade comprised isolates <10 SNPs apart, representing a likely outbreak involving 15 children, four presenting with diarrhea. Likely outbreaks, of typical O119:H6(ST28) and atypical O127:H29(ST7798) were additionally identified. EPEC circulating in southwestern Nigeria are diverse and differ substantially from well-characterized lineages seen previously elsewhere. EPEC carriage and outbreaks could be commonplace but are largely undetected, hence, unreported, and require genomic surveillance for identification.

Competing Interest Statement

The authors have declared no competing interest.