Characterisation of Typical Enteropathogenic Escherichia coli (tEPEC) and bfpA Genes From Five Bat Species Reveals Australian Pteropus Spp. Are Natural tEPEC Hosts

Humans have historically been considered the only natural host of typical enteropathogenic Escherichia coli (tEPEC), a cause of human infantile diarrhoea. Recent findings of bat-specific tEPEC in two Australian bat species (Pteropus poliocephalus and Pteropus conspicillatus) revealed that these Pteropus spp. are also tEPEC hosts. tEPEC pathogenicity is associated with key virulence factors including intimin (eae) and the bundle-forming pilus (bfp) operon, which contains the bfpA gene. This study characterised 63 tEPEC isolates from five Australian Pteropus spp.; four from mainland Australia (P. poliocephalus, P. conspicillatus, P. alecto and P. scapulatus) and one from Christmas Island (P. natalis). The 63 tEPEC isolates included 10 novel tEPEC strains and eight previously identified Pteropus tEPEC strains. Faecal DNA samples (n = 386) from the five Australian Pteropus spp. were screened for eae and bfpA genes to identify tEPEC-positive samples. The estimated true prevalence of tEPEC ranged from 14.2% to 37.0% across the five Pteropus spp. Typing of 119 bfpA alleles (63 tEPEC isolates and 56 faecal DNA samples) from the five Pteropus spp. identified 27 bfpA allele types, 24 of which belonged to bat-specific bfpA lineages. Bat-specific bfpA alleles were shared between tEPEC strains, Pteropus spp. and across regions, including the geographically isolated P. natalis endemic to Christmas Island. This study reveals that diverse bat-specific tEPEC strains and bfpA types have evolved in Pteropus spp. and have been circulating among populations for an extensive period, thereby confirming that all Australian Pteropus spp. are natural tEPEC hosts.