Extraintestinal pathogenic Escherichia coli O1:K1:H7/NM from human and avian origin: detection of clonal groups B2 ST95 and D ST59 with different host distribution.

BACKGROUND: Extraintestinal pathogenic Escherichia coli (ExPEC) strains of serotype O1:K1:H7/NM are frequently implicated in neonatal meningitis, urinary tract infections and septicemia in humans. They are also commonly isolated from colibacillosis in poultry. Studies to determine the similarities of ExPEC from different origins have indicated that avian strains potentially have zoonotic properties. RESULTS: A total of 59 ExPEC O1:K1:H7/NM isolates (21 from avian colibacillosis, 15 from human meningitis, and 23 from human urinary tract infection and septicemia) originated from four countries were characterized by phylogenetic PCR grouping, Multilocus Sequence Typing (MLST), Pulsed Field Gel Electrophoresis (PFGE) and genotyping based on several genes known for their association with ExPEC or avian pathogenic Escherichia coli (APEC) virulence.APEC and human ExPEC isolates differed significantly in their assignments to phylogenetic groups, being phylogroup B2 more prevalent among APEC than among human ExPEC (95% vs. 53%, P = 0.001), whereas phylogroup D was almost exclusively associated with human ExPEC (47% vs. 5%, P = 0.0000). Seven virulence genes showed significant differences, being fimAvMT78 and sat genes linked to human isolates, while papGII, tsh, iron, cvaC and iss were significantly associated to APEC. By MLST, 39 of 40 ExPEC belonging to phylogroup B2, and 17 of 19 belonging to phylogroup D exhibited the Sequence Types (STs) ST95 and ST59, respectively. Additionally, two novel STs (ST1013 and ST1006) were established. Considering strains sharing the same ST, phylogenetic group, virulence genotype and PFGE cluster to belong to the same subclone, five subclones were detected; one of those grouped six strains of human and animal origin from two countries. CONCLUSION: Present results reveal that the clonal group B2 O1:K1:H7/NM ST95, detected in strains of animal and human origin, recovered from different dates and geographic sources, provides evidence that some APEC isolates may act as potential pathogens for humans and, consequently, poultry as a foodborne source, suggesting no host specificity for this type of isolates. A novel and important finding has been the detection of the clonal group D O1:K1:H7/NM ST59 almost exclusively in humans, carrying pathogenic genes linked to the phylogenetic group D. This finding would suggest D O1:K1:H7/NM ST59 as a host specific pathotype for humans.

Poultry as reservoir for extraintestinal pathogenic Escherichia coli O45:K1:H7-B2-ST95 in humans.

Escherichia coli strains O45:K1:H7 are implicated in severe human infections such as meningitis. Since an increasing prevalence of serogroup O45 among avian pathogenic (APEC) and human extraintestinal pathogenic (ExPEC) E. coli strains isolated in Spain have been noticed, the aims of the present study were to investigate similarities between poultry and human O45 isolates, and to investigate the evolutionary relationship of ST95 types. The genetic relatedness and virulence gene profiles of 55 O45 APEC obtained from an avian colibacillosis collection (1991-2011) and 19 human O45 ExPEC from a human septicemic/uropathogenic (UPEC) E. coli collection (1989-2010) were determined by multilocus sequence typing (MLST), pulsed-field-gel-electrophoresis (PFGE), ECOR phylogrouping, and PCR-based genotyping. Two main clonal groups were established. The most prevalent and highly pathogenic O45:K1:H7-B2-ST95 shows a successful persistence since the 90s to the present, with parallel evolution both in human and poultry, on the basis of their PFGE and virulence gene profile similarities (9 human strains and 15 avian strains showed ≥85% PFGE identity). Comparison of this group with other ST95 closely related members (O1:K1:H7 and O18:K1:H7 isolates from our collections) shows pathogenic specialization through conserved virulence genotypes. The other prevalent O45 clonal group characterized in this study, the O45:HNM/H19-D-ST371/ST2676 was only detected in APEC strains suggesting host specificity. In conclusion, poultry could be acting as a reservoir of O45:K1:H7-B2-ST95 and other pathogenic ST95 serotypes in humans. Further studies would be necessary to clarify if pathogenic mechanisms used by ST95 strains are the same in avian and human hosts.