BackgroundMany Escherichia coli strains are considered to be a component of the normal flora found in the human and animal intestinal tracts. While most E. coli strains are commensal, some strains encode virulence factors that enable the bacteria to cause intestinal and extra-intestinal clinically-relevant infections. Colibactin, encoded by a genomic island (pks island), and cytotoxic necrotizing factor (CNF), encoded by the cnf gene, are genotoxic and can modulate cellular differentiation, apoptosis and proliferation. Some commensal and pathogenic pks+ and cnf+ E. coli strains have been associated with inflammation and cancer in humans and animals.ResultsIn the present study, E. coli strains encoding colibactin and CNF were identified in macaque samples. We performed bacterial cultures utilizing rectal swabs and extra-intestinal samples from clinically normal macaques. A total of 239 E. coli strains were isolated from 266 macaques. The strains were identified biochemically and selected isolates were serotyped as O88:H4, O25:H4, O7:H7, OM:H14, and OM:H16. Specific PCR for pks and cnf1 gene amplification, and phylogenetic group identification were performed on all E. coli strains. Among the 239 isolates, 41 (17.2%) were pks+/cnf1−, 19 (7.9%) were pks−/cnf1+, and 31 (13.0%) were pks+/cnf1+. One hundred forty-eight (61.9%) E. coli isolates were negative for both genes (pks−/cnf1−). In total, 72 (30.1%) were positive for pks genes, and 50 (20.9%) were positive for cnf1. No cnf2+ isolates were detected. Both pks+ and cnf1+ E. coli strains belonged mainly to phylogenetic group B2, including B21. Colibactin and CNF cytotoxic activities were observed using a HeLa cell cytotoxicity assay in representative isolates. Whole genome sequencing of 10 representative E. coli strains confirmed the presence of virulence factors and antibiotic resistance genes in rhesus macaque E. coli isolates.ConclusionsOur findings indicate that colibactin- and CNF-encoding E. coli colonize laboratory macaques and can potentially cause clinical and subclinical diseases that impact macaque models.Electronic supplementary materialThe online version of this article (10.1186/s13099-017-0220-y) contains supplementary material, which is available to authorized users.

bEnteropathogenic Escherichia coli (EPEC) is the most important cause of persistent diarrhea in children, particularly in developing countries. Animals serve as pathogenic E. coli reservoirs, and compelling evidence for cross-species EPEC transmission exists. In this report, enzootic EPEC infection associated with up to 10.5% diarrhea-associated morbidity in a large laboratory Dutch Belted rabbit colony was investigated. These rabbits were obtained from a commercial vendor and had acute diarrhea following shipment. Fecal culture of 20 rabbits yielded 48 E. coli isolates, 83% of which were eae positive. Repetitive sequencebased PCR (REP-PCR) and serologic analysis identified a single disease-associated EPEC O145:H2 strain. In sampled rabbits, EPEC-positive culture and the presence of diarrhea were significantly associated. This strain displayed a localized adherence-like HEp-2 cell adherence pattern, as seen in diarrheic human infant EPEC isolates. Treatment was instituted with the fluoroquinolone antibiotic enrofloxacin, to which all isolates were susceptible. Preshipment parenteral enrofloxacin administration reduced diarrhea-associated morbidity 22-fold and mortality 12-fold in subsequent deliveries. This report emphasizes the zoonotic potential of animal EPEC strains and the need for virulence determinant-based screening of E. coli isolates from diarrheic animals.

Escherichia coli is a gram-negative bacillus that colonizes the gastrointestinal tract of humans and animals. 46 Although some strains are considered commensals, various intestinal and extraintestinal pathogenic E. coli pathotypes are associated with a wide range of clinical disease states in the host; 16,41 these strains are responsible for the deaths of more than 2 million humans annually. 65 Specific pathotypes often harbor similar virulence factors and correspond to distinct clinical and histologic lesions. Intestinal pathotypes include enteropathogenic E. coli, enterohemorrhagic E. coli, enteroinvasive E. coli, enterotoxigenic E. coli, enteroaggregative E. coli, diffusely adhering E. coli, and adherent-invasive E. coli. 65 Extraintestinal pathotypes include uropathogenic E. coli and neonatal meningitis E. coli, both of which have an enhanced ability to translocate through the intestinal epithelium and cause severe clinical disease.E. coli strains typically are classified into 1 of the 4 major phylogenetic groups: A, B1, B2, and D. 10,14,60 Groups B2 and D are often associated with pathogenicity, whereas fecal strains belonging to groups A and B1 generally lack virulence factors. 22,60 Strains belonging to pathogroup B2 have been isolated from the feces of persons from developed countries with increasing frequency. 52,70 These pathogenic strains encode various combinations of virulence genes and pathogenicity islands which promote invasion and colonization, evasion of host defenses, and damage to host tissues. Associated virulence factors include cytotoxins such as genotoxic cyclomodulins, cytotoxic necrotizing factors (cnf), cytolethal distending toxin (cdt), and the genotoxin colibactin (pks). These virulence factors modulate host cellular differentiation, proliferation, and apoptosis and promote cytopathic effects. 7,21,69 CNF is a 115-kDa cyclomodulin protein that induces cell-cycle alterations and cytoskeletal changes by activating rho GTPases, which leads to a variety of aberrant phenotypic effects including micropinocytosis, megalocytosis, and multinucleation. 62 cnf1 is chromosomally encoded, 23 whereas cnf2 is plasmid-encoded. 20 cnf-producing E. coli are considered necrotoxigenic and are associated with intestinal, urinary, 23 and meningeal infection of humans. 41 cnf + E. coli have previously been isolated from clinically

Escherichia coli strains have not been fully characterized in laboratory mice and are not currently excluded from mouse colonies. Colibactin (Clb), a cytotoxin, has been associated with inflammation and cancer in humans and animals. We performed bacterial cultures utilizing rectal swab, fecal, and extra intestinal samples from clinically unaffected or affected laboratory mice. Fifty-one E. coli were isolated from 45 laboratory mice, identified biochemically, and selected isolates were serotyped. The 16S rRNA gene was amplified and sequenced for specific isolates, PCR used for clbA and clbQ gene amplification, and phylogenetic group identification was performed on all 51 E. coli strains. Clb genes were sequenced and selected E. coli isolates were characterized using a HeLa cell cytotoxicity assay. Forty-five of the 51 E. coli isolates (88 %) encoded clbA and clbQ and belonged to phylogenetic group B2. Mouse E. coli serotypes included: O2:H6, O−:H−, OM:H+, and O22:H−. Clb-encoding O2:H6 mouse E. coli isolates were cytotoxic in vitro. A Clb-encoding E. coli was isolated from a clinically affected genetically modified mouse with cystic endometrial hyperplasia. Our findings suggest that Clb-encoding E. coli colonize laboratory mice and may induce clinical and subclinical diseases that may impact experimental mouse models.

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