Cytotoxic strains encoding colibactin and cytotoxic necrotizing factor (CNF) colonize laboratory macaques.

Background: Many strains are considered to be a component of the normal flora found in the human and animal intestinal tracts. While most 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 ( island), and cytotoxic necrotizing factor (CNF), encoded by the gene, are genotoxic and can modulate cellular differentiation, apoptosis and proliferation. Some commensal and pathogenic + and + strains have been associated with inflammation and cancer in humans and animals.

Results: In the present study, 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 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 and gene amplification, and phylogenetic group identification were performed on all strains. Among the 239 isolates, 41 (17.2%) were +-, 19 (7.9%) were -/+, and 31 (13.0%) were +/+. One hundred forty-eight (61.9%) isolates were negative for both genes (-/-). In total, 72 (30.1%) were positive for genes, and 50 (20.9%) were positive for . No + isolates were detected. Both + and + strains belonged mainly to phylogenetic group B2, including B2. Colibactin and CNF cytotoxic activities were observed using a HeLa cell cytotoxicity assay in representative isolates. Whole genome sequencing of 10 representative strains confirmed the presence of virulence factors and antibiotic resistance genes in rhesus macaque isolates.

Conclusions: Our findings indicate that colibactin- and CNF-encoding colonize laboratory macaques and can potentially cause clinical and subclinical diseases that impact macaque models.