Prevalence and pathologic effects of colibactin and cytotoxic necrotizing factor-1 (Cnf 1) in Escherichia coli : experimental and bioinformatics analyses.

Background: The colibactin and cytotoxic necrotizing factor 1 (Cnf 1) are toxins with cell cycle modulating effects that contribute to tumorgenesis and hyperproliferation. This study aimed to investigate the prevalence and pathologic effects of Cnf 1 and colibactin among hemolytic uropathogenic Escherichia coli ( UPEC ). The bioinformatics approach incorporated in this study aimed to expand the domain of the in vitro study and explore the prevalence of both toxins among other bacterial species. A total of 125 E. coli isolates were recovered from UTIs patients. The isolates were tested for their hemolytic activity, subjected to tissue culture and PCR assays to detect the phenotypic and genotypic features of both toxins. A rat ascending UTI in vivo model was conducted using isolates expressing or non-expressing Cnf 1 and colibactin (ClbA and ClbQ). The bioinformatics analyses were inferred by Maximum likelihood method and the evolutionary relatedness was deduced by MEGA X.
Results: Only 21 (16.8%) out of 125 isolates were hemolytic and 10 of these (47.62%) harbored the toxins encoding genes ( cnf 1 ⁺ , clbA ⁺ and clbQ ⁺ ). The phenotypic features of both toxins were exhibited by only 7 of the ( cnf 1 ⁺ clbA ⁺ clbQ ⁺ ) harboring isolates. The severest infections, hyperplastic and genotoxic changes in kidneys and bladders were observed in rats infected with the cnf 1 ⁺ clbA ⁺ clbQ ⁺ isolates.
Conclusion: Only 33.3% of the hemolytic UPEC isolates exhibited the phenotypic and genotypic features of Cnf 1 and Colibactin. The in vivo animal model results gives an evidence of active Cnf 1 and Colibactin expression and indicates the risks associated with recurrent and chronic UTIs caused by UPEC . The bioinformatics analyses confirmed the predominance of colibactin pks island among Enterobacteriaceae family (92.86%), with the highest occurrence among Escherichia species (53.57%), followed by Klebsiella (28.57%), Citrobacter (7.14%), and Enterobacter species (3.57%). The Cnf 1 is predominant among Escherichia coli (94.05%) and sporadically found among Shigella species (1.08%), Salmonella enterica (0.54%), Yersinia pseudotuberculosis (1.08%), Photobacterium (1.08%), Moritella viscosa (0.54%), and Carnobacterium maltaromaticum (0.54%). A close relatedness was observed between the 54-kb pks island of Escherichia coli , the probiotic Escherichia coli Nissle 1917, Klebsiella aerogenes , Klebsiella pneumoniae and Citrobacter koseri .
Competing Interests: Competing interestsThe authors declare that they have no competing interests.