ABSTRACT
The pks genomic island encodes non-ribosomal peptide synthase (NRPS), polyketide synthases (PKS), and hybrid NRPS/PKS synthetase. This genomic island is mainly found in the members of the family Enterobacteriaceae, and is especially common in Escherichia coli of phylogroup B2 while frequently coexisting with other virulence factors. The pks-positive E. coli is able to synthesize colibactin, a genotoxic chemical compound. Thus, this pks-positive bacteria may induce the breaking of DNA double-strand and chromosomal instability, which lead to senescence and apoptosis of cells. As a result, pks-positive E. coli is positively associated with the occurrence of diseases such as colorectal neoplasms, neonatal meningitis, and septicemia. Epidemiological studies have also confirmed that pks-positive E. coli is associated with a variety of diseases. However, the exact pathogenic mechanism of pks-positive E. coli is still not understood. Despite its genotoxicity, the pks-positive E. coli also exhibits some positive effects including anti-inflammatory, analgesic, and antibiotic abilities. Therefore, the biological role of pks-positive E. coli is complicated. In this review, an overview of the pks genomic island and its prevalence in Enterobacteriaceae, as well as the biological function of pks-positive E. coli is described, aiming to provide references for further researches.
ABSTRACT
Ojective To explore the effect of the hydroxyapatite(HAp)and gelatin(Gel)coating on the healing of the polyethylene terephthalate(PET)artificial ligament.Methods The artificial ligaments were divided into a PET group with a pure PET surface and a PET/HAp/Gel group coated with HAp and Gel.Both coatings were observed using the scanning electron microscope(SEM).Forty-eight male New Zealand rabbits were randomly divided into two groups and underwent anterior cruciate ligament reconstruction,before two kinds of artificial ligaments were implanted respectively.Four weeks and 8 weeks after the operation,the rabbits were sacrificed,and histological hematoxylin and eosin (HE)staining as well as the biomechanical examination were performed.Results HAp/Gel coating was found depositing on the surface of PET artificial ligaments.Histological HE staining showed a thick fibrous connective tissue forming at the graft-host bone interface 4 weeks postoperatively,and the interface width of both groups were narrowed,with significantly more shrinking in the PET/HAp/Gel coating group.And new bone tissues were found in the interface of PET/HAp/Gel group 8 weeks after the operation.The biomechanical examination found significant differences in the failure load between the PET(46.16 ± 2.88 N) and PET/HAp/Gel group(71.32 ± 3.92 N)8 weeks after the surgery(P=0.0021).And 4 weeks and 8 weeks after the surgery,significant differences were found in the stiffness between the PET group and the PET/HAp/Gel group(11.06 ± 1.14 N/mm vs 16.20 ± 1.17 N/mm,P=0.0199;14.37 ± 0.88 N/mm vs 24.35 ± 1.35 N/mm,P=0.0008).Conclusion HAp/Gel coating can enhance the osteogenesis of PET artificial ligaments,promoting the new bone formation at the graft-host bone interface and herein strengthening the graft-host bone healing.