Healthy children in urban areas have a high prevalence of fecal carriage of drug-resistant E. coli.

In a previous study, we detected unexpectedly high levels of acquired antibiotic resistance in commensal Escherichia coli isolates from a remote Guaraní Indian (Bolivia) community with very low levels of antibiotic exposure and limited exchanges with the exterior. Here we analyzed the structure of the resistant E. coli population from that community and the resistance mechanisms. The E. coli population (113 isolates from 72 inhabitants) showed a high degree of genetic heterogeneity, as evidenced by phylogenetic grouping (77% group A, 10% group B1, 8% group D, 5% group B2) and genotyping by randomly amplified polymorphic DNA (RAPD) analysis (44 different RAPD types). The acquired resistance genes were always of the same types as those found in antibiotic-exposed settings [bla TEM , bla PSE-1 , catI, cmlA6, tet(A), tet(B), dfrA1, dfrA7, dfrA8, dfrA17, sul1, sul2, aphA1, aadA1, aadA2, aadA5, aadB, and sat-1]. Class 1 and class 2 integrons were found in 12% and 4% of the isolates, respectively, and harbored arrays of gene cassettes similar to those already described. The cotransferability of multiple-resistance traits was observed from selected isolates and was found to be associated with resistance conjugative plasmids of the F, P, and N types. Overall, these data suggest that the resistance observed in this remote community is likely the consequence of the dissemination of resistant bacteria and resistance genes from antibiotic-exposed settings (rather than of an independent in situ selection) which involved both the clonal expansion of resistant strains and the horizontal transfer/recombination of mobile genetic elements harboring resistance genes.The notion that the global dissemination of microbial drug resistance observed in the antibiotic era is related to the selective pressure generated by the use of antibiotics in clinical and veterinary practices, animal husbandry, and agriculture is supported by studies that have clearly correlated the emergence and dissemination of resistance with the use of antibiotics (1,10,19) and by the absence of acquired resistance in clinical isolates from the preantibiotic era (13,14). Surprisingly, however, antibiotic-resistant bacteria have also recently been detected in humans and wild animals living in remote areas where antibiotic exposure has been absent or minimal (2,9,11,22,30,32), raising a question about the mechanisms of resistance spread in those settings. To the best of our knowledge, the most isolated human context thus far investigated is represented by a very remote community of Guaraní Indians in the Bolivian Chaco, where we detected high levels of acquired antibiotic resistance in commensal Escherichia coli isolates (2). In that community, exchanges with inhabitants of other areas were very limited; antibiotic exposure at the time of the study had been minimal; and locally collected rainwater was the only water source, ruling out the possibility of sustained contamination of drinking water from the exterior (2).In this work we have analyzed the population struc...

Inactivation of the retinoblastoma protein (pRb) by phosphorylation triggers uncontrolled cell proliferation. Accordingly, activation of cyclin-dependent kinase (CDK)/cyclin complexes or downregulation of CDK inhibitors appears as a common event in human cancer. Here we show that Pin1 (protein interacting with NIMA (never in mitosis A)-1), a peptidylprolyl isomerase involved in the control of protein phosphorylation, is an essential mediator for inactivation of the pRb. Our results indicate that Pin1 controls cell proliferation by altering pRb phosphorylation without affecting CDK and protein phosphatase 1 and 2 activity. We demonstrated that Pin1 regulates tumor cell proliferation through direct interaction with the spacer domain of the pRb protein, and allows the interaction between CDK/cyclin complexes and pRb in mid/late G1. Phosphorylation of pRb Ser 608/612 is the crucial motif for Pin1 binding. We propose that Pin1 selectively boosts the switch from hypo-to hyper-phosphorylation of pRb in tumor cells. In addition, we demonstrate that the CDK pathway is responsible for the interaction of Pin1 and pRb. Prospectively, our findings therefore suggest that the synergism among CDK and Pin1 inhibitors holds great promise for targeted pharmacological treatment of cancer patients, with the possibility of reaching high effectiveness at tolerated doses. The retinoblastoma protein (pRb), the product of the RB1 gene (i.e., the tumor-suppressor gene involved in hereditary and sporadic retinoblastoma pathogenesis), is mainly responsible for the control of cell proliferation via two different mechanisms. The first is based on the interaction between pRb and different chromatin-modifying enzymes: pRb interacts with histone deacetylases (HDACs) 1, 2, and 3, histone methylase SUV39H1, and chromatin-remodeling enzymes Brg1 and Brm, thus repressing gene expression. 1 The second mechanism involves pRb controlling the cell cycle through interaction with the E2F family of transcription factors 2 in a phosphorylation-dependent way: in early and mid G1, the protein complex D-type cyclins/CDK4, 6 whereas in late G1, cyclins E(A)/CDK2 gradually phosphorylate pRb. Hyperphosphorylated pRb releases E2F transcription factors and allows the expression of genes that mediate entry into the S phase. 3 As pRb protein holds a central role in the cell cycle, its inactivation is necessary for enabling cancer cell proliferation. Different mechanisms of pRb inactivation have been described, although inactivation through phosphorylation is most common in human sporadic cancers. In this context, cyclin D1 overexpression induces CDK4/6 activation and thus pRb hyperphosphorylation. 4,5 In addition, the cyclindependent kinase (CDK) inhibitory partner, p16 protein (i.e.,

Cell cycle deregulation is one of the first steps that transform normal cells into tumor cells. CDKs are a family of proteins devoted to controlling cell cycle entry, progression and exit. Studies from animal models show a tissue-specific essentiality of the single CDKs. In cancer cells, mis-regulation of CDK function is a common event. For this reason the pioneer compound Flavopiridol was developed and many new drugs are currently under development. ATP and the last generation of non-ATP competitive inhibitors are now emerging as one of the most potentially powerful target therapies. Many clinical trials are ongoing, as either a single agent or in combination with the classical cytotoxic agents. In this review, we discuss new strategies and methods to design more potent, selective and specific CDK inhibitors, starting from evidence emerging from animal and cancer cell models.