2'-O-ribose methylation levels of ribosomal RNA distinguish different types of growth arrest in human dermal fibroblasts.

The 2'-O-methylation (2'-O-Me) of ribosomal RNA (rRNA) shows plasticity that is potentially associated with cell phenotypes. We used RiboMeth-seq profiling to reveal growth arrest-specific 2'-O-Me patterns in primary human dermal fibroblasts from three different donors. We exposed cells to hydrogen peroxide to induce cellular senescence and to high cell densities to promote quiescence by contact inhibition. We compared both modes of cell cycle arrest to proliferating cells and could indeed distinguish these conditions by their overall 2'-O-Me patterns. Methylation levels at a small fraction of sites showed plasticity and correlated with the expression of specific small nucleolar RNAs (snoRNAs) but not with expression of fibrillarin. Moreover, we observed subtle senescence-associated alterations in ribosome biogenesis. Knockdown of the snoRNA SNORD87, which acts as a guide for modification of a hypermethylated position in non-proliferating cells, was sufficient to boost cell proliferation. Conversely, depletion of SNORD88A, SNORD88B and SNORD88C, which act as guides for modification of a hypomethylated site, caused decreased proliferation without affecting global protein synthesis or apoptosis. Taken together, our findings provide evidence that rRNA modifications can be used to distinguish and potentially influence specific growth phenotypes of primary cells.

Extended-spectrum ß-lactamases, transferable quinolone resistance, and virulotyping in extra-intestinal E. coli in Uruguay.

INTRODUCTION: To characterize extended-spectrum ß-lactamases (ESBLs) and plasmid-mediated quinolone resistance (PMQR) genes in Escherichia coli isolates obtained from extra-intestinal samples in three Uruguayan hospitals. METHODOLOGY: Fifty-five ESBL-producing E. coli isolates were studied. Virulence genes, ESBLs, and PMQR genes were detected by polymerase chain reaction. ESBL-producing isolates were compared by pulsed-field gel electrophoresis. Multi-locus sequence typing was also performed on 13 selected isolates. RESULTS: Thirty-seven isolates harbored blaCTX-M-15 (67.3%), eight blaCTX-M-2 (14.6%), five blaCTX-M-14 (9.1%), three carried both blaCTX-M-2 and blaCTX-M-14, one blaCTX-M-9, and one blaCTX-M-8. Among the CTX-M-15 producers, 92% belonged to sequence types ST131 and ST405, and carried aac(6')Ib-cr as well. Isolates harboring blaCTX-M-2, blaCTX-M-14, blaCTX-M-9, or blaCTX-M-8 were found to be genetically unrelated. CONCLUSIONS: The successful dissemination of CTX-M-15-producing E.coli isolates seems to be linked to the spreading of high-risk clones and horizontal gene transfer. A trade-off between carrying more antibiotic resistance and less virulence-related genes could partially account for the evolutionary advantages featured by successful clones.