Catalyzes the 2'-O-methylation at nucleotide C1920 in 23S rRNA (PubMed:24796671, PubMed:29404277). Enhances motility (PubMed:24796671, PubMed:29404277, PubMed:32134554). Enchances biofilm formation (PubMed:29404277, PubMed:32134554). Involved in the assembly of 70S ribosomes (PubMed:24796671). Involved in virulence by promoting adherence and invasion to host cells (PubMed:18389311, PubMed:23971210, PubMed:32134554). Involved in pathogenicity by modulating secretion of host-protective chemokine interleukin 8 (IL-8) (PubMed:32134554). Involved in susceptibility to antibiotic capreomycin (PubMed:24796671, PubMed:32134554). cytidine(1920) in 23S rRNA + S-adenosyl-L-methionine = 2'-O-methylcytidine(1920) in 23S rRNA + H(+) + S-adenosyl-L-homocysteine kcat is 0.0048 min(-1) for 50S ribosomal subunit. kcat is 0.0044 min(-1) for S-adenosyl-L-methionine. High methylation activity of the 50S ribosomal subunit at 37 degrees Celsius. Loss of activity at 42 degrees Celsius. Cells lacking this gene have no 2'-O-methylation activity at nucleotide C1920 in 23S rRNA (PubMed:29404277). Impeded motility (PubMed:24796671, PubMed:29404277, PubMed:32134554). Impaired biofilm formation (PubMed:29404277, PubMed:32134554). Cells form clumps which lack the structural roughness seen in the wild-type. The cells are less bulky, but otherwise they have no obvious alteration in dimensions, shape or flagellar structure (PubMed:29404277). Accumulation of 50S ribosomal subunits and reduced amount of functional 70S ribosomes (PubMed:24796671). Reduced adherence to the surface of Caco-2 human intestinal epithelial cells and impaired capacity to invade them (PubMed:18389311, PubMed:23971210, PubMed:32134554). Reduced interleukin 8 (IL-8) chemokine secretion by the Caco-2 cells. Impaired adhesion and invasion to RAW264.7 murine macrophage cells, but no effect on survival within the macrophages as both the wild-type and mutant cells are killed within 48 hours (PubMed:32134554). Resistant to capreomycin indicated by increased minimal inhibitory concentration (MIC) value (PubMed:24796671, PubMed:32134554). No difference in hemolytic activity between the mutant and the wild-type (PubMed:18389311). Belongs to the TlyA family.