Intragenic recombination leading to mosaic gene formation is known to alter resistance profiles for particular genes and bacterial species. Few studies have examined to what extent aminoglycoside resistance genes undergo intragenic recombination. We screened the GenBank database for mosaic gene formation in homologs of the aph(3′)-IIa (nptII) gene. APH(3′)-IIa inactivates important aminoglycoside ...