Abstract: Methods for differentiating E. coli sequence type 131 are described. In one implementation, a method that employs example techniques in accordance with the present disclosure for determining E. coli sequence type 131 includes amplifying a gene target in the presence of a fluorescent reporter dye; exposing the gene target and the fluorescent reporter dye to an increasing temperature gradient to denature and reduce the helicity of a double-stranded oligo of the gene target; recording fluctuations in fluorescence using a High Resolution Melting analysis (HRM)-capable thermocycler; and producing a melt curve unique to the gene target.