Multilocus sequence typing (MLST) analysis has been emerging as a powerful tool for genotyping specific bacterial species. MLST utilizes internal fragments of multiple housekeeping genes and the combination of each allele defines the sequence type for each isolate. MLST databases contain reference data and are freely accessible via internet websites. The standard method for investigating short-term hospital outbreaks is still pulse-field gel-electrophoresis and MLST analysis is not a substitute. However, analysis of sequence types and clonal complexes (closely related sequence types) enables identification and understanding of a specific clone that is widely spreading among drug-resistant organisms, or a key clone that is important for evolution of the organism. In the case of Escherichia coli, CTX-M-15 or CTX-M-14 extended-spectrum beta-lactamase producing ST131 clone has emerged and spread globally in the last 10 years. MLST analysis is an unambiguous procedure and is becoming a common typing method to characterize isolates.