Dendrogram depicting the relationships of Mexican Typhimurium strains based on Xba I restriction patterns resolved by PFGE. The fingerprints were clustered by the UPGMA algorithm using Dice coefficients with 1.5% band position tolerance. Detailed information about strains can be found in Additional file 2. The strain column depicts the nomenclature used in the MLST database for the MEXSALM collection. Abbreviations for the state column: YU, Yucatán; MI, Michoacán; SL, San Luis Potosí; SO, Sonora. Abbreviations for the source column: HE, human enteric; HS, human systemic; HA: human asymptomatic; PM, pork meat; SI, swine intestine; BM, beef meat; CM, chicken meat; BI, beef intestine. The strains positive for the presence of pCMY-2 or pSTV are indicated by a plus symbol (+), the two strains marked with a +' in the pSTV column are the strains for which rck could not be amplified. The nomenclature of integron profiles (IP1–IP4) is explained in the text. The five main clusters (I-V) are highlighted by dotted rectangles, and the four subgroups (a, b, c and d) in cluster I are indicated by oval boxes. Cophenetic values are shown for the clusters formed above 90% similarity.