Rapid detection of Salmonella in milk by combined immunomagnetic separation-polymerase chain reaction assay

Agarose gel analysis of amplified DNA obtained from 1-mL artificially contaminated milk samples. Samples were collected after 8h of pre-incubation and immunomagnetic separation. Lane 1 (top and bottom) = 100-bp molecular weight ladder; lane 2 (top and bottom) = positive control; lanes 4, 5, and 6 (top) = first replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lanes 7, 8, and 9 (top) = second replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lanes 10, 11, and 12 (top) = third replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lanes 13 and 14 (top) and 4 (bottom) = fourth replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lanes 5, 6, and 7 (bottom) = fifth replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lane 16 (top and bottom) = negative control; lanes 3 and 15 were empty.

Agarose gel analysis of amplified DNA obtained from 1-mL artificially contaminated milk samples. Samples were collected after 10h of pre-incubation and immunomagnetic separation. Lane 1 (top and bottom) = 100-bp molecular weight ladder; lane 2 (top and bottom) = positive control; lanes 4, 5, and 6 (top) = first replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lanes 7, 8, and 9 (top) = second replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lanes 10, 11, and 12 (top) = third replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lanes 13 and 14 (top) and 4 (bottom) = fourth replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lanes 5, 6, and 7 (bottom) = fifth replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lane 16 (top and bottom) = negative control; lanes 3 and 15 were empty.

Agarose gel analysis of amplified DNA obtained from 1-mL artificially contaminated milk samples. Samples were collected after 12h of pre-incubation and immunomagnetic separation. Lane 1 (top and bottom) = 100-bp molecular weight ladder; lane 2 (top and bottom) = positive control; lanes 4, 5, and 6 (top) = first replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lanes 7, 8, and 9 (top) = second replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lanes 10, 11, and 12 (top) = third replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lanes 13 and 14 (top) and 4 (bottom) = fourth replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lanes 5, 6, and 7 (bottom) = fifth replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lane 16 (top and bottom) = negative control; lanes 3 and 15 were empty.

Agarose gel analysis of amplified DNA obtained from 1-mL artificially contaminated milk samples. Samples were collected after 14h of pre-incubation and immunomagnetic separation. Lane 1 (top and bottom) = 100-bp molecular weight ladder; lane 2 (top and bottom) = positive control; lanes 4, 5, and 6 (top) = first replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lanes 7, 8, and 9 (top) = second replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lanes 10, 11, and 12 (top) = third replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lanes 13 and 14 (top) and 4 (bottom) = fourth replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lanes 5, 6, and 7 (bottom) = fifth replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lane 16 (top and bottom) = negative control; lanes 3 and 15 were empty.

Agarose gel analysis of amplified DNA obtained from 1-mL artificially contaminated milk samples. Samples were collected after 16h of pre-incubation and immunomagnetic separation. Lane 1 (top and bottom) = 100-bp molecular weight ladder; lane 2 (top and bottom) = positive control; lanes 4, 5, and 6 (top) = first replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lanes 7, 8, and 9 (top) = second replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lanes 10, 11, and 12 (top) = third replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lanes 13 and 14 (top) and 4 (bottom) = fourth replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lanes 5, 6, and 7 (bottom) = fifth replicate with 10², 10¹, and 1 cfu/mL of milk, respectively; lane 16 (top and bottom) = negative control; lanes 3 and 15 were empty.