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PCR Detection of Microbial Pathogens PCR Detection of Microbial ...

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Identification <strong>of</strong> B. abortus by <strong>PCR</strong> 103<br />

Fig. 1. Predicted amplified loci (rows) for various categories <strong>of</strong> unknowns (columns).<br />

(A) The four loci for each category are shown with their hybridizing primers;<br />

(B) the predicted products resulting from successful amplification. , 16S locus;<br />

, alkB locus; , IS711; , wboA locus; , eri locus; , DNA absent; , hybridizing<br />

amplification primer; , nonhybridizing primer.<br />

A 500-bp product from the IS711-alkB locus is amplified with all B. abortus<br />

(biovar 1, 2, and 4) templates including those from the vaccine strains. Other<br />

Brucella species and bacteria do not have this DNA sequence, and no product<br />

will be amplified. A 300-bp product will be amplified from the IS711-wboA<br />

locus found only in the vaccine strain RB51. A 180-bp product is amplified<br />

from the eri gene present in all Brucella species and strains except B. abortus<br />

vaccine strain S19. Other bacterial genomes lack this locus and will not<br />

amplify the 180-bp product. Sample results are shown in Fig. 2.<br />

3.6. Troubleshooting<br />

The B. abortus RB51 positive control should amplify all four products. If some<br />

or all <strong>of</strong> the products are missing, then there was a problem with the Master Mixture<br />

or the cycling parameters. Repeat the assay with fresh Master Mixture.<br />

The presence <strong>of</strong> amplification in the negative controls indicates a contamination<br />

problem. If both negative controls are contaminated, then the entire<br />

batch <strong>of</strong> Master Mixture was probably contaminated and should be discarded.

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