Identifying bacterial species by making cloned DNA probes

Many bacterial species that are part of the Campylobacter group have been identified as disease – causing agents of animals and humans. One species that is of veterinary importance is Campylobacter hyointestinalis, which causes proliferative enteritis in pigs and other animals. However, many Campylobacter species appear similar, making it difficult to confidently diagnose which species is infecting a patient using visual identification methods. This delays proper treatment and causes confusion as to which species is causing disease if there are multiple species present.

Instead of using visual differences between species to determine which Campylobacter species is causing disease in a patient, probes for particular species are being developed by cloning DNA fragments from the bacteria’s chromosomes. These DNA probes will allow for rapid identification of different Campylobacter species because a DNA probe will only form a hybrid with the DNA of the species it was cloned from and not any other species, even if they are similar.

Campylobacter hyointestinalis probes were made by cloning fragments of chromosomal DNA into a plasmid vector, and allowing the fragments to be combined into the plasmid DNA as it replicated. The probes were then mixed with Campylobacter hyointestinalis and Campylobacter fetus, to see which probes would show specificity for Campylobacter hyointestinalis. When these probes were tested in samples from animal specimens, they only formed hybrids with Campylobacter hyointestinalis. This demonstrates cloned DNA probes are a quick, efficient method of identifying specific disease – causing bacteria in an animal, leading to faster diagnosis and treatment of diseases.

If you wish to read about other experiments within veterinary medicine that involve cloning DNA, follow these links:

http://cvi.asm.org/cgi/reprint/12/2/334

http://journals.cambridge.org/download.php?file=%2FPAR%2FPAR125_03%2FS0031182002002019a.pdf&code=62919565bfd61c5f0e7fa9d615b280fd