1st Student's Major

Biological Sciences

1st Student's College

Science, Engineering and Technology

Students' Professional Biography

Kelly E. Rock was a student in the Department of Biological Sciences at Minnesota State University, Mankato.

Mentor's Name

Timothy Secott

Mentor's Email Address


Mentor's Department

Biological Sciences

Mentor's College

Science, Engineering and Technology


Mycobacterium avium subsp. paratuberculosis (Mpt) is the etiologic agent of Johne’s disease, a chronic intestinal disease in cattle that threatens the economic viability of dairy farming. Diagnostic culture is typically unrewarding until several years after infection when clinical signs can be observed. This leads to widespread infection within the herd. Difficulty in culturing Mpt may be a result of oxidative damage due to the increased metabolic rate when dormant organisms are recovered in a nutrient rich medium. In order to improve recovery it is believed that some organisms secrete a growth factor in times of environmental stress which enables them to grow more quickly when conditions improve. The purpose of the project was to test conditioned medium (CM) and its components as a method of improving the recovery of Mpt. The conditioned medium from Mpt was separated into 4 fractions based on molecular weight using centrifuge filters. Unsupplemented media (Middlebrook 7H9C or Luria-Bertani broth) and those containing serial dilutions of fractionated or unfractionated Mpt-conditioned medium were inoculated with Mpt or Mycobacterium smegatis (MS); a non-pathogenic species. Growth was monitored by measuring the optical density of the cultures for up to 30 days. Unfractionated Mpt-conditioned medium promoted a two fold or greater enhancement of Mpt growth, but had no effect on that of MS. Results of treatment with conditioned medium fractions are pending. Recovery of dormant Mpt was increased by the use of conditioned medium.

Creative Commons License

Creative Commons Attribution-NonCommercial 4.0 International License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License



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