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Abstract
Tim Bolton

Fellow – Tim Bolton

Mentor – Noah Cohen

Project – Genotyping of Rhodococcus equi isolates from a single foal by REP PCR

Objective – (1) To evaluate the capacity of the DiversiLab system to genotype R. equi; and, (2) To describe the extent to which multiple pulmonary and extra-pulmonary isolates from an individual foal were the same strain (i.e., were clonal), or whether multiple strains (i.e., polyclonal or mixed infection) can be found in a given host.

Animals or Sample Population – A 10 week old foal containing 9 distinct pyogranulomatous lesions. Four isolates were obtained from different regions of the lung and 5 were from abscessed intraabdominal lymph nodes (LN).

Procedure – The isolates underwent DNA extraction and rep-PCR amplification using commercial kits. Next, rep-PCR amplicons underwent electrophoresis in an automated microfluidics chip format, and a virtual gel, dendrogram, and similarity matrix were generated using commercial data analysis software.

Results – Five distinct genotypes were identified among the 9 isolates. None of the pulmonary isolates were identical; however, a pulmonary isolate was found to be identical to isolates recovered from a small intestinal, a cecal, and a small colonic LN, and another pulmonary isolate was identical to an isolate from a mesenteric LN.

Conclusions and Clinical Relevance – These results indicate that foals can be infected with multiple strains of virulent R. equi. Furthermore, identical strains can be found in multiple, remote anatomic locations in an infected foal, and this can occur for >1 strain in the same foal. The automated system used in this study provided a rapid, reproducible, and discriminating method for typing R. equi isolates. Thus, this system might be used as a standard method for genotyping R. equi isolates.