Detection of strain variation in isolates of Rhodococcus equi from an affected foal using repetitive sequence-based polymerase chain reaction.

This research aimed to investigate the extent of strain variation among isolates of Rhodococcus equi, a significant pathogen in young foals, within individual animals. Using advanced laboratory techniques, the researchers found that foals could be infected by multiple strains of the pathogen, and identical strains could occur in different parts of the body.

Objective and Context of the Research

• This research project addresses the existence and extent of genotypic variation in Rhodococcus equi bacteria isolated from the same foal. R. equi is a significant bacterial pathogen that affects foals aged between 1 and 6 months.
• Despite some data showing that foals are exposed to diverse R. equi strains within their environment, the extent to which differing strains infect individual foals is not well known.
• Understanding the variation and movement of R. equi strains within a single organism could provide insights into the disease’s pathophysiology and management.

Methodology: Repetitive Sequence-Based Polymerase Chain Reaction

• The team used a technique called repetitive sequence-based polymerase chain reaction (rep-PCR) electrophoresis, using an automated microfluidics chip format to genotype 9 virulent R. equi isolates.
• The isolates were obtained from different anatomic locations within a single foal, including various regions of the lung and intra-abdominal lymph nodes.
• Microfluidics technology allows researchers to manipulate and control fluids at an extremely small scale, often using a “lab-on-a-chip” system. This method allowed for rapid, reproducible, and discriminating typing of R. equi isolates and, as such, was a highly suitable choice for this investigation.

Findings: Genotypic Variation and Multiple Infections

• The research team discovered six distinct genotypes within the nine isolates, challenging for the notion that individual foals are infected by a single R. equi strain.
• All the isolates taken from the lungs were different. However, one of them matched an isolate from an intestinal lymph node, and another matched one from a mesenteric lymph node.
• Therefore, the same R. equi strain can infect different and remote anatomical locations within the same organism, and more than one strain can coexist within the same foal.

Implications and Potential Applications of the Findings

• The phenomenon of a single organism being infected by multiple strains of a pathogen and the occurrence of identical strains in varied locations within an individual may have significant implications for disease treatment and control strategies.
• Understanding the genotypic variation and multiplicity of infections in R. equi could be valuable to improve medical interventions for affected foals, including targeted antibiotic therapy and potential vaccination strategies.
• The research design and the “lab-on-a-chip” methodology can have applications in broader microbiology and genetic research, particularly those involving genotypic variation in bacteria and multiple infection parsimony.