Comparative genomic analyses reveal a lack of a substantial signature of host adaptation in Rhodococcus equi (‘Prescottella equi’).

The research article discusses the genomic comparison among different strains of Rhodococcus equi, a harmful bacterium primarily affecting horses and occasionally humans. The study found slight differences among the strains but overall, there seemed to be a lack of significant signature of host adaptation in the organism.

Objective of the Research

• The research aimed to analyze and compare the genomic structures of varied strains of Rhodococcus equi, also named ‘Prescottella equi,’ a pathogenic actinomycete primarily known for infecting horses but has recently emerged as an opportunistic pathogen in humans.

Method

• Researchers sequenced the genome (the whole DNA set) of the type strain of R. equi known as C7(T).
• Comparative genomics was then carried out with the sequenced genome of another foal strain, 103S, and a human strain, ATCC 33707.

Findings

• It was observed that the R. equi strains were closely related to each other, suggesting high genetic similarity among strains regardless of the host.
• However, these strains were found to be substantially genetically distant to other Rhodococci and Nocardia brasiliensis, indicating unique genomic features in R. Equi.
• Further analysis revealed only minor differences which could possibly be associated with host adaptation when the bacterium transitions from infecting foals to infecting humans.
• One such difference was the presence of the ‘paa operon’ in the human strain. This group of genes is often found in bacteria and potentially involved in the process of pathogenesis – the ability to cause disease. However, this finding was not substantial enough to indicate a strong host-adaptation signature in R. equi.

Conclusion

• Even though minor genomic differences were identified among strains of R. equi, a significant evidence indicating a substantial host-adaptation signature in the R. equi bacterium was lacking.
• This implies that this organism does not demonstrate significant genetic changes or development of specialized traits when transitioning between different hosts. Or in other words, R. equi may maintain its set of genes irrespective of whether it’s infecting horses or humans.