Comparative molecular characterization of Corynebacterium pseudotuberculosis of different origin.

This research aims to characterize Corynebacterium pseudotuberculosis in different animals and locations through ribotyping and testing its susceptibility to antimicrobial agents. Striking differences emerged in its nitrate reduction capability and unique genomic variants identified through endonuclease ribotyping, contributing to understanding antimicrobial resistance.

Objective and Methodology

• The researchers targeted to categorize and contrast 37 isolates of Corynebacterium pseudotuberculosis obtained from distinctive lesions and varied geographical strata. The source animals for these bacterial isolates included horses (28), cattle (1), sheep (3), and goats (5).
• Approaches adopted for this comparison were ribotyping and testing bacterial susceptibility to 17 distinct antimicrobial agents.
• Ribotyping, a genotyping method that analyses fragment patterns derived from restriction endonucleases on the ribosomal RNA of the bacteria, was done using two restriction endonucleases, specifically Apa 1 and Pst 1.
• The ability of the isolates to reduce nitrate (nitrate positivity or negativity) was also evaluated, as this property varies among bacteria and serves as an essential differentiation parameter.

Findings

• Almost all isolates from horses proved nitrate-positive, that is, they could reduce nitrate, barring one. Conversely, all isolates extracted from sheep and goats couldn’t reduce nitrate (nitrate-negative).
• Differences in ribotype patterns emerged in the study. Notably, one nitrate-negative isolate from a horse was ribotypically identical to other equine isolates but differed from the nitrate-negative isolates procured from sheep and goats.
• Ribotyping with Apa 1 endonuclease revealed inter-biotype differences but didn’t register differences within each biotype.
• Contrastingly, ribotyping using Pst 1 endonuclease unraveled one variant within each equine and ovine biotype, signifying intra-biotype genomic variants.

Antimicrobial Susceptibility

• The minimum inhibitory concentration (MIC; microgram/ml) of antimicrobials, signifying the smallest amount of an antimicrobial that inhibits visible bacterial growth, showed consistent outcomes between nitrate-negative and nitrate-positive groups with one exception.
• The C. pseudotuberculosis isolates from sheep and goats exhibited higher MIC for amikacin, an antibiotic. This indicates that they were more resistant to this drug, requiring a more significant amount to inhibit bacterial growth, compared to isolates from horses and cattle.

Implication

• This research enhances understanding of the genetic diversity in C. pseudotuberculosis across different hosts and locations, promising an enriched understanding of the bacterial pathogenicity and drug resistance which, in turn, assists in devising effective therapeutic strategies.