[Characterization of Rhodococcus equi isolates from horse and man].

The research article focuses on the characterization of ‘Rhodococcus equi’ bacteria which have been isolated from both horses and humans. The study identified the bacteria through their morphological, biochemical and serological properties, and evaluated their sensitivity to different antibiotics.

Morphological, Biochemical and Serological Properties

• The study evaluated the characteristics of ‘Rhodococcus equi’ isolates from 19 diseased horses and 22 human cases. It found that almost all cultures displayed a consistent life cycle involving a transformation from rod-shape to coccus-shape and vice versa.
• The biochemical and serological properties of the isolates were found to be consistent with the typing system described by Prescott in 1981. The predominant serotypes were 1 and 2.
• Among the horse isolates, those belonging to serotype 1 were primarily haemagglutination-positive (causing red blood cells to clump together), while the serotype 2 isolates were haemagglutination-negative.
• In contrast, human isolates did not show clear links between serotypes and haemagglutinating properties.

Antibiotic Susceptibility

• The research tested sensitivity of the ‘Rhodococcus equi’ cultures to several antibiotics. They were most susceptible to erythromycin, gentamicin, imipenem, minocycline, neomycin, rifampicin, streptomycin and vancomycin.
• However, they were resistant or moderate susceptible to tetracycline and penicillin G, with resistance observed in 71% and 75% of cultures, respectively.
• Almost all cultures were resistant to the antibiotic ceftazidime. Meanwhile, most cultures showed susceptibility to cefotaxime.

DNA Characterization

• DNA extraction and pulsed field gel electrophoresis techniques were employed for further characterization of the cultures.
• Upon digestion with the restriction enzyme AsnI, the resultant DNA profiles allowed for strain-specific characterization, further enhancing the understanding of differences between ‘Rhodococcus equi’ isolates from different hosts.