Rhodococcus equi pneumonia in 48 foals: response to antimicrobial therapy.

This study reviews the medical records of 48 foals suffering from Rhodococcus equi pneumonia and their response to antimicrobial therapy. The researchers found no significant difference between survivors and non-survivors in terms of age, duration of illness, and some medical parameters. However, a decline in mortality was observed with a specific combination treatment, and none of the foals treated with a certain other treatment survived.

Research Background and Purpose

• The research aimed at reviewing and analyzing the case records of 48 foals (young horses) afflicted with Rhodococcus equi pneumonia. Rhodococcus equi is a common bacterium causing severe pneumonia in foals.
• The review focused on understanding the foals’ responses to various antimicrobial treatments. The goal was to identify if any specific treatment strategy impacted the survival rates.

Findings

• Out of the 48 foals, 20 survived the pneumonia while 28 didn’t. The researchers found that the age of onset of illness, duration of illness prior to admission, WBC (white blood cell count), and plasma fibrinogen content (a protein vital in clotting process) had no significant effect on the survival outcome. In other words, these characteristics were not markedly different between the survivors and non-survivors.
• All of the foals had R. equi isolated from either a tracheobronchial aspirate (a sample from the airways) or lung specimens from necropsies (post-mortem examinations). This confirms that all foals were indeed suffering from Rhodococcus equi pneumonia.
• All of the isolated R. equi bacteria were found to be susceptible (that is, vulnerable) to erythromycin and gentamicin in lab conditions. Susceptibility to other drugs varied, with resistance being highest to cephalothin and penicillin.

Treatment and Outcome

• 13 out of 20 surviving foals were treated with either erythromycin or rifampin or both. This suggests a positive effect of these medicines on survival outcomes, but more data would be needed to establish a firm link.
• There was a noticeable decline in the mortality rate with the introduction of the combination of erythromycin and rifampin, corroborating the above observation.
• Conversely, none of the foals treated with a combination of penicillin and gentamicin survived, suggesting that this treatment strategy was ineffective.
• Symptoms of chronic, active, non-septic synovitis (inflammation of the synovial membrane in the joints) were confirmed in 17 foals. These foals displayed joint distension (swelling), with slight or no apparent lameness.