Relationship of mixed bacterial infection to prognosis in foals with pneumonia caused by Rhodococcus equi.

The study investigates the influence of mixed bacterial infections on the prognosis of foals (young horses) diagnosed with pneumonia induced by the Rhodococcus equi bacteria. The findings suggest that the existence of various other microorganisms alongside R. equi in the foal’s respiratory tract does not have a significant bearing on the disease’s outcome.

Research Methodology

• The research team thoroughly analyzed the case records of 155 foals diagnosed with R. equi pneumonia. The diagnoses were based on cultures of the respiratory tracts of these foals, and were done at two referral hospitals; the University of Florida (UF) and Texas A&M University (TAMU).
• R. equi bacteria were cultured from a tracheobronchial aspirate (TBA) in 115 of these foals and from lung tissues in 38 foals.
• The records also included information about any other microorganisms apart from R. equi that were also found in the cultures.

Key Findings

• The study unveiled a significantly higher survival rate of 71% (70 out of 99 foals) at UF compared to 50% (28 out of 56 foals) at TAMU. It also found that the growth of R. equi in pure cultures was much more common in samples sourced from UF (55%; i.e., 54 out of 99) than those from TAMU (23%; i.e., 13 out of 56).
• Other microorganisms such as Gram-positive bacteria, Gram-negative bacteria, and fungi were cultured alongside R. equi in 40, 41, and 23 cases respectively. Notably, the most common types of bacteria found in tandem with R. equi were beta-hemolytic streptococci and Escherichia coli.
• Mixed infections emerged more frequently in tracheobronchial aspirates than in lung tissues.

Conclusion

• The researchers found that the presence of additional bacteria or fungi in a TBA along with R. equi does not negatively affect the prognosis.
• After adjusting for hospital effects using multivariate logistic regression, the study concluded that there was no significant association between the isolation of multiple bacteria or fungi and the disease’s outcome.