[Detection of rhodococcus equi by microbiological culture and by polymerase chain reaction in samples of tracheobronchial secretions of foals].

The research investigates if newer PCR-methods enhance the diagnosis of Rhodococcus equi, a bacterium causing pneumonia in foals. The methods were compared with standard microbiological culture in terms of sensitivity and specificity. The results suggested the combination of both methods for comprehensive diagnosis.

Objective of the Study

• The study aimed at assessing if the novel PCR (polymerase chain reaction) techniques improve the diagnostic accuracy of Rhodococcus equi infections, which cause pneumonia in foals.

Methodology

• Researchers carried out a two-step process. Initially, they determined the sensitivity and specificity of the PCR methods with respect to microbiological culture methods, often referred to as the “gold standard”.
• Next, they examined the sensitivity and specificity of both microbiological and PCR methods with respect to clinical diagnosis.
• The sample comprised tracheobronchial secretions of 48 foals with pulmonary abscesses and 37 healthy foals. The evaluations were performed by bacteriological culture as well as four PCR methods: aceA-, ideR-, vapA- and VP-PCR.

Results

• In terms of sensitivity, most PCR methods ranged between 63.9 to 69.4% except for vapA-PCR with 27.8%.
• The specificity of all PCR methods ranged between 98 to 100%, suggesting these methods have a high probability of correctly identifying healthy foals.
• In comparison, the clinical diagnosis showed a low sensitivity (66.7%) and low specificity (51.0%).
• When analysed against the clinical diagnosis, the microbiological culture method demonstrated a sensitivity of 50.0% and specificity of 67.7%.
• The sensitivity of aceA-, ideR-, and VP-PCR methods was between 33.3 and 37.5%, with vapA-PCR showing lower sensitivity (10.4%).
• However, specificity of all PCR methods ranged from 78.4 to 86.5%.

Conclusion

• The research concluded that the “Culture” and “PCR” techniques offer different diagnostic potentials in terms of detecting Rhodococcus equi infections.
• Therefore, a combination of microbiological culture and PCR methods should be employed when examining tracheobronchial secretion samples from foals for a more accurate diagnosis of R. equi pneumonia.