Evaluation of a guarded bronchoscopic method for microbial sampling of the lower airways in foals.

This research examines a new method of reducing contamination during bronchoscope microbial sampling within the lower airways of foals. Conducted via the use of methylene blue as a nasopharyngeal dye marker, the study suggests a contaminated bronchoscope may cause problems in the interpretation of isolates from bronchoalveolar lavage (BAL) specimens from foals. The tested “guarded” bronchoscope method, which involves a clear sterile sheath, showed a significant reduction in contamination.

Methodology

• The research made use of a specific dye marker, methylene blue (MB), to examine relative contaminations from the upper airways of BAL specimens. This was applied during both standard bronchoscopy (SB) and guarded bronchoscopy (GB).
• In the GB method, a clear sterile cellulose sheath was fitted over the bronchoscope with the aim of shielding the endoscope tip and channel from contamination.
• The presence of methylene blue, a sign of contamination, was visually assessed in the BAL specimens obtained from foal subjects.

Results

• The results showcased the presence of methylene blue in seven out of eight BAL samples taken from the foals following the standard bronchoscopy however, there was no detection of MB in any samples retrieved via the guarded method.
• Statistically, this difference was significant, with the GB method experiencing less contamination as evidenced by less detectable amounts of MB.
• The guarded bronchoscopy was further used to examine the microbial flora of the lower airways in healthy weaned foals.
• Bacteria were isolated in 97% of the BAL samples, and in moderate or large quantities in 87% of the foals. These included potential pathogens like Bordetella bronchiseptica, Streptococcus zooepidemicus, Staphylococcus aureus, Mycoplasma felis and Streptococcus pneumoniae.

Conclusion

• The research paper concludes that a bronchoscope and bronchoalveolar lavage samples could be readily contaminated by a dye marker located in the nasopharynx of foals.
• Within the study, containment was significantly reduced by sheathing the endoscope, suggesting that the Guarded Bronchoscopy method might offer a more accurate procedure, less prone to contamination.
• The researchers also suggest that this contamination during bronchoscopy could obscure the interpretation of isolates from BAL specimens from foals, which may have a bacterial flora in the lower airways without cytological evidence of inflammation.