Abstract
Infections of the respiratory tract are a common cause for morbidity in dolphins.1,2 Obviously, identifying the disease-causing microorganism is of great importance in management. Historically, blowhole swabs and exhalation plates have been used as a tool for this purpose. More recently, flexible bronchoscopy with bronchial washings has shown to be helpful.3,4 However, during passage through the pharynx, a bronchoscope will be contaminated with resident microbial flora. Therefore, a bronchial washing is likely to be polluted with microorganisms of the proximal airways. A technique that might overcome this problem is the Protected Brush Specimen (PBS), in which a sterile brush catheter is pushed out of its sealed sheath only after reaching the spot of interest with the bronchoscope.5-7 This technique has been known in human medicine for two decades and was also tested for use in horses.8 The purpose of this study was twofold. First, we wanted to determine whether the PBS showed less contamination with resident upper airway flora compared with bronchial washings. Second, we wanted to investigate whether the conducting airways of healthy dolphins were contaminated with bacterial flora.
Bronchoscopy was performed in five healthy specimens of Tursiops truncatus as part of their health checkup. In all animals, bronchial washings were collected from the lower airways and a protected brush sample was taken from the lower tracheal area just above the carina. The washings and PBS samples were immediately transported to the microbiology laboratory for culturing. We observed that in two out of the five animals the PBS culture remained sterile, even though PBS cultured in broth is a highly sensitive method to find bacterial presence. In the other animals, the PBS showed considerably less species of microorganisms than the washings, leaving the question whether this is the result of partial contamination during the procedure or that it represents resident flora in the lower respiratory tract of these animals. Another observation was the fact that in the bronchial washings several species of water bacteria (species commonly found in an aqueous environment without a host animal) were cultured and in the PBS none. It is very clear that no firm conclusions can be drawn from measurements in only five animals, but our observations indicate that PBS sampling might be a better diagnostic tool than bronchial washings in respiratory infections allowing a more precise and prudent use of antibiotic treatment. Furthermore, our findings suggest that in healthy animals the bacterial contamination of the conducting airways could be low or even absent. Repeating this study in a larger number of animals should be helpful in confirming and clarifying our results. Performing quantitative cultures could be a useful addition.
References
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