How to Interpret Respiratory Fluids in Terms of Microbiology?

The microbiological analysis of respiratory fluids, generally performed in the laboratory, is with cytological evaluation of these fluids an ancillary examination of choice in the clinical and functional investigation of the respiratory system. This presentation aims to provide the practitioner with sufficient information to be able to interpret objectively both isolation and quantification of respiratory fluids being performed by the laboratory. Microbiological assessment classically includes virology, parasitology, bacteriology and mycology. These methods are conventionally used in three situations: - when clinical signs are present, suggesting an acute disease (purulent nasal discharge …); - when non-specific clinical signs are observed (cough …); - when clinical signs are not obvious or even absent (poorperformance …). Upper respiratory tract represents the area predominantly involved in primary replication of many viruses (rhinitis viruses, herpesviruses, influenza …). Analysing nasopharyngeal swabs is then the method of choice during acute respiratory troubles. Concerning respiratory fluids, tracheal wash (TW) is a sample both easy to perform and, in some circumstances, potentially useful. All microbiological investigations (virology, parasitology, bacteriology and mycology) may be performed on this fluid. In the same principle, lavage fluid may be collected from guttural pouches for bacteriological research. While some contamination of these different samples may occur, it is almost impossible to achieve a bronchoalveolar lavage (BAL) avoiding nasopharyngeal contamination. Microbiological investigation of this latter is then not recommended as a routine procedure […]