Under normal circumstances, fluids collected from any enclosed body space should be sterile. When an infection occurs within a body cavity, the fluid that is collected from that site for diagnostic purposes will potentially have infectious organisms present on the cytospin. Several types of organisms can be observed on the Wright-stained preparation. Bacteria and fungus are the most common, but it is possible to demonstrate the presence of protozoan parasites as well.
Spirochetes and acid fast bacilli (AFB), such as mycobacteria, do not stain with Wright stain; they will not be detected, even if they are present.
Since bronchoalveolar lavage (BAL) is collected through an open airway, it is normal to observe normal respiratory flora. However, yeast and hyphae are never normal in a BAL.
It is standard practice before reporting the presence of bacteria in a fluid to correlate/confirm the findings with the microbiology lab.