SputumA sputum sample is the name given to the mucus that is coughed up from the lungs. In is usually used for microbiological investigations of respiratory infections. The best sputum samples contain very little saliva, as this contaminates the sample with oral bacteria. When a sputum specimen is plated out, it is best to get the portion of the sample that most looks like pus onto the swab. If there is any blood in the sputum, this should also be on the swab. Microbiological sputum samples are usually used to look for infections by Branhamella catarrhalis, Streptococcus pneumoniae and Haemophilus influenzae. Other pathogens can also be found.