Impact of mouth rinsing before sputum collection on culture contamination

Sputum culture is more sensitive than smear microscopy for the diagnosis of tuberculosis and facilitates the performance of drug susceptibility testing. Initiatives are underway in high burden countries to expand capacity for sputum culture to improve TB case detection and patient care. Contamination by other bacteria and fungi is a limitation of sputum culture despite laboratory decontamination procedures. Potential sources of contamination include normal oral flora, poor dental hygiene and gingivitis or oral thrush, contamination of sputum containers by patients and staff due to poor collection technique or collecting saliva or pharyngeal specimens rather than deep respiratory secretions from the chest, and poor laboratory handling procedures. We studied whether mouth rinsing with clean boiled water before sputum collection would decrease culture contamination. Persons with suspected tuberculosis being evaluated at a TB clinic at Mulago Hospital, the largest public hospital in Uganda, underwent sputum collection for smear and culture during diagnostic evaluation.