Selection and counting of aerobic gram-negative bacilli in saliva by the spiral system

A four-month pilot study involving 100 volunteers, 100 hospitalised patients not on antibiotics and 100 patients on antibiotics was performed using a non labor-intensive system involving inoculator, laser colony counter and 14-cm petri dishes containing MacConkey medium to determine the number of aerobic gram-negative bacilli present in saliva. All colonies greater than or equal to 0.75 mm in diameter were found to be aerobic gram-negative bacteria. This was also valid for Pseudomonas aeruginosa, but only after incubation for 48 h. This study showed that the novel and practical technique used can be applied to a large number of saliva specimens, and antibiotics have limited impact on the buccal microflora (intensive care unit excluded).