Negative correlation between oral malodour and numbers and activities of sulphate-reducing bacteria in the human mouth

The majority of cases of oral malodour are thought to be due to bacterial a ctivities in the mouth, but many of the bacterial species responsible have not been identified. Volatile sulphide compounds have been proposed as cons tituents of oral malodour. Therefore, the relation between intensity of odo ur and numbers of bacteria in the mouth that are sulphide-producing from su lphate was investigated. Numbers of such dissimilatory sulphate-reducing ba cteria (SRB) and sulphide reduction rates were evaluated in samples from di fferent oral sites in relation to measures of oral malodour. Results showed that sulphate-reducing bacterial numbers and activities were negatively co rrelated with malodour, as determined by organoleptic assessment and measur ement with a sulphide-monitoring instrument, the Halimeter. The data indica te that sulphide produced by oral SRB may not be an important contributor t o oral malodour. A rather poor correlation was observed between Halimetric and organoleptic values, indicating that these methods may measure differen t aspects of oral malodour intensity. (C) 1999 Elsevier Science Ltd. All ri ghts reserved.