Diurnal Variation of Oral Bacterial Counts among Patients with Reduced ADL

Abstract

Numerous studies have reported the effectiveness of oral care in the elderly, as well as the association between oral bacteria and aspiration pneumonia. Given that oral bacterial counts constantly change, it is difficult to interpret counts from just one sampling. The purpose of this study was to assess diurnal variations in oral bacterial counts.

Subjects were 36 patients from rehabilitation centers and hospitals in a certain prefecture in Japan who satisfied the following conditions: 1) age of 50 years or older, 2) capable of self-care, 3) capable of gargling for 30 s with 10 ml of sterile physiological saline and expelling it, 4) capable of performing the routine seven times a day; and 5) not having taken any antibiotics for the preceding 3 weeks prior to sampling. Seven samples of oral bacteria were collected in 1 day, each corresponding to the time before and after each of the three meals as well as just before sleep. After gargling for 30 s with sterile physiological saline, a portion of the saline was collected into a test tube to be delivered for examination. We then cultured samples and determined oral bacterial counts (CFU/ml).

Oral bacterial counts were highest before breakfast and lowest after dinner. When bacterial counts were compared before and after each meal, counts after each meal were significantly lower than those before each meal. Moreover, counts significantly increased between the time after each meal and that before the subsequent meal. Bacterial counts were also higher among women than men. We did not find a correlation between bacterial counts and the presence or absence of cerebrovascular diseases. There was also no correlation between bacterial counts and whether or not dentures were worn. Furthermore, bacterial counts were unaffected by the number of remaining teeth. While there was no significant difference in bacterial counts based on whether or not dentures were worn, subjects with dentures did show higher bacterial counts. When diurnal variation in bacterial counts was compared between subjects with or without dentures, those with dentures on average showed higher bacterial counts for all seven data points, suggesting that they may require oral care more than those without dentures.

Taken together, our results revealed that the most influential factor on oral bacterial counts was the particular meal. If the goal is to prevent the development of aspiration pneumonia caused by subclinical aspiration, oral-care just before sleep would be effective.