Effect of erythritol and xylitol on Streptococcus pyogenes causing peritonsillar abscesses

Abstract

Polyols are effective against caries-causing streptococci but the effect on oropharynx-derived pyogenic streptococci is not well characterised. We aimed to study the effect of erythritol (ERY) and xylitol (XYL) against Streptococcus pyogenes isolated from peritonsillar abscesses (PTA). We used 31 clinical isolates and 5 throat culture collection strains. Inhibition of bacterial growth by polyols at 2.5%, 5% and 10% concentrations was studied and the results were scored. Amylase levels in PTA pus were compared to polyol effectivity scores (PES). Growth curves of four S. pyogenes isolates were analysed. Our study showed that XYL was more effective than ERY inhibiting 71-97% and 48-84% of isolates, respectively, depending of concentrations. 48% of clinical and all throat strains were inhibited by polyols in all concentrations (PES 3). PES was negative or zero in 26% of the isolates in the presence of ERY and in 19% of XYL. ERY enhanced the growth of S. pyogenes isolated from pus with high amylase levels. Polyols in all concentrations inhibited the growth in exponential phase. In conclusion, ERY and XYL are potent growth inhibitors of S. pyogenes isolated from PTA. Therefore, ERY and XYL may have potential in preventing PTA in the patients with frequent tonsillitis episodes.

Figure 1

Effect of different concentrations (2.5%, 5% and 10%) of erythritol ERY and xylitol XYL on the growth of S. pyogenes PTA isolates (n = 31).

Figure 2

The growth of 31 S. pyogenes isolates from PTA pus in the presence of ERY erythritol, XYL xylitol and BHI brain heart infusion. Minimal, maximal, median, 25 percentile and 75 percentile values of optical density are presented.

Figure 3

Effect of erythritol and xylitol on S. pyogenes PTA isolates and type strains compared to BHI. For each condition (e.g. for polyol ERY at 2.5%), the difference between the polyol growth data and BHI growth data (OD value of BHI minus OD value of polyol solution) is represented. The colored circles above the value “0” in Y axis are “inhibited growth”, values below the value “0” are enhanced growth, and on the value “0” is “no change”. The growth inhibition was detected in 28/31 of the isolates in the presence of at least one concentration of ERY and in 30/31 isolates of XYL.

Figure 4

Distribution of S. pyogenes PTA isolates based on combined polyol effectivity scores (PES) for ERY and XYL. PES was calculated as a summary effect of three polyol concentrations (2.5%, 5% and 10%), where each polyol concentration contributed − 1, 0 or + 1 points depending on whether the S. pyogenes isolate growth increased, remained unchanged or decreased in the presence of the polyols, respectively. Size of the bubble represents number of isolates with different scores.

Figure 5

Amylase levels in PTA pus (red dots—high level, black dots—low level) and polyol effectivity score (PES) against S. pyogenes isolates from PTA pus. PES was calculated as a summary effect of three polyol concentrations (2.5%, 5% and 10%), where each polyol concentration contributed − 1, 0 or + 1 points depending on whether the S. pyogenes growth increased, remained unchanged or decreased in the presence of the polyols, respectively.

Figure 6

S. pyogenes growth curves with ERY erythritol, XYL xylitol and BHI brain heart infusion. Isolates with high polyol effectivity scores (a) S. pyogenes 152, (b) S. pyogenes 184 and low polyol effectivity scores (c) S. pyogenes 179, (d) S. pyogenes 193.