Periodontitis increases risk of viable bacteria in freshly drawn blood donations

Abstract

Background: The aim of the study was to determine if periodontitis, which often causes transient bacteraemia, associates with viable bacteria in standard blood donations.

Materials and methods: This was a cross-sectional study of 60 self-reported medically healthy blood donors aged over 50 years. According to standard procedures, whole blood was separated by fractionation into plasma, buffy-coat, and red blood cell (RBC)-fractions. The buffy-coat was screened for bacterial contamination using BacT/ALERT. Samples from plasma and RBC-fractions were incubated anaerobically and aerobically at 37°C for 7 days on trypticase soy blood agar (TSA). For identification, colony polymerase chain reaction was performed using primers targeting 16S rDNA.

Results: From 62% of the donors with periodontitis, bacterial growth was observed on at least 1 out of 4 plates inoculated with plasma or RBCs, whereas only 13% of plates inoculated with plasma or RBCs from periodontally healthy controls yielded bacterial growth (relative risk 6.4, 95% CI: 2.1; 19.5; p=0.0011). None of the donors tested positive for bacterial contamination using BacT/ALERT. Cutibacterium acnes was found in 31% of the donations from donors with periodontitis and in 10% of the donations from periodontally healthy donors. In addition, Staphylococcus species, Bacillus mycoides, Aggregatibacter aphrophilus, and Corynebacterium kroppenstedtii were detected.

Discussion: Periodontitis increased the risk of bacterial contamination of blood products. Contaminating bacteria are often associated with the RBC-fraction. As the BacT/ALERT test is generally performed on platelet products, routine screening fails to detect many occurrences of viable bacteria in the RBC-fraction.

Figure 1. Frequency of viable bacteria in blood from donors

Freshly drawn blood from 60 blood donors was fractioned into RBCs, buffy-coat and plasma. Plasma and RBCs were plated on trypticase soy blood agar (TSA) plates under aerobic or anaerobic conditions. Blood products were defined as positive if at least 1 colony was observed on at least one of the TSA plates. Shown are the frequencies of donors for whom bacteria were found in the RBC-fraction only, in the plasma-fraction only, in both fractions, or in none of the fractions. Donors with periodontitis (n=29) are shown in (A) and periodontally healthy donors (n=31) are shown in (B).

Figure 2. Example of a growth-positive plate

Plasma from a donor with periodontitis plated on a trypticase soy blood agar (TSA) plate under anaerobic conditions for 7 days. Bacterial growth was identified as colonies of Staphylococcus epidermidis and Cutibacterium acnes.