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Objectives: High throughput sequencing of bacterial DNA from clinical samples provides untargeted, open-ended information on the entire microbial community. The downside of this approach is the vulnerability to DNA contamination from other sources than the clinical sample. Here we describe contamination from sterile paper points (PPs) used in microbial sample collection., Methods: Peri-implant samples from 48 individuals were collected using sterile PPs. Control samples contained only PPs or DNA extraction blank controls. 16S rRNA gene libraries were sequenced using 454 pyrosequencing. 16S rRNA gene copy numbers were measured by quantitative PCR., Results: Nearly half of the sequencing reads belonged to two OTUs classified as Enterococcus (25% of reads) or Exiguobacterium (21%), which are not typical oral microorganisms. Of 87 peri-implant samples, only 10 samples (11%) contained neither of the two OTUs. The relative abundance of both unusual OTUs correlated with each other (p<0.001; r=0.828, Spearman correlation). The control samples showed that 2 of 4 (50%) of the sterile unused PPs contained bacterial DNA equivalent to 1.2 × 10(3) and 1.1 × 10(4) cells respectively, which was within the range of DNA in the clinical samples (average 1.8 × 10(7), SD 4.8 × 10(7), min 4.4 × 10(2), max 2.8 × 10(8)). The microbial profile from these PPs was dominated (>83% of reads) by the two unusual OTUs., Conclusions: Sterile PPs can contain contaminating bacterial DNA. The use of PPs as a sampling tool for microbial profiling of clinical samples by open-ended techniques such as sequencing or DGGE should be avoided., Clinical Significance: Clinicians working with PPs as sampling tools for bacterial DNA should consider using an alternative sampling tool, because sterile unused PPs can be a considerable source of foreign bacterial DNA. We recommend sterile curettes for collecting clinical samples for open-ended techniques, such as sequencing or DGGE., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Objective: To study the plasma treatment effects on deactivation effectiveness of oral bacteria., Methods: A low temperature atmospheric argon plasma brush were used to study the oral bacterial deactivation effects in terms of plasma conditions, plasma exposure time, and bacterial supporting media. Oral bacteria of Streptococcus mutans and Lactobacillus acidophilus with an initial bacterial population density between 1.0×10(8) and 5.0×10(8)cfu/ml were seeded on various media and their survivability with plasma exposure was examined. Scanning electron microscopy was used to examine the morphological changes of the plasma treated bacteria. Optical absorption was used to determine the leakage of intracellular proteins and DNAs of the plasma treated bacteria., Results: The experimental data indicated that the argon atmospheric plasma brush was very effective in deactivating oral bacteria. The plasma exposure time for a 99.9999% cell reduction was less than 15s for S. mutans and within 5 min for L. acidophilus. It was found that the plasma deactivation efficiency was also dependent on the bacterial supporting media. With plasma exposure, significant damages to bacterial cell structures were observed with both bacterium species. Leakage of intracellular proteins and DNAs after plasma exposure was observed through monitoring the absorbance peaks at wavelengths of 280 nm and 260 nm, respectively., Conclusion: The experimental results from this study indicated that low temperature atmospheric plasma treatment was very effective in deactivation of oral bacteria and could be a promising technique in various dental clinical applications such as bacterial disinfection and caries early prevention., (Copyright © 2010 Elsevier Ltd. All rights reserved.)